Mosquitofish Research Articles

A Man and His Minnows: The Introduction of Gambusia affinis to Mandatory Palestine

While the ecological aspects of aquatic introductions have been thoroughly researched, lesser attention has been given to the social, historical, cultural, and ideological contexts of such intended introductions. The introduction of Gambusia affinis to Palestine was made quickly by one person, who documented the process—and hence may serve as an excellent case study: Israel Kligler's scientific reports and personal correspondence from the late 1920s and early 1930s provide us with an opportunity to witness the thoughts and ideas behind that introduction process. We find that the swift and quick introduction was facilitated by a combination of three factors: Zionist institutions' desire to test new scientific tools and methods, the colonial desire to control the environment and actively “ameliorate” it, and Kligler's close working ties with US-American institutions. We argue that histories of introductions should be regarded and analyzed by examining such technical-political conjunctures.

Color Discrimination Provides Insight into the Relationship between Personality Cognition and Brain Morphology in the Western Mosquitofish (Gambusia affinis)

Recent studies on the differences in cognitive ability between individuals focused on two aspects: one is whether the individual differences in cognitive ability are related to brain size, the other is whether they pertain to certain personality traits. To explore these two hypotheses, we tested the personality traits, cognitive abilities, and brain volumes of western mosquitofish (Gambusia affinis). First, a color preference test was conducted to select two unbiased colors for G. affinis for subsequent cognitive tests. The results showed that G. affinis had a great preference for red and green to yellow and blue; therefore, the red-green combination was selected for the study of cognitive abilities. Then, we explored the relationship among cognition, personality, and brain morphology through cognitive abilities tests, personality traits, and brain volume measurements. We found that there was a trade-off among cognition, personality, and brain morphology. For example, more active individuals found food faster, but had also poor memory; Those individuals with larger corpus cerebelli were bolder while they were less likely to find food; The individuals that found food faster were more active and had a smaller inferior lobe. The color preference test provides a reliable way for selecting unbiased colors for behavioral studies in G. affinis. Meanwhile, our study indicates that there exists a balance mechanism among cognition, personality, and brain morphology.

Plasticity and evolution shape the scaling of metabolism and excretion along a geothermal temperature gradient

Abstract Physiological rates are heavily dependent on temperature and body size. Most current predictions of organisms’ response to environmental warming are based on the assumption that key physiological rates such as metabolism and excretion scale independently with body size and temperature and will not evolve. However, temperature is a significant driver for phenotypic variability in the allometric scaling and thermal sensitivity of physiological rates within ectotherm species, suggesting that evolution may play a role in shaping these parameters. We common‐reared six populations of western mosquitofish that have recently established (~100 years ago) in geothermal springs along a broad thermal gradient (19–33°C) to determine whether these scaling parameters are affected by evolutionary and/or plastic responses to warming over ecological timescales. Each population was reared at four different temperatures (23, 26, 30 and 32°C). We measured routine metabolic and nitrogen excretion rates on mosquitofish across a wide body size range. We found evidence for plasticity, but not evolution, increasing the allometric scaling of metabolic rate with temperature. Plasticity in metabolism allometry reflected a decrease in thermal sensitivity at smaller body sizes. We found evidence for evolution of phenotypic plasticity on the allometry of excretion rate, reflecting evolutionary differences in how thermal sensitivity varies with body size across different populations. Evolutionary differences in excretion rate scaling did not influence the relationship between excretion and metabolism across rearing temperatures, suggesting that warming does not affect the balance between mosquitofish energy demands and nutrient recycling rates. Read the free Plain Language Summary for this article on the Journal blog.

Essential oil of Piper purusanum C.DC (Piperaceae) and its main sesquiterpenes: biodefensives against malaria and dengue vectors, without lethal effect on non-target aquatic fauna.

