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Cobham AE, Rohner N. Unraveling stress resilience: Insights from adaptations to extreme environments by Astyanax mexicanus cavefish. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2024; 342:178-188. [PMID: 38247307 DOI: 10.1002/jez.b.23238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 12/26/2023] [Accepted: 01/02/2024] [Indexed: 01/23/2024]
Abstract
Extreme environmental conditions have profound impacts on shaping the evolutionary trajectory of organisms. Exposure to these conditions elicits stress responses, that can trigger phenotypic changes in novel directions. The Mexican Tetra, Astyanax mexicanus, is an excellent model for understanding evolutionary mechanisms in response to extreme or new environments. This fish species consists of two morphs; the classical surface-dwelling fish and the blind cave-dwellers that inhabit dark and biodiversity-reduced ecosystems. In this review, we explore the specific stressors present in cave environments and examine the diverse adaptive strategies employed by cave populations to not only survive but thrive as successful colonizers. By analyzing the evolutionary responses of A. mexicanus, we gain valuable insights into the genetic, physiological, and behavioral adaptations that enable organisms to flourish under challenging environmental conditions.
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Affiliation(s)
- Ansa E Cobham
- Stowers Institute for Medical Research, Missouri, Kansas City, USA
| | - Nicolas Rohner
- Stowers Institute for Medical Research, Missouri, Kansas City, USA
- Department of Cell Biology & Physiology, University of Kansas Medical Center, Kansas City, Missouri, USA
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2
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Jolles JW, Böhm A, Brinker A, Behrmann-Godel J. Unravelling the origins of boldness behaviour: a common garden experiment with cavefish ( Barbatula barbatula). ROYAL SOCIETY OPEN SCIENCE 2024; 11:231517. [PMID: 38204784 PMCID: PMC10776215 DOI: 10.1098/rsos.231517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 12/06/2023] [Indexed: 01/12/2024]
Abstract
Many animals show an aversion to bright, open spaces, with significant variability seen across species, populations and individuals within populations. Although there is much interest in the underlying causes of this behaviour, few studies have been able to systematically isolate the role of heritable and environmental effects. Here, we addressed this gap using a common garden experiment with cavefish. Specifically, we bred and cross-bred cave loaches (Barbatula barbatula), Europe's only known cavefish, in the laboratory, raised the offspring in complete darkness or normal light conditions, and studied their light avoidance behaviour. Cavefish spent much more time in a light area and ventured further out, while surface fish spent considerable time in risk-assessment behaviour between the light and dark areas. Hybrids behaved most similarly to cavefish. Light treatment and eye quality and lens size only had a modest effect. Our results suggest light avoidance behaviour of cavefish has a heritable basis and is fundamentally linked to increased boldness rather than reduced vision, which is likely adaptive given the complete lack of macropredators in the cave environment. Our study provides novel experimental insights into the behavioural divergence of cavefish and contributes to our broader understanding of the evolution of boldness and behavioural adaptation.
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Affiliation(s)
- Jolle W. Jolles
- Limnological Institute, University of Konstanz, Konstanz, Baden-Württemberg, Germany
- Centre for Advanced Studies Blanes (CEAB), CSIC, Blanes, Catalunya, Spain
| | - Alexander Böhm
- Limnological Institute, University of Konstanz, Konstanz, Baden-Württemberg, Germany
| | - Alexander Brinker
- Limnological Institute, University of Konstanz, Konstanz, Baden-Württemberg, Germany
- Fisheries Research Station Baden-Württemberg, Langenargen, Germany
| | - Jasminca Behrmann-Godel
- Limnological Institute, University of Konstanz, Konstanz, Baden-Württemberg, Germany
- Ministry for Nutrition, Rural Affairs and Consumer Protection Baden-Württemberg (MLR), Stuttgart, Germany
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3
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Zheng A, Schmid S. A review of the neural basis underlying the acoustic startle response with a focus on recent developments in mammals. Neurosci Biobehav Rev 2023; 148:105129. [PMID: 36914078 DOI: 10.1016/j.neubiorev.2023.105129] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 03/07/2023] [Accepted: 03/10/2023] [Indexed: 03/13/2023]
Abstract
The startle response consists of whole-body muscle contractions, eye-blink, accelerated heart rate, and freezing in response to a strong, sudden stimulus. It is evolutionarily preserved and can be observed in any animal that can perceive sensory signals, indicating the important protective function of startle. Startle response measurements and its alterations have become a valuable tool for exploring sensorimotor processes and sensory gating, especially in the context of pathologies of psychiatric disorders. The last reviews on the neural substrates underlying acoustic startle were published around 20 years ago. Advancements in methods and techniques have since allowed new insights into acoustic startle mechanisms. This review is focused on the neural circuitry that drives the primary acoustic startle response in mammals. However, there have also been very successful efforts to identify the acoustic startle pathway in other vertebrates and invertebrates in the past decades, so at the end we briefly summarize these studies and comment on the similarities and differences between species.
