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Journal of Biological Rhythms

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• Description
• Aims and Scope
• Editorial Board
• Abstracting / Indexing
• Submission Guidelines

Every other month, the Journal presents work at the leading edge of understanding the basic nature, mechanisms, and functions underlying the generation, entrainment, and expression of biological rhythms in plants, animals, and humans.

Some of the important topics discussed include:

Sleep-Wake Cycles

Impact and Role of Rhythms in Health and Disease

Rhythms and Depression

Jet Lag and Shift Work

Hormonal and Metabolic Rhythms

Behavioral and Performance Rhythms

Reproductive Cycles

Photoperiodism, Seasonal Cycles, and Annual Cycles

Plant Rhythms and Their Mechanisms

Hibernation and Migration

Cellular Clock Mechanisms

Neuroanatomy and Neurobiology of Circadian Systems

Melatonin and Pineal Gland

Molecular Basis of Circadian Timing

Identification of Genes Underlying Rhythmicity

Control of Gene Expression by Clock Proteins

Comparison of Rhythm Mechanisms among Life Forms

Mechanisms of Photoreception and Photoentrainment

Information Transfer from and among Clock Cells

Mathematical Models of Circadian Oscillators

This journal is a member of the Committee on Publication Ethics (COPE)  

Journal of Biological Rhythms (JBR)   publishes original reports in English describing original research into all aspects of biological rhythms. Emphasis is placed on circadian and seasonal rhythms, but papers on other rhythms are also published. In addition to original research papers, the Journal publishes reviews, commentaries, editorials, letters, and other items of interest related to biological rhythms. Authors use genetic, biochemical, physiological behavioral, and modeling approaches to understand the nature, mechanisms, and functions of biological rhythms in plants and animals. They also study human rhythms in experimental,  clinical, and real world settings. Preliminary or incomplete studies will not be considered. Research reported in the journal must meet the highest standards of experimental design and data analysis. Opinion papers and reviews of significant timely issues will also be considered.

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This Journal is a member of the Committee on Publication Ethics and recommends that authors follow the Uniform Requirements for Manuscripts Submitted to Biomedical Journals formulated by the International Committee of Medical Journal Editors (ICMJE).

There are no publication charges except for circumstances requiring special printing, some instances of color print reproduction, or unusual length and number of illustrations; in these cases, the publisher will provide cost information before the paper is accepted.

Please read the guidelines below, then visit the journal’s submission site to upload your manuscript. Please note that manuscripts not conforming to these guidelines may be returned.

Sage disseminates high-quality research and engaged scholarship globally, and we are committed to diversity and inclusion in publishing. We encourage submissions from a diverse range of authors from across all countries and backgrounds.

Only manuscripts of sufficient quality that meet the aims and scope of the Journal of Biological Rhythms will be reviewed.

There are no fees payable to submit or publish in this Journal. Open Access options are available - see section 3.3 below.

As part of the submission process you will be required to warrant that you are submitting your original work, that you have the rights in the work, that you are submitting the work for first publication in the Journal and that it is not being considered for publication elsewhere and has not already been published elsewhere, and that you have obtained and can supply all necessary permissions for the reproduction of any copyright works not owned by you.

1. Article types 2. Editorial policies                  2.1 Peer review policy                  2.2 Authorship                  2.3 Acknowledgements                  2.4 Funding                  2.5 Declaration of conflicting interests                  2.6 Research ethics and patient consent                  2.7 Clinical trials                  2.8 Reporting guidelines 3. Publishing polices                  3.1 Publication ethics                  3.2 Contributor’s publishing agreement                  3.3 Open access and author archiving                  3.4 Permissions 4. Preparing your manuscript                  4.1 Word processing formats                  4.2 Title Page                  4.3 Introduction                  4.4 Materials and methods section                  4.5 Results section                  4.6 Discussion section                  4.7 Artwork, figures and other graphics                  4.7.1 Visual abstracts                  4.8 Supplementary material                  4.9 Reference style                  4.10 Abbreviations                  4.11 English language editing services 5. Submitting your manuscript                  5.1 How to submit your manuscript                 5.2 ORCID                 5.3 Title, keywords and abstracts                  5.4 Corresponding author contact details 6. On acceptance and publication                  6.1 Sage Production                  6.2 Access to your published article                  6.3 Online First publication 7. Further information

1. Article types JBR considers original reports in English as Research Articles , covering all aspects of biological rhythms, using genetic, biochemical, physiological, behavioural, epidemiological, and modelling approaches, including clinical trials. Emphasis is on circadian and seasonal rhythms, but other periodicities are also considered. Letters also report original research but of a narrower scope, with a few figure panels or equivalent-sized tables. Reviews , Commentaries , Editorials , and other items of interest related to biological rhythms are also encouraged, but pre-submission inquiries to the Editor in Chief by authors of such pieces are recommended. JBR does not publish case reports. 

    •  Original Research                  o Abstract (300 words)                  o Keywords (at least 5)      • Letters (about 2,000 words) 

    Total word count does not include abstracts, keywords or references.

2. Editorial policies

2.1 Peer review policy JBR adheres to a rigorous single-anonymize reviewing policy in which the identity of the reviewers is not known to the authors.

As part of the submission process you will be given the opportunity to provide the names of peers who could be called upon to review your manuscript. Recommended reviewers should be experts in their fields and should be able to provide an objective assessment of the manuscript. Please be aware of any conflicts of interest when recommending reviewers. Examples of conflicts of interest include (but are not limited to) the below: 

                • The reviewer should have no prior knowledge of your submission                  • The reviewer should not have recently collaborated with any of the authors                  • Reviewer nominees from the same institution as any of the authors are not permitted

You will also be given the opportunity to nominate peers who you do not wish to review your manuscript (opposed reviewers).

Please note that the Editor is not obliged to invite/reject any recommended/opposed reviewers to assess your manuscript.

The Editor or members of the Editorial Board may occasionally submit their own manuscripts for possible publication in the journal. In these cases, the peer review process will be managed by alternative members of the Board and the submitting Editor/Board member will have no involvement in the decision-making process.

2.2 Authorship Papers should only be submitted for consideration once consent is given by all contributing authors. Those submitting papers should carefully check that all those whose work contributed to the paper are acknowledged as contributing authors.

The list of authors should include all those who can legitimately claim authorship. This is all those who: 

        (i)    Made a substantial contribution to the concept or design of the work; or acquisition,                analysis or interpretation of data,          (ii)   Drafted the article or revised it critically for important intellectual content,          (iii)  Approved the version to be published,          (iv)  Each author should have participated sufficiently in the work to take public responsibility               for appropriate portions of the content

Authors should meet the conditions of all of the points above. When a large, multicentre group has conducted the work, the group should identify the individuals who accept direct responsibility for the manuscript. These individuals should fully meet the criteria for authorship.

Acquisition of funding, collection of data, or general supervision of the research group alone does not constitute authorship, although all contributors who do not meet the criteria for authorship should be listed in the Acknowledgments section. Please refer to the International Committee of Medical Journal Editors (ICMJE) authorship guidelines for more information on authorship.

Please note that AI chatbots, for example ChatGPT, should not be listed as authors. For more information see the policy on Use of ChatGPT and generative AI tools .

2.3 Acknowledgements All contributors who do not meet the criteria for authorship should be listed in an Acknowledgements section. Examples of those who might be acknowledged include a person who provided purely technical help, or a department chair who provided only general support.

