Gibberulus gibbosus (Röding, 1798)

Gibberulus gibbosus is abundant in many lagoon sand flats in the Marshalls. In some areas in seems to be the most common mollusk present. They are seen only rarely on the seaward reef. They range from about 1 to at least 20m depth, and probably often extend deeper as well. The largest we know of was about 49mm long. Sometimes the shell is pure white, but it often is variably marked with brown, and may have a purple or white aperture. Occasionally we see piles of shells that have been recently cleaned out by some predator without damaging the shell. We suspect some nocturnally active octopus is pulling the animals out of the shells and devouring them in large numbers. (Previously we had this species as Strombus gibberulus.)

The interior of the aperture can be purple or white.

They can frequently be seen gathering on sand flats to breed, leaving their eggs in mixtures of sand and mucus on the top of the sand.

We found this large group marching (well, hopping) down a sandy lagoon slope all in the same direction on 5 October 2009. You can see the crowded front line toward the upper part of the first photo below, with their tracks in the sand trailing toward the lower left. The front line extended a good 10 to 12m and there must have been thousands of the mollusks, all apparently of the same mind(?) about where to go.

Below is another marching horde observed on 22 July 2012.

Created 1 October 2009
Updated 14 October 2012

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