Geographical, seasonal, and sex dynamics of Shipleya inermis (Cestoidea: Dioecocestidae) in Limnodromus griseus Gmelin (Aves: Charadriiformes).

We recovered the cestode Shipleya inermis from 79 of 82 short-billed dowitchers, Limnodromus griseus Gmelin, collected at various locations and times along their migratory route. Previous studies that examined various aspects of the cestode's biology were limited to North America. Data collected from North and South America in the present study provide new information on the geographical and seasonal distribution of this cestode. Although prevalence of infection was high at all times of the year, mean abundance varied from season to season and was significantly higher during the winter months than in the summer, suggesting that most recruitment takes place on the wintering grounds. Sexually mature and gravid cestodes were recovered at all locations, indicating S. inermis is a ubiquitous parasite within the host's range. Shipleya inermis showed a marked tendency to occur in pairs of male and female strobila. Analysis of the patterns of occurrence suggests that S. inermis is a protogynous hermaphrodite that usually becomes regionally dioecious, possibly in response to some form of interaction between individuals.