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opencc-zeroDec 2010View details →

Data from: Temporal population-genetic structure of eastern mosquitofish in a dynamic aquatic landscape

We analyzed the effect of periodic drying in the Florida Everglades on spatio-temporal population genetic structure of eastern mosquitofish (Gambusia holbrooki). Severe periodic drying events force individuals from disparate sources to mix in dry-season relatively deep-water refuges. In 1996 (a wet year) and 1999 (a dry year), we sampled mosquitofish at 20 dry-season refuges distributed in three water-management regions and characterized genetic variation for 10 allozyme and 3 microsatellite loci. In 1996, most of the ecosystem did not dry, while in 1999, many of our sampling locations were isolated by expanses of dried marsh surface. In 1996, most spatial genetic variation was attributed to heterogeneity within regions. In 1999, spatial genetic variation within regions was not significant. In both years, a small but significant amount of variation (less than 1% of the total variation) was partitioned among regions. Variance was consistently greater than zero among long-hydroperiod sites within a region, but not among short-hydroperiod sites within a region, where hydroperiod was measured as time since last marsh surface dry-down forcing fishes into local refuges. In 1996, all sites were in Hardy-Weinberg equilibrium. In 1999, we observed fewer heterozygotes than expected for most loci and sites suggesting a Wahlund effect arising from fish leaving areas that dried and mixing in deep-water refuges.

opencc-zeroDec 2014View details →

Data from: Anthropogenic ecosystem fragmentation drives shared and unique patterns of sexual signal divergence among three species of Bahamian mosquitofish

When confronted with similar environmental challenges, different organisms can exhibit dissimilar phenotypic responses. Therefore, understanding patterns of phenotypic divergence for closely related species requires considering distinct evolutionary histories. Here, we investigated how a common form of human-induced environmental alteration, habitat fragmentation, may drive phenotypic divergence among three closely related species of Bahamian mosquitofish (Gambusia spp.). Focusing on one phenotypic trait (male coloration), having a priori predictions of divergence, we tested whether populations persisting in fragmented habitats differed from those inhabiting unfragmented habitats and examined the consistency of the pattern across species. Species exhibited both shared and unique patterns of phenotypic divergence between the two types of habitats, with shared patterns representing the stronger effect. For all species, populations in fragmented habitats had fewer dorsal-fin spots. In contrast, the magnitude and trajectory of divergence in dorsal-fin color, a sexually selected trait, differed among species. We identified fragmentation-mediated increased turbidity as a possible driver of these trait shifts. These results suggest that even closely related species can exhibit diverse phenotypic responses when encountering similar human-mediated selection regimes. This element of unpredictability complicates forecasting the phenotypic responses of wild organisms faced with anthropogenic change – an important component of biological conservation and ecosystem management.

opencc-zeroDec 2018View details →

Data from: Phenotypic and community consequences of captive propagation in mosquitofish

1. Captive propagation can lead to phenotypic change in fish populations, but the broader community-level consequences of captive phenotypes remain largely unknown. 2. Here we investigate the degree to which captive propagation alters the phenotypes and ecological roles of fish stocked into wild communities. We focus on captive propagation of western mosquitofish (Gambusia affinis) for biocontrol, which represents one of the largest-scale production efforts for any fish released into the wild. 3. Captive propagation in mosquitofish consistently generated novel mixtures of morphological and behavioral traits that deviate from those of wild populations. 4. A mesocosm experiment showed that mosquitofish from captive propagation facilities differ from wild fish in their effects on aquatic community structure by shifting their consumption to less-mobile, benthic prey. 5. Synthesis and applications: These findings provide evidence that captive-propagated and translocated wild stocks not only differ in phenotype, but can have substantially different ecological effects on the communities into which they are introduced. Therefore, captive propagation programs involving continual release should expand their concerns beyond altered phenotypes and fitness to include whether propagated fish actually provide the intended ecological roles and services associated with wild counterparts. Infusions of wild alleles and captive environments that mimic wild conditions are recommended strategies to retain the desired ecological role of captive propagated fish

opencc-zeroDec 2013View details →

Data from: Male body size and condition affects sperm number and production rates in mosquitofish, Gambusia holbrooki

