Fish Gambusia Affinis Research Articles

Internal lethal concentration and internal lethal volume fraction of chlorobenzenes in mosquito fish ( Gambusia affinis)

The internal lethal concentration (ILC) and internal lethal volume fraction (ILVF) of a series of chlorobenzenes with mosquito fish ( Gambusia affinis) were measured by a semistatic test approach in closed jars. Their variation with exposure times were also investigated. With different aqueous chemical concentrations and different exposure periods, the measured ILC values on wet weight and lipid weight bases ranged from 3–12 mmol kg −1 and 46–208 mmol kg −1 lipid, respectively. Measured ILVF values covered a range from 0.008-0.025 (L toxicant L −1 lipid). These values are consistent with those found in literature. Generally ILC and ILVF values decreased with increasing exposure time with rate constants ranging from 0.03 to 0.33 day −1 (wet and lipid weight) for ILC and 0.03 to 0.31 day −1 for ILVF.

A new cacospongionolide inhibitor of human secretory phospholipase A2 from the Tyrrhenian sponge Fasciospongia cavernosa and absolute configuration of cacospongionolides.

A new inhibitor of human secretory phospholipase A2 (PLA2), cacospongionolide E (4a), has been isolated from the Tyrrhenian sponge Fasciospongia cavernosa. The structure was proposed on the basis of spectroscopic data and by chemical transformations. The absolute configuration of cacospongionolides 2a-4a was established using the modified Mosher's method. Cacospongionolide E was the most potent inhibitor toward human synovial PLA2, showing higher potency than the reference compound manoalide and exerting no signs of toxicity on human neutrophils. It showed high activity in the Artemia salina bioassay and moderate toxicity in the fish (Gambusia affinis) lethality assay.

Population assessment of the endangered Green and Golden Bell FrogLitoria aureaat Port Kembla, New South Wales

The Green and Golden Bell Frog Litoria aurea has declined dramatically in distribution and abundance in NSW during the last 20 years. We describe the dynamics of the population found at Port Kembla near Wollongong, New South Wales during 1994-6. This population was formerly widespread in the region but has contracted to just tour sites, all found within a distance of 5 km. We conducted detailed surveys at three of these sites and a preliminary survey at the fourth site. These surveys revealed that only two of the sites contained breeding habitat that may have any short-term security. One of these breeding sites (Coomaditchy Lagoon) contained high densities of the Mosquito Fish Gambusia affinis, however, tadpole survival and adult recruitment at this site appeared high. In January 1996, more than 400 metaporphlings were observed. Ten months later there was a substantial increase in the number of adult bell frogs present at the site. The other site where significant breeding occurred was within the BHP stee...

Effects of Halobenzenes on Growth Rate of Fish (Gambusia affinis)

The growth rate reduction of mosquito fish (Gambusia affinis) fry was investigated with a range of sublethal exposure levels of four halobenzenes for 42 days. These compounds were found to produce growth rate reduction in mosquito fish fry at concentrations as low as 0.30, 0.18, 0.025, and 0.010 μmol liter−1for 1,4-dibromobenzene, 1,2,3-trichlorobenzene, 1,2,4-tribromobenzene, and pentachlorobenzene, respectively. The aqueous exposure concentrations causing growth rate reduction of 50 and 10% (EC50and EC10, respectively) for the halobenzenes were 0.067–3.4 and 0.0042–0.32 μmol liter−1, respectively. The EC50and EC10values are within the ranges of 5 to 8% and 0.1 to 3.9% of the LC50values, respectively. The percentage of growth rate reduction relative to the LC50could possibly be used to describe chronic toxicity effects of organic compounds with the aquatic organisms. The internal concentrations obtained from the analysis for the halobenzenes were generally consistent with the calculated internal concentrations. The lipid-based internal concentrations that gave 50 and 10% growth rate reductions were 8.3–27 and 0.5–1.6 mmol kg−1, respectively. These values have a more limited range than the corresponding external aqueous concentrations. The quantitative structure–activity relationships between the internal concentrations at 50 and 10% growth rate reduction and physicochemical parameters were found to be less satisfactory than those based on external aqueous concentrations.

Structure and function of the axillary organ of the gulf toadfish, Opsanus beta (Goode and Bean).