2.3.1 Third party submissions Where an individual who is not listed as an author submits a manuscript on behalf of the author(s), a statement must be included in the Acknowledgements section of the manuscript and in the accompanying cover letter. The statements must:

• Disclose this type of editorial assistance – including the individual’s name, company and level of input
• Identify any entities that paid for this assistance
• Confirm that the listed authors have authorized the submission of their manuscript via third party and approved any statements or declarations, e.g. conflicting interests, funding, etc.

Where appropriate, Sage reserves the right to deny consideration to manuscripts submitted by a third party rather than by the authors themselves.

2.3.2 Writing assistance Individuals who provided writing assistance, e.g. from a specialist communications company, do not qualify as authors and so should be included in the Acknowledgements section. Authors must disclose any writing assistance – including the individual’s name, company and level of input – and identify the entity that paid for this assistance. It is not necessary to disclose use of language polishing services.

Any acknowledgements should appear first at the end of your article prior to your Declaration of Conflicting Interests (if applicable), any notes and your References.

2.4 Funding JBR requires all authors to acknowledge their funding in a consistent fashion under a separate heading. Please visit the Funding Acknowledgements page on the Sa Journal Author Gateway to confirm the format of the acknowledgment text in the event of funding, or state that: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

2.5 Declaration of conflicting interests It is the policy of JBR to require a declaration of conflicting interests from all authors enabling a statement to be carried within the paginated pages of all published articles. Please ensure that a “Declaration of Conflicting Interests” statement is included at the end of your manuscript, after any acknowledgements and prior to the references. If no conflict exists, please state that “The Author(s) declare(s) that there is no conflict of interest”.

For guidance on conflict of interest statements, please see the ICMJE recommendations here .

2.6 Research ethics and patient consent Medical research involving human subjects must be conducted according to the World Medical Association Declaration of Helsinki .

Submitted manuscripts should conform to the ICMJE Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals , and all papers reporting animal and/or human studies must state in the methods section that the relevant Ethics Committee or Institutional Review Board provided (or waived) approval. Please ensure that you have provided the full name and institution of the review committee, in addition to the approval number.

For research articles and letters, authors are also required to state in the methods section whether participants provided informed consent and whether the consent was written or verbal.

Information on informed consent to report case series should be included in the manuscript text. A statement is required regarding whether written informed consent for patient information and images to be published was provided by the patient(s) or a legally authorized representative.

Please also refer to the ICMJE Recommendations for the Protection of Research Participants .

All research involving animals submitted for publication must be approved by an ethics committee with oversight of the facility in which the studies were conducted. The journal has adopted the Consensus Author Guidelines on Animal Ethics and Welfare for Veterinary Journals published by the International Association of Veterinary Editors or the U.S. National Institutes of Health Guide for the Care and Use of Laboratory Animals .

2.7 Clinical trials JBR conforms to the ICMJE requirement that clinical trials are registered in a WHO-approved public trials registry at or before the time of first patient enrollment as a condition of consideration for publication. The trial registry name and URL, and registration number must be included at the end of the abstract.

2.8 Reporting Guidelines The relevant EQUATOR Network reporting guidelines should be followed depending on the type of study. For example, all randomized controlled trials submitted for publication should include a completed Consolidated Standards of Reporting Trials (CONSORT) flow chart as a cited figure, and a completed CONSORT checklist as a supplementary file.

Other resources can be found at NLM’s Research Reporting Guidelines and Initiatives.

3. Publishing Policies

3.1 Publication ethics Sage is committed to upholding the integrity of the academic record. We encourage authors to refer to the Committee on Publication Ethics’ International Standards for Authors and view the Publication Ethics page on the Sage Author Gateway .

3.1.1 Plagiarism JBR and Sage take issues of copyright infringement, plagiarism or other breaches of best practice in publication very seriously. We seek to protect the rights of our authors and we always investigate claims of plagiarism or misuse of published articles. Equally, we seek to protect the reputation of the journal against malpractice. Submitted articles may be checked with duplication-checking software. Where an article, for example, is found to have plagiarized other work or included third-party copyright material without permission or with insufficient acknowledgement, or where the authorship of the article is contested, we reserve the right to take action including, but not limited to: publishing an erratum or corrigendum (correction); retracting the article; taking up the matter with the head of department or dean of the author's institution and/or relevant academic bodies or societies; or taking appropriate legal action.

3.1.2 Prior publication If material has been previously published it is not generally acceptable for publication in a Sage journal. However, there are certain circumstances where previously published material can be considered for publication. Please refer to the guidance on the Sage Author Gateway or if in doubt, contact the Editor at the address given below.

3.2 Contributor’s publishing agreement Before publication, Sage requires the author as the rights holder to sign a Journal Contributor’s Publishing Agreement. Sage’s Journal Contributor’s Publishing Agreement is an exclusive licence agreement which means that the author retains copyright in the work but grants Sage the sole and exclusive right and licence to publish for the full legal term of copyright. Exceptions may exist where an assignment of copyright is required or preferred by a proprietor other than Sage. In this case copyright in the work will be assigned from the author to the society. For more information please visit our Frequently Asked Questions on the Sage Journal Author Gateway.

3.3 Open access and author archiving Journal of Biological Rhythms  offers optional open access publishing via the Sage Choice programme and Open Access agreements, where authors can publish open access either discounted or free of charge depending on the agreement with Sage. Find out if your institution is participating by visiting Open Access Agreements at Sage . For more information on Open Access publishing options at Sage please visit Sage Open Access . For information on funding body compliance, and depositing your article in repositories, please visit Sage’s Author Archiving and Re-Use Guidelines and Publishing Policies .

3.4 Permissions Authors are responsible for obtaining permission from copyright holders for reproducing any illustrations, tables, figures or lengthy quotations previously published elsewhere. For further information including guidance on fair dealing for criticism and review, please visit our Frequently Asked Questions on the Sage Journal Author Gateway .

4. Preparing your manuscript

4.1 Word processing formats Manuscripts should be written clearly and concisely and should conform generally to the Council of Science Editors Style Manual (Scientific Style and Format: The CSE Manual for Authors, Editors, and Publishers, 7th ed.).

Preferred format for the text and tables of your manuscript is Word DOC; RTF, XLS, LaTeX files are also accepted. The text should be double-spaced throughout and with a minimum of 3cm for left and right hand margins and 5cm at head and foot. Text should be standard 10 or 12 point. Word and (La)Tex templates are available on the Manuscript Submission Guidelines page of our Author Gateway.

4.2 Title page Include the authors' names, the title and a short running title, and the institution(s) (with all words spelled out in full) from which the paper emanates. If current addresses are different, then these should be indicated in a footnote. Also include the name, mailing address, phone and fax numbers, and e-mail address of the person to whom correspondence and proofs should be sent.

4.3 Introduction Include an Introduction that provides a brief review of relevant background material and indicates the purpose of the study.

4.4 Materials and methods section This section should provide sufficient information for qualified investigators to reproduce the work in similar fashion. Reference to published procedures by appropriate succinct summary and citation is encouraged but should not replace adequate methodological description. Authors must confirm that they have conscientiously followed principles and practices in accord with these documents in experiments involving human subjects and experimental animals (see 2.6 Research ethics and patient consent ).

4.5 Results section Provide a concise description of the findings with appropriate reference to illustrations and tables.

4.6 Discussion section Include a summary of the main findings (no data), their relation to other published work, and a statement of their significance.

