. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 262 F. TETREAULT £7 AL belonging to the genus Neophasis, which has lile cycles involving one or two intermediate hosts (gastropod, lish) and a teleost final host (Bray and Gibson. 1991). Caudate cercaria develop in the gastropod, become l"ree-li\ing. and encyst as metacercaria in bivalve molluscs and tish that are later preyed upon by the final fish host. In \cnpliasis anar- rhichae. B. undatum apparentlv ser\es as the onlv obligate intermediate host. Caudate cercariac develop within rediae in the whelks. The cercarial
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 262 F. TETREAULT £7 AL belonging to the genus Neophasis, which has lile cycles involving one or two intermediate hosts (gastropod, lish) and a teleost final host (Bray and Gibson. 1991). Caudate cercaria develop in the gastropod, become l"ree-li\ing. and encyst as metacercaria in bivalve molluscs and tish that are later preyed upon by the final fish host. In \cnpliasis anar- rhichae. B. undatum apparentlv ser\es as the onlv obligate intermediate host. Caudate cercariac develop within rediae in the whelks. The cercarial tail is shed within the redia. and the noncaudate cercaria is considered a metacercaria thai does not encyst (Koie. 1973). l-'inal hosts are carnivorous teleosts belonging to the genus Anarhichas. which acquire the parasite by preying on infected whelks. Encysted meta- cercariae of an unidciitilied Xfophasis have been reported on the mesenterv of American plaice. Hippoglossoides plu- tessoides. and in the gut of Atlantic cod. Gudu.\ morhua, from Canadian waters (Appy and Burt. 19X2). Brav and Gibson (1991) indicated that this immature trematode mav be Neophasis burti Bray and Gibson. 1991. Biiccinum undatum is the most abundant carnivore in the henthic community in the Mingan Islands in the northern Gulf of St. Lawrence (Jalhert a <//.. 1989: Himmelman. 1991). It is also of commercial importance in the Gulf of St. Lawrence and St. Lawrence Estuary. From 1991 to 1993. 700 metric tons of whelks were harvested annually in Que- bec and 30% of this harvest came Irom the Mingan Islands (Savard, 1994). Several characteristics of the biologv of the common whelk make it especially vulnerable to lisherv over-exploi- tation. First, recoloni/ation of over-exploited sites is likely to he slow because the whelk lacks a pelagic larval stage and adults move only by crawling. Further, stocks arc- limited by a slow growth rate. In the Mingan Islands, whelks attain a shell length of 75 to SO
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