The structure of the axillary organ of a batrachoidid species, the gulf toadfish (Opsanus beta Goode and Bean 1879), has been examined and several simple experiments designed to elucidate its function performed. Electron microscopy (EM) studies revealed cells and structures suggesting secretory and iono regulatory roles (e.g., abundant intracytoplasmic secretory particles, rough endoplasmic reticulum, sparse Golgi bodies, indented epithelial cells with microvilli, numerous endocytotic vesicles, etc.). Our physiological experiments allowed us to reach several conclusions: the organs do not excrete significant quantities of urea relative to other areas of the fish (head and gills), the organs do not secrete a substance that is toxic to a teleost test fish (Gambusia affinis), the secretions do not induce short-term modifications in locomotory activity of other gulf toadfish (e.g., by pheromonal means) and the secretions do not inhibit the growth of several species of microorganisms in culture. The function of the organ and its secretions remains unknown, representing a fertile area for research on structure and function in comparative physiology.

Genetic Ecotoxicology III: the Relationship Between DNA Strand Breaks and Genotype in Mosquito Fish Exposed to Radiation

DNA polymorphism in mosquito fish (Gambusia affinis), as revealed by RAPD (randomly amplified polymorphic DNA) and allozyme analysis, was compared to relative amounts of DNA strand breakage in blood and liver tissues. Mosquito fish were exposed to radionuclide contamination in situ and to X-rays in the laboratory. The types of RAPD metrics used were the number of RAPD bands per individual and the frequency of certain RAPD bands. In a previous study, it was noted that in some instances the number of RAPD bands and the frequency of certain RAPD bands were elevated in radionuclide-contaminated sites relative to reference sites. In the present study, it was found that the median molecular length (MML) of the DNA (which is inversely proportional to the amount of DNA strand breakage) was correlated in several cases to the number of RAPD bands per individual. In addition, for those RAPD bands that occurred at a higher frequency in mosquito fish from radionuclidecontaminated sites, DNA strand breakage was often lower for those fish with than without these RAPD bands. RAPD data obtained on mosquito fish exposed to X-rays in the laboratory paralleled those from the field. Furthermore, analysis showed that heterozygotes for the allozyme locus nucleoside phosphorylase were more prevalent in radionuclidecontaminated sites and had fewer DNA strand breaks than did homozygotes. These results provide additional evidence that changes in population genetic structure of mosquito fish exposed to a genotoxicant (radiation) can be detected at the DNA level.

Cavernosolide, a New Sesterterpene from a Tyrrhenian Sponge

Cavernosolide (3a), a new sesterterpene, has been isolated from the Tyrrhenian sponge Fasciospongia cavernosa. The structure was proposed on the basis of spectroscopic data and by chemical transformations. Cavernosolide showed potent activity (LC50 = 0.37 μg/mL) in the Artemia salina bioassay and a moderate toxicity (LC50 = 0.75 μg/mL) in a fish (Gambusia affinis) lethality assay.

Absolute Configuration of 2,6-Dimethylheptyl Sulfate and Its Distribution in Ascidiacea

2,6-Dimethylheptyl sulfate (1) was isolated for the first time from a marine ascidian from Policitor adriaticus Drasche (class Ascidiacea, order Aplousobranchiata, family Polycitoridae). In this work, the absolute stereochemistry at C-2 of 1 was determined by 1H-NMR analysis of its (+)- and (−)-methoxy(trifluoromethyl)phenylacetic acid (MTPA) esters (Mosher's method). The distribution of 1 was investigated among the three orders (Aplousobranchiata, Phlebobranchiata, and Stolidobranchiata) of the class Ascidiacea. Compound 1 showed cytotoxicity (LC50 = 17.8 μg/mL) in the Artemia salina bioassay and was not toxic (not toxicity at 100 μg/mL) in a fish (Gambusia affinis) lethality assay.

