Populations Of Mosquitofish Research Articles

Chromosomal analysis of insecticide resistant and susceptible mosquitofish

The meiotic karyotypes of insecticide-resistant (R) and susceptible (S), and SR F1 mosquitofish were analyzed by preparing spread, silver-stained wholemounts of synaptonemal complexes (SC) from spermatocytes. The method reveals statistically significant differences in the relative length of certain SC's between susceptible and resistant individuals. However, careful study of SCs from SR F1 fish does not reveal detectable heterozygosity for chromosomal rearrangements. It is concluded that populations of SS and RR mosquitofish are geographically isolated and that minor karyotypIc differentiation has occurred. This differentiation may or may not be causally related to the acquisition of Insecticide resistance.

DISJUNCTIVE CLINE OF CRITICAL PHOTOPERIOD IN THE REPRODUCTIVE DIAPAUSE OF DROSOPHILA LACERTOSA.

EvolutionVolume 40, Issue 2 p. 418-421 Note and CommentFree Access DISJUNCTIVE CLINE OF CRITICAL PHOTOPERIOD IN THE REPRODUCTIVE DIAPAUSE OF DROSOPHILA LACERTOSA NOBUAKI ICHIJÔ, NOBUAKI ICHIJÔ Zoological Institute, Faculty of Science, Hokkaido University, Sapporo Hokkaido, 060 JapanSearch for more papers by this author NOBUAKI ICHIJÔ, NOBUAKI ICHIJÔ Zoological Institute, Faculty of Science, Hokkaido University, Sapporo Hokkaido, 060 JapanSearch for more papers by this author First published: March 1986 https://doi.org/10.1111/j.1558-5646.1986.tb00482.xCitations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume40, Issue2March 1986Pages 418-421 ReferencesRelatedInformation

Seasonal trends in body size of adult male mosquitofish,Gambusia affinis, with evidence for their social control

Collections from a natural population of mosquitofish,Gambusia affinis, in southern Indiana showed that males born early in the breeding season mature rapidly at a small body size, while males born later in the breeding season delay maturation and achieve larger body sizes. A field experiment, involving removal of males from pond populations, was conducted to test the hypothesis that delayed maturation by late summer males is, at least in part, under social control. Mean total length (TL) of adult and maturing males in late summer in ponds from which large numbers of males had previously been removed was significantly lower than mean TL of males in control ponds. These data support the hypothesis of social control and support Sohn's competition-predation hypothesis for control of adult male body size inGambusia.

Enzyme Levels in Natural Mosquitofish Populations

Adenosine deaminase (ADA), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) activity levels were measured in mosquitofish populations from contrasting natural environments. Significant differences in enzyme level, in the level of soluble protein, and in length and weight were observed among populations from different habitats. MDH and LDH activities were highest in running-water populations, whereas ADA was elevated in coastal environments. Still-water females were longer and weighed less than running-water females. The regression relationships of length vs. weight and protein vs. weight also varied significantly among populations. The proportion of enzyme activity variation which could be accounted for by habitat, location, or log length was not the same for the three enzymes, suggesting that biological and physical factors influence the activities of various enzymes in different ways.

BIOCHEMICAL GENETICS OF MOSQUITOFISH. IV. CHANGES OF ALLELE FREQUENCIES THROUGH TIME AND SPACE.

