Hatching in the monogenean parasiteDictyocotyle coeliacafrom the body cavity ofRaja naevus

Abstract

When eggs of the monogeneanDictyocotyle coeliaca, a parasite from the body cavity ofRaja naevus, are incubated in alternating 12 h periods of light and darkness at 12 °C the marginal hooklets appear between 75 and 90 days after collecting the eggs from the host's body cavity and hatching begins after about 102 (96–109) days. Hatching occurs continuously throughout the light and dark periods so that there is no daily hatching rhythm, and host skin mucus and fluid from the host's body cavity (previously deep frozen and thawed before use) are ineffective as hatching stimulants. The significance of these observations in relation to host behaviour is discussed.