Raymond E. Millemann

Glochidiosis of salmonid fishes. I. Comparative susceptibility to experimental infection with Margaritifera margaritifera (L.) (Pelecypoda: Margaritanidae).

This is the first report on the susceptibility of salmonid fishes to infection with the glochidia of the freshwater mussel Margaritifera margaritifera using known numbers of parasites under controlled conditions. The relative susceptibility of six species of salmonid fish, 20 to 80 mm in total length, to glochidiosis was determined by exposing fish individually to different numbers of parasites and plotting mortalities against these exposure levels at 70 days postexposure and also against the numbers of parasites recovered from fish 48 hr postinfection. The 70-day interpolated LE50 values (exposure concentrations of glochidia that killed 50% of the fish) for kokanee salmon (Oncorhynchus nerka kennerlyi), cutthroat trout (Salmo clarki), Atlantic salmon (S. salar), steelhead trout (S. gairdneri) and coho salmon (O. kisutch) were 17,500, 29,000, 35,000, 57,000, and 105,000, respectively. Chinook salmon (O. tshawytscha) was the most susceptible species. The LE50 values could not be estimated even at the lowest exposure levels because mortalities were too high. On the basis of the LE50 value, coho salmon was the most resistant species.

Acute Toxicity of the Insecticide Sevin® and Its Hydrolytic Product 1-Naphthol to Some Marine Organisms

Abstract The acute toxicity of Sevin® (1-naphthyl N-methylcarbamate) and its hydrolytic product 1-naphthol to 10 species of marine animals was determined. Sevin was more toxic to larval and adult crustaceans (Upogebia pugettensis, Callianassa californiensis, Hemigrapsus oregonensis, Cancer magister) than to larval and adult mollusks (Mytilus edulis, Crassostrea gigas, Clinocardium nuttallii) and juvenile fishes (Cymatogaster aggregata, Parophrys vetulus, Gasterosteus aculeatus). Sevin was 30 to 300 times more toxic than 1-naphthol to the crustaceans but less toxic than 1-naphthol to the mollusks and fishes.

GLOCHIDIOSIS OF SALMONID FISHES. IV. HUMORAL AND TISSUE RESPONSES OF COHO AND CHINOOK SALMON TO EXPERIMENTAL INFECTION WITH MARGARITIFERA MARGARITIFERA (L.) (PELECYPODA: MARGARITANIDAE)*

Coho salmon (Oncorhynchus kisutch) are more resistant than chinook salmon (O. tshawytscha) to experimental infection with the glochidia of the freshwater mussel Margaritifera margaritifera. Histological sections of gills from coho salmon 16 hr postinfection (p.i.) showed that parasite encystment either did not occur or had progressed incompletely, which accounted for the loss of many glochidia from the gills. The remaining encysted glochidia were sloughed within 2 days (p.i.) by a well-developed hyperplasia. On chinook salmon, the parasites developed normally with no sloughing or hyperplasia. Analysis of blood samples taken from coho salmon at intervals during the infection showed significant increases in hematocrit, hemoglobin, the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and leukocyte numbers when compared with control fish. In infected chinook salmon only the hematocrit, erythrocyte numbers, and MCV increased while the MCHC decreased. Total plasma protein increased in coho salmon but decreased in chinook salmon during infection. Glochidial antibodies were demonstrated in the blood plasma of coho and chinook salmon 8 to 12 wk p.i. Fewer glochidia attached to the excised gills of coho salmon than to the gills of chinook salmon. Also, the in vitro survival time of parasites in mucus and plasma from coho salmon was less than in the same chinook salmon fluids.

Biology of Nanophyetus salmincola and 'salmon poisoning' disease.

