THE OCCURRENCE OF METACERCARIAE OF BUCEPHALOIDES-GRACILESCENS (DIGENEA, GASTEROSTOMATA) IN AN INTERMEDIATE HOST, THE 4-BEARDED ROCKLING, ENCHELYOPUS-CIMBRIUS (GADIDAE)

Infections with metacercariae of Bucephaloides gracilescens in the fou r-bearded rockling Enchelyopus cimbrius were studied for a year in a N orwegian fjord. The prevalence was at all times high, but abundance sh owed a marked decline in spring to a low level during summer. A rise i n abundance, variance-to-mean ratio and frequency of smaller metacerca riae in early autumn (August-September) shows infection to have occurr ed mainly in autumn. There were no differences in level of infection b etween host sexes, but a highly significant positive correlation of pa rasite burden with host length. No influence on the condition factor o f the host was revealed, the parasite cysts in the central nervous sys tem are believed to have low pathogenicity. A detailed account of the distribution of metacercarial cysts is given. No support for infection being via the lateral line canals is revealed, cercarial penetration is believed to be through the general surface of the head and through the unpaired fins of the trunk and tail.