Robert Jan "Roy" van de Hoek, President
Los Angeles, California
June 17, 2014
A Note on the Feeding Behavior in Tagelus californianus
Department of Biology, San Fernando Valley State College
(1 Text figure)
C.M. YONGE (1952, p. 434) states "Tagelus californianus is a deposit feeder, and this requires long and separate siphons, bottom material actively taken in through the inhalant siphon . . . " My observations do not substantiate an active deposit feeding behavior for T. californianus.
In two other Tellinacea studies (Macoma nasuta and M. secta the animals actively feed on deposits as described by YONGE (1949). In M. secta, the inhalant siphon twists, rips off and ingests bottom material (Figure 1). Macoma secta does not move the siphons but actively ingests bottom material as depicted by YONGE (1949, fig. 16a).
Specimens of Tagelus californianus (CONRAD, 1837) were collected from four different sites ranging from San Diego to Tomales Bay, California. The animals were observed both in the field and in the laboratory. In the laboratory the animals were placed in the substratum and the position of the siphons and feeding behavior were noted over a period of several weeks. Carmine particles were placed on the substratum around the inhalant siphon and these were not drawn into the siphon. The same experiment was carried out with Macoma nasuta (CONRAD, 1837), and this animal did actively ingest the carmine particles.
In the field the siphonal openings of Tagelus californianus were observed, and at no time did the inhalant siphon appear to ingest bottom deposits. At all times the inhalant and exhalant siphons were observed flush with the substratum or contracted below the level of the substratum. Sweeping movements were never observed.
These observations indicate that Tagelus californianus is not an active deposit feeder but that it feeds on suspended material as do the majority of the Bivalvia.
The writer wishes to thank the U. S. Navy for permitting work to be carried out in Mugu Lagoon, California.
YONGE, CHARLES MAURICE.
1949. On the structure and adaptations of the Tellinacea, deposit-feeding Eulamellibranchia. Phil. Trans. Roy. Soc. London, Ser. B. 234: 29 - 76.
1952. Studies on Pacific coast Mollusks. IV. Observation on Siliqua patula Dixon and on the evolution within the Solenidae. Univ. Calif. Publ. Zool. 55: 421 - 438.
1966. Veliger 8 (4): 225. Tagelus californianus (Conrad, 1837) and Macoma nasuta (Conrad, 1837) was studied by Ross at 4 California locations (Tomales Bay, San Diego, Mugu Lagoon, and a 4th location?). Ballona Institute has obtained an original reprint from Italy. Joel Hedgpeth (1968: 519-521) listed 4 articles by Ross in the bibliography of Ed Ricketts' classic book, Between Pacific Tides, with a pithy nod to Ross Pohlo's discoveries on clam ecology: "Not a deposit, but a suspension feeder." Ross thanked U.S. Navy for access to Mugu Lagoon.