The mosquito vectors of the genera Aedes and Anopheles present resistance to several commercial insecticides, which are also toxic to non-predator targets. On the other hand, essential oils are a promising source of insecticides. Thus, in this work, the essential oil from the leaves of Piper purusanum was characterized by gas chromatography-based approaches and evaluated as biodefensive against malaria and dengue vectors. The main compounds of P. purusanum essential oil were β-caryophyllene (57.05%), α-humulene (14.50%), and germacrene D (8.20%). The essential oil inhibited egg hatching (7.6 ± 1.5 to 95.6 ± 4.5%), caused larval death (LC50 from 49.84 to 51.60ppm), and inhibited the action of acetylcholinesterase (IC50 of 2.29µg/mL), which can be related to the mechanisms of action. On the other hand, the biological activities of β-caryophyllene, α-humulene, and germacrene D were higher than that of essential oil. In addition, these sesquiterpenes and essential oil did not show a lethal effect on Toxorhynchites splendens, Anisops bouvieri, Gambusia affinis, and Diplonychus indicus (LC50 from 2098.80 to 7707.13ppm), although D. indicus is more sensitive (SI/PSF from 48.56 to 252.02ppm) to essential oil, representing a natural alternative against these relevant vectors.

Drivers of temporal variations in fish assemblages from mangrove creeks in Beihai, southern China.

Mangroves are regarded as important settlement grounds and nurseries for fishes due to the sheltered nature of these ecosystems. To identify the drivers of temporal variations in fish assemblages, seasonal variations of fish assemblages and environmental variables were investigated in Nanliu River Estuary, China, from July 2019 to May 2020. In total, 17,680 individuals weighing 24,724.73 g belonging to 23 families and 45 species were collected. The dominant species were Ambassis urotaenia, Mugil cephalus, Coptodon zillii, Gambusia affinis, and Bostrychus sinensis. Fish assemblages were significantly different in seasonal periodicity according to the results of nonmetric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA). Kruskal-Wallis test results revealed that species richness, fish abundance, and biomass were significantly different, seasonally. The highest number of fish specimens captured was recorded in winter and summer, while the highest biomass was observed in autumn. Different ecological types of fish utilized mangroves in different ways. Hence, the findings in this study are instrumental in understanding and the conservation of mangroves even coastal wetland and fish resources in the process of mangrove restorations.

Inconsistent evolution and growth-survival tradeoffs in Gambusia affinis.

Growth-survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish (Gambusia affinis) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth-survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

Predator-Prey Interactions between Nonnative Juvenile Largemouth Bass (Micropterus salmoides) and Local Candidate Prey Species in the Pearl River Delta: Predation Capacity, Preference and Growth Performance.

An ontogenetic dietary shift is crucial for the survival and growth of piscivorous largemouth bass (LB). However, there is much to learn about the predator-prey interaction during the switching process. We carried out a series of indoor experiments to examine the predation capacity, predation preference, and growth performance of exotic juvenile LB feeding on candidate prey species in the Pearl River Delta. The widely distributed oriental river prawn (Macrobranchium nipponense), barcheek goby (Ctenogobius giurinus), western mosquitofish (Gambusia affinis), silver carp (Hypophthalmichthys molitrix), and mud carp (Cirrhinus molitorella), with relatively similar total lengths, were selected as potential prey based on their availability and habitat use. Our results show that predation capacity and preference varied quantitatively and qualitatively among prey species. The number of oriental river prawns killed was significantly less than that of fish species, comparing the 1st hour with the 24th hour (p < 0.01). The feeding rhythm of LB varied significantly from crayfish to fish. Numerically, Jacobs’ selection index reinforced LB’s special preference for predating G. affinis. Although there were obvious variations in predation capacity and feed selection, no statistically significant growth differences were detected among LB groups feeding on live M. nipponense, G. affinis, H. molitrix, and C. molitorella (p < 0.05). These findings suggest that the successful ontogenetic dietary shift of juvenile LB may depend on the availability and vulnerability of local fish species. Further study on the reproductive phenology of potential fish prey may help to predict LB’s establishment.

Impacts of heavy metal pollution on the ionomes and transcriptomes of Western mosquitofish (Gambusia affinis)

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. 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.