4.7 Artwork, figures and other graphics For guidance on the preparation of illustrations, pictures and graphs in electronic format, please visit Sage’s Manuscript Submission Guidelines . Figures supplied in colour will appear in colour online regardless of whether or not these illustrations are reproduced in colour in the printed version. For specifically requested colour reproduction in print, the cost is $800 for the first color image in print, and $200 for any subsequent printed color images in the same article. Number the pages, illustrations, and tables. A list of figure legends should follow the references and be the last section in the text. A brief title and description of each illustration should be included. These should be typed consecutively on the same page(s).

4.7.1 Visual abstracts A visual or graphical abstract is one single-panel image meant to be a clear, quick, and concise pictoral representation of the research published in the journal. It is meant to support the written abstract that accompanies all papers submitted for review to the journal.

Please note visual abstracts are optional, but if you wish to submit a visual abstract with your paper, please follow the below guidelines:

• Label: The file should be labelled as "graphical abstract," so that it is clear the file is not an article figure (e.g., it should not be labelled as "Fig1," "Fig2," etc.).
• Caption: A caption should be provided with the graphic. The caption should read: "This is a graphical representation of the abstract."
• Format: JPG, TIF, or EPS
• Size: The image should be 1200 pixels square at 300dpi with Arial font (12-16 point) so it is readable on a phone.
• Copyright free: Do not use images subject to copyright clearance for graphical abstracts. The image should have no overlap with images in the figures of the paper.
• Submission: The final visual abstract image should be sent with accepted article.
• Clarity: Simplicity is the key to conveying information visually. Part of the image should convey the organism under study.

4.8 Supplementary material This journal is able to host additional materials online (e.g. datasets, podcasts, videos, images etc) alongside the full-text of the article. These will be subjected to peer-review alongside the article. For more information please refer to our guidelines on submitting supplementary files, which can be found within our Manuscript Submission Guidelines page. Number figures and tables S1, S2, etc.

4.9 Reference style References should be double spaced and listed sequentially in alphabetical order according to the name of the first author with (a) a full list of authors, (b) date, (c) full title of the paper, (d) journal titles abbreviated as per Index Medicus , (e) volume number, and (f) first and last pages. Only papers published or in press may be included in the reference list. Papers should be cited in the text by author(s) and date. 

                 Examples                   Aschoff J (1965) Response curves in circadian periodicity. In Circadian Clocks ,                 J Aschoff, ed, pp 95-111, North-Holland, Amsterdam.            

                Pittendrigh CS and Daan S (1976) A functional analysis of circadian pacemakers in nocturnal                  rodents: The stability and liability of spontaneous frequency. J Comp Physiol A 106:223-252. 

                Richter CP (1965) Biological Clocks in Medicine and Psychiatry , Charles C Thomas, Springfield,                 IL.

4.10 Abbreviations Abbreviations should be introduced in parentheses after the first occurrence of the term being abbreviated. Use standard metric units wherever possible.

4.11 English language editing services Authors seeking assistance with English language editing, translation, or figure and manuscript formatting to fit the journal’s specifications should consider using Sage Language Services. Visit Sage Language Services on our Journal Author Gateway for further information.

5. Submitting your manuscript

5.1 How to submit your manuscript JBR is hosted on Sage Track, a web based online submission and peer review system powered by ScholarOne™ Manuscripts. Visit https://mc.manuscriptcentral.com/jbrhythms  to login and submit your article online.

IMPORTANT: Please check whether you already have an account in the system before trying to create a new one. If you have reviewed or authored for the journal in the past year it is likely that you will have had an account created. For further guidance on submitting your manuscript online please visit ScholarOne Online Help .

5.2 ORCID As part of our commitment to ensuring an ethical, transparent and fair peer review process Sage is a supporting member of  ORCID, the Open Researcher and Contributor ID . ORCID provides a unique and persistent digital identifier that distinguishes researchers from every other researcher, even those who share the same name, and, through integration in key research workflows such as manuscript and grant submission, supports automated linkages between researchers and their professional activities, ensuring that their work is recognized.

The collection of ORCID IDs from corresponding authors is now part of the submission process of this journal. If you already have an ORCID ID you will be asked to associate that to your submission during the online submission process. We also strongly encourage all co-authors to link their ORCID ID to their accounts in our online peer review platforms. It takes seconds to do: click the link when prompted, sign into your ORCID account and our systems are automatically updated. Your ORCID ID will become part of your accepted publication’s metadata, making your work attributable to you and only you. Your ORCID ID is published with your article so that fellow researchers reading your work can link to your ORCID profile and from there link to your other publications.

If you do not already have an ORCID ID please follow this  link  to create one or visit our  ORCID homepage  to learn more.

5.2 Title, keywords and abstracts Please supply a title, short title, an abstract and at least five keywords to accompany your article. The title, keywords and abstract are key to ensuring readers find your article online through online search engines such as Google. Please refer to the information and guidance on how best to title your article, write your abstract and select your keywords by visiting the Sage Journal Author Gateway for guidelines on How to Help Readers Find Your Article Online .

5.3 Corresponding author contact details Provide full contact details for the corresponding author including email, mailing address and telephone numbers. Academic affiliations are required for all co-authors.

6. On acceptance and publication

6.1 Sage Production Your Sage Production Editor will keep you informed as to your article’s progress throughout the production process. Proofs will be sent by PDF to the corresponding author and should be returned promptly. Authors are reminded to check their proofs carefully to confirm that all author information, including names, affiliations, sequence and contact details are correct, and that Funding and Conflict of Interest statements, if any, are accurate.

6.2 Access to your published article Sage provides authors with online access to their final article.

6.3 Online First publication Online First allows final revision articles (completed articles in queue for assignment to an upcoming issue) to be published online prior to their inclusion in a final journal issue which significantly reduces the lead time between submission and publication. For more information please visit our Online First Fact Sheet .

7. Further information

Any correspondence, queries or additional requests for information on the manuscript submission process should be sent to the JBR editorial office as follows:

Mary E. Harrington, PhD Editor in Chief [email protected]

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Essays articulate a specific perspective on a topic of broad interest to scientists.

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Time is of the essence: The importance of considering biological rhythms in an increasingly polluted world

Roles Conceptualization, Funding acquisition, Investigation, Project administration, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected] (ESJT); [email protected] (MGB)

Affiliations Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden, TRANSfarm—Science, Engineering, & Technology Group, KU Leuven, Lovenjoel, Belgium, Department of Zoology, Stockholm University, Stockholm, Sweden

Roles Conceptualization, Investigation, Visualization, Writing – original draft, Writing – review & editing

Affiliation Department of Ornithology, Max Planck Institute for Biological Intelligence, Seewiesen, Germany

Affiliations Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden, Institute of Zoology, Zoological Society of London, London, United Kingdom

Affiliation Laboratory of Aquatic Ecology, Evolution, and Conservation, Department of Biology, KU Leuven, Leuven, Belgium

Affiliation Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden

Affiliations Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden, Department of Zoology, Stockholm University, Stockholm, Sweden, School of Biological Sciences, Monash University, Melbourne, Australia

• Eli S. J. Thoré, 
• Anne E. Aulsebrook, 
• Jack A. Brand, 
• Rafaela A. Almeida, 
• Tomas Brodin, 
• Michael G. Bertram

Published: January 30, 2024

• https://doi.org/10.1371/journal.pbio.3002478
• Reader Comments

Biological rhythms have a crucial role in shaping the biology and ecology of organisms. Light pollution is known to disrupt these rhythms, and evidence is emerging that chemical pollutants can cause similar disruption. Conversely, biological rhythms can influence the effects and toxicity of chemicals. Thus, by drawing insights from the extensive study of biological rhythms in biomedical and light pollution research, we can greatly improve our understanding of chemical pollution. This Essay advocates for the integration of biological rhythmicity into chemical pollution research to gain a more comprehensive understanding of how chemical pollutants affect wildlife and ecosystems. Despite historical barriers, recent experimental and technological advancements now facilitate the integration of biological rhythms into ecotoxicology, offering unprecedented, high-resolution data across spatiotemporal scales. Recognizing the importance of biological rhythms will be essential for understanding, predicting, and mitigating the complex ecological repercussions of chemical pollution.

