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Shuttlecock Egg Cowry Volva volva
Growing to around 120mm and ranging across the Indo-Pacific and from Japan to northern Australia, the Shuttlecock Egg Cowry is not commonly known to most divers.
It generally inhabits sandy rubble areas (mostly offshore) where in the past it was collected in large numbers by trawlers netting for prawns and scallops. Although I knew of this shell it took me over 35 years diving before I actually saw a live one underwater.
Similar to all members of the Ovulidae family, Egg Cowries and Spindle Cowries feed on soft corals, gorgonians and/or black corals.
Although this species is the largest of its type it only appears to attack and eat small colonies of Spiky Soft Corals Dendronephthya spp. and gorgonians, often eating the entire colony. The animals mantle is very well-developed with large papillae protruding from each ocellation making up the overall pattern.
As this display and pattern does not represent any visual details of its prey, and as it travels from one food source to another across open sandy bottom the mantle display is protective mimicry based on sand-dwelling opisthobranchs.
With muck diving becoming more popular and divers taking more notice of critters it is hoped we can discover more about this very interesting ovulid.
Photographed from an inverted lateral aspect allows the best view of the extensive mantle patterning. Notice the small Imperial Shrimp Periclimenes imperator on the mantle surface. These shrimps form loose asociations with many sand-dwelling opisthobranchs which supports the mimicry theory.
(Photo Neville Coleman)
This Imperial Shrimp Periclimenes imperator was the first one I had ever seen in association with a Shuttlecock Egg Cowry. Milne Bay PNG.
(Photo Neville Coleman)