scholarly journals Evidence for rapid phenotypic and behavioral change in a recently established cavefish population

2019 ◽  
Author(s):  
Suzanne E. McGaugh ◽  
Sam Weaver ◽  
Erin N. Gilbertson ◽  
Brianna Garrett ◽  
Melissa L. Rudeen ◽  
...  
Keyword(s):  
Behavioral Change ◽  
Extreme Environments ◽  
Behavioral Differences ◽  
Astyanax Mexicanus ◽  
Eye Size ◽  
Exciting Opportunity ◽  
Surface Population ◽  
Cave Population ◽  
Future Work ◽  
Rapid Environmental Change

AbstractSubstantial morphological and behavioral shifts often accompany rapid environmental change, yet, little is known about the early stages of cave colonization. Relative to surface streams, caves are extreme environments with perpetual darkness and low nutrient availability. The Mexican tetra (Astyanax mexicanus), has repeatedly colonized caves throughout Mexico, suggesting an ability to adapt to these conditions. Here, we survey for phenotypic and behavioral differences between a surface population and a cave population of A. mexicanus that has recently colonized Honey Creek Cave, Comal County, Texas, likely within the last century. We found that fish from Honey Creek Cave and fish from Honey Creek surface populations differ significantly in morphological traits including length, coloration, body condition, eye size, and dorsal fin placement. Cavefish also exhibit an increased number of superficial neuromasts relative to surface fish. Behaviorally, cavefish consume fewer worms when trials are performed in both lighted and darkened conditions. Cavefish are more aggressive than surface fish and exhibit fewer behaviors associated with stress. Further in contrast to surface fish, cavefish prefer the edges to the center of an arena and are qualitatively more likely to investigate a novel object placed in the tank. While cavefish and surface fish were wild-caught and developmental environment likely play a role in shaping these differences, our work demonstrates morphological and behavioral shifts for Texas cavefish and offers an exciting opportunity for future work to explore the genetic and environmental contributions to early cave colonization.

Evidence for rapid phenotypic and behavioural shifts in a recently established cavefish population

2019 ◽  
Author(s):  
Suzanne E McGaugh ◽  
Sam Weaver ◽  
Erin N Gilbertson ◽  
Brianna Garrett ◽  
Melissa L Rudeen ◽  
...  
Keyword(s):  
Extreme Environments ◽  
Time Frame ◽  
South Texas ◽  
Astyanax Mexicanus ◽  
North East ◽  
Surface Population ◽  
Cave Population ◽  
Cave Environment ◽  
Central Texas ◽  
Recent Origin

Abstract Cave colonization offers a natural laboratory to study an extreme environmental shift, and diverse cave species from around the world often have converged on robust morphological, physiological and behavioural traits. The Mexican tetra (Astyanax mexicanus) has repeatedly colonized caves in the Sierra de El Abra and Sierra de Guatemala regions of north-east Mexico ~0.20–1 Mya, indicating an ability to adapt to the cave environment. The time frame for the evolution of these traits in any cave animal, however, is poorly understood. Astyanax mexicanus from the Río Grande in South Texas were brought to Central Texas beginning in the early 1900s and colonized underground environments. Here, we investigate whether phenotypic and behavioural differences have occurred rapidly between a surface population and a geographically proximate cave population, probably of recent origin. Fish from the cave and surface populations differ significantly in morphological traits, including coloration, lateral line expansion and dorsal fin placement. Striking behavioural shifts in aggression, feeding and wall-following have also occurred. Together, our results suggest that morphological and behavioural changes accompanying cave colonization can be established rapidly, and this system offers an exciting and unique opportunity for isolating the genetic and environmental contributions to colonization of extreme environments.

scholarly journals Evidence for Late Pleistocene origin of Astyanax mexicanus cavefish