Gene frequency data from samples of Gambusia affinis populations at 76 localities across the Savannah River drainage were used to investigate temporal and spatial patterns in population genetic structure. Localities in the Par Pond system on the Savannah River Plant were sampled in 1971, 1977, and 1979. Allelic frequencies in these populations were generally stable through time, although significant temporal changes were observed among samples from Pond C, an impoundment receiving thermal effluent. Significant spatial heterogeneity in allele frequencies was observed on both microgeographic and regional scales. Populations within the Par Pond system were spatially subdivided at four of the five loci surveyed (mean FST = 0.051). Subdivision was even more pronounced when samples from across the Savannah River drainage were compared (mean FST = 0.196). A hierarchial analysis of gene diversity (GST ) demonstrated that most of the genic diversity across the drainage exists as within-subdivision diversity. Even when populations from such contrasting habitats as rivers, creeks, ponds, and reservoirs are compared, an average of only 13% of the total gene diversity was attributed to between-group diversity. Greatest between-group gene diversity was observed when reservoirs were compared with one another. This general pattern of low between-habitat diversity suggests that differential selection pressures are not playing a major role in producing the observed levels of subdivision. In the Par Pond system, neither single locus nor multilocus genetic distances were significantly associated with geographic distance or with its reciprocal. For samples from over the Savannah River drainage, significant correlations between genetic and geographic distance were observed only for the Gpi-2 and Pgm-2 loci. Thus, there was a general lack of concordance between genetic and geographic distances. Spatial autocorrelation demonstrated patterns consistent with Wright's isolation by distance model. Significant positive correlations in allelic frequencies among neighboring populations were observed for five of six alleles; allelic frequencies in more distantly separated populations were typically not correlated.

COAL ASH BASIN EFFECTS (PARTICULATES, METALS, ACIDIC pH) UPON AQUATIC BIOTA: AN EIGHT‐YEAR EVALUATION1

ABSTRACT Coal ash effluent effects including particulates, acidic pH excursions, elemental concentrations and bioconcentration in selected organisms have been studied as changes in water quality and densities of benthic macroinvertebrate and mosquitofish (Gambusia affinis) populations in a swamp drainage system over an eight‐year period. Three changes in the ash basin settling system were made between mid‐ 1973 and January 1982. Initial density of the aquatic biota was altered severely by heavy ash siltation, followed by acidic pH excursions and perhaps overall by elemental concentrations and bioaccumulation. Heavy ash siltation, followed by acidic Ph excursions (mean of 5.5, extreme of 3.5) after the addition of fly ash to the original settling basin system, had the most profound effect on biota. Dipterans (chironomids) and some odonates (Plathemis lydia and Libellula spp.) were resistant to heavy ash siltation, while mosquitofish, which showed no discernible responses to ash siltation, were absent at acidic pH, along with the few previously surviving invertebrate populations.Elemental concentrations of arsenic, cadmium, chromium, copper, selenium, and zinc did not appear to limit aquatic flora and fauna on a short‐term, acute basis. Long, chronic elemental exposures may have been instrumental in retarding the recovery of all forms of aquatic life in the receiving system. Elemental concentrations (except for arsenic and selenium) in the receiving system were generally one to two orders of magnitude higher than the Water Quality Criteria set by the U.S. Environmental Protection Agency (1980) for protection of aquatic life for the minimum and 24‐hour mean values. From collective elemental exposures in the receiving system, bioconcentration factors in macrophytes, invertebrates and fish were generally lower than those reported in the literature for laboratory, single elemental concentrations. By 1978, when the new settling basin systems were operating effectively, invertebrate populations were largely recovered, and mosquitofish populations recovered within one year afterward.

Notes on Fecundity of an Arrhenoid Population of Mosquitofish, Gambusia affinis holbrooki

Notes on Fecundity of an Arrhenoid Population of Mosquitofish, Gambusia affinis holbrooki

Heritability Estimates for Age and Length at Maturity in Two Populations of Mosquitofish that Shared Ancestors in 1905

Heritability Estimates for Age and Length at Maturity in Two Populations of Mosquitofish that Shared Ancestors in 1905

HERITABILITY ESTIMATES FOR AGE AND LENGTH AT MATURITY IN TWO POPULATIONS OF MOSQUITOFISH THAT SHARED ANCESTORS IN 1905.

