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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



topsis spores, probably this species, in Delaware 

 Bay and as far north as Great South Bay, New- 

 York. 



The northern limit of the known range is based 

 on Prytherch's (1938, 1940) observation of 

 Nematopsis spores in oysters as far north as 

 Mobjack Bay, Virginia.' Although N. ostrearum, 

 as originally described, contained two species, it 

 is believed that only the one considered at this 

 time extends as far north as Virginia. (See 

 A'^. prytherchi below.) 



3. Nematopsis prytherchi Sprague, 1949. 



Hosts: Molluscan host the oyster Crassostrea 

 virginica (Gmelin) , decapodan host the stone crab 

 Menippe mercenaria (Say). 



Organs involved: The intestinal tract of the 

 crab and the gills (principally) of the oyster. 

 The gamontocysts are distributed along the entire 

 rectum of the crab. 



Distribution: Widely distributed along the Gulf 

 coast and probably to North Carolina on the 

 Atlantic coast. North Carolina is presumed to be 

 the northern limit of the range of this species 

 since its only known decapodan host, according to 

 Rathbun (1930), occurs only that far north. 



Remarks: This species was separated from 

 Nematopsis ostrearum Prytherch, 1938, in a pre- 

 liminary note by Sprague in 1949 and described 

 in detail later (1950), with an account of extensive 

 infection experiments, in an unpublished report 

 submitted to Texas Agricultural and Mechanical 

 Research Foundation. 



4. Nematopsis penaeus n. sp.= Nematopsis (?) sp. 



Sprague, 1950. 



Hosts: Penaeus aztecus Ives, one of the common 

 commercial shrimp, is here designated as the host, 

 although the parasite seems to be identical with 

 one in P. setiferus (Linn.). No intermediate 

 host is known. The oyster, Crassostrea virginica 

 (Gmelin), has been eliminated, by means of 

 infection experiments, as a possible host. 



Organs involved: Intestinal tract of the decapod. 



Vegetative stages: Similar to those of weU- 

 known species of Nematopsis. Early stages are 

 small spherical bodies intracellular in the intestinal 

 epithelium. Epimerite spherical. Young greg- 

 arines early become associated in chains of two 

 or more individuals in linear or bifurcated syzygy. 



' Reported also from Delaware Bay and Great .South Bay. New York, by 

 n. Landau and P. S. Galtsofl (1951, Texas Jour. Sci., vol. 3). 



The posterior extremity in older associations 

 often appears somewhat more truncate than in 

 the described species of Nematopsis. 



Gamontocysts: Spherical; 132-260 microns in 

 diameter, the mean diameter being 177 microns 

 (based on measurements of 35 cysts from 2 host 

 specimens) ; attached to the chitinous lining of 

 the rectum and distributed along its entire length. 

 Note: "Gamontocyst" is used here in accordance 

 with the new terminology recently proposed by 

 Fihpponi (1949). 



Gymnospores: Smooth, spherical aggregates of 

 cells when mature. They are among the largest 

 known, being comparable in size with only those 

 of A'^. prytherchi. (Unfortunately, measurements 

 on living gymnospores are not on hand, and 

 measurements of stained ones are of little value for 

 comparing with living gymnospores of other 

 species.) 



Distribution: Barataria Bay, Louisiana, is here 

 designated as the type locality. The organism, 

 however, is probably widely distributed along 

 the Gulf and Atlantic coasts, since it has been 

 found in every one of hundreds of slirimp examined 

 from the Louisiana coast when the examination 

 was made soon after the shrimp were collected. 



Comparison and affinities: The vegetative stages 

 are similar to those of known species of Nematopsis. 

 Gynuiospores are very large, only those of N. 

 prytherchi being comparable in size. Gamonto- 

 cysts are about the same size as those of A^. 

 maraisi (Leger and Duboscq, 1911) in the crab 

 Portunus depurator and are exceeded in size only 

 by those of Porospora gigantea (Van Beneden 

 1869) ; in being distributed along the entire rectum 

 of the host they are like P. gigantea in the European 

 lobster and different from any known species of 

 Nematopsis excepting A^. pyrtherchi in the stone 

 crab. To summarize, A^. penaeus resembles A''. 

 maraisi in size of gamontocyst but is distinctly 

 different in having a larger gymnospore; it re- 

 sembles A^^. prytherchi in size of gymnospore and 

 distribution of gamontocyst but has a larger 

 gamontocyst and different host specificity; it 

 resembles Porospora gigantea also in distribution 

 of the gamontocysts in the rectum of the host and 

 by being an inhabitant of one of the macroura 

 but has a distinctly larger gymnospore and is 

 strikingly different in the vegetative stages. 



The writer's attention was first called to this 

 gregarine, the third member of the Porosporidae 



