Fish Gambusia Affinis Research Articles

The Suprapopulation Dynamics of Bothriocephalus acheilognathi in a North Carolina Reservoir: Abundance, Dispersion, and Prevalence

A 2 1/2-year study (September 1980-March 1983) of abundance, dispersion, and prevalence of the pseudophyllidean cestode, Bothriocephalus acheilognathi, in 3 species of fish (Gambusia affinis, Notropis lutrensis, and Pimephales promelas) was conducted in 3 ecologically distinct areas of a North Carolina cooling pond. Mean infrapopulation density and prevalence differed by site, season, and species and size of hosts. Degree of aggregation and abundance and prevalence of gravid worms differed by species of host. Abundance of gravid worms was significantly lower in metapopulations from localities that received power plant effluents. The differences in infrapopulation density, prevalence, and aggregation appeared to be related to predator-prey interactions, which varied with season and local community structure. Differences in abundance of gravid worms, on the other hand, were probably caused by differential suitability of hosts and by local variation in selenium concentration in the water column. Thus, it appears that both biotic and abiotic components of the host community determined the suprapopulation dynamics of B. acheilognathi in Belews Lake.

Acute toxicity of some hydrazine compounds to salamander larvae, Ambystoma spp.

Although hydrazine compounds have been used extensively by industry for a very long time, they have become important in recent years as propellants for aerospace operations. The study of hydrazine compounds in this laboratory began about two decades ago and developed into a large pharmacological and toxicological research program that included also environmental considerations. Subsequently, acute toxicity studies were conducted on the common guppy (Lebistes reticulatus Peters) using four hydrazine compounds of interest. The toxicity of these propellants were evaluated next on other species of aquatic organisms such as mosquito fish (Gambusia affinis) and amphibians. Two different studies were conducted on amphibians: One utilized amphibian eggs and the other amphibian larvae. The larvae of spotted and marbled salamanders (Ambystoma maculatum and A. opacum, respectively) were used primarily in numerous static bioassays to determine the acute toxicity of hydrazine, UDMH and Aerozine-50 on these organisms. The remaining larvae were used in other tests mainly to corroborate previous experimental results (e.g., to see whether toxicity is affected by organism size, aeration of test solutions, and water hardness). The results on the larvae are presented in this paper.

Cannibalism, Food Availability, and Reproduction in the Mosquito Fish (Gambusia affinis): A Laboratory Experiment

The relationship between food availability, cannibalism, and reproduction was investigated experimentally in the live-bearing fish Gambusia affinis. A two-way factorial design was used, with juvenile conspecifics (present or absent) and food (high, variable, or low) as the treatment variables. The results show a significant effect of food level on the occurrence of cannibalism. Cannibalism in turn has an interesting influence on reproductive output. Reproductive output is significantly different between groups in which the incidence of cannibalism is low (high-food treatment). Here, fish in the juveniles-present treatment have a much lower output than fish in the juveniles-absent treatment. The hypothesis that cannibalism allows the maintenance of a prior reproductive commitment when food availability declines is supported by trends in the data, but these patterns are not statistically significant. In Gambusia, cannibalism appears to provide the individual with a means of reducing the negative effects of competition for food on reproductive output. Hence, cannibalistic behavior may have important demographic consequences when it occurs in a natural population.

DNA damage benzo[α]pyrene in the liver of mosquito fish Gambusia affinis

Exposure of Gambusia affinis to water containing different concentrations of benzo[α]pyrene (bαP) causes an increase in benzo[α]pyrene monooxygenase (BPMO) activity which reaches a maximum on the second day. Concomitantly, the DNA is altered in such a way that nuclease S 1-sensitive sites (SSS) become measurable. The size distribution of liver DNA treated with nuclease S 1 in control fish shows two populations of DNA by length, with means of 30 × 10 6 and 60 × 10 6 Daltons, respectively. In fish treated with 100 ppb BαP, the population with longer molecules of DNA disappears and shorter molecules increase in number. This may be explained in terms of the introduction of an additional 0.31–0.46 DNA nicks per control DNA molecule caused by metabolically activated BαP derivatives.

