Procalpurnus lacteus (Lamarck, 1810)
Milky white ovulid, 13mm

This little pure white shell is not found often, but when it is there are usually several specimens all feeding on colonies of the soft corals Sinularia or Lobophytum. We have seen them only at night, crawling on the surface of the soft coral. During the day, they apparently hide effectively under or around the soft coral colony.

The shell of Procalpurnus lacteus is very similar to that of Procalpurnus semistriatus. Both species are shown in the photo below, with P. lacteus on the right. The shells of both are pure white and similar in size and shape, but P. lacteus is smooth while P. semistriatus is finely striated. The color of the mantle of the two species is similar, but as is evident in the photo below, the foot color differs considerably. Also, the siphon on P. semistriatus is solid yellowish tan color with a distinct red-brown margin, while that of P. lacteus (photos above) is brown spotted with white. Curiously, specimens of the two different species, including the two in the photo below, can sometimes be found together on a single soft coral colony. Since the vast majority of soft coral colonies host no specimens at all, it seems unlikely that the same coral colony would be inhabited by two different species. It almost seems less unlikely that the foot color in this species is simply variable. I do not think we can discount the possibility that these are simply two forms of one species. More detailed animal studies, including comparison of DNA, would be valuable in determining the relationships.

This one had a darker mantle and showed an interesting oval ring on top of the head between the tentacles.

The specimen above on the soft coral colony.

Below at least five specimens were exposed on their soft coral host at night, along with a crinoid curling up in reaction to the diver's light. All these have the foot color of P. lacteus.

Created 22 September 2008
Updated 17 September 2016

Return to ovulid list

Kwajalein Underwater home