Two broad methods can be used to infer selection pressures: direct observation of factors causing differential survival and fecundity in the field, and inference from estimates of heritabilities made in the laboratory. Where possible, both methods should be used, but for many species and many ecological situations, the laboratory method is more practical and is done first. This paper reports estimates of the heritability of two ecologically important traits, age and length at maturity, in two populations of mosquitofish (Gambusia afjinis: Poeciliidae) that shared ancestors in 1905. It also presents information on the significance of genetic effects on growth parameters in these two populations, and on age and length at maturity in an additional four populations. The use of quantitative genetics to investigate ecologically significant traits is a relatively recent development. Sokal (1970), Mertz (1975), Rose and Charlesworth (1980, 1981 a, 1981 b), Taylor and Condra (1980), Barclay and Gregory (1981), and Mueller and Ayala (1981) did selection experiments on flour beetles or fruit flies aimed at understanding the genetic relationship between longevity and fitness traits expressed early in life. Antagonistic pleiotropy is well-supported as the evolutionary mechanism leading to senescence in fruit flies (Rose and Charlesworth, 1980), and is consistent with results from flour beetles (Sokal, 1970; Mertz, 1975). These results suggest a second point that has been supported by other experiments. Dingle et al. (1977), Istock et al. (1976), Doyle (1981), Rez-

Biochemical Genetics of Mosquitofish. II. Demographic Differentiation of Populations in a Thermally Altered Reservoir

Mosquitofish (N = 7,580) from five sites along a thermal gradient in a reservoir were analyzed using electrophoretic techniques. Each sample was genetically different from the other four and none was in Hardy-Weinberg equilibrium for all loci. The populations also differed in their sex ratios and size structures. Juveniles tended to be less heterozygous than adults and heterozygotes tended to have longer body lengths than homozygotes within sex-age classes as indicated by single locus tests. Overall heterozygosity was highest in the population from the hottest water and lowest in those populations from the coldest water. Distributions of fish with different numbers of heterozygous loci were similar among sex-age classes within locations but significantly different for males and juveniles across locations. While stochastic processes are important in determining some of the genetic variation of the mosquitofish populations, selection is the probable explanation for the body length-genotype correlations and for the differences in genotypic proportions between males, females and juveniles.

Life History Variation among Experimental Populations of the Mosquitofish, Gambusia affinis

therodactylus. Quart. Jour. Florida Acad. Sci. 28: 375-391. TURNER, F. B., AND G. S. GIST. 1970. Observations of lizards and tree frogs in an irradiated Puerto Rican forest, p. E25-E50. In: A tropical rain forest. H. T. Odum (ed.). Division of Technical Information, USAEC TID-24270. erodactylus. Quart. Jour. Florida Ac d. Sci. 28: PUERTO RICO NUCLEAR CENTER AND SMITHSONIAN TROPICAL RESEARCH INSTITUTE, BOX 2072, BALBOA, PANAMA. PRESENT ADDRESS: (GED): OFFICE OF ENDANGERED SPECIES, US FISH AND WILDLIFE SERVICE, WASHINGTON, D.C. 20240. Accepted 2 Nov. 1982.

Phenol Tolerance in Populations of Mosquitofish from Polluted and Nonpolluted Waters

The phenol tolerances of three Alabama populations of mosquitofish Gambusia affinis were compared; two populations lived in industrially polluted streams and one in a nonpolluted lake. In 48-hour static tests, the median lethal concentration (LC50) of phenol was significantly higher for mosquitofish from a stream that received coke-treatment wastewater from a steel plant than for the other two populations. Especially at low phenol concentrations, most mortality occurred during the first few hours of exposure, indicating that some individuals were much more susceptible to phenol than others. Eight-hour assays of fish from the lake and the most polluted stream confirmed the presence of distinctly phenol-resistant and phenol-susceptible groups of fish. The differences in LC50 values for these two populations reflect differing proportions of resistant individuals. Resistant fish made up 67–80% of the polluted-stream population with the high LC50 and only 23–27% of the nonpolluted-lake population. Repeated nonlethal toxicity tests on individuals demonstrated that some fish are invariably susceptible and others show resistance at some times and susceptibility at others. Phenol resistance apparently depends on the induction of a genetically determined, rapidly acting detoxification mechanism. Received September 10, 1982 Accepted August 3, 1983