Citation: Thoré ESJ, Aulsebrook AE, Brand JA, Almeida RA, Brodin T, Bertram MG (2024) Time is of the essence: The importance of considering biological rhythms in an increasingly polluted world. PLoS Biol 22(1): e3002478. https://doi.org/10.1371/journal.pbio.3002478

Copyright: © 2024 Thoré et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: Support for this article was provided by the Kempe Foundations (JCK22-0037 to T.B.; SMK-1954 and SMK21-0069 to M.G.B.), the Swedish Research Council Formas (2018-00828 to T.B.), and a Swedish Research Council Formas Mobility Grant (2020-02293 to M.G.B.). Additionally, we would like to thank the Petra and Karl Erik Hedborg Foundation for their generous support (to E.S.J.T.) of a research exchange that contributed to the development of the ideas presented in this Essay. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: PCB, polychlorinated biphenyl; PFAS, polyfluoroalkyl substance; SSRI, selective serotonin reuptake inhibitor

Introduction

Chemical pollution is an urgent and escalating global concern [ 1 , 2 ]. The global production of chemicals, coupled with their release into the environment, has increased 50-fold since 1950 and is expected to triple again by 2050 compared with 2010 [ 3 ]. Chemical pollutants have the potential to profoundly alter wildlife biology and ecology, disrupt ecosystems, and pose a serious threat to biodiversity [ 4 , 5 ]. Despite this, our understanding of the ecological effects of chemical pollutants remains rudimentary, leaving us far from effectively managing the risks they pose [ 5 ]. As ecotoxicologists and regulators work towards solutions, it is becoming increasingly evident that nature’s inherent complexity challenges our ability to assess the full extent of the risks posed by chemical pollution. In this regard, time has a critical role in structuring biological patterns and processes, including how wildlife are affected by, and respond to, environmental change [ 6 , 7 ]. Indeed, biological rhythms represent a fundamental and universal feature of life, yet our understanding of their ecological and evolutionary underpinnings and consequences remains extremely limited [ 7 , 8 ], particularly within the context of chemical pollution (see also [ 9 , 10 ]).

In this Essay, we aim to highlight the urgent need to integrate biological rhythms into chemical pollution research. We first outline what biological rhythms are and provide an overview of their diversity and significance. We then examine why biological rhythms matter for understanding the ecological impacts of chemical pollution and identify the existing barriers to incorporating biological rhythms into chemical pollution research. Finally, we propose novel methods, tools, and resources that can help to overcome these barriers.

What are biological rhythms?

Biological rhythms govern the entire biosphere, covering processes as diverse as pulsatile hormone secretion, cyclic variation in appetite and food intake, intertidal activity of coastal and estuarine animals, daily plant leaf movements, the sleep–wake cycle, diurnal vertical migration of animals in oceans and lakes, the menstrual cycle, annual bird migration, and seasonal hibernation. In this Essay, we broadly define biological rhythms as repetitive molecular, physiological, and behavioral processes that occur in anticipation of, or response to, periodic environmental change. Such rhythms are highly diverse in nature ( Fig 1 ), can recur with a frequency that ranges from microseconds to hours (ultradian rhythms), days (diurnal rhythms), or even weeks, months, or years (infradian rhythms), and exist across the tree of life. Some biological rhythms are exclusively regulated by environmental signals, while others are also regulated by internal biological clocks [ 8 , 11 ]. One of the most well-known examples of such an internal regulator is the circadian clock, which operates roughly on a 24-hour cycle and governs the daily rhythms of organisms. While the circadian clock is synchronized or “entrained” by external cues known as zeitgebers (such as light), it runs even in the absence of time-of-day cues (i.e., it has a free-running rhythm [ 11 ]). Organisms typically have multiple biological clocks that are spread across several tissues and organs throughout the body, and which control diverse rhythms that are synchronized with each other and with environmental cycles [ 12 ]. Furthermore, biological rhythms can be superimposed on one another, giving rise to composite oscillations within biological systems, rather than just following a single cycling frequency [ 13 ]. Collectively, biological rhythms coordinate a myriad of essential biological processes and have a fundamental role in regulating life’s processes.

• PPT PowerPoint slide
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( A ) Environmental cycles such as seasonality, the lunar cycle, the day–night cycle, and tidal activity are characterized by periodic changes in, among other things, light, temperature, salinity, and oxygen availability. ( B ) Biological rhythms manage the biosphere. They occur across the tree of life and manifest across all levels of biological organization.

https://doi.org/10.1371/journal.pbio.3002478.g001

Why consider biological rhythms in chemical pollution research?

Although the study of biological rhythms (chronobiology) grew from ecological and evolutionary biology roots in the mid-20th century, the field quickly shifted its focus towards the mechanistic underpinnings of biological clocks, and circadian clocks in particular [ 8 ]. Thereafter, both fields developed largely independently. Consequently, the majority of insights into the workings and importance of biological rhythms have come from biomedical research. As such, biological rhythms represent a level of complexity that has long been realized but not routinely incorporated into ecology and evolutionary biology [ 7 ] and, by extension, global change and chemical pollution research.

Pioneering studies of biological rhythms and chemical toxicity date back to the 1960s. Such studies, which demonstrated circadian variation in pesticide toxicity, already highlighted the importance of considering biological rhythms in ecotoxicology. For example, adult boll weevils ( Anthonomus grandis ) and two-spotted spider mites ( Tetranychus urticae ) exhibit a daily rhythm in their susceptibility to the insecticides methyl parathion and dimethyl 2,2-dichlorovinyl phosphate, respectively. Specifically, weevils consistently experienced the least mortality at dawn [ 14 ] ( Fig 2 ), whereas mites were maximally susceptible right after dawn and were least affected just after nightfall [ 15 ]. Furthermore, the sensitivity of house crickets ( Gryllus domesticus ) to narcotics (ethyl ether, chloroform, and carbon tetrachloride) peaks during the first part of the nighttime period, corresponding to the species’ peak activity [ 16 ]. Conversely, house flies ( Musca domestica ) show maximum sensitivity to the pesticide trichlorfon at dawn and are least sensitive during dusk [ 17 ].

Despite having received relatively little research attention to date, the few studies that have tested for potential interactions between chemical pollution exposure and biological rhythms have demonstrated that these factors can interact at various spatiotemporal scales and in diverse biological systems ( A - C ). While our focus is on chemical pollution research, chronobiology is clearly relevant to all forms of environmental change (e.g., light pollution, D ).

https://doi.org/10.1371/journal.pbio.3002478.g002

While these are not the only studies demonstrating that wildlife susceptibility to toxicants can fluctuate during the day, sometimes by orders of magnitude [ 18 ], similar studies remain relatively rare (see also [ 9 , 18 , 19 ]), and studies that incorporate ultradian or infradian rhythms are even scarcer. This is a cause for concern because failure to integrate biological rhythms into chemical pollution research severely limits our understanding of the ecological and evolutionary responses to, and consequences of, this pervasive form of global change. We contend that biological rhythms should be integrated into chemical pollution research for 3 interconnected reasons: biological rhythms are adaptive (misaligned rhythms can dysregulate biological and ecological functioning); chemicals can affect biological rhythms, and these rhythms can influence the impacts of chemicals; and biological rhythms introduce variation that complicates the interpretation of results. In the following sections, we examine each of these reasons in turn.