2016 ◽  
Author(s):  
Julien Fumey ◽  
Hélène Hinaux ◽  
Céline Noirot ◽  
Claude Thermes ◽  
Sylvie Rétaux ◽  
...  
Keyword(s):  
Nuclear Dna ◽  
Middle Pleistocene ◽  
Population Divergence ◽  
Demographic Parameters ◽  
Summary Statistics ◽  
Astyanax Mexicanus ◽  
Phenotypic Changes ◽  
Surface Population ◽  
Cave Population ◽  
Recent Origin

AbstractBackgroundCavefish populations belonging to the Mexican tetra species Astyanax mexicanus are outstanding models to study the tempo and mode of adaptation to a radical environmental change. They share similar phenotypic changes such as blindness and depigmentation resulting from independent and convergent evolution. As such they allow examining whether their evolution involved the fixation of preexisting standing genetic variations and/or de novo mutations. Cavefish populations are currently assigned to two main groups, the so-called "old" and "new" lineages, which would have populated several caves independently and at different times. However, we do not have yet accurate estimations of the time frames of evolution of these populations.ResultsFirst, we reanalyzed the geographic distribution of mitochondrial and nuclear DNA polymorphisms and we found that these data do not support the existence of two cavefish lineages, neither the ancient origin of the “old” lineage. Using IMa2, a program based on a method that does not assume that populations are at mutation/migration/drift equilibrium and thus allows dating population divergence in addition to demographic parameters, we found that microsatellite polymorphism strongly supports a very recent origin of cave populations (i.e. less than 20,000 years). Second, we identified a large number of single-nucleotide polymorphisms (SNPs) in transcript sequences of pools of embryos (Pool-seq) belonging to the “old” Pachón cave population and a surface population from Texas. Pachón cave population has accumulated more neutral substitutions than the surface population and we showed that it could be another signature of its recent origin. Based on summary statistics that can be computed with this SNP data set together with simulations of evolution of SNP polymorphisms in two recently isolated populations, we looked for sets of demographic parameters that allow the computation of summary statistics with simulated populations that are similar to the ones with the sampled populations. In most simulations for which we could find a good fit between the summary statistics of observed and simulated data, the best fit occurred when the divergence between simulated populations was less than 30,000 years.ConclusionsAlthough it is often assumed that some cave populations such as Pachón cavefish have a very ancient origin, within the range of the late Miocene to the middle Pleistocene, a recent origin of these populations is strongly supported by our analyses of two independent sets of nuclear DNA polymorphism using two very different methods of analysis. Moreover, the observation of two divergent haplogroups of mitochondrial and nuclear genes with different geographic distributions support a recent admixture of two divergent surface populations before the isolation of cave populations. If cave populations are indeed only several thousand years old, many phenotypic changes observed in cavefish would thus have mainly involved the fixation of genetic variants present in surface fish populations and within a very short period of time.

scholarly journals An Asymmetric Genetic Signal Associated with Mechanosensory Expansion in Cave-Adapted Fish

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 1951
Author(s):  
Amanda K. Powers ◽  
Tyler E. Boggs ◽  
Joshua B. Gross
Keyword(s):  
Phenotypic Diversity ◽  
Genotypic Variation ◽  
Bone Morphology ◽  
Complete Darkness ◽  
Astyanax Mexicanus ◽  
Enhanced Sensitivity ◽  
Eye Size ◽  
The Face ◽  
Genetic Signal ◽  
The Right

A key challenge in contemporary biology is connecting genotypic variation to phenotypic diversity. Quantitative genetics provides a powerful technique for identifying regions of the genome that covary with phenotypic variation. Here, we present a quantitative trait loci (QTL) analysis of a natural freshwater fish system, Astyanax mexicanus, that harbors two morphs corresponding to a cave and surface fish. Following their divergence ~500 Kya, cavefish have adapted to the extreme pressures of the subterranean biome. As a consequence, cavefish have lost numerous features, but evolved gains for a variety of constructive features including behavior. Prior work found that sensory tissues (neuromasts) present in the “eye orbit” region of the skull associate with sensitivity to vibrations in water. This augmented sensation is believed to facilitate foraging behavior in the complete darkness of a cave, and may impact on evolved lateral swimming preference. To this point, however, it has remained unclear how morphological variation integrates with behavioral variation through heritable factors. Using a QTL approach, we discovered the genetic architecture of neuromasts present in the eye orbit region, demonstrating that this feature is under genetic control. Interestingly, linked loci were asymmetric–signals were detected using only data collected from the right, but not left, side of the face. This finding may explain enhanced sensitivity and/or feedback of water movements mediating a lateral swimming preference. The locus we discovered based on neuromast position maps near established QTL for eye size and a facial bone morphology, raising the intriguing possibility that eye loss, sensory expansion, and the cranial skeleton may be integrated for evolving adaptive behaviors. Thus, this work will further our understanding of the functional consequence of key loci that influence the evolutionary origin of changes impacting morphology, behavior, and adaptation.