Sperm number is an important predictor of paternity when there is sperm competition. Sperm number is often measured as maximum sperm reserves, but in species where mating is frequent, males will often be replenishing their reserves. Thus, variation in how quickly males can produce sperm is likely to be important in determining male success in sperm competition. Despite this, little is known about how male size, body condition or diet affects sperm production rates. We counted sperm number in large and small Gambusia holbrooki (eastern mosquitofish) after 3 weeks on either a high or low food diet. Sperm number was significantly higher in both larger males and in well-fed males. We then stripped ejaculates again either 1, 2, 3, 4 or 5 days later to investigate subsequent sperm production. The rate of sperm replenishment was influenced by an interaction between size and diet. Large, well-fed males had consistently high levels of sperm available over the 5 days (i.e. rapid replenishment), whereas small poorly fed males showed consistently low levels of sperm availability over the 5 days (i.e. slow replenishment). In contrast, large, poorly fed and small, well-fed males increased their sperm numbers over the first 3 days (i.e. intermediate replenishment). Our study highlights that when mating is frequent and sperm competition is high, size and condition dependence of maximal sperm number and of sperm production rate might both contribute to variation in male reproductive success.

F I G U R E 5 in Domperidone treatment attenuates stress-induced suppression of reproduction in viviparous mosquitofish Gambusia affinis

F I G U R E 5 Mean effect of stress and domperidone (DOM) treatment on follicular atresia in Gambusia affinis. Groups with identical superscripts indicate no significant difference (P <0.05; oneway ANOVA followed by Tukey's test; n = 10 in each experimental group; df = 49; F = 15.231)

F I G U R E 1 in Domperidone treatment attenuates stress-induced suppression of reproduction in viviparous mosquitofish Gambusia affinis

F I G U R E 1 Mean effect of stress and domperidone (DOM) treatment on a total body mass (MT) and b total length (LT) in five different experimental groups of Gambusia affinis. Groups with identical superscripts indicate no significant difference (P <0.05; oneway ANOVA followed by Tukey's test (n = 10 in each experimental group; df = 49; F = 8.325)

F I G U R E 3 in Domperidone treatment attenuates stress-induced suppression of reproduction in viviparous mosquitofish Gambusia affinis

F I G U R E 3 Photomicrographs of transverse sections of brain in Gambusia affinis showing the TH–immunoreactive (TH-ir) cells () and fibres () in different experimental groups: (a)–(c) initial control; (d)–(f) experimental control; (g)–(i) stress group; (j), (k) domperidone (DOM) treated group; (l)– (n) stress + DOM treated fish. Figures a, b, f, g & k-m are rhodamine labelled; other images are IHC labelled, wherein the colour was obtained after peroxidise action on chromogenic substrate, 3-amino–9-ethyl-carbazole. NPO, nucleus preopticus; POA, preoptic area; V, ventricle. Scale bar: (a) & (d) 200 μm; others 50 μm

F I G U R E 2 in Domperidone treatment attenuates stress-induced suppression of reproduction in viviparous mosquitofish Gambusia affinis

F I G U R E 2 Photomicrographs of alexa fluor 488 labelled transverse sections through the proximal pars distalis (PPD) of the pituitary gland (P) in Gambusia affinis showing the GnRH-ir fibres (!) in (a), (b), initial control; (c), experimental control; (d), stress group; (e), domperidone (DOM) treated group; (f), stress + DOM treated fish. Scale bar: (a) 200 μm; (b)– (f) 50 μm

F I G U R E 4 in Domperidone treatment attenuates stress-induced suppression of reproduction in viviparous mosquitofish Gambusia affinis

F I G U R E 4 Photomicrographs showing cross sections of the ovary Gambusia affinis from: (a), initial control; (b), experimental control; (c), (d) stress; (e), domperidone (DOM) treated; (f), stress + DOM treated groups. I, II, III, IV and V, stages of follicular development; AT, atretic follicle; ON, oogonial nest. Scale bar 200 μm

opencc-zeroJan 2022View details →

Raw mass-standardized ionomic data from seven fish species and raw transcriptome sequences for mosquitofish inhabiting the Tar Creek Superfund Site in OK, USA

