Richard S. Caldwell

A mycosis caused by Lagenidium sp. in laboratory-reared larvae of the Dungeness crab, Cancer magister, and possible chemical treatments☆

Abstract A mycosis in larvae of the Dungeness crab, Cancer magister, was observed about 48 hr after they had molted to second-stage zoeae in the laboratory during a chronic bioassay. The fungus was of the genus Lagenidium and caused about 40% mortality of larvae before the test was terminated. Hyphal development and subsequent sporulation of the fungus was observed over a range of 0–32‰ salinity, with an optimum around 16‰. Bioassays of eight fungicides and the herbicide trifluralin, using the larvae and fungus in separate tests, were performed to explore means of chemical treatment. Trifluralin was the most satisfactory of the chemicals screened, with captan, Cu2+, and benomyl also giving good results for certain treatment intervals of up to 96 hr. Malachite green was toxic to larvae at concentrations inhibiting the fungus.

Biochemical lesion in rat liver mitochondria induced by hexachlorophene

Abstract Mitochondria obtained from the livers of rats 18 hr after oral dosing with 20 and 100 mg/kg of 2,2′-methylenebis (3,4,6-trichlorophenol) (hexachlorophene; HCP) exhibited decreased oxidative phosphorylation, high adenosine triphosphatase (ATPase) activity, but no modification in the activities of electron transport enzymes when compared to controls. An inverse correlation between phosphorylation and the level of bound HCP was found, with 50 per cent uncoupling occurring at 0·1 mμmole HCP/mg of mitochondrial protein and complete uncoupling at approximately 0·6 mμmole/mg of protein. The concentration of HCP required for 50 per cent uncoupling in vitro was shown to be directly dependent on the mitochondrial protein concentration and was 0·5 μM when the latter was 2·5 mg protein/ml. Binding of HCP by mitochondrial protein was complete even when the ratio of bisphenol to protein in the incubation medium exceeded that necessary for 50 per cent uncoupling by 2000 times. Oxidative phosphorylation could be completely restored in HCP-inhibited mitochondria by the addition of a 200-fold molar excess of bovine serum albumin. In rats given a sublethal intraperitoneal injection of the drug, maximum uncoupling in liver mitochondria occurred within 15 min and complete recovery by about 6 hr. With a sublethal oral dose of HCP, maximal uncoupling occurred at 12–15 hr with complete recovery by about 36 hr. In both cases, the times for maximal uncoupling and subsequent recovery appeared to be nearly identical with the times for appearance and disappearance of gross symptomatology Significant uncoupling of oxidative phosphorylation still occurred when less than 50 per cent of the oral or intraperitoneal LD 50 doses were given. These observations suggest that uncoupling of oxidative phosphorylation may be the primary biochemical lesion in acute intoxication by HCP.

Growth, food conversion and survival of 0-group English sole (Parophrys vetulus Girard) at five temperatures and five rations☆

Abstract Laboratory experiments were conducted to determine the effects of temperature and food ration on growth, conversion efficiency and survival of 0-group English sole (Parophrys vetulus Girard). Young sole, fed a diet of Oregon Moist Pellets, were exposed to constant temperature-ration combinations between 9.5 and 21° C and between 0 and 16% rations (dry weight basis) for a 12-week experimental period. The juvenile sole, initially 4–6 g, grew at a rate of up to 0.95% per day at the most favorable temperature-ration combination, 9.5°C and 16% ration. Highest food conversion efficiency, 10.5%, was observed at the temperature-ration combination of 9.5°C and 8% ration. At 21°C, young sole lost weight at the ration levels fed. Based on growth rate, survival and food conversion efficiencies observed during the experiments and the temperatures to which the young sole are exposed in nature, the temperature at which greatest growth and maximum food conversion efficiency occurs is probably near or below 9.5°C. Although English sole juveniles were maintained for up to 1.5 years on Oregon Moist Pellets primarily, mortality was high during experiments (between 16 and 48%). The high mortality may have been associated with the pellet diet used, which is formulated to meet the nutritional requirements of salmonids and not flatfishes. The microsporidan protozoan Glugea sp., the monogenetic trematode Gyrodactylus sp., and Vibro bacteria also were associated with mortalities during the experiments, and one fish died of a large tumor.

