COUCH: DISEASES AND PARASITES OF PENAEID SHRIMPS 



cultured shrimp, the problem remains for depura- 

 tion of the drug from tissues prior to human con- 

 sumption of the shrimp. 



Subphylum Ciliophora Doflein 1901' 



Ciliate Protozoa are very common associates of 

 penaeids. As commensals, parasites, and patho- 

 gens, they are among the Protozoa more often en- 

 countered in or attached to penaeid shrimp. Their 

 role, however, in the health of penaeids has not 

 been conclusively demonstrated in most ciliate- 

 penaeid relationships. Sprague and Couch (1971) 

 presented a list of ciliates (and other Protozoa) 

 found on or in decapod Crustacea. Since that re- 

 port, several new finds of ciliates in penaeid 

 shrimps have been made. 



Ciliates discussed herein will be presented in 

 order of their frequency of occurrence in penaeid 

 shrimps (common to rare). 



Class Ciliatea Percy 1852 

 Order Peritrichida Stein 1859 

 Suborder Sessilina Kahl 1933 

 Famih Vorticellidae Ehrenberg 1838 

 Genus Zootbanniin>n Bory 1826 

 Zoothamnitim sp. 



An heretofore undescribed species of peritri- 

 chous ciliate, of the genus Zoothamnium, has been 

 reported on penaeid shrimps along the coast of the 

 southeastern United States Villella et al. (1970), 

 Overstreet ( 1973), Johnson (1974), D. V. Lightner 

 (pers. commun.), and I have found the colonial, 

 stalked peritrich to be very common and fre- 

 quently abundant on the gills of three commer- 

 cially valuable species of penaeid shrimps. 



Stalked peritrichs of the genera Vorticella, 

 Zoothamnium, Epistylis, Carchesium, Rhabdos- 

 tyla, and Opisthostyla are found attached to many 

 hard substrates in the marine environment. The 

 vast majority of species in these genera have not 

 been studied, described, and named. Therefore, 

 with this background in mind, I propose to de- 

 scribe, but not to formally name, the common 

 species of Zoothamnium on gills and body of 

 adults, juveniles, protozoea, and mysis ofPenaeus 

 aztecus, P. setiferus, andP. duorarum. This species 

 will be named after further study and comparison 

 with other species in the genus Zoothamnium. 



^Most ciliatologists and many protozoologists now consider the 

 Ciliophora as a phylum, but herein the Honigberg et al. (1964) 

 classification scheme is followed. 



Description. Vorticellid; colonial, rarely ob- 

 served as individuals; 3 to 30 trophonts per colony 

 (Figure 19); usually attached to the tips of gill 

 filaments of hosts listed above; trophonts variable 

 in form but usually resemble an inverted bell (45.2 

 )u.m X 33.9 ^(-m — means of measurement of 30 in- 

 dividuals); with long, branching stalks (8.1 /Am in 

 diameter); phase contrast and silver-stained (pro- 

 targol) specimens show that myonemes in stalks 

 are continuous and joined, and the diameter of 

 myonemes averages 2.0 jum (Figure 20a, b). 

 Silver-stained specimens (Figure 20c) also reveal 

 adoral kineties consisting of a three-component 

 polykinety (peniculus) and a haplokinety; telo- 

 troch (Figure 21) produced by division of stalked 

 trophont, slightly smaller than stalked trophont; 

 lifecycle direct, that is, the telotroch may swim 

 free of mother colony and attach to surface of gill 

 or body of shrimp, secrete a stalk, and become 

 progenitor of a colony; sexual reproductive cycle 

 not observed for this species, but probably is a 

 conjugative process as in other peritrichs having 

 microconjugants and macroconjugants. I have ob- 

 served only pairs and small colonies (3, 4 

 trophonts) oi Zoothamnium sp. attached to body 

 surfaces of larval (mysis and protozoea) brown 

 shrimp. 



Overstreet (1973) gave extensive data on the 

 frequency of occurrence of Zoothamnium on 

 penaeid shrimps. He found that an increase in 

 density of hosts held in captivity was paralleled by 

 an increase in density of peritrichs on gills. This is 

 similar to what Couch (1971) observed for blue 

 crabs infested -withLagenophrys callinectes Couch 

 (1967), a gill peritrich. Overstreet ( 1973) also was 

 able to correlate, positively in one test, increased 

 mortality in shrimp with heavy infestations by 

 Zoothamnium on their gills. However, he was not 

 convinced that the correlation was valid. More 

 extensive work on this relationship is needed. 



The mechanism of injury to penaeids infested 

 with peritrichous ciliates would probably be oxy- 

 gen starvation or asphyxiation due to blockage of 

 gas exchange at the gill surface. The attachment 

 stalk oi Zoothamnium sp. does not penetrate the 

 cuticle of shrimp. 



Famih Lagenophryidae Kahl 1935 

 Genus Lagenophrys Stein 1852 

 Lagenophty liinatiis, Imamura 1940 



A species of Lagenophrys was reported from the 

 cuticle of Penaeus setiferus by Johnson (1974) and 



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