Sex Studies on Schistosomatium douthitti (Cort, 1914) Price, 1931 ( Trematoda: Schistosomatidae)

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Abstract
A total of 204 laboratory-reared snails (Lymnaea stagnalis and L. palustris) were exposed individually to single miracidia of S. douthitti. Of 190 survivors, 24 (12.6%) were infected. Cercariae from each snail developed in laboratory-reared mice (Peromyscus maniculatus) into worms of one sex; cercariae from 14 snails developed into male worms, those from 10 into females. Three snails (2 with female and 1 with male inf.) lived for 687, 635 and 361 days, respectively. The estimated number of cercariae from these snails was 27,686, 34,417 and 11,083. Data on worms from mice killed and autopsied immediately indicate that female worms exert no appreciable influence on distr. of males, whereas, after 14 days, males cause a much larger % of females (74.4%) to occur in the extra-hepatic portal veins than occur there in unisexual infections (2.2%). Measurements of worms from unisexual and male-female infections indicate that males promote the body-growth of females, but females have no noticeable effect on the size of males. Sexual maturity was attained by both male and female worms in unisexual as well as male-female infections, and the presence of one sex had little or no effect on the age of attainment of sexual maturity of the other. The youngest males with spermatozoa were 12 and 13 days old in male-females infections and 14 days in unisexual infections. Female worms, with no males present, regularly produced eggs in which miracidia developed. Such miracidia developed partheno-genetically, for no spermatozoa were found in examinations of many of these females stained and mounted whole or in the genital ducts, seminal receptacle or eggs in uteri and ootypes of a few sectioned specimens. Mature miracidia were first observed at 26 days in both male-female and unisexual female infections, and it is estimated that about 13 days are required for miracidia to develop from either fertilized or unfertilized eggs. Twin embryos and miracidia are descr. from unisexual infections with female worms. Instances of polygamy and homosexual pairs of male worms were noted.