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Affiliation(s)
- Alice Zheng
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, Canada
| | - Susanne Schmid
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, Canada.
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Oliva C, Hinz NK, Robinson W, Barrett Thompson AM, Booth J, Crisostomo LM, Zanineli S, Tanner M, Lloyd E, O'Gorman M, McDole B, Paz A, Kozol R, Brown EB, Kowalko JE, Fily Y, Duboue ER, Keene AC. Characterizing the genetic basis of trait evolution in the Mexican cavefish. Evol Dev 2022; 24:131-144. [PMID: 35924750 PMCID: PMC9786752 DOI: 10.1111/ede.12412] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 04/20/2022] [Accepted: 04/26/2022] [Indexed: 12/30/2022]
Abstract
Evolution in response to a change in ecology often coincides with various morphological, physiological, and behavioral traits. For most organisms little is known about the genetic and functional relationship between evolutionarily derived traits, representing a critical gap in our understanding of adaptation. The Mexican tetra, Astyanax mexicanus, consists of largely independent populations of fish that inhabit at least 30 caves in Northeast Mexico, and a surface fish population, that inhabit the rivers of Mexico and Southern Texas. The recent application of molecular genetic approaches combined with behavioral phenotyping have established A. mexicanus as a model for studying the evolution of complex traits. Cave populations of A. mexicanus are interfertile with surface populations and have evolved numerous traits including eye degeneration, insomnia, albinism, and enhanced mechanosensory function. The interfertility of different populations from the same species provides a unique opportunity to define the genetic relationship between evolved traits and assess the co-evolution of behavioral and morphological traits with one another. To define the relationships between morphological and behavioral traits, we developed a pipeline to test individual fish for multiple traits. This pipeline confirmed differences in locomotor activity, prey capture, and startle reflex between surface and cavefish populations. To measure the relationship between traits, individual F2 hybrid fish were characterized for locomotor behavior, prey-capture behavior, startle reflex, and morphological attributes. Analysis revealed an association between body length and slower escape reflex, suggesting a trade-off between increased size and predator avoidance in cavefish. Overall, there were few associations between individual behavioral traits, or behavioral and morphological traits, suggesting independent genetic changes underlie the evolution of the measured behavioral and morphological traits. Taken together, this approach provides a novel system to identify genetic underpinnings of naturally occurring variation in morphological and behavioral traits.