Site selection and attachment duration of Anodonta woodiana (Bivalvia: Unionacea) glochidia on fish hosts

The relationship between parasitic glochidia of Anodonia woodiana (Unionidae: Anodonti‐nae) and potential fish hosts was investigated in the laboratory. Intensity of parasitism was highest on the exotic fish Gambusia affinis, lower on the native species Puntius semijascio‐latus and Metzia takakii, and least on Rhodeus sinensis. Glochidia generally attached at fin margins, particularly the pectorals and caudal. In Gambusia affinis, the incidence of glochidia on the pectorals was higher than would be expected on the basis of ratios between fin margin lengths. Apparently, the role of the pectoral fins in locomotion makes them more liable to glochidial contact, thereby increasing their susceptibility to attachment.The duration of glochidial attachment was shortened as temperatures increased. Mean values ranged from 14‐4 days at 15°C to 6 days at 27°C. At 33°C glochidia rapidly detached and metamorphosis was unsuccessful. Significantly, water temperatures in A. woodiana habitats in Hong Kong rarely exceed 30°C.

Fast ephemeral DNA damage upon BβP injection

Injection of high concentrations of benzo[α]pyrene (10–125 μg BαP/g body weight) into young frogs ( Xenopus laevis), fish ( Gambusia affinis) or tissue culture cells (L 5178 Y) in a state of logarithmic growth causes alterations in DNA. In frogs these alterations reach a maximum at 60–90 min after application, then they decrease and become undetectable after 3 h. Within 8–12 days after the single BαP dose, a new wave of DNA alterations can again be detected. Parallel measurements of mixed function oxygenases (MFO) showed no short term activity changes within the first day. There was, however, an increase of activity starting on the 8th day following injection in frogs, and lasting until day 14. DNA alterations have been assessed by two methods. One is a modification of the alkaline filter elution method of Kohn et al. (1976) and is believed to determine the number of events leading to single strand breaks at alkaline pH. The other method determines the number of S 1 nuclease sensitive sites in highly purified native DNA. Both results were found to be highly correlated. The effect does not seem to be caused by an impurity, unless an unknown, very minor, and extraordinarily active component is present. The effect in frogs is linked to nutritional status. Frogs fed a carbohydrate-rich, protein-poor diet do not give the fast response. The fast effect cannot be blocked by application of Actinomycin, Cordycepin, and Chloramphicol injected either 30 min before or simultaneously with the B aP. Benzo( e)pyrene, a non-tumorigenic isomer of B aP, does not cause any effects at similar doses.

Transformation of soft coral (Coelenterata: Octocorallia) terpenes by Ovula ovum (Mollusca: Prosobranchia)

The faecal pellets from specimens of the prosobranch mollusc Ovula ovum found feeding on the soft coral Sarcophyton sp. at Eclipse Island, Palm Island Group (18°46′S; 146°33′E) in November 1980 were analysed. The only terpene present in the faeces, 7,8-deoxysarcophytoxide, differed from the major constituent of the soft coral, sarcophytoxide, suggesting that the latter had been transformed into the former within the cowrie. This transformation is not trivial, and could not be produced simply by acid catalysis. Subsequent analysis of tissues dissected from different regions of O. ovum indicates that the transformation is probably effected by enzymes in the digestive diverticula stomach region of the prosobranch. The transformed compound is significantly less toxic to the mosquito fish Gambusia affinis Baird and Girard than the ingested compound.

Genetic Determination of Offspring Size in the Guppy (Poecilia reticulata)

Interpopulation differences in offspring size of guppies are closely associated with interpopulation differences in predation on guppies (Reznick 1980; Reznick and Endler 1982). In one class of localities, where guppies produce relatively large offspring, the killifish Rivulus hartii is the only potential guppy predator. Ten percent of the Rivulus examined by Seghers (1973) had eaten one or more guppies and they ate predominantly small, immature size classes. At a second class of localities, where guppies produce relatively small offspring, guppies co-occur with the pike cichlid Crenicichla alta and a variety of other potential predators. These predators prey selectively on large, mature size classes of guppies and exert higher overall levels of predation in comparison to Rivulus hartii (Seghers 1973; Liley and Seghers 1975; J. A. Endler, personal communication). These predation patterns are also associated with other guppy life history differences; guppies from Crenicichla localities mature at an earlier age and tend to have higher reproductive efforts than guppies from Rivulus localities (Reznick 1980; Reznick and Endler 1982). An experimental study of similar interpopulation differences in offspring size in the live-bearing mosquito fish Gambusia affinis revealed that offspring size is determined by the genotype of the mother (Reznick 1981). The paternal (P1) genome made no contribution to F1 offspring size but, in contributing to the F1 female genotype, helped to determine the size of F2 offspring. This delayed inheritance was named the grandfather effect and is believed to be a by-product of ovoviviparous reproduction. Female Gambusia fully provision eggs prior to fertilization and make little or no energy investment in the young during development other than to carry them until birth. Offspring weight is thus determined prior to the expression of the paternal genome. However, since the P1 males contributed to the genotype of F1 females, they also partially determined the size of the ova produced by these females and hence the weight of F2 offspring. Because guppies also appear to be ovoviviparous (Thibault and Schultz 1978; Reznick 1980), they should display a similar grandfather effect. The following

