92 



Journal of the Kentucky Academy of Science 66(2) 



7 9 11 13 15 



Day Of Experiment 



19 21 



3.5 



1.5 



Nil 



7 9 11 13 15 



Day Of Experiment 



17 19 



Ml 



7 9 11 13 15 17 19 21 



Day Of Experiment 



0 3 

 Si 



E 2 



3 



^ 1 



0 



iUl 



7 9 11 13 15 17 19 21 



Day Of Experiment 



Figure 3. Examples (4/36) of number of Proterotnetra macrostoma cercariae shed by individual snails over 21 days. 

 (A) Snail 4 shed 3 cercariae from 11 rediae. (B) Snail 14 shed 7 cercariae from 4 rediae. (C) Snail 13 shed 15 cercariae 

 from 28 rediae. (D) Snail 11 shed 28 cercariae from 26 rediae. 



eral days are probably required for the next 

 stage to mature following the release of the 

 most advanced (i.e., with functional genital or- 

 gans) cercaria. Even snails with many rediae 

 conformed to this limited pattern of cercarial 



w 25- 



"(5 

 c 



CO 20 - 

 >^ 



O 



2 3 4 5 6 7 8 9 10 11 12 



Days Shedding 



Figure 4. Relative frequency of cercarial shedding from 

 36 snails infected with Proterometra macrostoma over 21 

 days. 



emergence. This slow development may be 

 linked to a variety of factors. Mature rediae of 

 P. macrostoma lack a gut unlike rediae of most 

 digeneans, and thus acquisition of nutrients is 

 dependent solely on mediated transport by the 

 tegument (Uglem 1980). The mantle cavity 

 habitat confirmed in this study, by contrast to 

 preferred redial sites, such as the snail gonad 

 and digestive gland (Fried 1997), may contain 

 fewer nutrients for asexual reproduction of 

 cercariae in such rediae, but this will require 

 future verification. 



ACKNOWLEDGMENTS 



This study was supported by a grant from 

 the Undergraduate Research and Creative 

 Projects Program (URCPP) at Berea College 

 to Ronald Rosen. We acknowledge the late 

 Gary. L. Uglem, who provided the first author 

 much insight and support with the P. macros- 

 toma system; and Dr. Bernard Fried, Depart- 

 ment of Biology, Lafayette College, and Dr. 



