COUCH: DISEASES AND PARASITES OF PENAEID SHRIMPS 



Johnson ( 1975, footnotes 13, 14) has determined 

 toxic concentrations in penaeid shrimps for the 

 following chemicals: Formalin, potassium per- 

 manganate, potassium dichromate, copper sul- 

 fate, acriflavine, malachite green, and methylene 

 blue. His results are reported below. 



Essentially, Johnson found that for Formalin 

 the 96-h LC^o at 28 °C for pink shrimp was 235 to 

 270 ppm in seawater. He reported that 25 ppm 

 Formalin applications for killing of external pro- 

 tozoa on penaeid shrimps would be safe for in- 

 definite periods. 



Potassium permanganate LC50 at 96 h for pink 

 shrimp was 6 ppm. At this concentration a precipi- 

 tate was formed on the gills of shrimp and death 

 may have resulted from asphyxiation. 



Potassium dichromate, which may be of some 

 use as an antibacterial agent, was found to be 

 nontoxic for shrimps below concentrations of 5 

 ppm for short term exposures. 



Copper sulfate has been of use as a herbicide and 

 protozoan control agent in fisheries research. It 

 was found that copper sulfate at low concentra- 

 tions (0.5-1.0 ppm) was reasonably safe for 

 penaeids. 



Acriflavine, an antibacterial agent, had a 96-h 

 LCgp for pink shrimp of 1.0 ppm in seawater. This 

 compound was probably not safe for shrimps at 

 effective bacteriostatic concentrations. 



Malachite green, a parasiticide for freshwater 

 fishes, has a toxic effect in shrimp associated with 

 molting. Johnson (see footnote 14) reported that 

 newly molted shrimps are much more sensitive to 

 malachite green than intermolt shrimps. From 2.5 

 to 20 ppm of the compound in seawater resulted in 

 death of all exposed newly molted shrimps. Adult, 

 nonmolting, penaeid shrimps seemed to tolerate 

 higher concentrations of malachite green (20 

 ppm). Johnson believed that malachite green 

 holds promise as a fungistat for use in penaeid 

 shrimp culture. 



Methylene blue should be usable below concen- 

 trations of 1.0 ppm for prophylaxis of fungi and 

 protozoa in penaeids. 



Quinaldine (product of Eastman Kodak Com- 

 pany) was used by Johnson (see footnote 13) as an 

 anesthetic for white shrimp. He found that shrimp 

 become anesthetized when exposed to all concen- 



'^ Johnson, S. K. 1974. Use of Quinaldine with penaeid shrimp. 

 Texas A&M Univ., Fish Disease Diagnostic Lab. Note FDDL-S4, 

 2 p. 



'■* Johnson, S. K. 1974. Toxicity of several management chemi- 

 cals to penaeid shrimp. Texas A&M Univ., Fish Disease Diag- 

 nostic Lab. Note FDDL-S13, 10 p. 



trations of quinaldine, but after 48 h, 10%, 20%, 

 and 20% losses occurred respectively in 25-, 30-, 

 and 35-ppm treatment groups. A 25-ppm concen- 

 tration was set as the minimum effective anes- 

 thetic level with white shrimps. This concentra- 

 tion, however, results in death of some shrimp as 

 indicated above. Johnson also reported that spon- 

 taneous muscle necrosis occurred in abdominal 

 musculature of some shrimp that became hyper- 

 kinetic at concentrations of 25 ppm and above. 



SPONTANEOUS PATHOSES 



Under this heading are included diseases of 

 penaeid shrimps for which etiologic agents are not 

 known, or are uncertain. 



Tumors 



There have been no invasive neoplasms re- 

 ported for decapod crustaceans. Tumorlike 

 growths have been reported in lobsters (Herrick 

 1895, 1909; Prince 1897), in a crab (Fischer 1928), 

 and in a paleomonid shrimp (Savant and Kewal- 

 ramani 1964). 



To date, the only published report of a tumorlike 

 growth in a penaeid shrimp is that of Sparks and 

 Lightner (1973). They reported a papilliform, 

 tumorlike growth on the right ventrolateral as- 

 pect of the sixth abdominal segment of a specimen 

 oi Penaeus aztecus. This shrimp had been taken 

 from an experimental rearing pond at Palacios, 

 Tex. The growth was tentatively diagnosed as a 

 benign neoplasm, consisting of hypertrophied and 

 normal tissue. 



Robin Overstreet (Gulf Coast Research Lab- 

 oratory) recently presented me with two larval 

 penaeid shrimp each of which had one small 

 growth on an abdominal segment. Light micros- 

 copy and EM revealed that these enlargements 

 contained only striated muscle and sacroplasmic 

 reticulum (Figure 43). There was no evidence that 

 the growths were neoplastic or that parasites (in- 

 cluding viruses) were involved. Overstreet is pres- 

 ently completing a detailed study of this condition 

 and is describing the growths as hamartomas, pos- 

 sibly related to polluted water conditions from 

 which the affected shrimp were collected. 



Spontaneous Muscle Necrosis 



Penaeid shrimps often respond to handling, 

 temperature, and chemical stress by developing a 



37 