scholarly journals A chromosome level genome of Astyanax mexicanus surface fish for comparing population-specific genetic differences contributing to trait evolution.

2020 ◽  
Author(s):  
Wesley Warren ◽  
Tyler Boggs ◽  
Richard Borowsky ◽  
Brian Carlson ◽  
Estephany Ferrufino ◽  
...  
Keyword(s):  
Complex Traits ◽  
Fish Genome ◽  
Trait Evolution ◽  
Protein Coding ◽  
Astyanax Mexicanus ◽  
Eye Size ◽  
Genome Wide ◽  
Trait Locus ◽  
The Impact ◽  
Chromosome Level

Abstract Identifying the genetic factors that underlie complex traits is central to understanding the mechanistic underpinnings of evolution. In nature, adaptation to severe environmental change, such as encountered following colonization of caves, has dramatically altered genomes of species over varied time spans. Genomic sequencing approaches have identified mutations associated with troglomorphic trait evolution, but the functional impacts of these mutations remain poorly understood. The Mexican Tetra, Astyanax mexicanus, is abundant in the surface waters of northeastern Mexico, and also inhabits at least 30 different caves in the region. Cave-dwelling A. mexicanus morphs are well adapted to subterranean life and many populations appear to have evolved troglomorphic traits independently, while the surface-dwelling populations can be used as a proxy for the ancestral form. Here we present a high-resolution, chromosome-level surface fish genome, enabling the first genome-wide comparison between surface fish and cavefish populations. Using this resource, we performed quantitative trait locus (QTL) mapping analyses for pigmentation and eye size and found new candidate genes for eye loss such as dusp26. We used CRISPR gene editing in A. mexicanus to confirm the essential role of a gene within an eye size QTL, rx3, in eye formation. We also generated the first genome-wide evaluation of deletion variability that includes an analysis of the impact on protein-coding genes across cavefish populations to gain insight into this potential source of cave adaptation. The new surface fish genome reference now provides a more complete resource for comparative, functional, developmental and genetic studies of drastic trait differences within a species.

scholarly journals Contrasted gene decay in subterranean vertebrates: insights from cavefishes and fossorial mammals

2020 ◽  
Author(s):  
Maxime Policarpo ◽  
Julien Fumey ◽  
Philippe Lafargeas ◽  
Delphine Naquin ◽  
Claude Thermes ◽  
...  
Keyword(s):  
Evolutionary Process ◽  
Sharp Contrast ◽  
Functional Constraints ◽  
Loss Of Function ◽  
Astyanax Mexicanus ◽  
Gene Sets ◽  
Cave Population ◽  
Cave Ecosystems ◽  
Genome Ploidy ◽  
Gene Decay