Our understanding of the mechanisms mediating the resilience of organisms to environmental change remains lacking. Heavy metals negatively affect processes at all biological scales, yet organisms inhabiting contaminated environments must maintain homeostasis to survive. Tar Creek in Oklahoma, USA, contains high concentrations of heavy metals and an abundance of Western mosquitofish (Gambusia affinis), though several fish species persist at lower frequency. To test hypotheses about the mechanisms mediating the persistence and abundance of mosquitofish in Tar Creek, we integrated ionomic data from seven resident fish species and transcriptomic data from mosquitofish to test hypotheses about the mechanisms mediating the persistence of mosquitofish in Tar Creek. We predicted that mosquitofish minimize uptake of heavy metals more than other Tar Creek fish inhabitants and induce transcriptional responses to detoxify metals that enter the body, allowing them to persist in Tar Creek at higher density than species that may lack these responses. Tar Creek populations of all seven fish species accumulated heavy metals, suggesting mosquitofish cannot block uptake more efficiently than other species. We found population-level gene expression changes between mosquitofish in Tar Creek and nearby unpolluted sites. Gene expression differences primarily occurred in the gill, where we found upregulation of genes involved with lowering transfer of metal ions from the blood into cells and mitigating free radicals. However, many differentially expressed genes were not in known metal response pathways, suggesting multifarious selective regimes and/or previously undocumented pathways could impact tolerance in mosquitofish. Our systems-level study identified well characterized and putatively new mechanisms that enable mosquitofish to inhabit heavy metal-contaminated environments.

opencc-zeroDec 2021View details →

Separating the effects of paternal age and mating history: evidence for sex-specific paternal effect in eastern mosquitofish

Paternal age and past mating effort by males are often confounded, which can affect our understanding of a father's age effects. To our knowledge, only a few studies have standardized mating history when testing for effects of paternal age, and none has simultaneously disentangled how paternal age and mating history might jointly influence offspring traits. Here, we experimentally manipulated male mating history to tease apart its effects from those of paternal age on female fertility and offspring traits in the eastern mosquitofish (Gambusia holbrooki). Male age did not affect female fertility. However, males with greater past mating effort produced significantly larger broods. Paternal age and mating history interacted to affect sons' body size: sons sired by old-virgin males were larger than those sired by old-mated males, but this was not the case for younger fathers. Intriguingly, however, sons sired by old-virgin males tended to produce fewer sperms than those sired by old-mated males, indicating a potential trade-off in beneficial paternal effects. Finally, neither paternal age nor mating history affected daughter's fitness. Our results highlight that variation in offspring traits attributed to paternal age effect could partly arise due to a father's mating history, and not simply to his chronological age.

opencc-zeroDec 2012View details →

Data from: Regulation of thermal acclimation varies between generations of the short-lived mosquitofish (Gambusia holbrooki) that developed in different environmental conditions

1. Environmental variability and perturbations can influence population persistence. It is therefore important to understand whether and how animals can compensate for environmental variability, and thereby increase resilience of natural populations. Evolutionary theory predicts that in fluctuating environments selection should favour developmental modifiers that reduce phenotypic expression of genetic variation. The expected result is that phenotypes are buffered from environmental variation across generations. 2. Our aim was to determine whether phenotypes of mosquitofish (Gambusia holbrooki) remain stable across generations in which individuals were born into different thermal environments. We predicted that the spring generation (cool environment) would acclimate by increasing the concentration of regulatory transcription factor mRNA and activities of rate-limiting enzymes (hierarchical regulation) to compensate for the negative thermodynamic effects of lower temperatures on metabolic and locomotor performance. In contrast, the summer-born generation (warm environment) would show less capacity for acclimation and hierarchical regulation. 4. We show that fish from both generations acclimated, but that there were significant differences in the phenotypic consequences of acclimation. The overall result was that sprint performance, metabolic scope, and the activities of cyctochrome c oxidase and lactate dehydrogenase were buffered from environmental change, and did not differ between spring and summer fish at their natural water temperatures of 15oC and 25oC, respectively. However, there were differences between generations in sustained swimming performance and citrate synthase activity. 5. We used metabolic control analysis to show that modes of regulation of metabolic scope and locomotor performance differed between generations. Spring fish showed primarily hierarchical regulation, but regulation in summer fish relied to a lesser extent on rate-limiting enzymes and transcription factors. 6. We suggest that developmental modifiers are favoured in fluctuating environments to maximise phenotypic fitness of each generation. We show that the interaction between developmental and reversible acclimation can render physiological performance of a natural population independent from climate variation.

opencc-zeroJul 2021View details →

Field-realistic antidepressant exposure disrupts group foraging dynamics in mosquitofish

