The life-cycle of Prosorhynchus crucibulum(Rudolphi, 1819) Odhner, 1905, and a comparison of its cercaria with that of Prosorhynchus squamatus Odhner, 1905

• Published in: Parasitology
• Main Author: Matthews, R. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1973
• Subjects: Scophthalmus maximus
• Online Access: http://dx.doi.org/10.1017/s0031182000044504; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182000044504

The adult of P. crucibulum is redescribed to form a basis for comparison with the cercaria and metacercaria. Particular emphasis is given to the structure and function of the rhynchus, digestive system and reproductive system. Some features, notably prepharyngeal glands and spematophores, have not previously been recorded in this species. The sporocyst and cercaria which were found in Mytilus edulis are described for the first time. Out of 6907 mussels examined from Borth Rocks, Cardigan Bay, 0·26% were infected with P. crucibulum and 0·06 % with P. squamatus . The cercaria of the latter is redescribed on a comparative basis with that of P. crucibulum , to avoid confusion. The two cercariae are clearly distinguished by three features – flame-cell formula, shape of the excretory vesicle, and structure of the tail stem (this being bilobed in P. crucibulum and trilobed in P. squamatus ). The significance of the two types of tail in securing attachment to the second intermediate host is discussed. Metacercariae of P. crucibulum were obtained experimentally in ‘O’ group specimens of Scophthalmus maximus . Three other species of fish, namely Limanda limanda, Onus mustelus and Gobius minutus were also successfully infected. The metacercariae did not develop in the following fish: S. rhombus, Pleuronectes platessa, Cottus bubalis and Blennius pholis . Possible mechanisms which might account for host specificity within Pleuronectidae and Scophthalmus are suggested. The development of the metacercaria in the connective tissues and musculature of S. maximus was followed over a period of 10 months. Within 1 month of infection the hyaline cyst of parasitic origin breaks down, enabling the parasite to feed directly on the host tissues. This feature is thought to account for the advanced development of the metacercaria, which 1 month after infection could clearly be identified with the adult on the basis of comparative morphology, and at 2 months resembles the adult in every respect except the development of the vitellaria. ...