Taxonomy

Turbo marmoratus Linnaeus, 1758 is the type species of the Turbo subgenus Lunatica Röding, 1798.

The subgenus is entirely Indo-West Pacific in distribution and consists of 3 extant species:

  • 2 tropical:
    • T. marmoratus
    • T. imperialis - found in East Africa, Madagascar, Mauritius and Reunion
  • 1 temporate:
    • T. militaris - found in New South Wales and southern Queensland on the east coast of Australia

All three species are found subtidally, the first two in association with reefs.

T. marmoratus and T. imperialis, collectively known as 'the green snail', have been the focus of an intense fishery over the last century and both continue to be fished for their nacreous shell.

Distinguishing species

There is no genetic evidence for cryptic species in this subgenus based on the limited data available, but the three species are regularly confused. However, as well as differing in shell characteristics and distribution, they can be distinguished by their opercula:

  • Adult Turbo marmoratus have a smooth, white operculum whereas opercula of small specimens have granules.
  • Both T. imperialis and T. militaris have (sometimes lightly) coloured opercula of green with some brown, and have sharp, raised granules.
Opercula of the three species in the subgenus Lunatica.

Opercula of A. Turbo (Lunatica) marmoratus; B. Turbo (Lunatica) imperialis; C. Turbo (Lunatica) militaris.

Glossary

Cryptic species
These are species that resemble one another so closely that they have traditionally been considered a single species. In some cases close scrutiny of their morphology enables them to be distinguished, in other cases this is only possible by genetic analysis.

Extant
Living, still in existence (as opposed to 'extinct').

Nacreous
Consisting of nacre - an iridescent material composed of aragonite (a form of calcium carbonate). Nacre is also known as mother of pearl.

Operculum
A hard plate that serves to close the mouth when the animal is withdrawn into the shell.