COUCH: DISEASES AND PARASITES OF PENAEID SHRIMPS 



8 



10 



u 





13 



Figure 39. — Pink shrimp with black gill syndrome (above) associated with exposure to cadmium chloride. Control, nonexposed shrimp 



shown below (scale in inches). 



evidence for the presence of melanosomes, 

 melanocytes, or melanophores. An alternative 

 possibility, that cell death and necrosis lead to the 

 deposition of metal sulfides or other black deposits 

 in necrotic tissues in the living animal, could ac- 

 count for the blackened gill syndrome. At any rate, 

 the interesting concept of cell and tissue death 

 preceding organismic death is represented in the 

 pink shrimp's response to cadmium exposure. 

 Death of cells (in the gills) concerned with os- 

 moregulation and respiration would lead to dys- 

 function and eventual death of shrimp. 



Bahner'i has studied the uptake of cadmium in 



"Bahner.L. H. 1975. Mobilization ofcadmium in the tissues of 

 pink shrimp, Penaeus duorarum. In Program of the first work- 

 shop on the pathology and toxicology of penaeid shrimps. U.S. 

 EPA, Gulf Breeze, Fla., 8 p. 



the tissue of pink shrimp. He found that between 1 

 and 10 ppb Cd in water elicited uptake by 

 hepatopancreas, gills, and exoskeleton. Below 

 concentrations of 1 ppb Cd in water, there was no 

 accumulation of the metal in shrimp tissue. Little 

 is known concerning cadmium effects on feral 

 shrimp in nature. 



Mercury 



Mercury as a metal has not been suspect in toxic 

 effects on organisms. Mercuric salts and methy- 

 lated mercury, however, are extremely toxic with 

 both short-term and long-term chronic effects. 

 Mercuric chloride is used in a variety of histologi- 

 cal fixative fluids because of its protein-precipi- 

 tating effects in tissues of invertebrates (Sparks 



33 



