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Di Giovanni AJ, Jones TM, Benson TJ, Ward MP. Embryonic heart rate is higher in species that experience greater nest predation risk during incubation. Ecol Evol 2024; 14:e11460. [PMID: 38826173 PMCID: PMC11139974 DOI: 10.1002/ece3.11460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 04/27/2024] [Accepted: 05/07/2024] [Indexed: 06/04/2024] Open
Abstract
Avian eggs develop outside of the female body, and therefore embryonic development is subject to multiple internal (physiological) and external (ecological) factors. Embryonic developmental rate has important consequences for survival. Within species, embryos that develop too quickly often experience deformities, disorders, or mortality, while embryos that develop slowly risk inviability and increase the time they are exposed to various sources of mortality in the nest. These contrasting forces may lead to interspecific variation in developmental rates. We investigated potential factors affecting embryonic heart rate (EHR), a proxy of development, across 14 passerine species in the field. More specifically, we investigated if nest predation risk, clutch size, seasonality, and egg volume influenced EHR. From previous research, we expected, and found, that EHR was positively associated with embryonic age and egg temperature. Species with greater nest predation risk had higher EHR, shorter incubation periods, and lower nest temperature variance. EHR increased as the season progressed and with egg volume, while EHR declined with clutch size. Bird species exhibit varying strategies to increase nestling and fledgling survival in response to predation risk, and these results suggest that variation in embryonic development may be related to species-specific differences in nest predation risk.
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Affiliation(s)
- Alexander J. Di Giovanni
- Department of Natural Resources and Environmental SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIllinoisUSA
| | - Todd M. Jones
- Department of Natural Resources and Environmental SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIllinoisUSA
- Illinois Natural History Survey, Prairie Research InstituteUniversity of Illinois at Urbana‐ChampaignChampaignIllinoisUSA
- Smithsonian Conservation Biology Institute, Migratory Bird CenterNational Zoological ParkWashingtonDCUSA
| | - Thomas J. Benson
- Department of Natural Resources and Environmental SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIllinoisUSA
- Illinois Natural History Survey, Prairie Research InstituteUniversity of Illinois at Urbana‐ChampaignChampaignIllinoisUSA
| | - Michael P. Ward
- Department of Natural Resources and Environmental SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIllinoisUSA
- Illinois Natural History Survey, Prairie Research InstituteUniversity of Illinois at Urbana‐ChampaignChampaignIllinoisUSA
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Cones AG, Schneider ER, Westneat DF. The incubation environment does not explain significant variation in heart rate plasticity among avian embryos. J Exp Biol 2024; 227:jeb247120. [PMID: 38456553 PMCID: PMC10949066 DOI: 10.1242/jeb.247120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 01/29/2024] [Indexed: 03/09/2024]
Abstract
The conditions an organism experiences during development can modify how they plastically respond to short-term changes in their environment later in life. This can be adaptive because the optimal average trait value and the optimal plastic change in trait value in response to the environment may differ across different environments. For example, early developmental temperatures can adaptively modify how reptiles, fish and invertebrates metabolically respond to temperature. However, whether individuals within populations respond differently (a prerequisite to adaptive evolution), and whether this occurs in birds, which are only ectothermic for part of their life cycle, is not known. We experimentally tested these possibilities by artificially incubating the embryos of Pekin ducks (Anas platyrhynchos domesticus) at constant or variable temperatures. We measured their consequent heart rate reaction norms to short-term changes in egg temperature and tracked their growth. Contrary to expectations, the early thermal environment did not modify heart rate reaction norms, but regardless, these reaction norms differed among individuals. Embryos with higher average heart rates were smaller upon hatching, but heart rate reaction norms did not predict subsequent growth. Our data also suggests that the thermal environment may affect both the variance in heart rate reaction norms and their covariance with growth. Thus, individual avian embryos can vary in their plasticity to temperature, and in contrast to fully ectothermic taxa, the early thermal environment does not explain this variance. Because among-individual variation is one precondition to adaptive evolution, the factors that do contribute to such variability may be important.
