A NOTE ON THE BIOLOGY OF MARTESIA STRIATA L. (LAMELLIBRANCHIA)

Abstract

SUMMARY Healthy specimens of Martesia striata L. were obtained from timbers in the Johore Straits in March 1953, and were examined immediately. The siphonal process is of type “C” and resembles that of Pholadidea loscombiana. The shell valves possess a posterior flexible uncalcified portion, comparable with the siphonoplax of Pholadidea loscombiana, The scar of the anterior adductor muscle is smaller than that of the posterior adductor. In this respect Martesia resembles Pholadidea more closely than other genera in the Pholadidae. In large specimens which had ceased to bore, the pedal muscles and the anterior and posterior retractor muscles of the visceral mass had atrophied. The foot also had disappeared. The flat and homorhabdic ctenidia are of Atkins's type C 2. The ciliary sorting mechanisms on the ctenidia and labial palps are suited for the selection of few fine particles and for the rejection of larger quantities even of fine particles. This is considered to be well adapted to life in inshore waters that may occasionally have a very high silt content. The palps are extremely efficient sorting organs and the ciliary mechanisms on the folded surfaces are comparable with those reported for other genera in the Pholadidae. The ciliary cleansing mechanisms on the surfaces of the visceral mass and mantle are described. There is no appendix to the stomach. In other respects the alimentary canal is closely similar in structure and function to that of other members of the Pholadidae. There is an anterior median fenestra joining the cavities of the distal limbs of the left and right excretory organs as is found also in Barnea parva and Zirphaea crispata. There is a transverse connective between the left and right cerebrovisceral connectives, immediately anterior to the visceral ganglia. This transverse connective is slightly swollen to form an accessory visceral ganglion, as in other genera of the Pholadidae. There is an indication of slight sexual dimorphism, affecting the form both of the genital aperture and of the anal papilla.