﻿SNAIL HOST OF ORIENTAL LUNG FLUKE — ABBOTT 111 



bidae. The phylogenetic relationships of these two groups of gastro- 

 pods could hardly be farther apart. In all likelihood the choice of 

 mollusks is based on the physiological adaptations and ecological 

 preferences of the snails in each case. 



Thiara grmiifera serves as host for two different superfamilies of 

 trematodes, the Heterophyoidea {Metagonhmis, Haplorchis, and Di- 

 orchitrema) and the Troglotrematoidea {Paragonirmis). These same 

 trematode groups are also carried by other genera of Thiaridae {Semi- 

 mlcospira, Hua, Goniohasis^ and the subgenus of Thiara called Mela- 

 noides) . In addition, however, members of the snail families Amni- 

 colidae and Synceridae may also act as intermediate hosts, in some 

 cases being the only snail hosts in the local endemic area. 



In all likelihood Thiara granifera may be considered a potential host 

 cf the American Paragonimm kellicottii on epidemiological and eco- 

 logical grounds. 



An understanding of snail-host specificity will probably not arrive 

 from a study of molluscan phylogeny, but rather will have to await 

 an intensive study of the physiology of the many fresh- water species 

 that serve as hosts. The seeming tendency for certain families of 

 snails to serve as hosts to particular groups or species of flukes is 

 probably merely an expression of a common physiological condition 

 possessed by these snails. 



INTRODUCTION INTO THE UNITED STATES 



Thiara gramifera has established itself some 5,000 miles east of its 

 normal geographical limits in the Lithia Springs of Hillsborough 

 County, Fla. The thriving American colonies should be considered as 

 potential hosts for one or more of the trematodes that they are capable 

 of carrying in their native habitats. (See under Parasitology, p. 109.) 

 It appears, however, for the several reasons discussed subsequently, 

 that no danger exists in the establishment of these snails in our country. 



It appears from the information now at hand that there was only 

 one introduction of the snail into the United States. On March 23, 

 1935, an aquarium dealer of San Francisco, Calif., sent four specimens 

 to the United States National Museum for identification. In a letter 

 (March 23, 1935) to Dr. G. S. Myers, then curator of the division of 

 fishes, this dealer states, "I do not know just where their native habitat 

 might be, because here and there, from different points, Australia, 

 China, Hawaii, etc., where I get a small shipment, plant life comes 

 along and some small ones [snails] may be adhering to it." 



No further notice was taken of this species, since at that time the 

 parasitological importance of this species was overlooked. It was not 

 until 1947 that it reappeared, when Dr. C. Wythe Cooke, of the U. S. 

 Geological Survey, collected a number of specimens in Lithia Spring, 