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.

Accumulation and retention of mirex by brook trout fed a contaminated diet.

The detection of high levels of mirex in Lake Ontario fish has raised many questions regarding the utilization of this fishery for the present and future. Continuous monitoring programs, including trend analysis, are presently being conducted, but whether salmonids such as lake trout, Salvelinus namaycush, can effectively eliminate mirex is not known. IVIE et al. (1974) found that mosquito fish (Gambusia affinis) fed a diet containing 50 ppm mirex for 15 days contained 24 ppm mirex after that period. After being placed on clean feed for 130 days, the residues had dropped to 13 ppm, and the researchers reported that the half-life was, therefore, 130 days. LOWE et al. (1971) reported that the body burden of mirex in pinfish (Lagodon rhomboides) dropped from 30-40 ppm to 18 ppm after an elimination time of 56 days.

Wildlife Hazards from Furadan 3G Applications to Rice in Texas

Mortality of birds, fish, frogs, crayfish, earthworms, and nontarget insects occurred in rice fields after treatments of Furadan 3G granules in 3 Texas counties in 1970 and 1973-75. Three western sandpipers (Ereunetes mauri), 1 pectoral sandpiper (Erolia melanotos), and 2 red-winged blackbirds (Agelaius phoeniceus) were found dead or moribund between 17 and 24 hours after treatment. Cricket frogs (Acris crepitans blanchardi) were intoxicated 15 minutes post-treatment, and mosquito fish (Gambusia affinis) showed effects 1 hour post-treatment. Mortality of mosquito fish, Gulf menhaden (Brevoortia patronus), Atlantic croaker (Micropogon undulatus), and European carp (Cyprinus carpio) usually occurred between 24 and 28 hours after treatment. Mortality of frogs, crayfish, and nontarget insects generally occurred in rice field water between 1 and 45 hours after treatment. Mortality of earthworms in soil persisted for 52 hours. As a replacement for aldrin in Texas rice fields, Furadan 3G appeared to cause less mortality of birds than aldrin, but Furadan 3G was toxic to birds, fish, and invertebrates. J. WILDL. MANAGE. 44(1):190-197 When the U.S. Environmental Protection Agency suspended aldrin treatment of rice seed in 1974, aldrin was replaced with the systemic carbamate Furadan for control of rice-water-weevil larvae (Lissorhoptrus oryzophilus) in Texas. In rice fields, aldrin caused mortality of fulvous whistling ducks (Dendrocygna bicolor) and 31 other avian species (Flickinger and King 1972). Furadan is the registered trade name for insecticidal formulations of carbofuran (2,3-dihydro-2,2-dimethyl7-benzofuranyl methylcarbamate). The name Furadan is used predominately in the field, whereas carbofuran (the common name) accepted by the American Standards Association has become the accepted name in laboratories. The names Furadan and carbofuran have been used interchangeably (Niagara Chemical Division, FMC Corporation, unpubl.). Furadan, a systemic insecticide, can be applied to the soil and absorbed and translocated by the rice plant. Furadan 3G granular (3% carbofuran in sand core granules) and Furadan 2G granular (2% arbofuran) were tested in rice fields in Louisiana by the manufacturer in 1969. Furadan 3G granular treatments for ricewater-weevil control began in 1970 and eventually replaced aldrin in Texas. Fulvous whistling ducks feed and nest in rice fields and have been listed as endangered since 1972 by the Texas Organization for Endangered Species. In acute oral tests, 98.8% pure Furadan was highly toxic to fulvous whistling ducks (LD5s 0.238) and mallards (Anas platyrhynchos) (LD5o 0.397). One part per million of 98.8% pure Furadan in drinking water was toxic to fulvous whistling ducks in 7-day exposure tests (Tucker and Crabtree 1970). Formulations stronger than Furadan 3G were highly toxic to several species of waterfowl when applied to field crops in the United States and Canada. Furadan 10G granular (10% carbofuran) applied to vegetables reportedly killed about 1,400 ducks, largely green-winged 190 J. Wildl. Manage. 44(1):1980 1 On leave from the University of Illinois. This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 05:12:01 UTC All use subject to http://about.jstor.org/terms WILDLIFE HAZARDS FROM FURADAN 3G ? Flickinger et al. 191 teal (Anas carolinensis), mallards, pintails (A. acuta), and American wigeon (A. americana) in British Columbia from 1973 to 1975 (P. Whitehead, Canadian Wildlife Service, pers. comm.). Stickel (1975) reported that carbofuran (Furadan 4F flowable--40.65% carbofuran) foliar application to alfalfa killed 2,450 wigeon at 1 California locality in 1974. Furadan 4F flowable applied to alfalfa caused the death of 500 Canada geese (Branta canadensis) in southern Oklahoma in February 1976 (E. Jamison, U.S. Fish and Wildlife Service, pers. comm.), 1,000 American wigeon in Kansas in spring 1976 (U.S. Environmental Protection Agency, unpubl.), and over 1,063 wigeon in California in 1976 and 1977 (A. Bishoff, California Department of Fish and Game, pers. comm.). Our purpose is to present the comparative hazards of applications of Furadan 3G and aldrin (which Furadan 3G replaced) to wildlife that feed in and near treated rice fields along the Texas Gulf Coast. We thank A. Anderson of Wharton County, T. Pirtle and H. Rawlings of Brazoria County, and T. Thomas and J. Kasmierski of Colorado County, Texas, for permitting us to conduct the study in rice crops on land that they managed. We thank E. Hill and D. White, Patuxent Wildlife Research Center, U.S. Fish and Wildlife Service, for review of the manu-

