Bivalve Mollusc Hemocyte Behaviors: Characterization of Hemocyte Aggregation and Adhesion and Their Inhibition in the California Mussel (Mytilus californianus)

Abstract

Within minutes of removal from the California mussel, Mytilus californianus hemocytes become sticky for one another and for foreign surfaces. We sought to understand the cell surface changes responsible for this altered state. Hemocyte aggregation and adhesion assays were used in experiments in which a variety of reagents potentially capable of interfering with aggregation were screened. Caffeine, nor-ethylmaleimide, cytochalasin B, and EDTA were completely or partially inhibitory towards aggregation and adhesion. However, RGD-containing peptides, glycosaminoglycans, protease inhibitors, heparin, or poly-L-lysine were without effect. Low temperature (4°C) slowed hemocyte adhesion and hemocyte cohesion. Based on the findings, it appears that (1) Mytilus hemocyte aggregation, in vitro, is a two-step process that requires metabolic energy and divalent cations (calcium and magnesium), and is temperature-sensitive; and (2) Mytilus hemocyte adhesion and hemocyte aggregation are two associated but different cell behaviors.