Host skin mucus as a hatching stimulant inAcanthocotyle lobianchi, a monogenean from the skin ofRajaspp.

Abstract

When incubated at 13°C in alternating 12 h periods of light and darkness eggs ofAcanthocotyle lobianchirarely hatch. Hatching was not induced by shadowing or by mechanical disturbance. When skin mucus from the host ray was added to eggs which were more than 15 days old, hatching occurred almost immediately in about 60% of all eggs tested. Susceptibility to host mucus increased with the age of the eggs so that after 26–30 days of incubation over 80% of the eggs tested hatched. Some oncomiracidia were found to remain alive for up to 83 days in the egg, although they appeared to be fully developed at 15 days. Lipid droplets in the body of the 15-day-old oncomiracidia gradually disappeared as the eggs aged and it is suggested that these droplets serve as a food store for resting larvae.