Abstract
Bivalve mollusks are an important resource due to their socioeconomic value and to the historical and genetic value of some species. Two nationally important oyster species-Portuguese oyster (Crassostrea angulata) and Japanese oyster (Crassostrea gigas) from distinctive areas in Portugal were studied to evaluate their sanitary status. Oysters were sampled from four different sites in Portugal. Oysters collected from Japanese oyster populations were cultivated in a strong ocean-influenced environment and Portuguese oyster populations were cultivated in wild-beds. The histopathological examination of both oyster species revealed the presence of parasites in gills, mantle epithelium, digestive gland tubules and connective tissue, with a moderate prevalence. In both populations was observed hemocytosis in the connective tissue, edema and metaplasia in the digestive gland and tissues necrosis. In wild populations from Sado and Mira estuaries the prevalence of mud blisters and gill lesions were higher than from populations produced on 0.50 m tables from mudflats. Biosecurity measures and diagnostic techniques are fundamental to control pathogenic agents, including the identification of pathogens at an early stage in their life cycles. This will prevent diseases and improve pathogen reduction on transport of animals from different countries and regions to new production areas to avoid the transmission of diseases.
Highlights
Academic Editor: Snježana ZrnčićIn Portugal, in the late 20th century, the two most important commercial oysters were the flat Oyster (Ostrea edulis) and the Portuguese Oyster (Crassostrea angulata) [1]
Portuguese oysters sampled in Sado estuary, it was found a prevalence of 30% infections with Trichodina sp., characterized by a shape similar to a disc, a circlet of eosinophilic denticles, a ciliary fringe and a horseshoe shaped nucleous, in gills and mantle epithelium
Bivalve mollusks production depends on the external factors [37], including water parameters, such as temperature variations, food change, biotoxins and pathogens or anthropogenic, such as chemical contaminants, organic contaminants and overexploitation of natural banks [1,38]
Summary
In Portugal, in the late 20th century, the two most important commercial oysters were the flat Oyster (Ostrea edulis) and the Portuguese Oyster (Crassostrea angulata) [1]. The culture of bivalve mollusks is an activity with high expression in Portuguese aquaculture It represents 55% of the whole production, being the main species, clams, oysters and mussels [2]. Since 2009 a herpes virus (OsHV-1) has been the cause of massive mortalities in Japanese oyster (Crassostrea gigas), first in France and all over the most important European production countries of this species, including Portugal [3]. Contaminant metals can cause several problems in humans, and the contamination of bivalve mollusks with different concentrations of heavy metals can be dangerous, namely lead, cadmium and mercury They can accumulate high concentrations from water, and from the sediments and they have a wide bioaccumulation range of heavy metals depending on the species [33,34,35]. The objective was to describe the general health status, studying anatomo and histopathological lesions and parasites, in the Portuguese oyster (Crassostrea angulata) and Japanese oyster (Crassostrea gigas) from different production areas in Portugal, in order to evaluate their health condition
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