Bioconcentration of bromo- and chlorobenzenes by fish ( Gambusia affinis)

Bioconcentration factors, uptake rate constants ( k 1), and clearance rate constants ( k 2) were determined for bromo- and chlorobenzenes with the mosquito fish ( Gambusia affinis). The values of k 1 and k 2 on a lipid weight basis ranged from 3500 to 47,000 d −1 and 1.50 to 0.27 d −1, respectively. The rate constants exhibit good nonlinear correlations with the n-octanol/water partition coefficient ( K ow). The bioconcentration factors reach a maximum at pentachlorobenzene (log K ow = 5.2) and then decline. The bioconcentration factors on a lipid weight basis ( K BL) correlated well with K ow. The bioconcentration kinetics can be described by equivalent mass transfer models and experimental data indicate that the mass transfer process in the lipid phase is the rate-limiting step in the bioconcentration process.

Intermediate filaments in the testis of the teleost mosquito fish Gambusia affinis holbrooki: a light and electron microscope immunocytochemical study and Western blotting analysis

A light and electron microscope immunocytochemical study and Western blotting analysis has been performed on intermediate filaments (vimentin, desmin and cytokeratins) in the testis of the teleost fish Gambusia affinis holbrooki. An immunoreaction to vimentin was observed in the epithelium of the efferent ducts, testicular canal and their surrounding peritubular cells. Positive vimentin immunostaining was also observed in the cells located around seminiferous tubules (boundary cells), Leydig cells, interstitial fibroblasts, chromatophores, and blood vessel endothelial cells. In contrast to mammals, no vimentin immunoreactivity was found in the Sertoli cells. Immunoreactivity to desmin was weak in the epithelial cells of the efferent ducts and testicular canal and intense in the peritubular cells that surrounded these ducts. Desmin immunoreactivity was also observed in the seminiferous tubule boundary cells. The immunoreactivity was weak in the boundary cells that surrounded germ cell cysts containing spermatogonia or spermatocytes and intense in the boundary cells around cysts with elongated or mature spermatids. Immunoreactivity towards cytokeratins was observed only in testicular blood vessels. Cytokeratin immunolabelling was intense in the endothelium and weak in the vascular smooth muscle cells. No cytokeratin immunoreactivity was found in the Sertoli cells, germ cells, interstitial cells or in the efferent duct epithelium. The absence of intermediate filaments in the Sertoli cells, the absence of cytokeratins in the epithelium of the sperm excretory ducts, and the presence of desmin filaments in these epithelial cells are the most important differences with regards to the intermediate filament phenotype in mammalian testes.

Comparative evaluation of the larvivorous fish Gambusia affinis and Aphanius dispar as mosquito control agents

Under laboratory conditions Aphanius was more successful than Gambusia in preying upon the 3rd, 4th and pupal stages of mosquitoes. The reverse was found for the first two instars. However. Aphanius consumed more 2nd instar larvae under the cover of vegetation when larger fish were able to penetrate shallow water and feed on the mosquito larvae.

The testicular cycle of Gambusia affinis holbrooki (Teleostei: Poeciliidae)

Fifteen male mosquito fish (Gambusia affinis holbrooki) were collected in 1989 on the 15th of each month to perform a quantitative histologic study of the annual testicular cycle including a calculation of the gonadosomatic index, testicular volume, and the total volume per testis occupied by each germ cell type. The cycle comprises two periods: spermatogenesis and quiescence. The spermatogenic period begins in April with the development of primary spermatogonia into secondary spermatogonia, spermatocytes and round spermatids. In May, the first spermatogenic wave is completed and the testicular volume begins to increase up to June when the maximum testicular volume and gonadosomatic index are reached. Germ cell proliferation with successive spermatogenetic waves continues until August. In September germ cell proliferation ceases and neither secondary spermatogonia nor spermatocytes are observed. However, spermiogenesis continues until October. In November, spermiogenesis has stopped and the testis enters the quiescent period up to April. During this period only primary spermatogonia and spermatozoa are present in the testis. In addition, a few spermatids whose spermiogenesis was arrested in November are observed. Testicular release of spermatozoa is continuous during the entire spermatogenesis period. The spermatozoa formed at the end of this period (September‐October) remain in the testis during the quiescent period and are released at the beginning of the next spermatogenesis period in April. Developed Leydig cells appear all year long in the testicular interstitium, mainly around both efferent ducts and the testicular tubule sections showing S4 spermatids.