Effects of Early Feeding Experience on Chemical Preference of the Northern Water Snake, Natrix s. sipedon (Reptilia, Serpentes, Colubridae)

Motion picture analyses of tongue flicking behavior by 15 neonate northern watersnakes (Natrix s. sipedon) to chemical extracts were used to investigate possible evidence for: (1) increased tongue flicking to air-borne chemicals; (2) modificaton of chemical preference by early feeding experience; (3) a relationship between the number of tongue flicks per extract and the mean flick duration. A novel technique for presenting only air-borne chemical extracts without any visual cue indicated more tongue flicking by s. sipedon to air-borne odors of frog extract than to a distilled water control. Early feeding experience had no effect on subsequent chemical preference. Natrix s. sipedon demonstrated a preference for extracts from a sympatric species of frog (Rana sylvatica) but not for extracts from a nonsympatric species of fish (Gambusia affinis), regardless of being fed exclusively on either this species of frog or fish or on earthworm (Lumbricus terrestris). This finding supports the hypothesis that newborn snakes show innate preference for sympatric species of normally eaten prey, and further suggests that this preference predominates over the effect of early feeding. A significant correlation between increasing number of tongue flicks and increasing mean flick duration was found only for presentations of distilled water. A relationship between increased number of tongue flicks and longer flick duration for preferred odors may be masked, since these

Laboratory studies on food intake, growth and conversion efficiency of Palaemon lamarrei in relation to body size

The effects of body size on the food intake, growth and conversion efficiency of the freshwater prawn Palaemon lamarrei have been studied. In captivity, fed on a restricted diet of the muscles of the fish Gambusia affinis, moulting in these prawns occurred once in 18 ± 5 days at a temperature of 26 ± 1°C. The importance of these cast moults, contributing a sizable amount of organic matter to the detritus deposit of freshwater habitats has been indicated. In a log-log system, both food intake and growth per day, represented as a percentage of body weight, showed an inverse relationship to the body size. Animals in the size range of 600–800 mg exhibited the highest conversion efficiency. The present study indicates that these prawns can be successfully reared and grown under laboratory conditions.

