GULF OF MEXICO 



249 



described from American waters, by Prytlierch 

 (personal communication, 1946). Although the 

 known stages of the parasite are indistinguishable 

 from corresponding stages of Nematopsis (some of 

 them tlifferent from corresponding stages of 

 Porospora, the only other genus which it resem- 

 bles), it cannot be assigned to Nematopsis with 

 confidence until its life history is completely 

 known. Since it has gynniosporcs it can be 

 placed in Porosporidae (members of which are 

 unique among grcgarines in having gymnospores 

 and alternation of hosts), but there is not the 

 slightest clue as to what the intermediate host (if 

 anj-) may be. Since generic characters of the two 

 genera now in the family are based upon stages in 

 the intermediate host, definite generic determi- 

 nation caimot now be made. 



Sprague (1950) concluded, primarily on the 

 basis of infection experiments, that the oyster is 

 not the intermediate host of this gregarine. If 

 Nematopsis penaeus has an intermediate host one 

 would expect the latter to be an organism (possibly 

 a small mollusk or a worm) which constitutes the 

 chief or a very prominent item in the diet of 

 shrimp. The last statement is based upon the 

 belief that the host must acquire a new infestation 

 almost every day in order to maintain, at all times, 

 a large gregarine population consisting of individ- 

 uals representing essentially eveiy stage of devel- 

 opment. The problem of discovering the possible 

 intermediate host is complicated by the remarkable 

 fact that, as Burkenroad has pointed out in a 

 personal communication, we are almost completely 

 ignorant of the feeding habits of the very familiar 

 decapodan host. The possibility that the shrimp 

 become directly reinfested by ingesting the gymno- 

 spores which pass from their intestines requires 

 further consideration, although experimental data 

 by Sprague (1950) suggest that such studies would 

 give negative results. Slii-imp maintained in the 

 laboratory and fed upon oysters (containing Nema- 

 topsis spores) and fish became entirely free of 

 gregarines in less than a week. The tentative 

 conclusion from those data is that the shrimp 

 neither reinfest themselves nor become infested 

 by eating oysters (although Nematopsis spores 

 from oysters readily germinate in slirimp), but 

 that they acquire the gregarines by feeding almost 

 daily upon some specific but unknown organism 

 common in their natural habitat. 



Since these gregarines are intracellular in the 

 intestinal epithelium of the host during their early 

 development, and since the host seems to acquire 

 great numbers of tliem almost daily, the intestinal 

 epithelium is sul)ject to appreciable damage by 

 the parasites. In view of the great economic 

 importance of shrimp, the host-parasite relation 

 of these two organisms is of more than academic 

 interest and deserves intensive investigation. 



5. "Gregarine cysts" were reported by Pearse 

 (1932a) in the calico crab, Eriphia gonagra 

 (Fabricus) in Tortugas. 



Although Pearse (1932a) merely mentioned 

 gregarine cysts seen on the walls of the rectum 

 of the crab, it is quite probable that they were 

 Nematopsis. Not only are Nematopsis cysts at- 

 tached to the rectum in many species of crabs 

 very common, but A^^. legeri (de Beauchamp, 1910), 

 one of the best known species, occiu-s in a species 

 of Eriphia, E. spinijrons Herbst, on the coast of 

 France. 



UNIDENTIFIED SPECIES OF NEMATOPSIS 



As in Europe, several species of moUusks in 

 American waters have been found to harbor 

 Nematopsis spores of undetermined species. Al- 

 though some of those spores may represent stages 

 of well-laiown species of Nematopsis, it is quite 

 probable that others represent undescribed species. 

 A list of those mollusks is given in the table below. 



Table 1. — American mollusks in which spores of undeter- 

 mined species of Nematopsis have been observed 



• Hopkins, S. H., has called attention to the fact that this should bo 0. 

 cristata since O. equesiris occurs not in North America but in South America. 



Unidentified gregarines were foimd in Barataria 

 Bay, Louisiana, by Hopkins (personal communi- 