Survivorship and Parasite-induced Host Mortality among Mosquitofish in a Predator-free, North Carolina Cooling Reservoir

Survivorship of mosquitofish infected with the pseudophyllidean tapeworm Bothriocephalus acheilognathi was significantly reduced as compared with uninfected mosquitofish when fish were held at temperatures of 20, 25 and 30 C. Survivorship of infected and uninfected fish was also significantly reduced as water temperatures were increased to 25 and 30 C. When mosquitofish were maintained at 25 C, larger individuals with lower parasite densities survive longer than smaller individuals with higher densities of the cestode. Pearson correlation and multiple regression analyses of survival time of Gambusia affinis on density of Bothriocephalus acheilognathi and total host length indicate that survivorship is a function of parasite density and host size. Certain demographic characteristics of mosquitofish populations in a system devoid of piscivorous predators (but with B. acheilognathi) were compared with those in a system having piscivorous predators (but without B. acheilognathi). Random samples of mosquitofish taken monthly from the two systems revealed no significant differences in either sex ratios or in mean lengths of male or female mosquitofish. The Krumholz (1963) predation hypothesis would predict otherwise, to wit, that sex ratios in the predator-free system should be 1:1 (with predators, sex ratios should be approximately 1 male: 2 females) and that both males and females should be significantly larger than males and females in a system possessing a full complement of piscivorous fishes. It is hypothesized that similarities among demographic features of mosquitofish populations in the two systems investigated in the present study are the result of parasite-induced, size-selective host mortality in the predator-free system on the one hand and of predation pressure from piscivorous fishes on the other.

The Genetic Basis of Differences in Life-History Traits Among Six Populations of Mosquitofish (Gambusia affinis) that Shared Ancestors in 1905

The Genetic Basis of Differences in Life-History Traits Among Six Populations of Mosquitofish (Gambusia affinis) that Shared Ancestors in 1905

Size specific predation by herons and its effect on the sex-ratio of natural populations of the mosquito fish Gambusia affinis baird and girard.

Sex-ratios of Gambusia affinis populations in freshwater marshes in the Camargue (Rhône Delta), are highly biased in favour of males, whereas the sex-ratios in ditches are close to unity. Studies of the diet of free living birds and experimental studies on prey size selection in captivity show that the abnormal sex-ratios in marshes can be attributed to differential heron predation. Ditches are relatively free from predation. Mature female Gambusia are larger, and have an energy content 5-25 times greater than that of mature males. Handling times of Grey Heron (Ardea cinerea) and Little Egret (Egretta garzetta) are only slightly longer for female Gambusia than males. Hence, females represent a much more profitable prey.Analysis of nestling regurgitates show that Gambusia makes up a considerable proportion of the diet of four species of Camargue herons, and that the majority of Gambusia taken are females. Under experimental conditions, captive herons consume almost exclusively female fish, even when offered in ratios where they are heavily outnumbered by males.The relevance of these results to optimal diet theory is discussed.

A microsporidian infection in a natural population of mosquitofish, Gambusia affinis (Baird and Girard)

Abstract. A microsporidian parasite was found in a natural population of mosquitofish, Gambusia affinis, from southern California. The parasite, a Glugea sp, induced the formation of xenoma complexes in the mesenteries of infected fish. In cases of severe infection, the xenomas occupied the majority of the abdominal cavity and appeared to prevent efficient swimming. This report is an initial documentation of this infection and a description of some of the clinical signs observed.

