Van Diemen's Siphon Shell
Van Diemen's Siphon Shell's ranges from central New South Wales, through Victoria, around Tasmania, and across South Australia to southern Western Australia. (NSW, VIC, TAS, SA, WA)Features:
Van Diemen's Siphon Shell is oval and limpet-like, with a sharp, central apex, leaning slightly backwards. The shell length is 15-28 mm; width 24mm; and height 8-12mm. It is taller than the New Zealand Siphon Shell that often occurs on the same shores, but in more exposed situations.
Its shell sculpture consists of about 40 strong, irregular, radiating ribs which extend to the shell edge to form a scalloped margin. There is great variation in shells, often depending upon the habitat. Underneath, there is a channel (siphonal canal) running from the shell apex to slightly as a projection beyond the shell margin on the right hand side. The shell may be quite eroded.
Shell exterior dark brown interspaces with white radiating ribs. The interior of the shell is coloured chestnut brown and white alternating radial bands, with an orange apex spoon-shaped mark called a spatula. The animal is citron-yellow in colour speckled with yellow markings.Ecology/Way of Life:
Van Diemen's Siphon Shell occurs across a wide range across all tidal zones, but appears to be more common at higher shore levels than the New Zealand Siphon Shell, S. zelandica. This is a very common to abundant shell, and is gregarious. It tends to prefer more sheltered conditions than the New Zealand Siphon Shell, S. zelandica. All siphon shells are herbivores.
Because of their ability to bring oxygen into the mantle cavity along the siphon channel, these shells are able to extend their range across the complete tidal region on rocky ocean shores.
During the reproductive period, ova are produced in irregular, curved clumps. The egg mass is a light yellow gelatinous girdle that is curved into 2.5 to 3 spirals, and is 15-20mm in diameter and up to 6mm high. They are laid on rocks in crevices. If you look closely, you can see the small, pale yellow eggs that are only 0.1mm across. The eggs appear to be joined together by a fine thread, so they look like a string of beads immersed in a clear coloured jelly. These small eggs develop into small veligers that are released into the water to drift as plankton when the girdle disintegrates.Interaction with Humans/Threats:
Van Diemen's Siphon Shells are common to abundant upon many of the shores where it occurs, so it appears that there is no threat.Other Comments:
Another common name is Van Diemen's Land Air-breathing Limpet.Further Reading:
Bennett, I. (1987). W.J. Dakin's classic study: Australian Seashores. p. 307, Angus and Robertson.
Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. p. 117, New Holland Press.
Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p. 267, Reed.
Macpherson, J.H. and Gabriel, C.J. (1962). Marine Molluscs of Victoria. p. 262, Melbourne Univ. Press.
Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p. 78, Museum of Victoria.
Shepherd, S.A. and Thomas, I.M. (1989). Marine Invertebrates of Southern Australia. pt. II. p. 610, 876, South Aust. Govt. Press.
Short, J.W. and Potter, D.G. (1987). Shells of Queensland and the Great Barrier Reef. P. 122, Golden Press.
Text, map and photograph by Keith Davey.Sponsorship welcomed:
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