Fish, mosquito

In freshwater studies, mosquito fish, catfish, and freshwater eels were exposed to endosulfan in static tests. Maximum tissue concentrations in mosquito fish (933 pg/kg a-isomer) were found in fish exposed to 16 pg technical-grade endosulfan/L for 24 hours. The maximum tissue concentrations in fish exposed to 2 pg technical-grade endosulfan/L for 7 days was 143 pg a-isomer/kg. Mean endosulfan residues in... 

Hughes, J.M., D.A. Harrison, and J.M. Arthur. 1991. Genetic variation at the Pgj locus in the mosquito fish Gambusia affinis (Poecilidae) and a possible effect on susceptibility to an insecticide. Biol. Jour. Linnean Soc. 44 153-167. 

Batel, R., N. Bihari, B. Kurelec, and R.K. Zahn. 1985. DNA damage by benzo[a]pyrene in the liver of mosquito fish Gambusia affinis. Sci. Total Environ. 41 275-283. 

Application of radiolabeled mirex to plants grown in a terrestrial/aquatic laboratory model ecosystem indicated that when the plant leaves were eaten by caterpillars, the aquatic system became contaminated. Mirex was detected in all segments of two aquatic food chains (alga > snail and plankton > daphnia > mosquito > fish) within 33 days. Undegraded mirex contributed to over 98.6, 99.4, 99.6, and 97.9% of the radiolabel in fish, snails, mosquitoes, and algae, respectively. No metabolites of mirex were found in any of the organisms (Francis and Metcalf 1984 Metcalf et al. 1973). 

Sanborn, et al. (13) reported that mosquito fish liver mic-rosomes gave rise to the monoester as a metabolite from dioctyl phthalate and that this metabolism was blocked by paraoxon. 

Molinate (S-ethyl hexahydro-azepine-l-carbothioate) has been widely used for broadleaf and grass weed control in rice culture. The 96-hour LC50 of technical molinate in the common goldfish is 30 ppm (1) and the medium tolerance limits (LTm) for molinate in mosquito fish (Gambusia affinis) are 16.4 ppm for 96 hours (J2). Kawatsu (3) estimated the 20-day lethal concentration of molinate in Japanese carp (Cyprinus carpio) var. Yamato koi at 0.18 ppm. However, there was no toxic effect of molinate on American carp at concentrations of 10 ppm during a two-week observation (40. ... 

In a model aquatic ecosystem, methoxychlor degraded to ethanol, dihydroxy ethane, dihy-droxyethylene, and unidentified polar metabolites (Metcalf et al, 1971). Kapoor et al. (1970) also studied the biodegradation of methoxychlor in a model ecosystem containing snails, plankton, mosquito larvae, Daphnia magna, and mosquito fish Gambusia affinis). The following metabolites were identified 2-(/5-methoxyphenyl)-2-(p-hydroxyphenyl)-l,l,l-trichloroethane, 2,2-bis (p-hydroxyphenyl) -1,1,1 -trichloroethane, 2,2-bis (p-hydroxyphenyl) -1,1,1 -trichloroethylene,... 

EC50 (growth reduction) for mosquito fish Gambusia affini 37 nmol/L (Chaisuksant et al., 1998). 

LC50 (96-h) for bluegill sunfish 250 jg/L (Spehar et al., 1982), mosquito fish Gambusia affini 0.80 pmol/L (Chaisuksant et al., 1998) for Poecilia reticulata 135 pg/L (van Hoogen and Opperhuizen, 1988), Gyprinodon variegatus 800 ppb using natural seawater (Heitmuller et al, 1981). 

Concentrations that reduce the fertility of Daphnia magna in 2 wk for 50% (EC50) and 16% (ECie) of the population are 0.20 and 0.08 mg/L, respectively (Calamari et al., 1983). An EC50 value 540 nmol/L for growth rate reduction was determined for mosquito fish (Chaisuksant et al, 1994). 

Juveniles (elvers) of the European eel [Anguilla anguilla) migrate upstream in rivers. To test whether they might follow conspecific odors, elvers were taken from the Arno river in Italy and exposed to water in which other juvenile eels had lived for 8 months. They were attracted to this stimulus much more than to uncontaminated water or water from mosquito fish (Pesaro et ah, 1981). 

Odors can have delayed and unexpected effects. Garter snakes, T. sirtalis, were presented with either live earthworm or mosquito fish, Gambusia affinis, in a screen-covered bowl for several days. One day after transferring the snakes individually to a box free of prey odors, they were tested with aqueous extracts of fish and worms on cotton swabs. Snakes exposed to fish odor attacked fish extract less, and those exposed to worm attacked worm odor less. This is interpreted as habituation with a possible switch to other prey. This also demonstrates that in any experiment with chemical cues an odor not experienced for 22 hours may still have an effect (Burghardt, 1992). 

Mosquito fish Chain pickerel Esox Mucus coat of Swim to upper George, 1960... 

Mosquito fish, Gamhusia affinis, are being released into freshwater bodies to control mosquitoes. It appears that chemicals from the fish warn the mosquitoes and they avoid laying their eggs in ponds with these fish. The number of mosquito larvae reduced as more fish chemicals (2 liter/day from pools with mosquito fish) were added to outdoor pools in North Carolina. The problem is that if mosquitoes avoid stocked pools, the efforts to control these insects with fish may fail (Angelon and Petranka, 2002). 

Umbraculumin C (90), characterized by the presence of a trans-3-(methylthio)-acrylic acyl residue, is a diacylglycerol obtained from the skin of the opisthobranch mollusc Umbraculum mediterraneum [96]. Taylor and co-workers determined the absolute configuration of 90 by total synthesis [97] while Sodano et al. reached the same conclusion by derivatisation of the natural compound [98]. Compound 90 displayed ichthyotoxic activity against the mosquito fish at 0.1 pg/ml and should represent the deterrent of this organism against predators [96]. 

The development of strains resistant to insecticides is an extremely widespread phenomenon that is known to have occurred in more than 200 species of insects and mites, and resistance of up to several 100-fold has been noted. The different biochemical and genetic factors involved have been studied extensively and well characterized. Relatively few vertebrate species are known to have developed pesticide resistance and the level of resistance in vertebrates is low compared to that often found in insects. Susceptible and resistant strains of pine voles exhibit a 7.4-fold difference in endrin toxicity. Similarly pine mice of a strain resistant to endrin were reported to be 12-fold more tolerant than a susceptible strain. Other examples include the occurrence of organochlorine insecticide-resistant and susceptible strains of mosquito fish, and resistance to Belladonna in certain rabbit strains. 

Figure 26.5 Indirect toxicity of kraft pulpmill effluent to mosquito fish. Phytosterols in the mill effluent are converted to C19 steroidal androgens through the action of microorganisms in the environment. These androgens masculinize both anatomy and behavior of female mosquito fish. An arrow identifies the modified anal fln on the masculinized female.

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