Biological rhythms are adaptive

Biological rhythms are highly adaptive and are believed to be under strong selection, as they govern a broad range of essential processes for wildlife reproduction and survival [ 6 , 8 ]. Specifically, they have a vital role in coordinating the biology of organisms with periodic changes in the abiotic environment, such as changes in light, temperature, salinity, and oxygen availability related to tidal activity, the day–night cycle, the lunar cycle, and seasonality ( Fig 1 ). Further, biological rhythms can coordinate interactions among organisms, including potential mates, competitors, parasites, prey, predators, and symbionts (e.g., the microbiome). For example, dominant brown trout ( Salmo trutta ) forage most intensely from dusk until dawn to maximize food intake and minimize predation risk, whereas the foraging activity of subdominant trout peaks at alternative times of the day to minimize competition [ 20 ]. Such rhythms are not necessarily rigidly structured but can shift to help organisms respond to changes in their environment [ 21 ]. In the previous example, when competition for resources increases, differences in the timing of foraging activity between dominant and subdominant trout become more pronounced [ 20 ]. Similarly, Norway rats ( Rattus norvegicus ) that are generally nocturnal can shift to daytime foraging to avoid predation by nocturnal red foxes ( Vulpes vulpes ) [ 22 ]. In some cases, organisms can shift to or from arrhythmicity altogether, such as when male sandpipers ( Calidris melanotos ) shift from daily rhythmicity to almost round-the-clock activity during the breeding season to increase their reproductive success [ 23 ].

Although organisms can be equipped to cope with changes in the environment through plastic shifts in their rhythms, some may be far less able to instantly cope with abrupt and/or unpredictable changes than others [ 8 ]. In such cases, the timing of biological rhythms may become mismatched with environmental cues, as is the case when we experience jet lag: Travel across time zones shifts our circadian clock out of alignment with local time, which can lead to fatigue and reduced performance [ 24 ]. Jet lag in humans is temporary, as the circadian clock eventually resynchronizes, but prolonged misalignment of biological rhythms can result in substantial fitness consequences. For example, misalignment of the circadian rhythm with the 24-hour day–night cycle can come at a physiological cost that accelerates the aging process and decreases life span in rodents and primates [ 25 ]. In Drosophila fruit flies, experimentally induced desynchronization between rhythmic gene expression in the fat body (a mass of tissue used for energy storage) compared with the brain results in a lower reproductive output [ 12 ]. In fact, dysregulation of biological rhythms can often directly lead to various pathologies [ 26 ]. Shift work, altered timing of sleep on work days compared with non-work days (or “social jetlag”), and exposure to light-at-night can lead to dysregulations in humans that have been associated with metabolic disorders such as diabetes [ 27 ], cardiovascular diseases [ 28 ], cancer [ 29 ], and various mood disorders [ 30 ]. Similar effects occur in experimental animal studies, including the promotion of cardiomyopathy by circadian disruption in hamsters [ 31 ], as well as obesity [ 32 ] and anxiety-like behavior [ 33 ] in mice. Further, there is mounting evidence for a link between circadian clock disruption and increased cancer risk in mice [ 34 ]. Naturally, such effects could have strong implications for the survival and reproductive success of wildlife and may have far-reaching population-level impacts.

Beyond direct consequences for the health and performance of organisms, desynchronization of biological rhythms with environmental cycles or with those of other organisms can cascade through different levels of biological organization and have far-reaching ecological repercussions [ 6 , 35 ]. Desynchronized activity rhythms can disrupt social activities such as mating, parental care, or group foraging, which may have substantial demographic consequences [ 36 ], and novel “timescapes”(i.e., time periods with fitness-relevant heterogeneity in (a)biotic factors) could fundamentally alter species interactions when species perceive and respond differently to timescape changes [ 6 , 37 ]. This could lead to desynchronization along the food web in, for example, seasonal activity timing [ 38 ], and ultimately affect the functioning of whole ecosystems [ 39 ]. For example, exposure of wild mustard plants to ozone reduces vegetative growth but accelerates their flowering, which can foster desynchronization between plant and pollinator activities ( Fig 2 ) [ 40 ]. Conversely, symbiont–host interactions can contribute to the stabilization and coordination of circadian rhythms within the host organism. Specifically, the microbiome may be able to moderate the host’s response to external environmental cues, ensuring that internal biological processes remain synchronized with the external day–night cycle. This, in turn, promotes overall circadian synchrony within the host, thereby buffering against rapid environmental fluctuations [ 41 ].

Chemicals can affect biological rhythms and vice versa

It is increasingly evident from the biomedical literature that many emerging forms of pollution, including (inappropriate) exposure to biologically active chemicals (e.g., pharmaceutical drugs or endocrine-disrupting chemicals) can profoundly disrupt biological rhythms. Indeed, recent biomedical research has begun to investigate the direct interactions between disruptions in the human circadian system, mood regulation, and drug use. Even though our understanding of these complex relationships is still in its early stages, there is mounting evidence that several pharmaceutical compounds can modulate circadian rhythms in both humans and animal model species [ 42 ] and that inappropriate use of drugs may even disrupt the circadian system altogether [ 43 ] ( Fig 3 ). In humans, disruptions to the circadian system have furthermore been linked to a higher usage of hypnotic medication [ 44 ] and can increase the risk of drug dependence and addiction [ 45 ]. Vice versa, circadian rhythms can affect the pharmacokinetics and pharmacodynamics—including the biological effects—of drugs, to the extent that there is ongoing research into the potential for chronotherapy to improve the efficacy and safety of pharmaceutical agents [ 42 ]. The absorption, distribution, metabolism, and excretion of drugs and other compounds are influenced by circadian rhythms [ 46 ], such that their effects may vary over the course of a day ( Fig 3 ).

Chemical pollutants can disrupt biological rhythms, and, conversely, biological rhythms can influence an organism’s susceptibility and/or response to chemicals. The example presented here is one of many possible scenarios and is used for illustrative purposes.