Publisher Summary The digenetic trematode Nanophyetus salmincola (Chapin) is the vector for Neorickettsia helminthoeca, a rickettsia-like organism that causes “salmon poisoning” disease (SPD). The disease is usually fatal for dogs, foxes, and coyotes. Nanophyetus s. salmincola ( N.s. salmincola ) requires multiple hosts for completion of its life cycle. The first intermediate host is the pleurocerid stream snail, Oxytrema silicula. The second intermediate hosts are salmonid and some non-salmonid fishes and the Pacific giant salamander in which the cercariae encyst. The definitive hosts are fish-eating birds and mammals. The chapter reviews several aspects of SPD. Some of them are (1) geographical distribution, (2) etiology, (3) transmission, (4) symptoms, and (5) pathogenesis and pathology. The treatment of SPD is also reviewed. Various sulfanilamides given orally or parenterally have been successful in the treatment. Dosage at therapeutic blood levels should be maintained for at least 3 days. Effective results have also been obtained with penicillin, chlortetracycline, chloramphenicol, and oxytetracycline. The best results follow administration of large divided doses. If the animal is dehydrated, intravenous fluid therapy is essential to avoid nephrotoxic effects. Treatment in the late stages of the disease may not be successful.

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.

THE PREZOEAL STAGE OF THE DUNGENESS CRAB, CANCER MAGISTER DANA

1. Ninety-four per cent of eggs of the Dungeness crab, Cancer magister, held in sea water at 10.5 or 17.5° C and at salinities of 10 to 32% hatched into prezoeae during a 36-hour observation period. The highest and lowest numbers of eggs hatched at salinities of 15 and 10‰, respectively. At a salinity of 32‰, the mean percentages of eggs that hatched at 10.5 and 17.5° C were 30 and 73%, respectively.2. With increase of salinity, the percentages of prezoeae that molted to first-stage zoeae increased from 0% at 10‰ to 100% at 30 and 32‰.3. With increase of salinity from 15 to 32‰, the mean duration of the prezoeal stage decreased from more than 60 minutes to 11 minutes.4. The experimental results show that the occurrence of a free prezoeal stage of short duration is normal in the life history of C. magister. The possibility that this is true for other Brachyura is discussed.

STIMULATION OF SPAWNING IN THE MUSSELS, MYTILUS EDULIS LINNAEUS AND MYTILUS CALIFORNIANUS CONRAD, BY KRAFT MILL EFFLUENT

1. Kraft mill effluent is a very effective material in stimulating spawning in the mussels M. edulis and M. californianus. Bay mussels obtained at all times of the year and sea mussels during January and February from the Oregon coast spawned within 24 hours after exposure to 4% KME. The gametes so obtained were viable and capable of fertilization, as shown by the artificial fertilization and development of eggs to the shell stage.2. Electrical stimulation of intact mussels was also shown to stimulate spawning, but was not as effective as KME.3. Mechanical stimulation, such as scraping the shells, or changing the water in which the animals were maintained, was only slightly effective in stimulating spawning. Stimulation associated with the partial opening of the valves was more effective in this regard.4. Possible explanations for the mechanism of spawning in mussels are discussed.

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.

Pathology of acute poisoning with the insecticide Sevin in the bent-nosed clam, Macoma nasuta

Abstract Toxicity tests of 96-hr duration of the insecticide Sevin were done with adult bent-nosed clams, Macoma nasuta . Sevin concentrations of 15, 20, 25, and 30 mg/liter were used in duplicate tests. The criterion of “death” was the inability of clams to retract siphons or to close valves. About half of the animals so affected were removed from the test solutions and returned to clean sea water to observe if recovery occurred, and others were preserved for histological examination. No “dead” clams recovered within 96 hr after return to clean water. The histopathology consisted primarily of necrosis of epithelial tissue of the gill, mantle, siphon, and suprabranchial gland, and the severity of damage was directly related to the test concentrations. Vacuolization, rupture, and pycnosis of cells occurred. The gills were the most severely affected organs. Epithelial cells of the gill filaments bearing the frontal, laterofrontal, and lateral cilia were sloughed as early as 24 hr after the beginning of exposure to Sevin. About 50% of the exposed clams had lost one or both siphons and also the epithelia on still attached segments within 96 hr of exposure. There were no deaths of control clams, and their tissues were normal.