Moles, Tortoises, Calves and Cowries

The cowries of the family Cypraeidae are one of the most readily recognisable groups of tropical and subtropical shells. Their distinctive shape (with no spire and a long narrow aperture running the length of the shell) and highly polished appearance are guaranteed to catch the eye (to the extent that one species, the money cowry Monetaria moneta, famously has a history of being used as a form of currency in many regions around the Indian Ocean). Though there are a large number of cowry species found around the world, they tend to be similar enough to each other that, until relatively recently, many authors would place all within a single genus Cypraea. This approach has fallen out of fashion in more recent years and, indeed, the current favoured approach divides the family between several subfamilies. One such subgroup is the subfamily Luriinae.

Live mole cowry Talparia talpa, copyright Juuyoh Tanaka.

In a phylogenetic analysis of the cowries, Meyer (2003) recognised the Luriinae as including two tribes, the Luriini and Austrocypraeini. This concept of Luriinae was essentially based on molecular phylogenetic analysis though it was also corroborated by radular morphology (with a reduced shaft on all teeth). The underside of the shell in luriines is mostly smooth with the 'teeth' being restricted to alongside the aperture. As in other cowries, the mantle is widely extended and mostly covers the shell in life (this is how cowry shells stay so shiny). In most luriines, the mantle is covered by warty papillae. In species of the genus Luria these warts are obsolete (Schilder 1939) but they are particularly prominent in the Indo-west Pacific mole cowry Talparia talpa. Members of the Luriinae vary greatly in size: the Pacific Annepona mariae is only a centimetre or two in length but the tortoise cowry Chelycypraea testudinaria of the Indian and western Pacific Oceans grows to ten centimetres or more. Species of Luriini have shells that are banded in coloration, with three or four broad dark bands divided by narrower light bands. The Austrocypraeini are most commonly marked with brown speckles or blotches on a pale background; these blotches may be irregular as in Chelycypraea testudinaria or more regularly rounded as in Annepona mariae. The calf cowry Lyncina vitellus of the Indo-Pacific is marked with white spots on a brown background, and some species or forms of Austrocypraeini may have coloration patterns more like the banded arrangement of Luriini.

Lynx cowry Lyncina lynx, copyright Patrick Randall.

My impression is that species of Luriinae tend to be mostly nocturnal, sheltering in crevices in coral reefs during the day before emerging to feed at dusk (the name of the aforementioned mole cowry is, I suspect, more likely to refer to its appearance in some way than to any actual burrowing habit). Though I haven't (though a cursory search, at least) found any reference to species of Luriinae in particular being endangered, a number of cowries in general have been threatened by overcollecting for their shells. Certainly, luriines would be subject to the broad range of threats that currently hang over coral reefs and their inhabitants anywhere in the world.

REFERENCES

Meyer, C. P. 2003. Molecular systematics of cowries (Gastropoda: Cypraeidae) and diversification patterns in the tropics. Biological Journal of the Linnean Society 79: 401-459.

Schilder, F. A. 1939. Die Genera der Cypraeacea. Archiv für Molluskenkunde 71 (5–6): 165–201.