HOSTS OF 3RD STAGE LARVAE OF HYSTEROTHYLACIUM SP (NEMATODA, ANISAKIDAE) IN ZOOPLANKTON FROM OUTER OSLOFJORD, NORWAY

Zooplankton samples from the outer Oslofjord were digested in hydrocloric acid and pepsin, and searched for live nematode larvae. Two hundred and forty five third stage larvae of Hysterothylacium sp. were found. One hundred and seventy three larvae were found outside their host, and 72 larvae were recorded from seven planktonic host species: Sagitta elegans (52), Pleurobrachia pileus (9), Thysanoessa raschii (4), Calanus finmarchicus (2), Aglantha digitale (4), Parathemisto abyssorum (1), and Centropages typicus (1). The three latter species are first host records. Transport of larvae in the planktonic zone is discussed in view of the known feeding ecology of the recorded hosts. Three other parasite species were found: Anisakis simplex (Rudolphi, 1809) (Nematoda), Derogenes varicus (Müller, 1784) (Digenea) and Hemiurus luehei Odhner, 1905 (Digenea). Third stage larvae of A. simplex were found outside their hosts, and the metacercariae of the digeneans D. varicus and H. luehei were found in Sagitta elegans. Metacercariae of H. luehei from S. elegans have not previously been reported. © 1990 Taylor & Francis Group, LLC.