Male mate choice in mosquitofish: personality outweighs body size

BackgroundDespite its important implications in behavioural and evolutionary ecology, male mate choice has been poorly studied, and the relative contribution of personality and morphological traits remains largely unknown. We used standard two-choice mating trials to explore whether two personality traits (i.e., shyness and activity) and/or body size of both sexes affect mate choice in male mosquitofish Gambusia affinis. In the first set of trials involving 40 males, we tested whether males would prefer larger females and whether the preference would be affected by males’ body length and personality traits, and females’ activity level. In the second set of trials (using another 40 males), we tested whether males would prefer more active females and whether the preference would be affected by males’ body length and personality traits.ResultsBoth shyness and activity in males were significantly repeatable and constituted a behavioural syndrome. No overall directional preference for large (or small) females with the same activity levels was detected because larger males preferred larger females and smaller males chose smaller females. Males’ strength of preference for larger females was also positively correlated with the activity level of larger females but negatively with the activity level of smaller females. Males spent more time associating with active females regardless of their body lengths, indicating males’ selection was more influenced by female activity level than body size. Males’ preference for inactive females was enhanced when females became active. There was no convincing evidence for the effect of males’ personality traits or body length on their preferences for females’ activity level.ConclusionsOur study supports the importance of body size in male mate choice but highlights that personality traits may outweigh body size preferences when males choose mating partners.

Drivers and Cascading Ecological Consequences of Gambusia affinis Trait Variation.

AbstractPhenotypic trait differences among populations can shape ecological outcomes for communities and ecosystems. However, few studies have mechanistically linked heritable and plastic components of trait variation to generalizable processes of ecology, such as trophic cascades. Here, we assess morphological and behavioral trait variation in nine populations of common garden-reared western mosquitofish (Gambusia affinis) from three distinct ancestral predator environments (three populations per environment), each reared in the presence and absence of predator cues. We then use a pond mesocosm experiment to examine the ecological consequences of mosquitofish trait variation and density variation. Our results show significant among-population trait variation, but this variation was generally unrelated to ancestral predator environment. When traits did vary congruently with respect to ancestral predator environment, this trait variation was driven by gene-by-environment interactions. Variation in several mosquitofish traits altered the cascading effects of mosquitofish on zooplankton and primary producers, but the effect of any given trait was typically weaker than that of density. We note that the relatively stronger ecological effects of density may mask the effects of traits in some systems. Our example here shows that trait variation can be highly noncongruent with respect to a perceived selective agent, phenotypic change is a product of complex interactions between genes and the environment, and numerous interacting phenotypes generate significant but potentially cryptic cascading ecological change.

Coping With Urban Habitats Via Glucocorticoid Regulation: Physiology, Behavior, and Life History in Stream Fishes.

As environments become urbanized, tolerant species become more prevalent. The physiological, behavioral and life-history mechanisms associated with the success of such species in urbanized habitats are not well understood, especially in freshwater ecosystems. Here, we examined the glucocorticoid (GC) profiles, life-history traits, and behavior of two species of fish across a gradient of urbanization to understand coping capacity and associated trade-offs. We studied the tolerant live-bearing Western Mosquitofish (Gambusia affinis) for two years and the slightly less tolerant, egg-laying, Blacktail Shiner (Cyprinella venusta) for one year. We used a water-borne hormone method to examine baseline, stress-induced, and recovery cortisol release rates across six streams with differing degrees of urbanization. We also measured life-history traits related to reproduction, and for G. affinis, we measured shoaling behavior and individual activity in a novel arena. Both species showed a trend for reduced stress responsiveness in more urbanized streams, accompanied by higher reproductive output. Although not all populations fit this trend, these results suggest that GC suppression may be adaptive for coping with urban habitats. In G. affinis, GC recovery increased with urbanization, and individuals with the lowest stress response and highest recovery had the greatest reproductive allotment, suggesting that rapid return to baseline GC levels is also an important coping mechanism. In G. affinis, urban populations showed altered life-history trade-offs whereas behavioral traits did not vary systematically with urbanization. Thus, these tolerant species of fish may cope with anthropogenically modified streams by altering their GC profiles and life-history trade-offs. These results contribute to understanding the mechanisms driving species-specific adaptations and thereby community structure in freshwater systems associated with land-use converted areas.