Hydrolytic activation and detoxication of 2,4-dichlorophenoxyacetic acid esters in mosquito fish

Insecticide-resistant mosquito fish ( Gambusia affinis) were found to be slightly more tolerant to two thiol esters of 2,4-dichlorophenoxyacetic acid (2,4-D) than were fish of a susceptible population. DEF ( S,S,S,-tributyl phosphorotrithioate), at 0.1 ppm for 24 hr, slightly decreased the toxicity of both esters to both populations. Comparison of esterase activities in gill and liver preparations showed that the resistant fish had lower levels of liver esterases than the susceptible fish, but results with gill preparation were not consistent. With the ethyl thiol ester, susceptible fish had the higher activity, but with butyl thiol ester, resistant fish had the higher activity. DEF inhibited activities in both tissues of both populations, but inhibition was appreciably greater in the liver. Results suggest that (i) hydrolysis in the liver activaties 2,4-D esters, (ii) hydrolysis in the gill is a detoxication reaction, (iii) the slight increase in tolerance in the insecticide-resistant fish is primarily the result of decreased activation, and (iv) antagonism by DEF is the result of a greater inhibition of activation than of detoxication.

The Environmental Fate of Three Dichlorophenyl Nitrophenyl Ether Herbicides in a Rice Paddy Model Ecosystem

AbstractThe distribution and fate of three 14C radiolabeled diphenyl ether herbicides, nitrofen (2,4‐dichlorophenyl 4′‐nitrophenyl ether), X‐52 or methoxy‐nitrofen (2,4‐dichlorophenyl 3′‐methoxy‐4′‐nitrophenyl ether), and bifenox (2,4‐dichlorophenyl 3′‐carbomethoxy‐4′‐nitrophenyl ether), were evaluated in a laboratory rice (Oryza sativa L., Taichung Native No. 1) paddy model ecosystem. Nitrofen was relatively stable under model ecosystem conditions and was bioconcentrated and stored over a 33‐day period in tissues of alga (Oedogonium cardiacum Wittrock), snail (Physa sp.), mosquito (Culex pipiens quinquefasciatus Say), and fish (Gambusia affinis Baird & Girard). The carbomethoxy group of bifenox served as an effective degradophore and tissue storage of the parent compound was minimal. The methoxy group of the methoxynitrofen was not an effective degradophore. The laboratory rice paddy model ecosystem is a useful tool for evaluating the environmental effects and fate of pesticides to be used in rice culture.

Model Ecosystem Studies of Lead and Cadmium and of Urban Sewage Sludge Containing these Elements

AbstractThe environmental fate and effects of cadmium and lead were studied in a laboratory model ecosystem with a terrestrial/aquatic interface, using silica sand, Bloomfield soil (sandy loam) and Drummer soil (silty clay loam) as substrates. Applications were made directly to the substrates as lead and cadmium chloride and as sewage sludge as a source of heavy metals. The mobilization and incorporation of cadmium and lead into food chain organisms were proportional to sorption capacity of the substrate and were highest in silica sand and lowest in Drummer soil. Following the application of sewage sludge there was clear cut mobilization and transfer of cadmium, copper, lead, and zinc into food chains, alga (Oedogonium cardiacum), daphnia (Daphnia magna), mosquito larva (Culex pipiens quinquefasciatus), snail (Physa), and fish (Gambusia affinis). Cadmium exerted a particularly adverse affect on the various organisms in the model ecosystem and its presence in relatively high levels in sewage sludge could become a limiting factor in its use on soils and for crop production.

Isolation of a new toxin from the sponge Latrunculia magnifica in the Gulf of Aquaba (Red Sea)

The sponge Latrunculia magnifica was found to be toxic for fish. A toxin has been isolated from this sponge by organic extraction-column chromatography and thin-layer chromatography. Several chemical properties of the toxin were determined by spectroscopic analysis. Toxicity tests were performed on the fish Gambusia affinis. In vitro experiments showed the toxin to be a cholinesterase inhibitor.

Life History of Ascocotyle mcintoshi Price, 1936 (Trematoda: Heterophyidae)

