held in the Netherlands. Mason found infesta- 

 tions to be occasionally heavy, with a maximum 

 of 1,700 copepods on a single lobster. He con- 

 cluded that such heavy infestations could harm 

 the host through loss of blood and reduction in 

 gill surface available for gas exchange, but that 

 the usual level of infestation (100 or less per 

 lobster) caused little or no harm to the host 



Tumors 



One of the earliest observations of neoplasms 

 in invertebrates, according to Scharrer and 

 Lochhead (1950), was made by Mcintosh and 

 reported by Prince (1897). A lobster tumor 

 originated in the stomach wall and pushed 

 through the carap;ice behind the eyes, enlarged, 

 and finally killed the lobster. 



SHRIMPS 



Many shrimps of the families Penaeidae and 

 Pandaiidae are of worldwide commercial sig- 

 nificance. Shrimps are the most valuable fish- 

 ery resource in the United States (Lyles, 1966). 

 Parasites and diseases, which may have ad- 

 verse effects on shrimp stocks, have been stud- 

 ied, particularly in the Gulf of Mexico. Several 

 diseases caused by Microsporida are known, 

 and larval helminths — trematodes, cestodes, and 

 nematodes — have been reported. Isopods and 

 rhizocephalans have also been observed. 



Microbial Diseases 



Protozoan parasites have been shown to be 

 of significance to commercial shrimp popula- 

 tions of the Gulf of Mexico. Several microspo- 

 ridan Protozoa cause a condition known as 

 "cottony" or milky" shrimps. Nosema nelsoui 

 was described by Sprague (1950a) from the 

 brown shrimp, Penneus aztecus Ives. Aflfected 

 body muscles had an opaque white discolora- 

 tion, and black pigment spots occurred exter- 

 nally. The disease was common in bait shrimps 

 as well as in those processed as food. Infected 

 individuals did not survive well in bait tanks 

 and were also discarded in processing plants, 

 thus representing significant losses to the indu.s- 

 try (Woodburn, Eldred, Clark, Hutton, and 

 Ingle. 1957; Hutton, Sogandares-Bernal, and 

 Eldred, 1959). Sprague (1950a) found micro- 

 sporidan spores in the gonads of the white 

 shrimp, P. setiferus (L.), some of which he 

 described as Thelnhanin penaei. Earlier, Vio.sca 

 (1945) reported that "about 90 percent" of 



white shrimp in Louisiana waters were infected 

 in 1919 by .i protozoan disea.se (not further 

 identified) which destroyed the reproductive 

 organs. If the <lisea.so was caused by T. penaei, 

 the microsporidan may play a role in fluctua- 

 tions of the host species when present at epi- 

 zootic levels. Iversen and Manning (1959) de- 

 scribed still another microsporidan, Thcloha)iia 

 duorara, from the musculature of pink shrimp, 

 P. dnoranim RurkenroMd, of the Gulf of Mex- 

 ico. Infected individuals were relatively rare, 

 however, in landed catches. Brazilian brown 

 shrimp, P. l)ra.siHe)isis, also harbor the same 

 parasite (Iversen and Van Meter, 1964). 



Several gregarine Protozoa also occur in 

 shrimps. Sprague (1954) tentatively identified 

 as Neniatopsis penaeus a gregarine from the 

 digestive tract of brown shrimp from Louisiana. 

 The same parasite was observed by Kruse 

 (1959a. 1959b) and Hutton, Sogandares Bernal, 

 Eldred, Ingle, and Woodburn (1959) in .several 

 species of shrimps from Florida. Sprague men- 

 tioned the possibility of extensive damage to 

 the intestinal epithelium of individuals heavily 

 infected by Neniatopsis. Kruse described a sec- 

 ond gregarine from the digestive tracts of 

 brown and pink shrimps in Florida, and Hut- 

 ton, Sogandares-Bernal, Eldred, Ingle, and 

 Woodburn (1959) observed the same parasite 

 with high frequency in certain samples of pink 

 shrimp from Florida. 



Diseases Caused h\ Helminths 



Shrimps occasionally harbor larval helminths. 

 Metacercariae of the trematode Opecoeloides 

 fimbriatiis (Linton) were found by Hutton, 

 Sogandares-Bernal, Eldred, Ingle, and Wood- 

 burn (1959) and Sogandares-Bernal and Hut- 

 ton (1959) in several Florida species. Larval 

 Microphallus sp. have been reported from the 

 body muscles and hepatopancreas of pink 

 shrimp (Hutton, Sogandares-Bernal, and El- 

 dred, 1959; Hutton, Sogandares-Bernal, Eldred, 

 Ingle, and Woodburn, 1959). 



Several larval cestodes of the order Trypano- 

 rhyncha have been found in the digestive gland 

 and other organs of shrimps. Larval Prochris- 

 tianella penaei Kruse were identified from four 

 species of shrimp.s — brown, pink, white, and 

 humpback (Trachypeueus constrictus (Stimp- 

 -son)) — from the Florida coast (Sparks and 



360 



U.S. FISH AND WILDLIFE SERVICE 



