GULF OF MEXICO 



347 



Manatus lahrostris, from the delta of the Panuco 

 River, near Tampico, Mexico. 



STUDIES ON LARVAL STAGES AND LIFE 

 CYCLES OF TREMATODES OF THE 

 GULF OF MEXICO 



Miller (1925, 1926, 1927, 1929) and Miller and 

 McCoy (1929) have studied cercariae collected 

 chiefly from snails from coral reefs near the Biolog- 

 ical Laboratory at Tortugas. Most of these stud- 

 ies were on the behavior of the cercariae and only 

 brief prelimmary descriptions of the cercariae were 

 given. The cercariae were named alphabetically 

 as Cercaria A, Cercaria B, etc. In 1929, Cercaria 

 P was referred to as Cercaria foridensis. As is 

 usual among marine mollusks, only a small per- 

 centage of individuals are infected. During the 

 first season (1925) Miller examined 4,341 mollusks 

 belonging to 33 genera and including 50 species 

 and varieties, and found only 45 individuals in- 

 cluding 9 species infected. Miller's later work 

 indicates that the incidence of infection may vary 

 greatly from year to year. Altogether, 22 species 

 of cercariae were studied. The type of each cer- 

 caria is indicated. The following list includes the 

 mollusks found infected and the cercariae found 

 in each: 



Astrea americana 



Cercaria A cotylocercous. 



Cercaria B cotylocercous. 



Aslrea longispina 



Cercaria C immature sporocysts. 



Cerithium litter alum 



Cercaria D gymuocephalous. 



Cercaria E gymuocephalous. 



Cercaria F huge-tailed monostome. 



Cercaria G Xiphidiocercaria. 



Cercaria P binoeulate, lophocercou.s. 



Cercaria Q trioculate monostome. 



Cercaria R large furcoceroous. 



Cercaria S distome, gy mnocei)halous. 



Cercaria T huge-tailed monostome. 



Cercaria U huge-tailed monostome. 



Cercaria W huge- tailed monostomo. 



Cerithium atgicola 



Cercaria II gymnocephalous. 



Columbelta mercatoria 



Cercaria I cotylocercous ( ?) 



Cercaria .1 cotylocercous. 



Crepidula aculeata 



Cercaria K trichocercous. 



Cercaria L cystophorous. 



Gli/phis listeri 



Cercaria M cotylocercous. 



Pinna carnea 



Cercaria N gasterostome. 



Thaix drltoidea 



Cercaria O echinostomo. 



Except for the life cycles studied by McCoy 

 (1929, 1930) little attempt has been made to 

 associate these cercariae with adult trematodes. 

 The problem is usually difficult because many 

 characters used in classification do not appear in 

 the cercaria. The mollusks studied might be 

 infected with trematodes from such birds as the 

 pelican, tern, or frigate bird, or from marine 

 turtles, as well as from fishes. McCoy proved that 

 Cercaria A developed into Hamacreadium muta- 

 bile, and Cercaria B into Hamacreadium gulella. 

 He believed Cercaria P developed into some 

 species of Acanthochasrmis. Second intermediate 

 hosts were Thalassoma bijasciatus, bluehead, or 

 Halichoeres bimttatus, slippery dick. Manter 

 (1932, 1933a) found that Cercaria J from Col- 

 umbella mercatoria penetrated into and encysted 

 in the shrimp, Lysmafa intermedia. He found in 

 this same shrimp and in Crangon jormosum the 

 metacercariae of Helicometrina nimia. He also 

 pointed out that Cercaria L greatly resembles a 

 common juvenile trematode known as Distomum 

 fenestratum. 



Schechter (1943) reports cercariae of Parorchis 

 acanthus from the oyster-drilling snail, Thais 

 floridana haysae from Barataria Bay, La. The 

 adult of this echinostomid trematode is a parasite 

 of birds, e. g., the herring gull, Larus argentatus. 

 It has been reported from Cuba by Vigueras 

 (1940a) from the flamingo, Phoenicopterus ruber, 

 and from Nycticorax nycticorax hoactli. 



Cable and McLean (1943) described a "ratten- 

 konig" cercaria, C. clausii Monticelli, from the 

 gastropod, Lamellaria leucosphaera, from the west 

 coast of Florida. Miller (1929) described the same 

 colonial aggregation of individuals for his Cercaria 

 W from Cerithium litteratum at Tortugas. 



Larval stages of gasterostomes are common 

 parasites of bivalves. Oysters both of the Atlantic 

 and Gulf coasts are commonly infected with such 

 larvae. Pearse and Wharton (1938) reported 

 "Bucephalus gracilescens (Rudolphi)" from oysters 

 in Apalachicola Bay, Fla. A study of these 

 gasterostome larvae in oysters of the Gulf of 

 Mexico is being made by Sewell H. Hopkins of 

 Texas A. and M. Research Foundation. 