Alterations in zooplankton community structure after selenium-induced replacement of a fish community: a natural whole-lake experiment

Most of the fish species in Belews Lake, a cooling reservoir in the Piedmont area of North Carolina (USA), were eliminated in 1976–77 because of selenium poisoning. Zooplankton samples collected in 1974–75, prior to the fish kill, when the lake's fauna included a regionally-typical assemblage of piscivores and planktivores at a density of 14000 ha−1, were compared to those collected in 1984–86, when the piscine community was dominated by three planktivorous fish (Notropis lutrensis, Pimephales promelas and Gambusia affinis) at a density of 28000 ha−1. Zooplankton diversity was similar in 1984–86 compared to that in 1974–75. However, densities of the predominant cladocerans (Bosmina longirostris, Pseudosida bidentata, Ceriodaphnia pulchella, Holopedium amazonicum, Daphnia parvula, D. ambigua) and copepods (Diacyclops thomasi, Mesocyclops edax, Tropocyclops prasinus, Skistodiaptomus pallidus, S. reighardi) declined, though the magnitude of the reduction was greatest for the cladocerans and S. reighardi. Densities of copepod nauplii and rotifers also decreased markedly. No colonizations or extinctions of crustacean species occurred between 1975 and 1986. Thus, while crustacean species richness (n = 18 species) remained the same, the relative proportions of individual species changed dramatically, most notably among the Cladocera. The observed changes in crustacean species densities and dominance are attributed to the replacement of the regionally-typical fish fauna by one consisting primarily of planktivores.

Alarm reaction and alert state inGambusia Affinis (Pisces, Poeciliidae) in response to chemical stimuli from injured conspecifics

We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to mechanical and visual fright stimuli.

Genetic variation at the Pgi locus in the mosquito fish Gambusia affinis (Poecilidae) and a possible effect on susceptibility to an insecticide

Although some studies have been completed on genetic variation in relation to tolerance to heavy metals, none have considered pesticide pollution. This study examines the relationship between genotypes at the glucose phosphate isomerase (Pgi) locus in Gambusia and susceptibility to the organophosphate insecticide chlorpyrifos. Laboratory toxicity tests show significant differences in genotype frequencies between susceptible and tolerant groups offish from one site but not at others. A field survey examined genotype frequencies and levels of pesticide in the fish at seven sites. No chlorpyrifos was found at any of the sites, but a number of organochlorines were recorded. Significant correlations were found between three organochlorines (DDT/DDD, DDE and lindane) and frequences of particular genotypes. There were also significant differences in tolerance between populations and between size classes. These results are discussed in relation to previous work with heavy metals.

Toxicity of a soluble peptide from Microcystis sp. to zooplankton and fish

SUMMARY. A soluble cell fraction lethal to Daphnia magna was isolated by the disruption of net phytoplankton from eutrophic Aculeo Lake. The phytoplankton of this lake is dominated by Microcystis sp. The soluble fraction was also lethal to common native zooplankton, including the rotifers Keratella sp., Trichocerca similis, the copepod Boeckella sp., and the cladoceran Chydorus sphaericus. In addition, a partially purified soluble component of the lethal fraction caused the death of the fish Gambusia affinis. The specific toxicity of the soluble fraction from phytoptankton varied four‐ to six‐fold seasonally with peaks during periods of warm temperature. Our results suggest that releases of a toxic peptide from Microcystis sp. may be the cause of massive fish kills at the study site, Aculeo Lake.

Life‐history patterns of the mosquito‐fish, Gambusia affinis, in the estuary of the Guadalquivir river of south‐west Spain

SUMMARY. 1. The age, growth and reproduction of the small, introduced fish Gambusia affinis (Baird & Girard, 1853) were studied in the estuary of the Guadalquivir river.2. The life‐span was very short, the stock contained only two age groups: with annulus (1+ group; 10–12 months old) and without annulus (0+ group).3. In both sexes growth restarted in April when the annulus appeared, but whilst 1+ males stopped growth, 1+ females grew steadily to June. Growth of 0+ spawners was only evident in September, the last month of the reproductive period. A differential growth rate between sexes was also evident.4. 1+ specimens reproduced during May and June and their offspring from July to September. In both age groups somatic condition progressively declined during the spawning period.5. The loss of condition and the disappearance of 1 + and the larger 04‐specimens after reproduction may indicate the cost of a prolonged high level of reproductive effort.6. The total fecundity (taken as the number of embryos) of 1 + females was represented by the formula: Fec=5.08 T.L. (mm) ‐170.07 and that of 0+ specimens by: Fec=2.23 T.L. (mm) ‐42.92. The maximum average monthly fecundity was reached in June when the length of the mother was at its greatest.7. Length at first maturity was smaller in 0+ group than in the 1 + group; the difference between the two groups was greater in males (≅5 mm, T.L.) than in females (≅3 mm, T.L.). Also the average total length of 14‐spawners was greater than 0+ spawners. There were significant differences in the overall sex ratio of 956 males to 2057 females.8. The differences found in growth and reproduction between the two age groups suggest that life‐history tactics may vary not only between different stocks but also within the same stock among its different components.