https://doi.org/10.1371/journal.pbio.3002478.g003

Similar interactive effects between rhythmicity and the effects of chemical pollutants on wildlife are likely to be far more widespread and important than is currently appreciated. At the moment, over 350,000 chemicals are registered for commercial use worldwide [ 47 ], of which hundreds are routinely detected in all studied environmental compartments [ 4 , 48 ]. Many of these chemicals may not be present at high enough environmental concentrations to result in direct mortality of wildlife but can nevertheless trigger biological changes, even at extremely low concentrations, that compromise the health of our ecosystems (e.g., per- and polyfluoroalkyl substances (PFAS), pharmaceutical agents, polychlorinated biphenyls (PCBs)) [ 1 , 48 ]. In fact, when the International Union for Conservation of Nature compiled the Red List in 2022, more than 11,500 out of 83,669 assessed animal species were considered to be impacted by chemical pollution [ 4 , 49 ]. While our current knowledge about chemicals interfering with the regulation of circadian rhythms (so-called “circadian disruptors”) is extremely limited, at least 40 chemical pollutants were recently identified that interfere with circadian rhythms in fish at environmentally realistic concentrations [ 10 ]. These included steroid hormones, metals, pesticides and biocides, PCBs, neuroactive drugs, and cyanobacterial toxins (which are becoming more widespread due to nutrient pollution and climate warming). For example, neuroactive drugs such as selective serotonin reuptake inhibitors (SSRIs) are commonly used to treat depression or other mental illnesses but are also known to interfere with human circadian rhythms and the sleep–wake cycle [ 30 , 42 ]. Serotonin is also involved in the regulation of circadian rhythmicity and associated behaviors in fish [ 50 ], such that exposure to SSRIs has the potential to disrupt circadian rhythms in wildlife [ 51 ]. Indeed, chronic exposure to an environmentally relevant concentration (28 ng/L) of the antidepressant fluoxetine entirely eroded daily activity patterns in Nothobranchius killifish, suggesting strong circadian disruption [ 52 ] ( Fig 2 ). This finding was recently replicated in Gambusia mosquitofish after as little as 3 days of exposure to 30 to 300 ng/L of fluoxetine [ 53 ] and is consistent with the earlier finding that 96 hours of exposure to a mixture of organic contaminants, including fluoxetine, eroded daily activity patterns in male mosquitofish [ 54 ].

Given that our current knowledge about potential circadian-disrupting chemicals is extremely limited [ 10 ], it is likely that many more chemicals exist that can interfere with circadian rhythms in wildlife, or with biological rhythms more generally. In support of this expectation, over half of the top 100 best-selling drugs in the United States, and over 100 of the World Health Organization’s list of essential medicines, directly target the product of rhythmic genes [ 55 ]. The release of such chemicals into the environment is concerning given that disruption of biological rhythms by chemicals can interfere with organismal survival and reproductive success and, in turn, result in far-reaching population-level and ecological consequences. The issue may be exacerbated by the fact that several molecular components of xenobiotic metabolism and detoxification mechanisms, including cytochrome P450s [ 56 ] and antioxidant enzymes [ 57 ], seem to be, at least in part, regulated by circadian rhythms. This suggests that even chemicals that do not directly interfere with the circadian system could affect organisms differently depending on the timing of administration or observation [ 10 ]. However, this is only very rarely taken into account in ecotoxicological research.

Biological rhythms introduce variation

Even in the absence of potential interactive effects between chemicals and rhythmically controlled systems, it is essential to appropriately control for the possible confounding effects of rhythmicity in ecotoxicological research. For example, many molecular biomarkers [ 58 ] or behaviors [ 52 ] commonly considered in ecotoxicological experiments show daily variation in their expression. If experimental sampling is not time-controlled, biological rhythmicity may introduce substantial variation (or “noise”) that results in either false positive or false negative results or that could lead to inaccurate conclusions regarding the magnitude of the effects of chemicals. Accommodating the potential effects of sampling time is therefore critical to the reliability and reproducibility of ecotoxicological data. Furthermore, it is important for researchers to consider that not only light but also many other factors can be important zeitgebers that influence biological rhythmicity. These include temperature, social interactions, and food availability [ 7 ]. For example, nocturnal mice can shift their activity patterns to become diurnal when exposed to cold or hunger [ 59 ]. In Drosophila fruit flies, restricting food intake to a specific time of day during which feeding is typically low can desynchronize internal rhythms. This desynchronization does not directly affect food intake but instead leads to lower reproductive output [ 12 ]. Not accounting for such effects can introduce significant variation within and among studies and undermine test–retest reliability in chemical pollution research.

Barriers and solutions to incorporating biological rhythms into ecotoxicology

The lack of research investigating the interactions between chronobiology and chemical pollution is perhaps not surprising, considering the intensive sampling that is often required to measure biological rhythms [ 60 ]. For example, such analysis often requires repeated animal handling for assays (e.g., behavior, metabolic rate, and blood samples) over multiple time points, presenting logistical, economic, and even ethical constraints for certain species. Some of these concerns may be further exacerbated when considering longer-term biological rhythms, where animals need to be tracked across several months (e.g., infradian rhythms such as seasonal changes, migration, or hibernation). What is more, some aspects of biology are difficult to assess continuously and noninvasively altogether. For example, the measurement of (rhythmic) gene expression in animals can be hampered by the invasiveness of physical sampling of secretions or tissue (or sometimes the entire animal) after capture [ 58 , 61 ]. The expense of some techniques can also constrain the number of samples that researchers can analyze. These challenges can substantially limit the feasibility of studying the effects of chemical pollution on biological rhythms (and vice versa).

Fortunately, recent technological advances can help to overcome many of these issues. Improved sensitivity of noninvasive hormonal assays now allows repeated sampling of physiological traits without extensive animal handling, as seen with the increasing use of water and feces samples to measure cortisol or corticosterone expression in organisms including fish [ 62 ], aquatic and terrestrial dwelling amphibians [ 63 ], reptiles [ 64 ], birds [ 65 ], and mammals [ 66 ]. By sampling structures such as feathers, researchers can also gain insight into the physiological history of an animal, including feather growth rates, hormonal levels, and exposure to pollutants [ 67 , 68 ]. Developments in laboratory hardware and software have also considerably improved the ease of repeatedly recording behavioral observations over multiple time points (reviewed in [ 69 ]). In particular, high-resolution infrared-sensitive cameras are increasingly being used to continuously record the behavior of animals under both light and dark conditions, across multiple days. For example, infrared-sensitive cameras have been used to record how the insecticide endosulfan influences circadian rhythms in several parasitoid wasp species ( Leptophilina spp.) [ 70 ]. Furthermore, the increasing availability of high-throughput, often open-source, automated animal tracking technologies has reduced many of the economic and logistical constraints encountered when continuously recording the behavior of animals (see [ 69 , 71 ] for reviews). In combination with infrared-sensitive cameras, these automated tracking technologies allow the recording and measurement of animal behavior in the laboratory for extended periods, as was recently shown in research investigating the behavioral response of eastern mosquitofish ( Gambusia holbrooki ) to the pharmaceutical pollutant fluoxetine [ 53 ]. Technologies that measure animal behavior through disruptions in electric fields have also successfully been used to record the effects of chemical pollutants on biological rhythms in fish [ 54 , 72 ].

Improvements in both the cost and utility of field-based technologies are also enabling the measurement of biological rhythms in wild animals under seminatural and natural conditions at an unprecedented resolution and scale. In particular, advances in remote-sensing and biologging provide access to an enormous amount of high-resolution data capable of tracking both short- and long-term biological rhythms in the field [ 73 – 75 ]. For example, high-resolution three-dimensional tracking via acoustic telemetry allowed the measurement of daily activity rhythms in wild Arctic char ( Salvelinus alpinus ) over a full annual cycle [ 76 ]. These techniques can be implemented at large spatial and temporal scales, allowing the measurement of long-term biological rhythms (e.g., seasonal variation or migration) that cannot be quantified easily, or at all, in the laboratory. Similarly, biologging devices are increasingly available to record biological rhythms in suborganismal physiological traits in wild animals, as was recently shown in the measurement of brain activity and heart rate during sleep cycles in wild northern elephant seals ( Mirounga angustirostris ) [ 77 ]. Although these effects have been largely unexplored in chemical pollution research, key insights can be gained from the light pollution literature, in which researchers have taken advantage of remote-sensing technologies to investigate the influence of artificial light on the timing and characteristics of long-range migratory patterns [ 78 – 80 ] ( Fig 2 ). The implementation of such remote-sensing technologies in combination with slow-release chemical implants [ 81 , 82 ] will provide important information on the role of chemical pollutants in mediating biological rhythms in populations under ecologically realistic conditions.