AbstractEvolution sometimes proceeds by loss, especially when structures and genes become dispensable after an environmental shift relaxing functional constraints. Gene decay can serve as a read-out of this evolutionary process. Animals living in the dark are outstanding models, in particular cavefishes as hundreds of species evolved independently during very different periods of time in absence of light. Here, we sought to understand some general principals on the extent and tempo of decay of several gene sets in cavefishes. The analysis of the genomes of two Cuban species belonging to the genus Lucifuga provides evidence for the most massive loss of eye genes reported so far in cavefishes. Comparisons with a recently-evolved cave population of Astyanax mexicanus and three species belonging to the tetraploid Chinese genus Sinocyclocheilus revealed the combined effects of the level of eye regression, time and genome ploidy on the number of eye pseudogenes. In sharp contrast, most circadian clock and pigmentation genes appeared under strong selection. In cavefishes for which complete genomes are available, the limited extent of eye gene decay and the very small number of loss of function (LoF) mutations per pseudogene suggest that eye degeneration is never very ancient, ranging from early to late Pleistocene. This is in sharp contrast with the identification of several eye pseudogenes carrying many LoF mutations in ancient fossorial mammals. Our analyses support the hypothesis that blind fishes cannot thrive more than a few millions of years in cave ecosystems.

scholarly journals A chromosome level genome of Astyanax mexicanus surface fish for comparing population-specific genetic differences contributing to trait evolution

2020 ◽  
Author(s):  
Wesley C. Warren ◽  
Tyler E. Boggs ◽  
Richard Borowsky ◽  
Brian M. Carlson ◽  
Estephany Ferrufino ◽  
...  
Keyword(s):  
Complex Traits ◽  
Fish Genome ◽  
Trait Evolution ◽  
Protein Coding ◽  
Astyanax Mexicanus ◽  
Eye Size ◽  
Genome Wide ◽  
Trait Locus ◽  
The Impact ◽  
Chromosome Level

AbstractIdentifying the genetic factors that underlie complex traits is central to understanding the mechanistic underpinnings of evolution. In nature, adaptation to severe environmental change, such as encountered following colonization of caves, has dramatically altered genomes of species over varied time spans. Genomic sequencing approaches have identified mutations associated with troglomorphic trait evolution, but the functional impacts of these mutations remain poorly understood. The Mexican Tetra, Astyanax mexicanus, is abundant in the surface waters of northeastern Mexico, and also inhabits at least 30 different caves in the region. Cave-dwelling A. mexicanus morphs are well adapted to subterranean life and many populations appear to have evolved troglomorphic traits independently, while the surface-dwelling populations can be used as a proxy for the ancestral form. Here we present a high-resolution, chromosome-level surface fish genome, enabling the first genome-wide comparison between surface fish and cavefish populations. Using this resource, we performed quantitative trait locus (QTL) mapping analyses for pigmentation and eye size and found new candidate genes for eye loss such as dusp26. We used CRISPR gene editing in A. mexicanus to confirm the essential role of a gene within an eye size QTL, rx3, in eye formation. We also generated the first genome-wide evaluation of deletion variability that includes an analysis of the impact on protein-coding genes across cavefish populations to gain insight into this potential source of cave adaptation. The new surface fish genome reference now provides a more complete resource for comparative, functional, developmental and genetic studies of drastic trait differences within a species.

scholarly journals Untargeted Metabolomics of the Cavefish Astyanax mexicanus Reveals the Basis of Metabolic Strategies in Adaptation to Extreme Conditions

2020 ◽  
Author(s):  
J Kyle Medley ◽  
Jenna Persons ◽  
Robert Peuß ◽  
Luke Olsen ◽  
Shaolei Xiong ◽  
...  
Keyword(s):  
Behavioral Changes ◽  
Protein Glycation ◽  
Untargeted Metabolomics ◽  
Short Term ◽  
Astyanax Mexicanus ◽  
Surface Population ◽  
Shiny App ◽  
Metabolomics Study ◽  
Metabolic Strategies

The Mexican tetra, Astyanax mexicanus, has undergone remarkable physiological and behavioral changes in order to colonize a number of subterranean caves in the Sierra de El Abra region of Mexico. A hallmark of cave-adapted populations is enhanced survival under low-nutrient conditions coupled with hyperglycemia, increased body fat, and insulin resistance, but cavefish appear to avoid the progression of the respective pathologies associated with these conditions and do not exhibit reduced longevity. The metabolic strategies underlying these adaptations are not fully understood. Here, we provide an untargeted metabolomics study of longand short-term fasting in two A. mexicanus cave populations and one surface population. We find that, although cavefish share many similarities with metabolic syndrome normally associated with the human state of obesity, important differences emerge, including cholesterol esters, urate, intermediates of protein glycation, metabolites associated with hypoxia and longevity, and unexpectedly elevated levels of ascorbate (vitamin C). This work highlights the fact that certain metabolic features associated with human pathologies are not intrinsically harmful in all organisms, and suggests promising avenues for future investigation into the role of certain metabolites in evolutionary adaptation and health. We provide a transparent pipeline for reproducing our analysis and a Shiny app for other researchers to explore and visualize our dataset.