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Affiliation(s)
- Alexandra G. Cones
- Department of Biology, University of Kentucky, 101 Thomas Hunt Morgan Building, Lexington, KY 40506, USA
| | - Eve R. Schneider
- Department of Biology, University of Kentucky, 101 Thomas Hunt Morgan Building, Lexington, KY 40506, USA
| | - David F. Westneat
- Department of Biology, University of Kentucky, 101 Thomas Hunt Morgan Building, Lexington, KY 40506, USA
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3
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Kleindorfer S, Brouwer L, Hauber ME, Teunissen N, Peters A, Louter M, Webster MS, Katsis AC, Sulloway FJ, Common LK, Austin VI, Colombelli-Négrel D. Nestling Begging Calls Resemble Maternal Vocal Signatures When Mothers Call Slowly to Embryos. Am Nat 2024; 203:267-283. [PMID: 38306283 DOI: 10.1086/728105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2024]
Abstract
AbstractVocal production learning (the capacity to learn to produce vocalizations) is a multidimensional trait that involves different learning mechanisms during different temporal and socioecological contexts. Key outstanding questions are whether vocal production learning begins during the embryonic stage and whether mothers play an active role in this through pupil-directed vocalization behaviors. We examined variation in vocal copy similarity (an indicator of learning) in eight species from the songbird family Maluridae, using comparative and experimental approaches. We found that (1) incubating females from all species vocalized inside the nest and produced call types including a signature "B element" that was structurally similar to their nestlings' begging call; (2) in a prenatal playback experiment using superb fairy wrens (Malurus cyaneus), embryos showed a stronger heart rate response to playbacks of the B element than to another call element (A); and (3) mothers that produced slower calls had offspring with greater similarity between their begging call and the mother's B element vocalization. We conclude that malurid mothers display behaviors concordant with pupil-directed vocalizations and may actively influence their offspring's early life through sound learning shaped by maternal call tempo.
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Gomes LG, Stocco MB, Sousa NPD, Martini AC, Morgado TO, Spiller PR, Moreira LFB, de Souza RL. Influence of incubation temperature and embryonic motility on the growth of members of Caiman yacare (Daudin, 1802). BRAZ J BIOL 2021; 84:e252845. [PMID: 34932637 DOI: 10.1590/1519-6984.252845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 10/20/2021] [Indexed: 11/21/2022] Open
Abstract
This study aimed to evaluate whether skeletal development of the Pantanal Caiman (Caiman yacare) is similarly influenced by temperature variation and controlled increases in embryo motility. All eggs were incubated at 90% humidity and 29 °C for the first 45 days. Thereafter, the incubation temperature was either maintained at 29 °C and embryos were treated with 4-aminopyridine (4-AP) on days 46, 47, 48, and 49 (Group I, 29 °C 4-AP, n = 15); maintained at 29 °C (n = 14; Group II); or at 33 °C (n = 14, Group III). Embryonic movement was measured using an Egg Buddy® digital monitor on days 30, 35, 42, 49, 56, and 60, at which point embryos were euthanized and samples were collected for analysis. No differences were observed between groups with varying incubation temperatures. In contrast, embryonic motility was greater in embryos treated with 4-AP (P < 0.001) on day 49, and this was associated with higher proportions of snout-vent and hand lengths. This study demonstrates for the first time that pharmacologically induced increases in embryo motility result in phenotypic changes to the proportion of elements during prenatal ontogeny, thereby effectively altering the adaptation of the species to specific environments.