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Affiliation(s)
- Camila Oliva
- NIH U‐RISE ProgramFlorida Atlantic UniversityJupiterFloridaUSA
| | | | - Wayne Robinson
- NIH U‐RISE ProgramFlorida Atlantic UniversityJupiterFloridaUSA
| | | | - Julianna Booth
- NIH U‐RISE ProgramFlorida Atlantic UniversityJupiterFloridaUSA
| | | | | | - Maureen Tanner
- NIH U‐RISE ProgramFlorida Atlantic UniversityJupiterFloridaUSA
| | - Evan Lloyd
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA,Department of BiologyTexas A&M UniversityCollege StationTexasUSA
| | - Morgan O'Gorman
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA,Department of BiologyTexas A&M UniversityCollege StationTexasUSA
| | - Brittnee McDole
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Alexandra Paz
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Rob Kozol
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Elizabeth B. Brown
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Johanna E. Kowalko
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA,Department of Biological SciencesLehigh UniversityBethlehemPennsylvaniaUSA
| | - Yaouen Fily
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Erik R. Duboue
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Alex C. Keene
- Jupiter Life Science InitiativeFlorida Atlantic UniversityJupiterFloridaUSA,Department of BiologyTexas A&M UniversityCollege StationTexasUSA
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Lloyd E, McDole B, Privat M, Jaggard JB, Duboué ER, Sumbre G, Keene AC. Blind cavefish retain functional connectivity in the tectum despite loss of retinal input. Curr Biol 2022; 32:3720-3730.e3. [PMID: 35926509 DOI: 10.1016/j.cub.2022.07.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 04/07/2022] [Accepted: 07/07/2022] [Indexed: 11/26/2022]
Abstract
Sensory systems display remarkable plasticity and are under strong evolutionary selection. The Mexican cavefish, Astyanax mexicanus, consists of eyed river-dwelling surface populations and multiple independent cave populations that have converged on eye loss, providing the opportunity to examine the evolution of sensory circuits in response to environmental perturbation. Functional analysis across multiple transgenic populations expressing GCaMP6s showed that functional connectivity of the optic tectum largely did not differ between populations, except for the selective loss of negatively correlated activity within the cavefish tectum, suggesting positively correlated neural activity is resistant to an evolved loss of input from the retina. Furthermore, analysis of surface-cave hybrid fish reveals that changes in the tectum are genetically distinct from those encoding eye loss. Together, these findings uncover the independent evolution of multiple components of the visual system and establish the use of functional imaging in A. mexicanus to study neural circuit evolution.
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Affiliation(s)
- Evan Lloyd
- Department of Biological Science, Florida Atlantic University, Jupiter, FL 33458, USA; Department of Biology, Texas A&M University, College Station, TX 77843, USA; Harriet Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Brittnee McDole
- Department of Biological Science, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Martin Privat
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - James B Jaggard
- Department of Biological Science, Florida Atlantic University, Jupiter, FL 33458, USA; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Erik R Duboué
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - German Sumbre
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France.
| | - Alex C Keene
- Department of Biology, Texas A&M University, College Station, TX 77843, USA.
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Lunsford ET, Paz A, Keene AC, Liao JC. Evolutionary convergence of a neural mechanism in the cavefish lateral line system. eLife 2022; 11:77387. [PMID: 35708234 PMCID: PMC9246366 DOI: 10.7554/elife.77387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 06/15/2022] [Indexed: 11/13/2022] Open
Abstract
Animals can evolve dramatic sensory functions in response to environmental constraints, but little is known about the neural mechanisms underlying these changes. The Mexican tetra, Astyanax mexicanus, is a leading model to study genetic, behavioral, and physiological evolution by comparing eyed surface populations and blind cave populations. We compared neurophysiological responses of posterior lateral line afferent neurons and motor neurons across A. mexicanus populations to reveal how shifts in sensory function may shape behavioral diversity. These studies indicate differences in intrinsic afferent signaling and gain control across populations. Elevated endogenous afferent activity identified a lower response threshold in the lateral line of blind cavefish relative to surface fish leading to increased evoked potentials during hair cell deflection in cavefish. We next measured the effect of inhibitory corollary discharges from hindbrain efferent neurons onto afferents during locomotion. We discovered that three independently derived cavefish populations have evolved persistent afferent activity during locomotion, suggesting for the first time that partial loss of function in the efferent system can be an evolutionary mechanism for neural adaptation of a vertebrate sensory system.
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Affiliation(s)
- Elias T Lunsford
- Department of Biology, University of Florida, Saint Augustine, United States
| | - Alexandra Paz
- Department of Biological Sciences, Florida Atlantic University, Jupiter, United States
| | - Alex C Keene
- Texas A&M University, College Station, United States
| | - James C Liao
- Department of Biology, University of Florida, Saint Augustine, United States
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