Oxidative stress responses of microplastic-contaminated Gambusia affinis obtained from the Brantas River in East Java, Indonesia

The biological impact of microplastic (MP) contamination on freshwater biota has sparked interest. Microplastics are thought to have a high potential for toxicity, affecting organism metabolism. The goal of this study was to investigating the antioxidant indicators on the gills and digestive tract of Gambusia affinis fish in the Brantas River reacted to microplastic pollution. The obtained data was evaluated using path analysis. The digestive tract had much greater levels of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) than the gill. SOD concentration in the gills was 13.7 ± 5.3 U/mL, while SOD concentration in the digestive tract was 16.3 ± 3.6 U/mL. The CAT concentration in the gills (5.3 ± 2.9 ng/mL) was higher than the CAT concentration in the digestive tract (10.5 ± 2.8) ng/mL, while the MDA concentration in the gills (690.8 ± 135.6 mU/mL) was higher than the MDA concentration in the digestive tract (869.6 ± 122.2) mU/mL. MP abundance has a direct effect on SOD and MDA in the gills. Meanwhile, the quantity of MP in the digestive tract has a direct effect on SOD and CAT, which affects the development of the MDA response.

CD4 cell activation with the CD8 marker and metallothionein expression in the gills of cadmium-exposed mosquito fish (Gambusia affinis Baird and Girard 1853) juveniles

This experiment aimed to determine how Cd exposure impacts CD4 cell activation, macrophage cells, pinocytosis activity, metallothionine expression, and Cd levels in juvenile Gambusia affinis gills. Four treatment groups were used, with one control and treatments A, B, C, and D at dosages of 0.03 mg/L, 0.023 mg/L, 0.015 mg/L, and 0.008 mg/L, respectively. The results showed that the number of CD4 with CD8 cell markers differed significantly from each treatment compared to the control (0.33%). The value in A, namely 0.54%, was the highest, followed by B, C, and D of 0.46%, 0.44%, and 0.42%, respectively. The number of macrophages increased as the Cd level of the medium increased, as did the activity of pinocytosis. Furthermore, the immunofluorescence test on the gills with the Anti-MT Mouse and goat IgG fluoresce in Rhodamine on the gills showed that luminescence increased with increasing Cd levels in the gills. Similarly, the MT intensity increased at Cd-exposed gills as compared to the control. As the Cd level in the gills increased, the MT levels ascended significantly.

Thyroid Endocrine Disruption and Neurotoxicity of Gestodene in Adult Female Mosquitofish (Gambusia Affinis)

Thyroid Endocrine Disruption and Neurotoxicity of Gestodene in Adult Female Mosquitofish (Gambusia Affinis)

Morphometric Characteristics of Gambusia holbrooki and Gambusia affinis (Cyprinodontiformes: Poeciliidae) Distributed on the Plains of the Chirchik River, Uzbekistan

Morphometric Characteristics of Gambusia holbrooki and Gambusia affinis (Cyprinodontiformes: Poeciliidae) Distributed on the Plains of the Chirchik River, Uzbekistan

Thyroid Endocrine Disruption and Neurotoxicity of Gestodene in Adult Female Mosquitofish (Gambusia Affinis)

Thyroid Endocrine Disruption and Neurotoxicity of Gestodene in Adult Female Mosquitofish (Gambusia Affinis)

Adverse Effects of Heavy Metals on Aquatic life

The metals that are highly dense and toxic at low quantities are termed as heavy metals. These metals include Lead, Mercury, Cadmium, Copper, Zinc, Manganese, Nickel, Arsenic and Silver etc. Among these metals Arsenic, Cadmium, Chromium and Lead are considered most toxic to humans, animals and fish. Heavy metals enter the aquatic ecosystem through disposal of industrial, agricultural and municipal wastes and bioaccumulates in the food chain. Chromium is generally present in aquatic ecosystems between the range 1-10 µg/L which is highly toxic. Higher concentration of Chromium in aquatic ecosystem can result in accumulation in fish and have adverse effects on consumers’ health. Cadmium and Lead deposit on the gills of the fish and cause suffocation which may lead to death of the fish. Accumulation of Cadmium is generally associated with organ damage and anemia that results in death of the fish and its consumer. In the presence of Cadmium, the toxicity of Lead generally increases the toxicity drastically in Gambusia affinis.

