Observations on the Glochidial Stage of the Freshwater Mussel Hyridella (Hyridella) drapeta (Iredale) (Mollusca : Pelecypoda)

Abstract

The early life history of the freshwater mussel H. (H.) drapeta was investigated between September 1975 and November 1976. Observations from this study are basically consistent with those from previous investigations of glochidia of Australian freshwater mussels.

The glochidia were found to be subtriangular in outline and possess an S-shaped larval tooth on the ventral margin of each valve. The dimensions (average±standard deviation) of the glochidia were: height 0.23± 0.01 mm; length 0.33±0.01 mm; height/length ratio 70.6±2.7%.

The glochidia were observed to parasitize the river blackfish, Gadopsis marmorutus and the galaxiids Galaxias maculatus and G. olidus. Peak infections occurred between July and February. A single brown trout, Salmo trutta, was observed to be infected during one peak infection period. The gills of host fish were the major site of attachment and the glochidia were observed to be surrounded with a layer of epithelial tissue.