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Brachidontes erosus (Family Mytilidae)

Rough Beaked Mussel

Distribution:

The Rough Beaked Mussel ranges from San Remo in Victoria, west to Albany in Western Australia, including northern Tasmania (VIC, TAS, SA, WA).

Features:

The Rough Beaked Mussel is an elongate bivalve mussel that is narrow at the front (anterior) and wide at the rear (posterior). Both valves are equal in size (equivalve) but are curved and not symmetrical (inequilateral). It grows to 70 mm long and 22 mm high. It resembles the Beaked Mussel, Brachidontes rostratus, but has fewer grooves, and its grooves are deeper. They are so deep that they form keels, like the keel on the bottom of a boat. The sculpture consists of radial, coarse ribs, becoming much finer below the keel. There are several hinge teeth, with the front ones being large, becoming smaller until they form crenulations.

The base colour of the Rough Beaked Mussel is brown, opal green or horn coloured. If the covering protective periostracum is removed, the shell is whitish, with a purple or blue tinge.

Ecology/Way of Life:

The Rough Beaked Mussel prefers sheltered rocks and reefs. It is found from mid tidal level down to 4 metres. Their posterior ends are often embedded into firm, spongy, green algae. In this location, the shell may be greatly deformed, apparently by compression where many shells are crushed together as they grow. It may also be found subtidally attached to rocks in mud bays. They are often found high in the tidal zone, lying embedded in spongy green algae.

Interaction with Humans/Threats:

This was one of the mussels described by Lamarck from specimens collected by the Frenchman Peron at Kangaroo Island, South Australia, while sailing the "Geographe".

Further Reading:

Davey, K. (1988) A Photographic Guide to Seashore Life of Australia. p. 123. New Holland Press.

Edgar, G.J. (1997) Australian Marine Life: the plants and animals of temperate waters. p. 288. Reed.

Macpherson, J.H. & Gabriel, C.J. (1962) Marine Molluscs of Victoria. p, 289, Melbourne University Press.

Shepherd, S.A. & Thomas, I.M. (1989) Marine Invertebrates of Southern Australia. pt. II. p. 634. South Aust. Govt. Press.

Acknowledgments:

Text, map & photograph by Keith Davey.

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