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Affiliation(s)
- L G Gomes
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - M B Stocco
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - N P de Sousa
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - A C Martini
- Universidade de Mineiros - UNIFIMES, Departamento de Ciências Agrárias, Mineiros, GO, Brasil
| | - T O Morgado
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - P R Spiller
- Universidade de Cuiabá - UNIC, Programa de Pós-Graduação em Biociência Animal, Cuiabá, MT, Brasil
| | - L F B Moreira
- Universidade Federal de Mato Grosso - UFMT, Instituto Nacional de Pesquisas do Pantanal - INPP, Museu Paraense Emílio Goeldi - MPEG, Cuiabá, MT, Brasil
| | - R L de Souza
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
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McClelland SC, Reynolds M, Cordall M, Hauber ME, Goymann W, McClean LA, Hamama S, Lund J, Dixit T, Louder MIM, Safari I, Honza M, Spottiswoode CN, Portugal SJ. Embryo movement is more frequent in avian brood parasites than birds with parental reproductive strategies. Proc Biol Sci 2021; 288:20211137. [PMID: 34702076 PMCID: PMC8548802 DOI: 10.1098/rspb.2021.1137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 10/04/2021] [Indexed: 12/24/2022] Open
Abstract
Movement of the embryo is essential for musculoskeletal development in vertebrates, yet little is known about whether, and why, species vary. Avian brood parasites exhibit feats of strength in early life as adaptations to exploit the hosts that rear them. We hypothesized that an increase in embryonic movement could allow brood parasites to develop the required musculature for these demands. We measured embryo movement across incubation for multiple brood-parasitic and non-parasitic bird species. Using a phylogenetically controlled analysis, we found that brood parasites exhibited significantly increased muscular movement during incubation compared to non-parasites. This suggests that increased embryo movement may facilitate the development of the stronger musculoskeletal system required for the demanding tasks undertaken by young brood parasites.
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Affiliation(s)
- Stephanie C. McClelland
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Miranda Reynolds
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Molly Cordall
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Mark E. Hauber
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL 61801, USA
- American Museum of Natural History, New York, NY 10024, USA
| | - Wolfgang Goymann
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Str. 6a, D-82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
| | - Luke A. McClean
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Silky Hamama
- c/o Musumanene Farm, PO Box 630038, Choma, Zambia
| | - Jess Lund
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Tanmay Dixit
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Matthew I. M. Louder
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL 61801, USA
| | - Ignas Safari
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Str. 6a, D-82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
- Department of Biology, University of Dodoma, PO Box 338, Dodoma, Tanzania
| | - Marcel Honza
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Květná 8, 603 65 Brno, Czech Republic
| | - Claire N. Spottiswoode
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Steven J. Portugal
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
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Rolfe RA, Scanlon O'Callaghan D, Murphy P. Joint development recovery on resumption of embryonic movement following paralysis. Dis Model Mech 2021; 14:dmm048913. [PMID: 33771841 PMCID: PMC8084573 DOI: 10.1242/dmm.048913] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/17/2021] [Indexed: 12/30/2022] Open
Abstract
