STUDIES ON TRIPLOID OYSTERS IN AUSTRALIA .7. ASSESSMENT OF 2 METHODS FOR DETERMINING TRIPLOIDY IN OYSTERS - ADDUCTOR MUSCLE DIAMETER AND NUCLEAR SIZE

Two methods for distinguishing triploid Pacific oysters [Crassostrea g igas (Thunberg)] from diploid oysters were assessed. Adductor muscle d iameter in relation to valve height was significantly (p < 0.001) grea ter in samples of triploid oysters than in diploid samples and was inf luenced by site. However, variation in this measure was too large to a llow individual oysters to be distinguished as either triploid or dipl oid. A second method was assessed that used differences in the nuclear size of hemocytes and the intensity of staining of hemocyte nuclei to distinguish between diploids and triploids. Histological sections, pr epared by standard paraffin histology, were stained for nuclear histon es with Gill's hematoxylin. Integrated nuclear optical density and nuc lear area were recorded with image analysis. This method was effective in distinguishing individual oysters as diploid or triploid. When his tological specimens are required, this method is less expensive than o ther techniques used to determine triploidy.