| Summary: | Freshwater mussels (Unionoida) are a very old group of bivalve molluscs found in rivers, lakes and other wetlands on all continents but Antarctica, which includes 854 species in two superfamilies (Unionoidea and Etherioidea) that are distinguished by larval forms. Larvae of Unionoids (Hyriidae, Margaritiferidae and Unionidae) are glochidia, distinct from the lasidia or haustoria of etherioids (Etheriidae, Iridinidae, Mycetopodidae). Unionoids are dioecious and reproduce sexually. Males release sperm into the water, which are then drawn into gills (ctenidia), of the females, where the eggs are fertilized within modified brood chambers (marsupia). The embryos then develop to become mature glochidia, and are brooded in the marsupia. They then attach to a suitable host, generally a fish, on the gills or body surface (often the fins or mouth) where they are encapsulated by epithelial tissue and, as obligate parasites, begin a metamorphosis and emerge as juvenile mussels. The host-glochidia relationship is an obligatory stage in the life cycle of mussels, and also provides a means of dispersal. Glochidial attachment is facilitated by specialized structures on the ventral margin of shells, known as larval teeth, which vary in morphology, but are generally hooked. In Australia, freshwater mussels are represented by 18 species (eight genera) of Hyriidae. Glochidia tooth morphology of Australian Hyriidae has been described for several species and implicated as a useful taxonomic tool to distinguish species. In this poster, we present the first images (Scanning Electron Microscopy) of Westralunio carteri Iredale, 1934 larval teeth, which appear to be unique and may have taxonomic value.
|
|---|