Fetal activity in utero is a normal part of pregnancy and reduced or absent movement can lead to long-term skeletal defects, such as Fetal Akinesia Deformation Sequence, joint dysplasia and arthrogryposis. A variety of animal models with decreased or absent embryonic movements show a consistent set of developmental defects, providing insight into the aetiology of congenital skeletal abnormalities. At developing joints, defects include reduced joint interzones with frequent fusion of cartilaginous skeletal rudiments across the joint. At the spine, defects include shortening and a spectrum of curvature deformations. An important question, with relevance to possible therapeutic interventions for human conditions, is the capacity for recovery with resumption of movement following short-term immobilisation. Here, we use the well-established chick model to compare the effects of sustained immobilisation from embryonic day (E)4-10 to two different recovery scenarios: (1) natural recovery from E6 until E10 and (2) the addition of hyperactive movement stimulation during the recovery period. We demonstrate partial recovery of movement and partial recovery of joint development under both recovery conditions, but no improvement in spine defects. The joints examined (elbow, hip and knee) showed better recovery in hindlimb than forelimb, with hyperactive mobility leading to greater recovery in the knee and hip. The hip joint showed the best recovery with improved rudiment separation, tissue organisation and commencement of cavitation. This work demonstrates that movement post paralysis can partially recover specific aspects of joint development, which could inform therapeutic approaches to ameliorate the effects of human fetal immobility. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Rebecca A. Rolfe
- Department of Zoology, School of Natural Sciences, University of Dublin, Trinity College Dublin, Dublin, Ireland
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Gomes L, Stocco M, Sousa N, Martini A, Morgado T, Flôres F, Moreira L, Ferraz R, Souza R. Método não invasivo para avaliação da movimentação embrionária de Caiman yacare (Daudin, 1802). ARQ BRAS MED VET ZOO 2019. [DOI: 10.1590/1678-4162-11260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- L.G. Gomes
- Universidade Federal de Mato Grosso, Brazil
| | | | - N.P. Sousa
- Universidade Federal de Mato Grosso, Brazil
| | | | | | | | | | | | - R.L. Souza
- Universidade Federal de Mato Grosso, Brazil
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van der Pol CW, van Roovert-Reijrink IAM, Gussekloo SWS, Kranenbarg S, Leon-Kloosterziel KM, van Eijk-Priester MH, Zeman M, Kemp B, van den Brand H. Effects of lighting schedule during incubation of broiler chicken embryos on leg bone development at hatch and related physiological characteristics. PLoS One 2019; 14:e0221083. [PMID: 31415653 PMCID: PMC6695123 DOI: 10.1371/journal.pone.0221083] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 07/30/2019] [Indexed: 12/12/2022] Open
Abstract
Providing a broiler chicken embryo with a lighting schedule during incubation may stimulate leg bone development. Bone development may be stimulated through melatonin, a hormone released in darkness that stimulates bone development, or increased activity in embryos exposed to a light-dark rhythm. Aim was to investigate lighting conditions during incubation and leg bone development in broiler embryos, and to reveal the involved mechanisms. Embryos were incubated under continuous cool white 500 lux LED light (24L), continuous darkness (24D), or 16h of light, followed by 8h of darkness (16L:8D) from the start of incubation until hatching. Embryonic bone development largely takes place through cartilage formation (of which collagen is an important component) and ossification. Expression of genes involved in cartilage formation (col1α2, col2α1, and col10α1) and ossification (spp1, sparc, bglap, and alpl) in the tibia on embryonic day (ED)13, ED17, and at hatching were measured through qPCR. Femur and tibia dimensions were determined at hatch. Plasma growth hormone and corticosterone and pineal melatonin concentrations were determined every 4h between ED18.75 and ED19.5. Embryonic heart rate was measured twice daily from ED12 till ED19 as a reflection of activity. No difference between lighting treatments on gene expression was found. 24D resulted in higher femur length and higher femur and tibia weight, width, and depth at hatch than 16L:8D. 24D furthermore resulted in higher femur length and width and tibia depth than 24L. Embryonic heart rate was higher for 24D and 16L:8D in both its light and dark period than for 24L, suggesting that 24L embryos may have been less active. Melatonin and growth hormone showed different release patterns between treatments, but the biological significance was hard to interpret. To conclude, 24D resulted in larger leg bones at hatch than light during incubation, but the underlying pathways were not clear from present data.