Parental care and foraging ability in male water bugs (Belostoma flumineum)

The predatory water bug Belostoma flumineum is one well-known insect example of male parental care. Male water bugs, while brooding eggs, may suffer several potential costs. These include the following: energetic costs, increased vulnerability to predation, and decreased foraging ability. We conducted investigations to determine whether encumbered males exhibited decreased foraging ability on two different prey types: fast moving fish (Gambusia affinis) and slower moving snails (Physella virgata virgata). Encumbered males encountered and captured snails at the same rate as did unencumbered males and females; however, encumbered males were less likely to encounter and capture the more mobile Gambusia than were unencumbered males and females. These results demonstrate that the magnitude of parental care costs in Belostoma depends in part on the relative abundance of sessile and mobile prey.

Ecological studies on the mosquito fish, Gambusia affinis for encephalitis control with special reference to selective feeding on mosquito larvae and competition with the medaka, Oryzias latipes.

The mosquito fish (Gambusia affinis) that was transferred to Tokushima City, Tokushima Prefecture in 1969 was studied in relation to the control of mosquitoes. A number of the fish were collected at several ponds and ditches where the fish had increased in number and were repeatedly released into swamps, sewers, fallow rice fields, etc. They were established in 7 places in 1970, 36 in 1971, 76 in 1972 and 104 in 1973. In 27 of those places, both the medaka (Oryzias latipes) and mosquito larvae co-existed, but after the establishment of Gambusia in these places, no mosquito larvae were found. The population density of Oryzias became low and that of Gambusia increased. The water areas with high densities of Gambusia were still or had an inflow of household waste water causing eutrophy. When Gambusia and Oryzias were found together in a water area, the total number of fish was as large as 400-500 per 1 m2. The result from laboratory observations demonstrated that Gambusia prey on more mosquito larvae than Oryzias. If Gambusia were raised together with Oryzias in the same water tank, Gambusia attacked and eventually exterminated Oryzias. The feeding habits of Gambusia and Oryzias depend on the availability of food in the environment and are highly variable. It was shown that both species are involved in the competition for space and food in connection with their ecological niche. The above results indicated that Gambusia is more suitable for the control of mosquito larvae than Oryzias. In fact, it was observed that Gambusia became more predominant and more expansive in its habitat in the water areas examined.

Life-Cycle and Biology of Prototransversotrema-Steeri Angel, 1969 (Digenea, Transversotrematidae)

A population of Prototransversotrema steeri Angel, 1969 is recorded from the introduced fish Gambusia affinis and the native species Pseudomugil signifer and Mugil cephalus in fresh water in Queensland, Australia. Adults of P. steeri are considerably smaller than adults previously described from marine fish. This appears to be a host-related phenomenon, possibly reflecting the size of the subscale niche offered by the host. The intermediate host is Posticobia brazieri, a hydrobiid snail. It is suggested that different hydrobiid snails may act as intermediate hosts in other parts of Australia. The miracidium develops into a mother sporocyst which produces a single mother redia. Mother rediae produce daughter rediae which may produce further daughter rediae or cercariae. Cercariae emerge from the redia while still embryonic and develop independently in the tissues of the snail. Upon emergence the cercariae attach directly to the definitive host and commence egg-production within 6 days. Gambusia affinis, Xiphophorus rnaculatus, X. helleri, Craterocephalus marjoriae and Mugil cephalus were all infected experimentally. I discuss various theories concerning the phylogenetic position of the Transverso- trematidae within the Digenea and conclude that the family occupies an isolated position not closely allied with any other group.