Although our primary focus has been on chemical pollution, it is important to emphasize that chronobiology is also relevant to other forms of pollution and environmental change. Factors such as light, noise, and temperature can impact biological rhythms [ 83 – 85 ], and, conversely, biological rhythms can influence the effects of these factors on other aspects of biology. A better understanding of various forms of environmental disturbance, including those beyond chemical pollutants, will therefore require the integration of chronobiology with ecological and evolutionary frameworks [ 7 ]. Nevertheless, the relevance of chronobiology is better recognized in some fields of environmental pollution research than others. In light pollution research, for example, biological rhythms are deemed important, likely because light is a well-established, critical zeitgeber that regulates biological clocks [ 86 ]. As a result, there are many examples of light pollution studies that directly measure effects on biological rhythms or at least consider biological rhythms when designing sampling protocols [ 87 – 89 ]. Such studies, together with other biomedical and chronobiological research, offer useful resources for ecologists who are seeking to integrate chronobiology into their own research.

Conclusions

Biological rhythms occur across the tree of life and manifest across all levels of biological organization. Recognizing their fundamental role in shaping the biology and ecology of species, we contend that integrating biological rhythmicity into chemical pollution research is necessary. Furthermore, incorporating biological rhythmicity into ecological and evolutionary frameworks more broadly will be crucial for fully understanding, predicting, and mitigating the ecological repercussions of chemical pollution. This is particularly significant given that chemicals can disrupt biological rhythms, which, vice versa, govern the efficacy and toxicity of chemicals. In addition, an improved understanding of chronobiology—including ultradian, diurnal, and infradian rhythms, and their combinations—will be essential for aligning data collection with biological rhythmicity and enabling accurate inference regarding the direction and magnitude of effects in chemical pollution studies.

Looking to the future, recent advancements in remote-sensing and biologging technologies are offering unprecedented access to high-resolution data across different spatiotemporal scales, both in laboratory settings and in (semi)natural field conditions, which will facilitate the integration of biological rhythms into research efforts. The field can also advance by drawing upon insights from the biomedical and light pollution literature, where the underlying mechanisms and functional significance of biological rhythms have been more extensively studied, and which can greatly benefit chemical pollution researchers. Recognizing that biological timing is of the essence, we anticipate a promising future for this field as we strive to enhance our understanding and mitigation strategies in an increasingly polluted world.

Acknowledgments

We are grateful to Julie Johnson (Life Science Studios) for the creation of visuals.

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• 18. Pszczolkowski MA. Chronotoxicology. In: Capinera JL, editor. Encyclopedia of Entomology. Dordrecht, The Netherlands: Springer; 2008. p. 867–873.

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• v.32(1); Jan-Feb 1998

Biological Rhythms: The Science of Chronobiology

Josephine arendt.

Professor of Endocrinology, School of Biological Sciences, University of Surrey, Guildford

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Biological Rhythm Research

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What Are Biological Rhythms?

Biological rhythms are everywhere . The daily changes in sleep and wakefulness, annual bird migration, and the tidal variations in behavior of coastal animals: these are all examples of biological rhythms. The field of chronobiology studies these rhythms in living organisms and how they are tuned by cues from the outside world.

Circadian rhythms (rhythms that repeat approximately every 24 hours) are the most prominent biological rhythms. Not only sleep and wakefulness are influenced by circadian rhythms, also many other bodily functions show a circadian rhythm, such as body temperature, the secretion of hormones, and metabolism, and organ function. These rhythms allow organisms to anticipate and adapt to cyclic changes in the environment that are caused by the daily rotation of the Earth on its axis.

In humans and other mammals, circadian rhythms in the body are synchronized to the environment by a master clock that is located in the suprachiasmatic nuclei (SCN), a tiny brain region that is located just above the crossing of the optic nerves. The SCN receive information about light and darkness directly from the eyes, integrates this input, and  relays it to cellular circadian clocks located throughout the rest of the body . In this way, circadian rhythms in behavior and physiology are synchronized to the external light-dark cycle.

Although circadian rhythms require input (such as light) from the environment to synchronize to the 24-h day, a key feature of these rhythms are that they are self-sustained, meaning that they continue to cycle with a period of approximately 24 hours in the absence of any time-giving cues from the environment. Thus, even in constant darkness under controlled laboratory conditions, many bodily functions continue to show an approximately 24-h rhythm. In humans, the intrinsic circadian period is on average 24.2 h, ranging from about 23.5 to 24.6 in the healthy population . This variation in circadian period explains why some people are early birds and others are night owls.

On a molecular level, circadian rhythms are generated by a feedback mechanism involving cyclic changes in the expression of certain genes. The proteins encoded by two of these genes, called CLOCK and BMAL1 switch on the activity of other genes, called Per and Cry. In turn, PER and CRY proteins turn down the activity of CLOCK and BMAL1 proteins, creating a recurring loop of genes being switched on and switched off that repeats approximately every 24 hours. This molecular feedback mechanism is present in virtually every cell in the body – from the cells in your liver to the cells in your skin. Ultimately, it drives the circadian rhythms in cellular processes, metabolism, physiology, and behavior, ensuring all these functions are occurring at the right place at the right time of day.

Disruption to the circadian clock may contribute to health problems. This occurs for example during night shift work or jet lag, in which there is a mismatch between light exposure, food intake, and other cues from the external environment with the timing of the circadian rhythms in the body. In the long term, repeated loss of coordination between the circadian rhythms and environmental cues may increase the risk for a range of diseases such as diabetes, heart disease, and certain types of cancer. Getting in tune with your internal clock may be key to health and wellbeing.

The regulation of circadian rhythms in other organisms, ranging from cyanobacteria to fungi and from plants to insects, all follow the same general principles. Indeed, it was the discovery of the molecular feedback mechanism in fruit flies that led to the Nobel Prize in Physiology or Medicine in 2017 . Plants can use their circadian clocks to time flowers to the correct season .

Further reading:

NIGMS – NIH fact sheet National sleep foundation BioClock Studio – Introduction to Chronobiology

A Study Reveals Trees Have Hidden Clocks—and They’ve Started Going Haywire

Something sinister is throwing off the silent timekeepers in trunks.

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• Trees use unseen circadian rhthyms, or genetic oscillations, to keep track of sequestering carbon or when to go dormant.
• A new study by the National Scientific and Technical Research Council says that a warming world can disrupt this biological clock, which can be a big problem for species that are not tolerant to warmer weather.
• Future temperature increases could drastically change the compositions of forests around the worl

Go on a globe-trotting flight and you’ll quickly get acquainted with your circadian rhythm. That grogginess you feel the next morning post-flight? That’s your internal clock completely out of whack. Humans and animals aren’t the only beings that rely on this unseen timekeeping, trees also can track time independent of inputs from their surrounding ecosystem, but a warming world could be confusing this system that trees rely on to sequester carbon — or even survive.

Plant survival in a warmer world requires the timely adjustment of biological processes to cyclical changes in the new environment. Circadian oscillators have been proposed to contribute to thermal adaptation and plasticity in plants,” the paper reads. “We revealed that the upper thermal limits for accurate clock function are linked to the species’ thermal niches and contribute to seedling plasticity in natural environments.”

