Distribution of glycogen resulting from degradation of 14C-labelled bacteria in the American oyster, Crassostrea virginica

Differential localization and bacteriostasis of Vibrio campbellii among tissues of the Eastern oyster, Crassostrea virginica

In bivalve mollusks the roles of individual tissues in antimicrobial defense remain unclear. In this study, Crassostrea virginica were injected in the adductor muscle with 10(5) live Vibrio campbellii. Major tissues were dissected at 10, 30, 60 or 120 min postinjection (PI); in each tissue undegraded (intact) bacteria were quantified by real-time PCR and culturable bacteria were enumerated by selective plating. At 10 min PI, accumulation of bacteria varied among tissues from approximately 2.4 x 10(3) (labial palps, digestive gland) to 24.2 x 10(3) (gonads) intact Vibrio g(-1). Neither distribution nor accumulation of intact bacteria changed with time except in the hemolymph. In most tissues, more than 80% of intact bacteria were culturable at 10 min PI and culturability decreased with time. In contrast, only 19% of intact bacteria in gonadal tissue could be cultured at 10 min PI, pointing to a major role for the gonadal tissues in antibacterial defense of molluscs.

Cytometric, morphologic and enzymatic characterisation of haemocytes in Anodonta cygnea

The haemocytes in bivalve mussels are involved in many processes such as lesion repair, shell repair, elimination of small particles and toxic substances. In Anodonta cygnea there are two categories of haemolymph cells, the granulocytes and hyalinocytes. Two groups of cells were identified by flow cytometry and morphological studies: one with larger size and granularity representing 75%, and another group of cells (25%) which were approximately half the size. The cytochemical reactions showed peroxidase activity in the larger cells and a weak prophenoloxidase activity in the smaller cells. These characteristics suggest that the most common haemocytes are granulocytes and hyalinocytes are less common. Enzymatic studies showed clear activities of few enzymes in different compartments of the mantle. Both haemocytes presented significant variations for alpha-manosidase and beta-glucurosidase activities depending on the acid or alkaline pH. Almost all were sensitive to the pH changes, mainly the beta-galactosidase in the haemolymph plasma. On the contrary, the same enzymatic analysis in the extrapallial elements showed more stabilised activities. The simulation of acidic and alkaline condition with the observation of significant morphological and enzymatic activity changes, allow us to speculate some functional role, mainly in the haemolymph elements. The granulocytes may be speculated to have intense involvement in the digestion of small residues with the formation of calcareous stores while the hyalinocytes are more responsible for the elimination of soluble cytotoxic compounds.