Thursday, November 5, 2009

Jurassic Scallops

We spent most of the afternoon in Opunohu bay, brushing the underside of reef overhangs and cavelets with a brush and collecting the stuff that fell off. It is mucky work, stirring up clouds of silt and urchin spines. The results however are worth it. These habitats hold all sorts of specialities, some of which are limited to very specific areas of the reef.

This parthenopid crab matches the silt and algae covering the rocks perfectly, but fell into the net when brushed off.

The real find of the search were of propeamusid bivalves called Chlamydella. These little "proto-scallops" are living fossils that had their glory days back in the Mezozoic. During the Jurassic these were one of the dominant bivalve groups, before being replaced by modern scallops. Now, they survive only in the deep oceans, and in caves, where they have taken on a miniaturized existence. Like many other cave taxa, they brood their eggs, instead of releasing them into the water column, and have young that crawl away to set up shop near their parents.