title: The seasonal occurrence of Trilocularia acanthiaevulgaris (Cestoda: Tetraphyllidea) from spiny dogfish in the Irish Sea.
abstract: Trilocularia acanthiaevulgaris occurs in the stomach and spiral valve of the spiny dogfish. Statistical analyses show that the stomach and spiral valve worms of male fish and the stomach worms of female fish exhibit seasonal trends in prevalence and mean worm burden, with peaks occurring in May, June and July of each year. Spiral valve worms of female fish do not show this trend. Calculation of the product-moment correlation coefficient shows that the peak in the number of stomach worms occurs approximately 1 month before that of spiral valve worms in male fish. Strobilization of the adult spiral valve worms and development of the resulting free proglottides is also seasonal, and takes place in June/July in both sexes. Seasonal trends in prevalence, mean worm burden and maturation of T. acanthiaevulgaris may be related to water temperature, and the cyclical changes in levels of reproductive hormones and thyroid activity associated with migration and mating of spiny dogfish. It is suggested that the availability of infected intermediate hosts and diet of the dogfish may also be important in explaining the seasonality of infection.
mesh_terms: D000818:Animals; D002589:Cestoda / Q000254:growth & development*; D002590:Cestode Infections / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D004284:Dogfish / Q000469:parasitology*; D005260:Female; D005393:Fish Diseases / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D012621:Seasons; D012623:Seawater; D012754:Sharks / Q000469:parasitology*; D013696:Temperature