CERCARIA-PATELLAE LEBOUR, 1911 DEVELOPING IN PATELLA-VULGATA IS THE CERCARIA OF ECHINOSTEPHILLA-PATELLAE (LEBOUR, 1911) N-COMB (DIGENEA, PHILOPHTHALMIDAE)

The echinostome cercaria, Cercaria patellae Lebour, 1911, which develo ps in the limpet Patella vulgata (Prosobranchia, Diotocardia, Patellid ae), was investigated by light and scanning microscopy. The highest pr evalence of limpets with rediae/cercariae occurred on bare rocks on th e upper part of the shore. The prevalence was higher in larger snails and in those which had an orange foot-sole. The cercariae penetrated i nto other gastropods, Aplysia punctata (Opisthobranchia, Cephalaspidea , Aplysiidae), Acanthodoris pilosa (Opisthobranchia, Nudibranchiata, L amellidorididae) and P. vulgata. No differences in size were found bet ween metacercariae which naturally infected only P. vulgata and five-d ay-old metacercariae from experimental infections. In in vitro experim ents excystation of metacercariae from natural infections took place a s a passive process after a double treatment with pepsin and trypsin w hich caused the dissolution of the cyst wall. After metacercariae from natural infections were fed to one-day-old chickens, the young adults developed. Detailed morphometrical data on rediae, cercariae and meta cercariae are compared with previously published measurements of livin g specimens. Chaetotaxy demonstrated a distinct distribution of tegume ntal papillae of cercariae, resembling that of the Echinostomatidae or Philophthalmidae. Scanning electron microscopy of adults revealed sho rt, blunt spines anteriorly, while flattened serrated spines occurred on the posterior tegument. Morphometry revealed no major differences t o previously published data. Considering all ecological data and compa ring the morphological data with those of previous publications by dif ferent authors, we conclude that C. patellae Lebour, 1911, the cercari a in the limpet, is a developmental stage of a digenean in the intesti ne of the oystercatcher Haematopus ostralegus and should be referred t o Echinostephilla patellae (Lebour, 1911) n. comb.