GULF OF MEXICO 



251 



Crustacea, in particular, arc very susceptible hosts 

 and are abunilantly represented in the Gulf. 

 Nevertheless, Microsporidia occurring in the Gulf, 

  even in economically very important animals, 

 seem to have been almost completely neglected. 

 The writer knows of only three species which have 

 been definitely identified as Microsporidia, al- 

 though others have probably been observed in 

 the Gulf. 



Family NOSEMATIDAE Labb§ 



1. Nosema nelsoni Sprague, 1950. 



In the muscles of Penaeus aztecus Ives, one of 

 the common commercial shrimp, was reported 

 from Barataria Bay, Louisiana, but apparently 

 is widely distributed along the Gulf and Atlantic 

 coasts. 



Burkenroad (personal communication) believes 

 that he has seen the parasite also in P. setiferus 

 (Linn.). It is remarkable that this very common 

 parasite which causes a conspicuous discoloration 

 of the host and an appreciable economic loss to 

 the shrimp industry seems never to have been the 

 subject of serious investigation. 



2. Thelohania penaei Sprague, 1950. 



In se.x organs of Penaeus setiferus (Linn.), a 

 common commercial shrimp, was reported from 

 the vicinity of Grand Isle, Louisiana, but probably 

 is widely distributed. 



After Sprague (1950a) described the polar 

 filament of this parasite as being unique in its 

 structure he learned that Jirovec (1937) described 

 a very similar polar filament in a new species of 

 Plistophora, P. schafernai, which he found in 

 Daphnia pulex. The author is pleased to take 

 this opportunity to correct his error. 



Burkenroad (personal communication) thinks 

 he has seen this parasite also in Penaeus aztecus 

 Ives. 



Since species of Thelohania in the sex organs of 

 certain other decapods allegedly cause parasitic 

 castration, the possible role of T. penaei m the 

 fluctuation of shrimp populations is a matter of 

 considerable economic interest and should be 

 thoroughly investigated. In this connection, 

 Viosca (1943) has made some interesting observa- 

 tions. He stated (p. 276), "Some years ago (1919) 

 about 90 percent of the salt water shrimp, Penaeus 

 setiferus, existing in the waters along the Louisiana 

 coast were infected with a protozoan disease which 



destroyed their reproductive organs. Yet during 

 the following two years, 1920 and 1921, the 

 shrimp crops were the largest then known and 

 were greater than for several succeeding years. 

 Thus, 10 percent of the adult shrimp population 

 produced a larger succeeding crop than 10 times 

 their number did the preceding year, while the 

 large 1921 crop again produced a smaller number. 

 This evidence shows that with a prolific species, 

 the food supply and other ecological factors are 

 far more important than the actual number of 

 eggs laid." 



3. Thelohania sp. Sprague, 1950. 



In all the muscles of Petrolisthes armatwi 

 (Gibbes), a small flat crab very common on oyster 

 reefs. Known only from a particular shell reef 

 near Grand Terre Island in Barataria Bay, 

 Louisiana. 



Pending further information on the affinities of 

 this parasite, it was not named at the time it was 

 reported. It is now definitely believed to be dis- 

 tinct from previously recorded species. 



Order 4 HELICOSPORIDIA Kudo 1931 



This order contains only one species, and there 

 is no reason to suspect that any occiu-s in the 

 Gulf of Mexico. 



Subphylum 2 CILIOPHORA 

 Doflein 1901 



Class 1 CiLIATA Perty 1852 



Subclass 1 Protociliata Metcalf 1918 



Most of the Protociliata inhabit the colon of 

 Salientia, rarely marine fish or other vertebrates. 

 Probably none has been observed in vertebrates 

 of the Gulf of Mexico. 



Subclass 2 Euciliata Metcalf 1918 



Although more than half of the ciliates re- 

 ported from the Gulf of Mexico have been new 

 species, there is no doubt that numerous pre- 

 viously known ones are represented there. Since 

 the free-living ciliates are essentially cosmopolitan, 

 it is not surprising when one finds a particular 

 form in any locality where there is a favorable 

 habitat. BuUington (1940), and undoubtedly 

 many other persons as well, saw many ciliates 

 which he did not have an opportunity to identify. 



