Marine Biology (2+1)

15.Creseis acicula (Fig. )

Species: Creseis acicula  (Fig. )

Phylum : Mollusca

Class : Gastropoda

Subclass : Opisthobranchia

Order : Thecostomata (shelled pteropods)

Common name  : Sea butterfly

Description: This is an advanced mollusc and a fast swimmer . It possesses a shell which is straight and tapering and is made of calcium carbonate . The maximum length of the shell may be a few centimetres . The front part of the body of these animals is drawn out on either side into two symmetrical wing-like lobes and hence they are popularly known as 'sea butterflies'. These lobes or parapodia are a modified foot and form an important part of the feeding mechanism. They are ciliated and by the action of the cilia, food particles such as diatom

and other small organisms are sent to the mouth in a steady stream. Further, by the slow flapping movements of these lobes, the animal progresses through water.