Dark rock shell

Haustrum haustorium

Haustrum haustorium, (common name: the brown or dark rock shell) is a large species of predatory sea snail, a marine gastropod mollusc in the family Muricidae, the murex snails or rock snails.

Haustrum haustorium used to be the only species in the genus Haustrum. However, Beu (2004) reclassified a number of New Zealand's whelks, considering the genera Lepsiella (species: Lepsiella scobina) and Lepsithais (species: Lepsithais lacunosa) to be synonyms.

Distribution

This species is endemic to New Zealand.

Habitat

This rock snail is typically found in the mid and lower eulittoral zone of New Zealand's semi-exposed rocky intertidal shores. It is less common on algal-dominated sheltered shores.

Shell description

The shell is rather large and solid with a low conical spire, and a rapidly expanding body whorl that tapers gradually to the anterior end. The aperture is large, and the outer lip is thin and crenulated. The inner lip has a broad smooth excavated callus. Sculpture is coarse uneven spiral ridges, separated by linear grooves. The operculum is ovate-lunate. The coloration of the exterior of the shell is dull purplish-brown, with the aperture and parietal callus white except for a splash of reddish-brown within, and a border of purplish-brown streaks inside the outer lip. A reliable characteristic for distinguishing Haustum haustorium from its congeners is the angle by which the aperture lip inserts on the shell: In Haustrum haustorium the angle is near-perpendicular, whereas in other species the angle is more acute (~45 degrees). Tan (2003) provides the most recent review.

Life habits

The food of this species varies regionally, but generally consists of other gastropods (including other whelks such as the oyster borer, limpets and chitons). Juveniles often feed on barnacles. Access is gained by the rock snail drilling through the prey's shell with its radula. Large specimens of Haustrum haustorium can also dislodge the operculum of their prey directly by smothering prey and enveloping it with their mantle.

Historic specimens attain a shell height up to 65 mm, and a width of up to 45 mm. Today, however, it is difficult to find individuals larger than 55 mm.

References

  • Powell A W B, New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1
  • Glen Pownall, New Zealand Shells and Shellfish, Seven Seas Publishing Pty Ltd, Wellington, New Zealand 1979 ISBN 85467 054 8
  • Miller M & Batt G, Reef and Beach Life of New Zealand, William Collins (New Zealand) Ltd, Auckland, New Zealand 1973
  • Beu, A. G. 1990. Molluscan generic diversity of New Zealand Neogene stages: extinction and biostratigraphic events. - Palaeogeography, Palaeoclimatology, Palaeoecology 77: 279-288.
  • Tan, K. S. 2003. Phylogenetic analysis and taxonomy of some southern Australian and New Zealand Muricidae (Mollusca: Neogastropoda). - Journal of Natural History 37: 911–1028.

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