The Biological Bulletin, Vol 197, Issue 3 315-318, Copyright © 1999 by Marine Biological Laboratory

RESEARCH NOTE

Cropping of Sea Anemone Tentacles by a Symbiotic Barnacle

Y. Yusa and S. Yamato
Seto Marine Biological Laboratory, Kyoto University, Shirahama, Wakayama 649-2211, Japan

As sessile animals, barnacles (Cirripedia: Thoracica) are generally suspension feeders, extending their cirri into the surrounding water to collect food particles (1). Although it has been suggested that some symbiotic barnacles obtain nutrients directly from their hosts, either by absorbing body fluids (2-4) or by rasping the host's tissue (4-6), most of these cases are inferred from their morphology. Direct evidence, such as gut content analysis, has been limited (for an exception, see ref. 5), and no actual feeding on their hosts has been observed. Koleolepas avis (Hiro, 1931) is a pedunculate barnacle symbiotic with the sea anemone Calliactis japonica, which lives on gastropod shells occupied by large hermit crabs (7), mainly Dardanus arrosor. Symbiotic relationships between various hermit crabs and sea anemones have been well documented (8), but the relationship between the barnacle and its host sea anemone has been virtually unknown. From February to April 1996, we collected living individuals of K. avis from lobster nets landed at Minabe Fishery Port, southwestern Japan (33{deg} 44' N, 135{deg} 20' E). On the basis of behavioral observations in the laboratory and analyses offecalpellets and gut contents, we concluded that this barnacle feeds actively on its host's tentacles.