The crustacean and molluscan fauna of Tasmanian saltmarshes

Abstract

The crustaceans and molluscs of 65 saltmarshes and brackish marshes around the coast of Tasmania and the major Bass Strait islands were surveyed. Over 50 species were collected, but only eight (three talitrid amphipods, one crab and four gastropods) were confined to saltmarshes; the typical saltmarsh assemblage consisted of two talitrid amphipods, three oniscoid isopods, two crabs, two prosobranch snails and two pulmonate snails. The greatest species richness was found in marshes from the southeast and the far northwest, where the most extensive saltmarshes have developed. Several undescribed talitrids were collected and the range of two coastal species was extended significantly. The native woodlouse Plymophiloscia ulverstonensis was commonly found on the upper parts of the marshes, as was the introduced slater Porcellio scaber. The burrowing grapsid crab Helograpsus haswellianus was common on the marshes, though it was replaced by the ocypodid Heloecius cordiformis in brackish marshes, and by another grapsid, Paragrapsus gaimardii, in the only marsh examined on King Island. The hymenosomatid crab Amarinus paralacustris was recorded from the state for the first time at Hendersons Lagoon. Amphibolid and ellobiid snails typified the molluscan fauna of the marshes. The introduced ellobiid Phytia myosotis appears to have a major disjunction in its distribution between the southeast and northern sites. Tasmanian saltmarshes have a similar diversity of crustaceans and molluscs to those of New Zealand and South Africa. They are richer in species than saltmarshes of the northeast Atlantic coasts but have fewer crustaceans than the temperate east coast marshes of North America, and fewer molluscs than those of the coasts of the Pacific northwest.