Psychoactive pollutants, such as antidepressants, are increasingly detected in the environment. Mounting evidence suggests that such pollutants can disrupt the behaviour of non-target species. Despite this, few studies have considered how the response of exposed organisms might be mediated by social context. To redress this, we investigated the impacts of two environmentally realistic concentrations of a pervasive antidepressant pollutant, fluoxetine, on foraging behaviour in fish (Gambusia holbrooki), tested individually or in a group. Fluoxetine did not alter behaviour of solitary fish. However, in a group setting, fluoxetine exposure disrupted the frequency of aggressive interactions and food consumption, with observed effects being contingent on both the mean weight of group members and the level of within-group variation in weight. Our results suggest that behavioural tests in social isolation may not accurately predict the environmental risk of chemical pollutants for group-living species and highlight the potential for social context to mediate the effects of psychoactive pollutants in exposed wildlife.

opencc-zeroAug 2021View details →

Sex-specific responses to intraspecific competition in the mosquitofish Gambusia holbrooki

Intraspecific competition constitutes an important source of selection that can influence the development, expression and evolution of phenotypic traits. Although often neglected in studies of intraspecific competition, the sex of competitors can alter the nature and intensity of competition between individuals, and in turn can influence the development of resource-dependent traits. We examine here how the sex of focal and of competitor individuals interact to affect developmental responses to competition in the Eastern mosquitofish Gambusia holbrooki. We raised individuals of both sexes either alone or in the presence of a male or female competitor, and measured their juvenile growth rate, time to maturity and size at maturity; for males we also measured their gonopodium length, sperm quantity, and sperm velocity. We found that plastic phenotypic responses to competition were dependent on the sex of the focal individual, the sex of their competitor and sometimes an interaction between the two. When there was a competitor present, regardless of its sex, males had slower growth rates and took longer to mature, but eventually matured at the same size. Like males, females also showed slower growth rates in the presence of a competitor, but in contrast to males, reached maturity sooner and at a smaller size than when there was no competitor present. Presence of a competitor influenced male sexual traits, however there was little evidence that these effects were mediated by the sex of the competitor. Males that were reared with competitors had longer gonopodia for their body size, as well as fewer and faster sperm. Overall our results suggest that the effects of competition on resource-dependent traits are different for males and females, potentially due to sex differences in adult life history strategies. Further, for males, both life history traits and sexual traits were influenced by competition. For life history traits this effect appears to result from decreased resources and/or increased energy expenditure, but for sexual traits, effects appear to be mediated, at least in part, by the social environment, which also differs in the presence of competitors.

opencc-zeroApr 2023View details →

Data from: Legacy effects in temporally-separated tadpole species are not mediated by invasive Western Mosquitofish (Gambusia affinis)

Temporally separated species are often thought to have limited competition over a shared resource. However, early arriving species may consume a limited resource such that later arriving species have access to fewer resources and thus experience competitive effects, even if they are temporally separated (i.e., they experience legacy effects from the early species). The presence of a predator might affect potential legacy effects by influencing the behavior or survivorship of the early species. Using a mesocosm experiment, I examined whether the presence of non-native Western Mosquitofish (Gambusia affinis) mediated legacy effects in the interaction of two temporally separated species of tadpoles, early arriving American Toads (Anaxyrus americanus) and late arriving Bullfrogs (Rana catesbeiana). Anaxyrus americanus tadpoles reduced R. catesbeiana tadpole growth despite all A. americanus tadpoles metamorphosing 8 d before the introduction of R. catesbeiana tadpoles into the mesocosms (i.e., legacy effects). Gambusia affinis had limited effects on A. americanus (1 d delay in metamorphosis but no effect on survivorship or size at metamorphosis) and positive effects on R. catesbeiana (increased growth). There were no significant interactions between the A. americanus tadpole density and G. affinis treatments. In conclusion, I found evidence of significant legacy effects of A. americanus tadpoles on R. catesbeiana tadpoles, but no evidence that G. affinis mediated the legacy effects.

publicApr 2019View details →

Data from: Phenotypic and community consequences of captive propagation in mosquitofish

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publicApr 2015View details →

Data from: Anthropogenic ecosystem fragmentation drives shared and unique patterns of sexual signal divergence among three species of Bahamian mosquitofish

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