According to New Scientist , when the circadian rhythms were reset, the tree showed continued patterns of “genetic oscillation.” These changes in oscillations and warmer temperatures made the saplings of the cold-loving Andean beech smaller than the warm-loving N. obliqua . While data about the effects of these circadian oscillations is scarce, misaligned temperatures cues have caused other species of trees to go into out-of-season dormancy, the period when a tree prepares for freezing temperatures.

This is particularly bad news for trees like N. pumilio , whose warm-weather aversion could be an issue as global temperatures continue to climb.

“In this context, the investigation of genes responsible for thermal stability of the circadian clock may contribute to the selection of plant genotypes/populations with increased resistance to warming,” the paper reads. “The effect of increasing temperatures on oscillator function may be one factor which constrains the regeneration of the dominant species N. pumilio , potentially jeopardizing the integrity of the ecosystem of the Andean-Patagonian forests.”

It’s obvious that climate change will change our world, but the unseen temporal worlds of the plant kingdom also won’t escape unscathed.

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough. 

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N.C. A&T’s Jazz Ensemble Presents Spring Concert Featuring Tunes from Miles Davis

By Markita C. Rowe / 04/09/2024 College of Arts, Humanities and Social Sciences

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EAST GREENSBORO, N.C. (April 9, 2024) – The North Carolina Agricultural and Technical State University Jazz Ensemble will host its annual spring concert featuring the timeless tunes of the “Cool Jazz” era. The musical pieces will take inspiration from the nonet album “Birth of the Cool” by late American jazz trumpeter and bandleader Miles Davis.

The concert will take place Thursday, April 18, at 7 p.m. in Harrison Auditorium, 1009 Bluford St.

Jonovan Cooper, DMA, teaching assistant professor and director of the University Jazz Ensemble, expressed enthusiasm for the concert’s unique blend of instrumentation and repertoire.

“We want to captivate audiences with a diverse array of instruments, including violin, French horn, tuba, flute, vibraphone and the steel drum,” said Cooper.

In addition to the University Jazz Ensemble, the concert will spotlight performances by the vocal and faculty Jazz ensembles, offering a mix of jazz, neo soul, original compositions and favorite standards.

The N.C. A&T Jazz Ensemble has earned a reputation for excellence, performing at various venues across the state and nation throughout the school year.

The concert is free and open to the public, inviting jazz enthusiasts and music lovers alike to experience the talent and innovation of A&T's jazz musicians.

“We invite the community to join us as we celebrate the growth and artistry of our students over the past three years,” said Cooper. “Your support helps us continue to cultivate musical excellence at A&T and prepare our students for success in the music industry.”

For more information about the concert or the N.C. A&T Jazz Ensemble, contact Cooper at [email protected] or 336-285-2020.

Media Contact Information: [email protected]

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Premium Content

Just one pregnancy can add months to your biological age

A landmark new study confirms that growing a human being in nine months takes a toll—and multiple pregnancies can have a cumulative effect.

Surprising no one who has ever been pregnant, scientists have found that growing a human being from scratch makes your body “older."

New research suggests that a single pregnancy can add between two to 14 months to your biological age.  

“Pregnancy has a cost that appears to be detectable even" as early as your 20s, says study leader Calen Ryan , a human biologist at Columbia University’s school of public health in New York City.

It’s a “landmark study” that reaffirms what women already know—pregnancy takes a tremendous toll on the body, says Yousin Suh , a Columbia University professor who researches how pregnancy affects aging and wasn’t involved in the study, published April 8 in Proceedings of the National Academy of Sciences .  

Your chronological age—or the number of trips you’ve made around the sun—may be different than your biological age, which is how old your cells and organs seem based on their biochemistry.  

Ryan studies the reasons why our bodies may age faster or slower than we expect them too, and a lot of that comes down to epigenetics, or how and when our bodies decide to turn genes on and off. (Read how scientists are finally studying women's bodies—and what they're learning.)

Certain life events—including major illnesses, trauma, or periods of intense stress —seem to cause “jumps” in epigenetic age as the body redirects energy and resources toward coping with these challenges.

And since there are few biological functions more arduous than growing an entire person in just nine months, the recent study confirms the scientists’ suspicion that pregnancy—particularly multiple pregnancies—come at a cost to biological age.

Your epigenetic clock

If our genome is an instruction manual, the epigenome is a complex system of bookmarks, highlights, and underlines that tells our cells which genes to read and when. This often happens through methylation, a process by which tiny chemical tags called methyl groups attach to a section of DNA .

Which genes need to be active changes constantly in response to our environment and experiences, so those methyl groups need frequent moving and replacing. Yet as we age, this maintenance machinery appears to start making errors, causing methylations to accumulate in some places and disappear in others. (Read how influencing your genes could help you live longer.)

By taking a blood sample and tallying methyl bookmarks in key locations along the genetic code, scientists can calculate a person’s epigenetic age via a suite of algorithms called “clocks.” These clocks predict your risk of death and health complications, but less known is how fertility impacts your biological age .

To learn more, Ryan and his colleagues turned to a long-running study on intergenerational health in the Philippines . In 2005, they analyzed blood samples from 825 women participants between the ages of 20 and 22. (Learn about simple innovations that could help millions of pregnant women.)

The scientists identified a striking difference—the number of epigenetic changes in their DNA revealed that women who had been pregnant were between four and 14 months were biologically older than their peers who hadn’t, even after controlling for factors such as income level and smoking habits.

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A cumulative effect.

Despite being close in age, the women in the study were already on very different fertility trajectories—some had never been pregnant, some reported one or more previous pregnancies, and some were pregnant at the time the samples were collected.

That raised a crucial question: Did multiple pregnancies create a cumulative effect of aging, with each additional pregnancy further raising the mother’s epigenetic age?

Using the first blood samples as a baseline, the researchers collected new samples from 331 of the same women while they were pregnant between four and nine years later.   (Learn how babies develop in the womb.)

By comparing the two snapshots of each woman’s epigenetic age, Ryan and his team calculated the impact of each additional pregnancy during the intervening years.

“Women who had more pregnancies during that time had more change in epigenetic aging,” Ryan says, with each pregnancy tacking on two to three months to the parent’s biological age.

Suh, who studies the cost of reproduction on the human body, says Ryan’s findings represent an important advancement in our understanding of how multiple pregnancies affect biological age, as the bulk of existing research has examined just one pregnancy.

The new research, she says, squares with what we know about high birthrates—that experiencing many pregnancies can lead to a shorter life span and higher risk of cardiovascular disease.

Reason for optimism  

But would-be parents shouldn’t despair, Suh and Ryan agree—it’s not certain that a slightly higher epigenetic age during your childbearing years will lead to complications decades down the road.

In fact, some research suggests there may be a “sweet spot” for fertility, Suh says. For instance, one or two pregnancies may be better than none in some cases, as pregnancy is linked to lower risks of certain cancers and having at least one child is associated with a slightly longer life expectancy .

As scientists learn more about aging and fertility, “we can work towards identifying people who might be at higher risk,” Ryan adds, and come up with strategies to lessen the negative impacts of pregnancy.

Recent studies indicate the epigenetic cost of pregnancy may differ by country and culture, suggesting that parental support and access to healthcare may play a significant role—improving these could soften pregnancy’s blow to epigenetic age.

Suh adds more research will be needed to untangle the impact of child- rearing   from childbirth on epigenetic age, as well as investigate whether the burden of pregnancy is greater when parents are older than those in the study.

While it may feel like common knowledge that pregnancy ages you, it’s a relatively new concept in the scientific literature—and Suh says that research like Ryan’s is long overdue.

“I’m so encouraged that this kind of study is now being done,” she adds.

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