Annachlamys Flabellata

Annachlamys flabellata is a species of scallop, a marine bivalve mollusk belonging to the family Pectinidae. It can be found in the sublittoral zone of the continental shelf north of Australia.

This species has the potential to grow between 2.4 and 3.9 inches in length. The shell is inequitable and moderately compressed. The valve on the right is more inflated and is less convex than the left one. The shape is generally circular with two broad auricles extending on either side of the umbones. There are 18 to 20 broad radial ribs which are more prominent and have larger interstices between them on the right valve. There is sculpturing in the form of concentric growth rings as well. Some of all of the ribs on the left valve are pink, mauve, or orange, while the right valve is entirely white. The space between the ribs is narrower than in the otherwise similar and closely related, Annachlamys reevei. On the inside of the valve there is often a red colored tinge or a concentric ring of red colored dots.

This species is normally found on sandy seabeds in the neritic zone reaching depths of down to 417 feet on the coasts of the Australian states of Western Australia, Queensland, Northern Territory and New South Wales, in New Guinea and in Indonesia.

Annachlamys flabellata is a filter feeder, drawing water into the gill chambers through a gap between the valves towards the back of the shell. At the same time as oxygen is being absorbed by the gills, food particles, mainly microscopic algae, are sieved out and transported to the mouth and the water is expelled again.

Individuals of this species reach maturity at about 1.8 inches in length. They seem to show partial protandric sex reversal in that smaller individuals are mainly males but females predominate among the larger individuals. Nevertheless, some small females and large males do exist.

Image Caption: Annachlamys flabellata J. B. Lamarck, 1819, a scallop from the family Pectinidae; Australia. Credit: Jan Delsing/Wikipedia