Invasive fish retain plasticity of naturally selected, but diverge in sexually selected traits

Invasive alien species (IAS) have become a major threat to ecosystems worldwide. From an evolutionary ecological perspective, they allow teasing apart the relative contributions of plasticity and evolutionary divergence in driving rapid phenotypic diversification. When IAS spread across extensive geographic ranges, climatic variation may represent a source of strong natural selection through overwinter mortality and summer heat stress. This could favour local adaptation, i.e., evolutionary divergence of certain traits. IAS, however, are likely to show plasticity in survival-related traits, and environmental fluctuation in their new distribution range could favour the maintenance of this pre-existing phenotypic plasticity. By contrast, sexually selected traits are more likely to undergo evolutionary divergence when components of sexual selection differ geographically. Here, using data from a common-garden rearing experiment of Western mosquitofish (Gambusia affinis Baird and Girard, 1853) from five populations across the species' invasive range in China, we show that invasive mosquitofish have retained plasticity in key physiological (thermal tolerances), morphological and life-history traits even 100 years after their introduction to China, but exhibit heritable population differences in several sexually selected traits, including the shape of the male copulatory organ. Adaptive plasticity of traits linked to immediate survival in different thermal environments—while likely responsible for the species' extraordinary invasion success—could slow down genetic evolution. Several sexually selected traits could diverge geographically and show rapid evolutionary change, e.g., because climate alters selective landscapes arising from mate competition as an indirect consequence of variation in overwinter mortality.

Population genetics and independently replicated evolution of predator-associated burst speed ecophenotypy in mosquitofish.

Many species show replicated ecophenotypy due to recurring patterns of natural selection. Based on the presence or absence of pursuit predators, at least 17 species of fish repeatedly differentiated in body shape in a manner that increases burst swimming speed and the likelihood of predator escape. The predator-associated burst speed (PABS) ecophenotype is characterized by a small head and trunk and enlarged caudal region. Mechanisms promoting replicated phenotype-environment association include selection (without evolution), a single instance of adaptive evolution followed by biased habitat occupation, repeated instances of local adaptation, or adaptive phenotypic plasticity. Common garden rearing of mosquitofish, Gambusia affinis, demonstrated a likely heritable basis for PABS phenotypy, but it is unknown whether populations are otherwise genetically distinct or whether replicated ecophenotypy represents a single or replicated instances of adaptation. To genetically characterize the populations and test hypotheses of single or multiple adaptations, we characterized variation in 12 polymorphic DNA microsatellites in the previously studied G. affinis populations. Populations were genetically distinct by multilocus analysis, exhibited high allelic diversity, and were heterozygote deficient, which effects were attributed to G. affinis's shoaling nature and habitat patchiness. Genetic and phenotypic distances among populations were correlated for non-PABS but not PABS morphology. Multilocus analysis demonstrated ecophenotype polyphyly and scattered multivariate genetic structure which support only the replicated-adaptation model. As all of the diverse tests performed demonstrated lack of congruence between patterns of molecular genetic and PABS differentiation, it is likely that divergent natural selection drove multiple instances of adaptive evolution.

Behavioral Interactions between a Native and an Invasive Fish Species in a Thermally Heterogeneous Experimental Chamber

Mechanisms of the displacement of native fish by nonnative fish can include agonistic behaviors that push native fish species out of their preferred habitat, including their thermal optima. To examine these interactions, we built an experimental thermal preference chamber to evaluate: (1) the thermal preference of native, glacial relict northern redbelly dace Chrosomus eos; (2) if the thermal preference and movement changed in the presence of the invasive western mosquitofish Gambusia affinis; and (3) the direction of agonistic interactions. We hypothesized that G. affinis would express agonistic behavior toward C. eos, because G. affinis is widely recognized as an aggressive invader. Given the temperature range of the experimental chamber, i.e., 20–30 °C, C. eos selected an average of 24.3 °C as its thermal preference. After G. affinis’ introduction, the thermal preference of C. eos increased by 1.7 °C and the movement, given by distance (cm) travelled, increased by 21%. Contrary to our prediction, more agonistic interactions were observed in C. eos toward G. affinis. These results indicate that agonistic behavior of G. affinis toward native fish species may be species- and condition-specific, and may not always be the primary mechanism of native species’ displacement. Biological invasions are a global issue and altered thermal regimes are expected to continue. This study provided the novel approach using of a thermally heterogeneous thermal chamber to examine thermal preferences and aggressive interactions between a native and an invasive species. Future research should examine other life history traits that may be conveying the competitive advantage to G. affinis.