Abstract

Scallop (Argopecten purpuratus) cultivation is an important economic activity in the central-northern region of Chile, and diseases are a permanent concern for farmers and fishing authorities. A one year-long survey was undertaken to find out what parasites and putative pathogens are present in cultivated scallops from three locations: Caldera, Guanaqueros and Tongoy. Ninety adult scallops were sampled from each location, on each season of the year. The soft parts were fixed in Davidson's fluid, and processed routinely for histology. The prevalence of infection for each parasite and pathologic condition were assessed. Larvae were sampled from three hatcheries and fixed for transmission electron microscopy. The same was done with digestive gland and gill tissues from the first 10 adults of each group sampled for histology. The same parasites and pathologic conditions were found in scallops from the three locations studied: inclusions of rickettsial-like organisms (RLOs) in epithelial digestive gland tubule cells of adults, and in the velar rim of one larva, haemocyte infiltration in gills and digestive gland, two types of granulomas of unknown aetiology in visceral and mantle connective tissues, mineral concretions in kidney, and the protozoan Trichodina sp., a ciliate ectoparasite, on the gills. However, the prevalences of all conditions varied greatly between the three sites and/or seasons. Based on the absence of significant mortalities among cultured scallops at the three sites during the reported survey year, it is concluded that the surveyed scallops were healthy, and that the pathological conditions reported here are generally benign.