A survey of some parasites and diseases of several species of bivalve mollusc in northern Western Australia

Pteriid oysters (Pinctada maxima, Pinctada margaritifera, Pinctada albina, Pteria penguin), rock oysters (Saccostrea glomerata, Saccostrea cuccullata, Saccostrea echinata) and representatives of other taxa (Malleidae, Isognom onidae, Pinnidae, Mytilidae, Spondylidae, Arcidae) from the wild, and 4670 hatchery-reared P, maxima, from northern and Western Australia, were examin ed for parasites and diseases. Rickettsiales-like inclusions and metacestod es Of Tylocephalum occurred in most species. Intranuclear virus-like inclus ions occurred in 1/415 wild P. maxima, 1/1254 S. cuccullata, 3/58 Isognomon isognomum, 1/80 Pinna bicolor and 1/45 Pinna deltodes. Perkinsus was histo logically observed in 1/4670 P. maxima spat, 2/469 P. albina, 1/933 S. glom erata, 16/20 Malleus meridianus, 12/58 I. isognomum, 1/45 P. deltodes, 5/12 Spondylus sp., 1/16 Septifer bilocularis and 3/6 Barbatia helblingii. One of 1254 S. cuccullata was heavily systemically infected with Perkinsus mero zoites, meronts and schizonts, and was patently diseased. Other potentially serious pathogens included Haplosporidium sp. in 6/4670 P. maxima spat, Ma rteilia sydneyi from 1/933 S. glomerata, and Marteilia sp. (probably M. len gehi) (1/1254) and Haplosporidium sp. (125/1254) from S. cuccullata. The la tter were associated with epizootics on offshore islands, with heaviest pre valence (45%) in oysters with empty gonad follicles. Marteilioides sp. infe cted the oocytes of 9/10 female S. echinata from Darwin Harbour. Details of geographical distribution and pathology are given, and the health of the b ivalves examined is discussed.