Abnormal Expression of Secondary Sex Characters in a Population of Mosquitofish, Gambusia affinis holbrooki: Evidence for Environmentally-Induced Masculinization

Paper mill effluents are discharged into Elevenmile Creek at Cantonment, Escambia County, Florida. The total population of mosquitofish, Gambusia affinis holbrooki, inhabiting the stream below the effluent discharge exhibits abnormal sexuality. All females are strongly masculinized, displaying both physical secondary sex characters and reproductive behavior of males. Males exhibit precocious development of physical secondary sex characters and reproductive behavior. Elevenmile Cr. above the paper-mill effluent, as well as tributaries to this creek, all contain Gambusia with normal secondary sex characters. This evidence strongly suggests that some yet unidentified chemical or combination of chemicals associated with the paper-mill effluent exerts a strong androgenic effect upon this population. This constitutes the first report of possible environmentally-induced masculinization involving a total natural population of vertebrates.

MALADAPTATION IN A MARGINAL POPULATION OF THE MOSQUITO FISH, GAMBUSIA AFFINIS.

Field biologists commonly assume that the organisms with which they deal are well adapted-even optimally adaptedto local circumstances. Both Ehrlich and Raven (1969) and Endler (1977) have de-emphasized the role of gene flow in preventing large scale geographic differentiation and local adaptation. This paper documents a case in which gene flow may have prevented small scale local adaptation in one population of mosquito fish, Gambusia affinis. It carries two messages: field-workers should check the assumption that their study organisms are adapted to the local environment because that assumption does not always hold, and there are limiting cases involving high dispersal rates over short distances in which gene flow can overwhelm local selection pressures. Evidence that local populations are being maintained away from the locally optimum phenotype is rare. Camin and Ehrlich (1958) analyzed the banding patterns of water snakes (Natrix sipedon) on islands in Lake Erie. They showed that on the islands, where snakes were probably confined to a band of sandy substrate near shore by lack of water inland, patternless, light-colored snakes were most common. In contrast, on the mainland where water snakes inhabit wooded streams with darker, more complex substrates, richly patterned, dark-colored snakes predominated. However, a small proportion of the island snakes were patterned, and therefore maladapted to the local environment, an observation that

Tolerance of low oxygen stress in insecticide-resistant and susceptible populations of mosquitofish ( [formula omitted][formula omitted

The tolerance of low oxygen stress in insecticide-resistant and susceptible populations of mosquitofish ( Gambusia affinis ) was investigated. Dissolved oxygen was reduced chemically with formaldehyde and sodium sulfite treatment. Available oxygen was reduced physically through barriers, both by preventing oxygen exchange at the air-water interface and by preventing the fish from contacting the surface of the water. In all cases, the tolerance to low oxygen stress was reduced in the insecticide-resistant population compared to the susceptible population. The results indicate that although tolerance of pesticides in the resistant population has been dramatically increased by environmental selective pressures, tolerance to other stresses has not been concomitantly increased.

Recovery of Invertebrate and Vertebrate Populations in a Coal Ash Stressed Drainage System

The influence of coal ash effluent upon the densities of macrobenthic invertebrate and mosquitofish (Gambusia affinis) populations in a swamp drainage system was studied for a period of 50 mo. Density of the aquatic biota was periodically altered by three major perturbations: (1) heavy ash siltation from inefficient basin operation, (2) lowered pH from the fly ash addition, and (3) coal ash associated elemental concentrations. Siltation appeared to be most influential in reducing the invertebrate densities while low pH (mean change from 7.2 to 5.5, extreme of 3.5) was more effective in reducing mosquitofish populations and retarding the recovery of invertebrates. Dipterans (chironomids) and odonates (Plathemis lydia and Libellula spp.) were the invertebrates most tolerant to coal ash stress. Upon the completion of an efficient primary–secondary retaining basin system, most invertebrate groups in the swamp were able to recover to a level of abundance equal to or greater than that which existed 4 yr earlier. Key words: coal ash stress, heavy ash siltation, fly ash acidity, elemental accumulation, benthic macroinvertebrates, Gambusia affinis