Histological survey of symbionts and other conditions of pod razor clam Ensis siliqua (Linnaeus, 1758) in Galicia (NW Spain)

Abstract

The aim of the present study was to carry out a survey of parasites and other conditions affecting pod razor clam populations, Ensis siliqua, in two beds from Galicia (NW Spain). In Galicia, the production of E. siliqua has increased in recent years due to the development of specific plans for its exploitation, however few and quite recent pathological studies have been carried out in this species. The results of this study showed the presence of different protozoa as the more prevalent group, especially Nematopsis sp. gregarines, unidentified branchial protozoa, renal coccidia and Trichodina sp. ciliates. Larval stages of trematodes and neoplastic disorders were also observed with lower prevalences. Furthermore, an ultrastructural analysis of two types of unidentified basophilic inclusions, both found in the digestive gland, revealed the presence of icosahedral viral particles and prokaryotic organisms, respectively. None of the parasites detected in E. siliqua from this study was notifiable to the World Organisation for Animal Health (OIE) and the majority of the symbionts and conditions observed in their tissues did not cause host damage. Nevertheless, parasites like bucephalid digenean sporocysts, viral inclusions, prokaryotic infections, disseminated neoplasm or germinoma detected in some samples could cause moderate or severe damage to the host depending on the intensity of infection.