Robert Jan "Roy" van de Hoek, President
Ballona Institute
Los Angeles, California
roy@naturespeace.org
June 17, 2014
Feeding and Associated Morphology in Sanguinolaria nuttallii
Ross H. Pohlo
Department of Biology, San Fernando Valley State College, Northridge, California 91324

INTRODUCTION
          Sanguinolaria Conrad, 1837 is a large tellinacean that inhabits sandy areas in bays and ranges from Bodega Bay, California to Magdalena Bay, Baja California. (McLEAN, 1969).

MATERIALS and METHODS
          This organism was obtained from Mugu Lagoon and Newport Bay, California where the species occurs in great abundance. It occurs intertidally in clean sand, although McLEAN (1969) reports it also occurs in gravel, and lives in the substratum at a depth of about 15 - 25 cm.
          Several methods of study were used to ascertain the feeding behavior of this form. Direct underwater observations of siphons were made using an underwater viewer in shallow water. Observations of this nature were also made in aquaria in the laboratory.
          To study the diet of these organisms, the animals were unearthed in the field, the mantle cavity was opened, and the soft parts were then immediately preserved in 70% alcohol solution.

FEEDING OBSERVATIONS
          Sanguinolaria nuttallii was observed in situ in Mugu Lagoon. Observations were made when the organisms were covered with about 10 to 30 cm of water. Animals were also kept in an aquarium and the feeding behavior was noted.
          In the field the siphons were never observed above the level of of the substratum. Most of the time the inhalant siphon appeared about 0.5 to 1 cm below the level of the substratum in what appeared to be a semipermanent siphonal burrow. The siphons were inactive, in contrast to the siphons of animals as Donax gouldii Dall, 1921, Tagelus californianus (Conrad, 1837), and Macoma nasuta (Conrad, 1837), where they are quite active. The inhalant siphon was never observed actively ingesting deposits as seen in Macoma nasuta (MacGINITIE, 1935) or Macoma secta (REID & REID, 1969).
          The mantle cavities of numerous specimens were opened in the field. Some organisms showed little or no sand grains in the mantle cavity, while others contained a considerable amount. Usually, most of the sand was on the foot or in the area of the pseudofeces accumulation, just ventral to the inhalant siphon. These clams were immediately preserved and later the contents of the digestive tract were observed. As with the contents of the mantle cavity, some organisms had no sand grains in the stomach while in others some sand was present. Diatoms, flagellates, and amorphous, green debris were always present in the stomach and appear to be the main sources of nourishment.
          From the above mentioned information it is apparent that Sanguinolaria nuttallii feeds primarily on suspended material. But, because the siphons have no effective straining tentacles and the siphons are below the level of the substratum, deposits can and do fall into the inhalant opening and, if small enough, these particles can reach the stomach. But the main source of food is still suspended material.

DISCUSSION
          I classify Sanguinolaria nuttallii as a non-selective suspension feeders. It is of interest to compare its behavior and morphology with those of Tellinacea that are clearly deposit feeders, e. g. Macoma secta (Conrad, 1837) or M. secta and those that are suspension feeders, e. g. Donax gouldii.
          Also, these organisms lie on their side.
          Donax gouldii, a suspension feeding tellinacean that actively rejects deposits (POHLO, 1967) ...
          These morphological and behavioral associations and the type of feeding in this form indicate that Sanguinolaria nuttallii is somewhere in between the deposit and purely suspension feeders. On the basis of its feeding and morphology it seems to be more closely allied with suspension feeders.

ACKNOWLEDGMENT
          I wish to thank Dr. Marvin Cantor for reading the paper.

LITERATURE CITED
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