COUCH: DISEASES AND PARASITES OF PENAEID SHRIMPS 

 Mirex 



Juvenile pink and brown shrimps died after ex- 

 posure to low concentrations of mirex. Twenty-five 

 percent of a sample of pink shrimp died during 7 

 days exposure to 1.0 ppb mirex. However, all sur- 

 vivors from this test died after 4 days in mirex-free 

 seawater, demonstrating a delayed toxic effect of 

 mirex (Lowe et al. 1971). 



I have examined both shrimp and blue crabs 

 exposed to low concentrations of mirex for long 

 periods (30 days or more) for histopathological ef- 

 fects. No pathologic effects at the tissue level were 

 found in the animals which I examined. Organs 

 studied were muscle, hepatopancreas, and gonads. 



PCBs (Polychlorinated Biphenyls) 



These industrial chemicals have been at large in 

 the aquatic environment for many years due to 

 leakage from water and waste effluents, disposal 

 of dielectric fluids, and other industrial sources 

 (Broadhurst 1972). It is a well-established fact 

 that certain fresh and marine bodies of water are 

 contaminated with various compounds of PCB 

 (Sodergren et al. 1972; Nimmo, Blackman, Wil- 

 son, and Forester 1971; Nimmo, Wilson, 

 Blackman, and Wilson 1971; Nimmo et al. 1975). 

 As recently as 1970, Duke et al. reported PCB, 

 Aroclor 1254, in water, sediments, and tissue of 

 animals (including penaeid shrimps) from Escam- 

 bia Bay, near Pensacola. 



At the U.S. Environmental Protection Agency 

 Laboratory (Gulf Breeze, Fla.), much research has 

 been done on the effects of PCB's on estuarine 

 species with emphasis on pink and brown shrimps. 

 These two penaeids were killed in 2-wk exposures 

 to 0.9, 1.4, and 4.0 ppb Aroclor 1254 in flowing 

 seawater. The minimum level causing mortality 

 was 0.9 ppb. Penaeid shrimps appeared to suffer 

 greatest mortality when exposed during premolt 

 (just before molting) and during molt. Most ex- 

 posed shrimp became lethargic, stopped feeding, 

 and did not dig into the substrate (digging is a 

 normal activity for penaeids). Subtle to dramatic 

 chromatophore changes in the cuticle of exposed 

 shrimp were more frequent and obvious than in 

 control shrimp. 



On the light microscopical level, no lesions were 

 consistently found that were indicative of PCB 

 exposure in shrimp (Couch and Nimmo 1974a). 

 However, several interesting cytopathic changes 

 were noted in exposed shrimp studied with EM. 



Pink shrimp were exposed to 3 ppb Aroclor 1254 

 in flowing seawater for 30 to 52 days. During these 

 exposures, up to 50'7f of the animals died. Living 

 and dead shrimp were analyzed by gas chromatog- 

 raphy and from 33 ppm to 40 ppm Aroclor 1254 

 was found in their hepatopancreatic tissues. Aro- 

 clor uptake in hepatopancreas was linear with 

 time (Couch and Nimmo 1974b). Hepatopancreas 

 was fixed and processed for EM. Hepatopancreatic 

 absorptive cells from exposed shrimp revealed the 

 following departures from those of controls: 1 ) 30 

 to 50*^ of cells had increased or proliferated rough 

 endoplasmic reticulum (Figure 36); 2) production 

 of membrane whorls with enclosed lipid droplets 

 (Figure 37); and 3) nuclear degeneration charac- 

 terized by the occurrence of vesicles in the nu- 

 cleoplasm (20-50 nm and 100-700 nm in diameter) 

 (Figure 38a, b). 



The proliferation of smooth endoplasmic re- 

 ticulum in hepatocytes of higher animals has been 

 described as indicative of toxic responses to drugs 

 or chemicals such as phenobarbitol, dilantin, diel- 

 drin, and carbon tetrachloride. This proliferation 

 has been related to detoxification of poisons and 

 may, in shrimp, represent an attempt, on the part 

 of hepatopancreatic cells, to metabolize PCB ab- 

 sorbed from the lumen of hepatopancreatic ducts. 

 If this is the case, cellular alterations at the ultra- 

 structural level may be valuable as early indi- 

 cators of sublethal effects of certain pollutants in 

 penaeid shrimps. 



Another PCB, Aroclor 1016, has been more re- 

 cently introduced for limited use in the United 

 States. This compound has been tested for toxicity 

 in brown shrimp. Aroclor 1016 was found to have 

 nearly the same toxicity for penaeid shrimp as 

 Aroclor 1254: 0.9 ppb Aroclor 1016 in flowing sea- 

 water killed 87c of test shrimp in 96 h; 10 ppb 

 Aroclor 1016 killed 43'7f of test shrimp in 96 h 

 (Hansen, Parrish, and Forester 1974). 



It is apparent from research results now pub- 

 lished that PCB's as pollutants pose a threat to 

 penaeid shrimps which show a high level of sen- 

 sitivity to these compounds. In this regard, 

 Nimmo, Blackman, Wilson, and Forester (1971) 

 and Nimmo, Wilson, Blackman, and Wilson 

 (1971) demonstrated that pink shrimp could ab- 

 sorb a PCB (Aroclor 1254) from sediments taken 

 from a PCB-polluted estuary — Escambia Bay, 

 Fla. Hansen, Schimmel, and Matthews (1974) 

 found that some estuarine species could avoid 

 waters contaminated with Aroclor 1254, but pink 

 shrimp showed no avoidance reaction when given 



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