Toxicity of the insecticide methoxychlor to the Dungeness crab Cancer magister

The toxicity of methoxychlor, determined in acute and chronic studies using larval, juvenile, and adult stages of the Dungeness crab, Cancer magister Dana, was inversely related to the age of the crabs after hatching and increased with the length of exposure. The 96-h LC50s for zoeae, juveniles, and adults were 0.42, 5.10, and 130 μg/l, respectively. Levels causing decreased survival of these same stages during exposures of more than 60 days were 0.05, 0.40, and 4.0 μg/l, respectively. Hatching of eggs was not adversely affected by methoxychlor concentrations up to 10 μg/l, and molting from prezoeae to zoeae was reduced only 30% from controls at the latter exposure concentration. Methoxychlor concentrations of 0.05 and 4.0 μg/l delayed motting of larval and juvenile crabs, respectively, and this delay was as much as 10 days for the juveniles. Sensitivity of adult and juvenile crabs to methoxychlor increased during ecdysis. In uptake experiments, juvenile crabs concentrated methoxychlor more rapidly than did adults. Juveniles exposed to 2.0 μg/l of methoxychlor and adults exposed to 1.8 and 7.5 μg/l had whole body methoxychlor concentrations after 12 days of 0.88, 0.10, and 0.51 mg/kg, respectively. Loss of the pesticide from adult crabs was rapid, and was 95% complete after 15 days of depuration. Concentrations of methoxychlor in individual tissues were found to be highest in the exoskeleton, gill, and hepatopancreas, in declining order, with less than a two-fold difference among these tissues. About 81% of the methoxychlor measured in whole body samples was associated with the exoskeleton, but it is not known whether or not the pesticide was transported through the culticle to internal tissues.

Heavy metals in estuarine shellfish from Oregon

The concentrations of Hg, Zn, Mn, Fe, Cu, and Cd were determined in marine shellfish from the Oregon coast. The levels of these metals in both crustaceans and molluscs were generally typical of those reported from other geographic areas. The primary exception was Cd, which in crustaceans was 5 to 40 times lower and in three of the six marine bivalve molluscs studied was 5 to 25 times lower than that found in most previous studies. The low concentrations of Cd may be due to the lower level and types of industrial activity in coastal Oregon estuaries compared to other regions of the world, and/or to a lower rate of input of this metal from natural weathering processes in this region. No significant variations due either to season or geographical location were apparent in the three principal shellfish species studied.

Toxicity of the herbicides 2,4-D, DEF, propanil and trifluralin to the Dungeness crab, Cancer magister.

Lethal and sublethal responses to the herbicides 2,4-D, DEF®, propanil, and trifluralin of various life history stages of the Dungeness crab,Cancer magister, were examined to estimate maximum acceptable toxicant concentrations (MATC) of each compound for this species. Zoeae were found, in long term tests, to be the most sensitive stage. Based on the experiments with this stage, MATCs were concluded to be >0.95, <6.9μg for DEF, ≥26, <220μg/L for trifluralin, ≥80, < 1,700μg/L for propanil, and < 1,000μg/L for the free acid form of 2,4-D.

Toxicity of the fungicide captan to the Dungeness crab Cancer magister

Captan did not affect the survival of Dungeness crab (Cancer magister Dana) zoea exposed to 30 μg l-1 during a chronic toxicity test lasting 69 days, but larvae were quickly killed (mean survival time = 9 days) in the same test by exposure to 450 μg l-1 of the fungicide. Delay of molting occurred, however, for later stages at 30 μg l-1. Survival of juvenile crabs was not reduced by exposure to captan for 36 days at 510 μg l-1 or, in a second test, for 80 days at 290 μg l-1. No deaths of adults exposed for 75 days to 340 μg l-1 of captan were observed. Captan appeared to accelerate hatching of eggs at all concentrations tested from 100 to 10,000 μg l-1. The development from prezoeae during a 24-h period was not inhibited by the fungicide, but at 3,300 and 10,00 μg l-1, the two highest concentrations tested, developing zoeae exhibited a morphological deformity and were largely inactive. Under the prevailing conditions in the toxicity tests, the half-life of captan was estimated to be from 23 to 54 h. Because of the relatively low toxicity of captan to crab stages and its high rate of degradation in sewater, it is suggested that the agricultural application of captan near marine waters is not likely to affect natural crab populations or crabs in laboratory culture. Further-more, the prophylactic use of captan as a fungicidal treatment for Lagenidium sp. in larval crab cultures is considered safe when used at recommended dosages.