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Opalia australis (Family Epitoniidae)




The Wentletrap has a range that extends from Sydney, New South Wales, around southern shores to Fremantle, Western Australia. (NSW, VIC, TAS, SA, WA)


The Wentletrap has a polished, elegant looking shell that is elongated and slender with numerous, rather straight whorls, and deep sutures. Its width is one-third its height. It grows to a length of 35 mm, but is more commonly 25 mm.

Its sculpture consists of eight, thick, longitudinal ribs that extend across the whorls, but not all of the way around the shell. Near the aperture, on the last whorl, is a thickened ridge called a keel that extends around the shell to meet the horizontal ribs at right angles. Between these ridges, the shell is microscopically marked with delicate concentric and radial markings called striations. The shell aperture is small and rounded, but has a thickened lip and a flattened base. The operculum is horny.

The Wentletrap shell is pure white in colour and with its fine form and delicate sculpture this species is quite distinctive.

Ecology/Way of Life:

The Wentletrap occurs under stones at the lowest tide levels. It feeds on anemones. The Wentletrap attaches itself to the anemone by its proboscis and uses its radula tongue to scrape off fragments of anemone to consume. If it is disturbed, it can emit a violet fluid as a defence. Wentletraps are protandric; they become fully developed males in the early part of their lives and as they mature, they become female and remain female for the rest of their lives. They appear to have an accelerated lifecycle and may have a lifespan lasting only one year.

Preferred Image

Interaction with Humans/Threats:

Researchers from the Marine Research Group of Victoria consider the Wentletrap to be uncommon in Victoria (CIOV). Shepherd and Thomas consider it to be uncommon across southern Australia, and Wells and Bryce (from Western Australia) consider it to be uncommon as well. However, Wilson and Gillett consider it to be common across its range. Therefore, it appears that this mollusc may in fact be uncommon across its range and may be a threatened species.

Further Reading:

Davey, K. (1988). A Photographic Guide to Seashore Life of Australia. p. 111, New Holland Press.

Macpherson, J.H. & Gabriel, C.J. (1962). Marine Molluscs of Victoria. p. 114, Melbourne Univ. Press.

Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p. 48, Museum of Victoria.

Robertson, R. (1963). Wentle traps (Epitoniidae) feeding on sea-anemones and corals. Proc. Malac. Soc. Lond. 35, 51-63.

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

Wells, F.E., & Bryce, C.W. (1988), Seashells of Western Australia. p. 58, Western Australian Museum.

Wilson, B.R. & Gillett, K. (1971). A Field Guide to Australian Shells: Prosobranch Gastropods. p. 62, A.H. & A.W. Reed.


Resource by Keith Davey.

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Images and Multi-media:  
Attached Image  
image/jpeg 12916 bytes Wentletrap
Distribution Map  
image/gif 3834 bytes Distribution of Wentletrap

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