FISHERY BULLETIN: VOL. 76, NO. 1 



Figure 45. — Black gill in feral shrimp not exposed to any known pollutant; grossly resembles cadmium-associated black gill 



syndrome. 



Black gills are often observed in shrimp taken 

 from natural populations (Figure 45). Grossly, the 

 black gills of feral shrimp and those of shrimp 

 experimentally exposed to cadmium are indistin- 

 guishable. The cause of black gills in feral pen- 

 aeids is unknown, but I have found shrimp heavily 

 infested w^ith apostome ciliate phoronts to have 

 considerable areas of black gill. Therefore, black 

 gill has been associated with heavy metal expo- 

 sure, protozoan infestation, and with fungal infec- 

 tion [Fusarium: Solangi and Lightner 1976), 

 suggesting multiple causes. Probably, any injury 

 that causes death of cells in gills of shrimp could 

 cause some form of blackened gill due to necrotic 

 tissues, and, perhaps, melanization. 



Broken-Back Syndrome 



Shrimp suffering from severe salinity, cold 

 temperature, and handling stresses in combina- 

 tion, display a characteristic dorsal separation of 

 the pleural plates covering the third and fourth 



abdominal segments (Figure 46). This results in 

 bulging of muscle through the separation. I have 

 observed this in 100% of 1,800 captive pink shrimp 

 dying from a sudden drop in salinity (15-18%o to 

 3%o) combined with cold water (8°C). The separa- 

 tion of cuticular plates and bulging of muscle ap- 

 parently results from uptake of water and severe 

 flexures of the abdomen in shrimp attempting to 

 escape unfavorable conditions. 



OVERVIEW AND FUTURE RESEARCH 



Some major problem areas in our knowledge of 

 penaeid shrimp diseases become apparent in a re- 

 view such as this. Although considerable 

 parasitology has been done for penaeid shrimps, 

 new protozoan and worm parasites, some 

 pathogenic, continue to be found. Until recently no 

 viruses were reported for shrimp; now at least one 

 is known. Mycology and bacteriology have yet to 

 contribute in major ways to our understanding of 

 penaeid shrimp diseases and health. Relatively 



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