The trematode utilizes the prosobranch freshwater snail, Littoridinops monroensis, in which a simple redia produces an ophthalmogymnocephalous type of cercaria, notably different from the pleurolophocercous and parapleurolophocercous cercariae reported for other species in the Ascocotyle complex. The method of infecting the fish hosts, Poecilia latipinna and Gambusia affinis, is unique in that the cercaria is ingested and penetrates through the intestinal wall to the coelom. Metacercariae produce thickwalled cysts attached to the viscera. Adults were produced within a 48 to 60-hr period by feeding metacercariae to day-old chicks. Price (1936) described Ascocotyle mcintoshi from the small intestine of the white ibis, Guara alba, from Florida. This is a report on the life history of this trematode in which the prosobranch snail, Littoridinops monroensis (Frauenfeld) (identified by Dr. F. G. Thompson, Florida State Museum, Gainesville, Florida), was found to serve as the first intermediate host and small fishes, Poecilia latipinna and Gambusia affinis holbrookii, serve as second intermediate hosts. Day-old unfed chicks were used as experimental definitive hosts. Sogandares and Lumsden (1963) reviewed the status of the Ascocotyle complex and listed 25 species which they separated into three subgenera. They retained within the genus Ascocotyle Loos, 1899, the subgenus Ascocotyle Travassos, 1930, and the subgenus Phagicola Faust, 1920. They established a new subgenus Leighia and placed in it A. mcintoshi, as the type species, and A. megalocephala Price, 1932. Since the above revision appeared, additional species have been added to the Ascocotyle complex: A. (L.) chandleri Lumsden, 1963, which becomes the third species in the subgenus Leighia, A. (A.) pachycystis Schroeder and Leigh, 1965, and A. sexidigitata Martin and Steele, 1970. Stein (1968) referred to an undescribed species of the genus which he found as metacercariae in the viscera and musculature of the fish, Cyprinodon variegatus. He was unable to obtain the adults from experimental hosts, but found a resemblance of metacercariae with adults, taken from two American mergansers, representing an undescribed species related to A. pachycystis. Received for publication 3 August 1972. Few complete life histories of species in the genus Ascocotyle complex are known. Scott (1964) reported the life history of A. (P.) diminuta (Stunkard and Haviland, 1924) Stunkard and Uzmann, 1955. SogandaresBernal and Lumsden (1963) concluded that A. diminuta is a synonym of A. angrense Travassos, 1916. Schroeder and Leigh (1965) reported the life history of A. pachycystis and Stein (1968) made many observations on the rediae, cercariae, metacercariae, and adults of A. leighi Burton, 1965, A. pachycystis, A. angrense, and A. ampullacea Miller and Harkema, 1962. Observations on metacercariaadult transformations have been made by others on several additional species. MATERIAL AND METHODS The snail host, Littoridinops monroensis, was collected in the field and reared in the laboratory in aerated tap water containing about 10% seawater. While it seemed to do well on decayed lettuce, it was routinely fed on the periphyton grown on vertical glass plates placed in aquaria exposed to sunlight. Poecilia latipinna and Gambusia affinis holbrookii used for infection were reared in the laboratory and exposed to cercariae individually in small dishes. Morphology of the larval stages was studies with the aid of a phase microscope. Redial and cercarial measurements were made on specimens fixed in hot 10% formalin. Metacercariae and adults were fixed in hot AFA solution and stained in Semichon's carmine. Measurements of these latter stages were made on mounted material. All measurements cited are given in microns. Day-old unfed chicks were infected orally by pipette and fed on either Purina Startena or a crumbled dried fish diet. The chick appears to be a satisfactory laboratory host for bringing A. mcintoshi to sexual maturity.

Effect of running water on the predatory efficiency of the larvivorous fish Gambusia affinis.

Effects of standing and running water on the predatory efficiency of the larvivorous fish Gambusia affinis was tested at 6 different current speed: 0.0, 0.8, 2.4, 4.5, 8.5 and 10.2 ml/sec. G. affinis predated 25 Anopheles stephansi or 21 Culex fatigans (IV instar) during the test period of 10 hours. The predatory efficiency of G. affinis decreased remarkably to about 60% and thereafter gradually to about 30% in aquaria containing running water at the speed of 2.4 and 10.2 ml/sec, respectively.

Temperature tolerance of the mosquitofish, Gambmia affinis (Baird and Girard)

The capacity of a warm‐adapted population of mosquito fish (Gambusia affinis) from the Sonoran Desert and a cold‐adapted population from northern Utah to adjust to changing environmental temperatures has been described in terms of four criteria: (1) critical thermal maxima, (2) resistance times at high, lethal temperatures, (3) upper incipient lethal temperatures, and (4) lower lethal temperatures. Non‐genetic scope for adaptation as related to changes in the thermal history of the individual and expressed in terms of the tolerance domain was identical for both populations. Genetic differences in adaptive capacity were apparent. The cold‐adapted population was less tolerant of heat and more tolerant of cold as would be anticipated.