Robert Jan "Roy" van de Hoek, President
Ballona Institute
Los Angeles, California
roy@naturespeace.org
June 17, 2014
Page 98 to 104         THE VELIGER          Volume 6; Number 2
Morphology and Mode of Burrowing in Siliqua patula and Solen rosaceus
(Molusca: Bivalvia)
BY
ROSS H. POHLO
Scripps Institution of Oceanography, La Jolla, California
(6 Text figures)

Mode of Life

Solen rosaceus CARPENTER, 1865

          This organism lives in a permanent burrow in which it can freely move up and down. It is found in mud flats in sheltered bays and ranges from Santa Barbara, California to Baja California, Mexico. Its occurrence in these areas has been described by WEYMOUTH (1920) and RICKETTS (1952).
          The burrowing behavior of certain species of Solen has been described by FRAENKEL (1927). The behavior of Solen rosaceus conforms to the general pattern outlined by him and is described below.
          When the animal is unearthed and place on the substratum, it first extends the foot out of the shell in an anterior direction (fig. 1a). The muscles at the tip of the foot contract causing the very tip to extend and become pointed. The foot is pushed into the soil by simultaneously extending the tip and forcing the bulk of the foot out from between the valves. This action continues until the foot is well below the soil, where it swells at the end and forms a bulbous anchor (fig. 1b). Next, the pedal retractor muscles contract, and the shell portion of the animal is drawn into the sand toward the anchor (fig. 1c). The sequence of movements is repeated until the animal reaches the required depth in the substratum.
          Movement within the burrow was not seen in Solen rosaceus, but it is probably the same as I have observed for Solen sicarius GOULD, 1846. This movement differs slightly.....

Siliqua patula (DIXON, 1788)
          This clam occurs on exposed sandy beaches, often in the zone of heavy surf, as described by WEYMOUTH (1920), .................. It ranges from the Aleutian Islands to Pismo Beach, California (Burch, 1944). The animal lives vertically in the sand and forms no permanent burrow as its related bay living forms Solen rosaceus and S. sicarius.

This muscle is elongated in many species of the genus Solen, and it reaches its maximum extent in the genus Ensis.

ACKNOWLEDGMENTS
          I wish to thank Dr. Charles Stasek for his help in preparation of the manuscript. Research funds were provided in part by the National Science Foundation Grant B-8755, and also in part by some field expenses given by Scripps Institution of Oceanography. This paper was completed while the author was a Sverdrup Post-doctoral Fellow in Oceanography at Scripps Institution of Oceanography.

LITERATURE CITED
BURCH, JOHN Q. (Editor)
1944 to 1946. Distributional list of the west American marine mollusks from San Diego, California to the Polar Sea. Conch. Club Southern California, minutes; 2 parts; pagination by issue; plates 1 - 3.

RICKETTS, EDWARD F., and JACK CALVIN
1952. Between Pacific Tides. Stanford University Press, v - viii; 3 - 502; 46 plates. Stanford, California.

WEYMOUTH, FRANK W.
1920. The edible clams, mussels and scallops of California. Calif. Fish & Game Bull. 4: 77 pp.