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Affiliation(s)
- Carla W. van der Pol
- Research department, HatchTech B.V., Veenendaal, the Netherlands
- Adaptation Physiology Group, Wageningen University and Research, Wageningen, the Netherlands
- * E-mail:
| | | | - Sander W. S. Gussekloo
- Experimental Zoology Group, Wageningen University and Research, Wageningen, the Netherlands
| | - Sander Kranenbarg
- Experimental Zoology Group, Wageningen University and Research, Wageningen, the Netherlands
| | | | - Margaretha H. van Eijk-Priester
- Research department, HatchTech B.V., Veenendaal, the Netherlands
- Adaptation Physiology Group, Wageningen University and Research, Wageningen, the Netherlands
| | - Michal Zeman
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University Bratislava, Bratislava, Slovak Republic
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Bas Kemp
- Adaptation Physiology Group, Wageningen University and Research, Wageningen, the Netherlands
| | - Henry van den Brand
- Adaptation Physiology Group, Wageningen University and Research, Wageningen, the Netherlands
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Kleindorfer S, Evans C, Hauber ME, Colombelli-Négrel D. Could prenatal sound discrimination predict vocal complexity later in life? BMC ZOOL 2018. [DOI: 10.1186/s40850-018-0038-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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10
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Kodirov SA, Psyrakis D, Brachmann J, Zhuravlev VL. Limulus and heart rhythm. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2018; 331:61-79. [PMID: 30251467 DOI: 10.1002/jez.2235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/24/2018] [Accepted: 08/28/2018] [Indexed: 01/08/2023]
Abstract
Great interest in the comparative physiology of hearts and their functions in Animalia has emerged with classic papers on Limulus polyphemus and mollusks. The recurrent cardiac activity-heart rate-is the most important physiological parameter and when present the kardia (Greek) is vital to the development of entire organs of the organisms in the animal kingdom. Extensive studies devoted to the regulation of cardiac rhythm in invertebrates have revealed that the basics of heart physiology are comparable to mammals. The hearts of invertebrates also beat spontaneously and are supplied with regulatory nerves: either excitatory or inhibitory or both. The distinct nerves and the source of excitation/inhibition at the level of single neurons are described for many invertebrate genera. The vertebrates and a majority of invertebrates have myogenic hearts, whereas the horseshoe crab L. polyphemus and a few other animals have a neurogenic cardiac rhythm. Nevertheless, the myogenic nature of heartbeat is precursor, because the contraction of native and stem-cell-derived cardiomyocytes does occur in the absence of any neural elements. Even in L. polyphemus, the heart rhythm is myogenic at embryonic stages.
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Affiliation(s)
- Sodikdjon A Kodirov
- Department of General Physiology, Saint Petersburg University, Saint Petersburg, Russia.,Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, Atlanta, Georgia.,Department of Molecular Biology and Genetics, Almazov Federal Heart, Blood and Endocrinology Centre, Saint Petersburg, Russia.,Laboratory of Emotions' Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.,Department of Cardiology, University Hospital, Heidelberg, Germany
| | - Dimitrios Psyrakis
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany
| | - Johannes Brachmann
- Department of Cardiology, Klinikum Coburg, Teaching Hospital of the University of Würzburg, Coburg, Germany.,Department of Cardiology, University Hospital, Heidelberg, Germany
| | - Vladimir L Zhuravlev
- Department of General Physiology, Saint Petersburg University, Saint Petersburg, Russia.,Department of Cardiology, University Hospital, Heidelberg, Germany
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Limb proportions show developmental plasticity in response to embryo movement. Sci Rep 2017; 7:41926. [PMID: 28165010 PMCID: PMC5292730 DOI: 10.1038/srep41926] [Citation(s) in RCA: 238] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 01/03/2017] [Indexed: 02/06/2023] Open
Abstract
Animals have evolved limb proportions adapted to different environments, but it is not yet clear to what extent these proportions are directly influenced by the environment during prenatal development. The developing skeleton experiences mechanical loading resulting from embryo movement. We tested the hypothesis that environmentally-induced changes in prenatal movement influence embryonic limb growth to alter proportions. We show that incubation temperature influences motility and limb bone growth in West African Dwarf crocodiles, producing altered limb proportions which may, influence post-hatching performance. Pharmacological immobilisation of embryonic chickens revealed that altered motility, independent of temperature, may underpin this growth regulation. Use of the chick also allowed us to merge histological, immunochemical and cell proliferation labelling studies to evaluate changes in growth plate organisation, and unbiased array profiling to identify specific cellular and transcriptional targets of embryo movement. This disclosed that movement alters limb proportions and regulates chondrocyte proliferation in only specific growth plates. This selective targeting is related to intrinsic mTOR (mechanistic target of rapamycin) pathway activity in individual growth plates. Our findings provide new insights into how environmental factors can be integrated to influence cellular activity in growing bones and ultimately gross limb morphology, to generate phenotypic variation during prenatal development.
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