scholarly journals Contrasting Gene Decay in Subterranean Vertebrates: Insights from Cavefishes and Fossorial Mammals

2020 ◽  
Author(s):  
Maxime Policarpo ◽  
Julien Fumey ◽  
Philippe Lafargeas ◽  
Delphine Naquin ◽  
Claude Thermes ◽  
...  
Keyword(s):  
Specific Gene ◽  
Functional Constraints ◽  
Limited Extent ◽  
Loss Of Function ◽  
Astyanax Mexicanus ◽  
Cave Population ◽  
Opsin Genes ◽  
Cave Ecosystems ◽  
Genome Ploidy ◽  
Gene Decay

Abstract Evolution sometimes proceeds by loss, especially when structures and genes become dispensable after an environmental shift relaxes functional constraints. Subterranean vertebrates are outstanding models to analyze this process, and gene decay can serve as a readout. We sought to understand some general principles on the extent and tempo of the decay of genes involved in vision, circadian clock, and pigmentation in cavefishes. The analysis of the genomes of two Cuban species belonging to the genus Lucifuga provided evidence for the largest loss of eye-specific genes and nonvisual opsin genes reported so far in cavefishes. Comparisons with a recently evolved cave population of Astyanax mexicanus and three species belonging to the Chinese tetraploid genus Sinocyclocheilus revealed the combined effects of the level of eye regression, time, and genome ploidy on eye-specific gene pseudogenization. The limited extent of gene decay in all these cavefishes and the very small number of loss-of-function mutations per pseudogene suggest that their eye degeneration may not be very ancient, ranging from early to late Pleistocene. This is in sharp contrast with the identification of several vision genes carrying many loss-of-function mutations in ancient fossorial mammals, further suggesting that blind fishes cannot thrive more than a few million years in cave ecosystems.

Positive Effects of Video Gaming on Human Behavior

2020 ◽  
pp. 155-172
Author(s):  
Aaron Cochrane ◽  
Sara Prot ◽  
Jorge Blanco ◽  
C. Shawn Green ◽  
Douglas A. Gentile
Keyword(s):  
Video Games ◽  
Video Game ◽  
Behavioral Change ◽  
Extended Period ◽  
Dynamic Environments ◽  
Video Gaming ◽  
Video Game Play ◽  
Positive Effects ◽  
Psychological Science ◽  
Future Work

The enormous rise in the popularity of video games can be accounted for, at least in part, by their engaging and enjoyable nature. Interestingly, from the perspective of psychological science, the same basic mechanics that give rise to these motivating and pleasure-provoking attributes also make games powerful environments for inducing behavioral change. Indeed, it is easy to identify mechanics in video games that are known to facilitate learning (e.g. feedback, reinforcement, adaptive difficulty). It is therefore unsurprising that video game play has been linked with differences in a host of core psychological processes. Research has included several types of converging methods. This includes correlational methodology, where individuals who play certain types of video games are contrasted against individuals who do not play those types of games; longitudinal methodology, in which players are followed over an extended period of time; and true experiments, in which individuals are randomly assigned to be trained on certain video games. Reported game-related improvements range from heightened visual perception to increased pro-social behaviors to enhanced ability to perform surgery. Although these effects are wide-ranging, it must be emphasized that not all games are equal with respect to the psychological changes they induce. Instead the observed changes are clearly linked to the dynamics, mechanics, and content inherent in individual games. Future work treating video games as rich learning environments will improve our understanding of the interplay between humans and designed dynamic environments.

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