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Pyrazus ebeninus (Family Batillariidae)

Hercules Club Whelk


The Hercules Club Whelk ranges from northern Queensland, to Lakes Entrance, Victoria. (QLD, NSW, VIC)


The Hercules Club Whelk is a distinctive mollusc found in countless numbers on muddy estuarine flats. It has a large, elongate, turreted shell and rounded whorls, with a flared rounded aperture. It grows to 90 mm in length. It has a sculpture of low, longitudinal ridges that become angular and noduled on the last two whorls with irregular concentric ridges. The anterior canal is short and broad. The columella is broad with a reflected inner lip. The operculum is horny, flat, rounded and sculptured with concentric ridges.

The Hercules Club Whelk shell exterior is dull dark brown to grey. The aperture is shiny. The interior is brown, becoming white towards lip, margined dark brown. It has a brown operculum.

Ecology/Way of Life:

It occurs on estuarine mudflats and mangrove swamps, often in countless numbers. Its tracks across mudflats are distinctive. The crew of the Endeavour collected it first in 1770.

Interaction with Humans/Threats:

The Hercules Club Whelk is one of the host animals for schistosome dermatitis that is known as Bathers' Itch, Pelican Itch, Weed Itch, Terrigal Itch, Clam Diggers' Itch and Swimmers' Itch. Bathers' Itch can be contracted when wading or bathing in salt or fresh water in areas infested by parasitic schistosome flat worms. The adult flat worms are blood parasites of estuarine and seashore birds. They attach themselves to the swimming host bird by one or more suckers. Birds affected are seagulls, swans and other waterfowl. The eggs pass into the faeces of the birds and hatch into miracidae, which commonly infest water snails such as the Hercules Club whelk and other whelks, periwinkles, and rock platform animals. The microscopic, mobile cerceriae larvae develop inside the mollusc intermediate host, to be released into the surrounding water in search of the bird host. Although humans are not hosting animals, the cerceriae penetrate the skin, but cannot reach blood and soon die. They produce a foreign body reaction, followed by an antibody reaction that produces characteristic skin lesions that last 2-10 days. Further attacks may be more severe, some leading to anaphylactic shock.

Other Comments:

Other common names are the Sydney Club Whelk and Club Mud Whelk.

Further Reading:

Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. p.106. New Holland Press.

Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p.247. Reed.

Edmonds, C. (1989). Dangerous Marine Creatures. P.129. Reed.

Macpherson, J.H. and Gabriel, C.J. (1962). Marine Molluscs of Victoria. p. 104. Melbourne Univ. Press.

Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p.47. Museum of Victoria.

Shepherd, S.A. and Thomas, I.M. (1989). Marine Invertebrates of Southern Australia. pt. II. p.572. South Aust. Govt. Press.

Robinson, K. and Gibbs, P. (1982) A Field Guide to the Common Shelled Molluscs of New South Wales Estuaries. p.42. Coast and Wetlands Society.

Short, J.W. and Potter, D.G. (1987). Shells of Queensland and the Great Barrier Reef. p.24. Golden Press.

Wilson, B.R. and Gillett, K. (1971). A Field Guide to Australian Shells: Prosobranch Gastropods. p.57. A.H. and A.W. Reed.


Text, map and photograph by Keith Davey.

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