Reports in the literature have shown that sex ratios of adult schistosomes, in mammalian hosts, are usually biased toward males despite the finding that sex is determined (ZZ males, ZW females) in the zygote, giving the expectation of a 50:50 sex ratio for miracidia. The ability to identify the sex of Schistosoma mansoni larvae by examining interphase nuclei for W-chromatin (Liberatos and Short, 1983, J. Parasitol., 69:1084-1089) made possible the monitoring of sex ratios as the life cycle progressed from miracidia to adults. / The sex ratio of miracidia (within 1 hr after hatching) was 211 males:216 females, and did not differ significantly from 50:50. The adult sex ratio was biased toward males (3:1), and the bias was caused by greater male infectivity of miracidia for snails and cercariae for mice. A significantly higher percentage of male miracidia developed to cercarial production in unimiracidial infections (57 male, 34 female snail infections), and a significantly higher percentage of male cercariae developed to adulthood in mice (143 male, 79 female worms resulted from 900 male and 900 female cercariae). / No significant differences were found between male and female parasites for longevity of miracidia (about 10 hr) and cercariae (males 21.3 (+OR-) 5.75, females 25.0 (+OR-) 7.02 hr), prepatent periods of snail hosts (males 34 (+OR-) 2.92, females 33 (+OR-) 2.36 days), longevity of snail infections (males 96.6 (+OR-) 25.15, females 115.2 (+OR-) 82.43 days), and the number of cercariae produced (males 30,751.44 (+OR-) 18,064.33, females 34,083.00 (+OR-) 33,732.82 per snail lifetime). / Present results are of theoretical significance for theories of biased sex ratios, which at present cannot account for the male-biased ratio of S. mansoni. Present results also suggest that transmission models for schistosomiasis that assume a 50:50 sex ratio at all stages of the life cycle should be reassessed. / Source: Dissertation Abstracts International, Volume: 47-05, Section: B, page: 1827. / Thesis (Ph.D.)--The Florida State University, 1986.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75828 |
| Contributors | LIBERATOS, JAMES DAMERON., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 57 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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