USGS Science⌕ Search

Geology topics

R.J. Hall

Publications and source records attributed to R.J. Hall.

26 records · Page 2Linked to original sources
USGS1982

Responses of the iguanid lizard Anolis carolinensis to four organophosphorus pesticides

Dose related mortality and cholinesterase effects of parathion, methyl parathion, azinphos-methyl and malathion on Anolis carolinensis were investigated. The comparative effects of the four compounds on fish, birds and mammals are well known, but the effects of organophosphates on reptiles have not been studied critically. Sensitivity and patterns of mortality from exposure to the pesticides resemble those of birds and mammals rather than those of other poikilothermic vertebrates. Possible symptoms of epinephrine accumulation were observed in exposed animals; this side effect is consistent with the known mechanisms of the pesticides. Our findings indicate that brain cholinesterase activity is related to dose, that 50% inhibition of cholinesterase is associated with death and that 40% inhibition indicates sublethal exposure. Anolis lizards are frequently exposed to pesticides in the field and they may be useful in monitoring the hazards posed to a variety of wildlife species.

Environmental Pollution (Series A)↗
USGS1981

Acute toxicities of toxaphene and endrin to larvae of seven species of amphibians

Seven species of amphibian larvae were exposed to toxaphene and endrin in a continuous-flow dosing system to determine differences in sensitivity to the two compounds, EC50 and LC50 estimates varied from those for Rana sphenocephala by no more than one order of magnitude when calculated on the basis of intended concentrations. Removal of pesticides from water by the test animals was significant and it makes interpretation of results difficult. Continuous-flow toxicity tests conflict with the adaptations of amphibian larvae for static water; use of such tests for amphibians requires further evaluation.

Toxicology Letters↗
USGS1980

Toxic effects of endrin and toxaphene on the southern leopard frog Rana sphenocephala

Eggs, larvae and sub-adults of the southern leopard frog Rana sphenocephala were exposed to endrin and toxaphene. Exposure was in water by a continuous-flow technique, following standards that have been used successfully in the study of fish and invertebrates. R. sphenocephala is more sensitive to both pesticides than are higher vertebrates but is slightly less sensitive than fish. Eggs seem to be resistant to the effects of both pesticides and are probably poor indicators of environmental hazard. The toxic level of endrin is about equal in larvae and transformed frogs (LC 50 , 0·005-0·015 ppm). Toxaphene is less toxic to sub-adults (LC 50 , 0·37-0·790 ppm) than to larvae (LC 50 , 0·032-0·054 ppm). Delayed mortality, behavioural aberrations and effects on growth have been seen in toxaphene-dosed larvae observed over 30-day periods. Behavioural effects are more severe than those reported in other groups of animals. Effects on growth resulting from a 96-h exposure begin in the 0·013-0·018 ppm range. The maximum accumulation of residues observed for each chemical represented bioconcentration factors of about 100. Endrin residues are apparently lost more readily than toxaphene residues; relative depuration rates correlate well with the time course of toxic action in each chemical. Although less sensitive to these pesticides than fish, amphibians may not be protected in their natural habitats. Future studies of the effects of toxicants on amphibians should employ larvae if only one stage can be tested, should expose subjects for at least 96 h and should continue observations for a total of at least 30 days.

Maryland↗
USGS1979

Organochlorine residues in eggs of the endangered American crocodile (Crocodylus acutus)

Most of the 27 species and subspecies of surviving crocodilians have declining populations and 22 of them are considered to be severely endangered (IUCN 1971). The United States population of the American Crocodile is no exception; it probably numbers between I00 and 300 individuals (OGDEN 1976). Nests of the species have been regularly surveyed by the staff of Everglades National Park. Our sample consists of eggs that remained in nests after the hatching of broods and of one clutch laid in captivity by an unmated female. Analysis of these samples for organochlorine contaminants has permitted a detailed examination of their contaminant loads and has allowed comparisons with a small sample analyzed in 1972 (OGDEN et al. 1973).

Florida↗
USGS1979

Uptake of methoxychlor from food and water by the American toad (Bufo americanus)

Various studies (Mulla et al. 1963; Ferguson and Gilbert 1967; Cooke 1973) have examined the effects of pesticides on anuran amphibians, but the routes of contaminant uptake by transformed amphibians have not been evaluated. The need of frogs and toads to imbibe water from natural surface water would seem to make them vulnerable to uptake from this source. Fish are known to accumulate pesticides from both food and water (Jarvinen et al. 1977). Toads are more terrestrial and tend to lose water less readily than most other amphibians (Thorson and Svihla 1943); hence they should he a conservative estimator of the potential for uptake of pesticides from water. Methoxychlor is an analogue of DDT and has been widely used to replace it. It is a good model of many pesticides in current use in its low persistence in animal tissues (Gardner and Bailey 1975), and its long half life in water (Wolfe et al. 1977). It is also suitable for study because of its relatively low toxicity to amphibians (Kaplan and Overpeck 1964) and its easily detected residues. In the present study we measured the accumulation of methoxychlor from food and water in a preliminary evaluation of the two routes of exposure.

Bulletin of Environmental Contamination and Toxico↗
USGS1977

A population analysis of two species of streamside salamanders, genus Desmognathus

Desmognathus fuscus and Desmognathus ochrophaeus mere studied over a 6-wk period by mark-recapture and removal methods. Density is ~. 0.8/m2 in D. fuscus and 0.6 - l.l/m2 in D. ochrophaeus; respective biomass densities are 1.5 and 1.0 g/m2. Adjusted estimates indicate a greater proportion of adults in D. ochrophaeus. The observed sex ratio is unbalanced in favor of males but may be close to 1:1 in each species. Adult male age structures based on testis lobes indicate greater adult survivorship in D. ochrophaeus than D. fuscus. Local populations of D. ochrophaeus may differ from others studied in having a shortened larval period. Indirect evidence may indicate greater predation on D. fuscus than on D. ochrophaeus. Fecundity is positively correlated with the size of females in both species and the slopes of the regression lines are similar. Mean egg complements are 21.2 for D. fuscus and 15.6 for D. ochrophaeus. Most observations support the hypothesis that demographic differences are related to differences in degree of terrestrialism between the two species.

Herpetologica↗