Short Communication Chemoreception in Sea Anemones: Betaine Stimulates the Pre-feeding Response in Urticina Eques and U. Felina

Chemical stimulation can evoke complex behaviour patterns in sea anemones. In pre-feeding behaviour a diffusible component of food causes the oral disc to expand and the column to extend and bend from side to side. These movements may increase the chance of catching nearby food (Pollock, 1883). The response is coordinated by the ectodermal slow conduction system (SSI). In Urticina eques, food extracts that excite the pre-feeding response evoke a low-frequency series of SSI pulses; and electrical stimulation of the SSI, in the absence of food, causes pre-feeding movements (McFarlane, 1970). The SSI, the SS2 (an endodermal slow system) and a through-conducting nerve net (TCNN) are the three known conducting systems that appear to coordinate sea anemone behaviour (McFarlane, 1982). Other conducting systems have been proposed (e.g. Lawn & Ross, 1982) but not confirmed. Although the SSI plays an important part in the coordination of many behaviour patterns, no chemical that stimulates it has been identified. We have investigated SSI excitation during the pre-feeding response of Urticina felina and U. eques (previously known as Tealia felina var. coriacea and var. lofotensis, Manuel, 1981), using the technique developed by Lawn (1975). We have screened many possible activators, chosen from published analyses of known stimulatory foods, e.g. muscles from fish (Long, 1961), Nephrops (Robertson, 1961) and Mytilus (Bricteux-Gregoire, Duchateau-Bosson, Jeuniaux & Florkin, 1964). Anemones were bisected longitudinally, pinned cut edge down, and allowed to recover for 24 h. Test solutions were either applied in the bath to give a known final concentration or were drawn into a suction electrode (2 mm internal tip diameter) that was then attached to the column. Suction electrodes on tentacles were used to record electrical activity in all three conducting systems. As spontaneous SSI pulses were rare, responses to the applied chemical were obvious. The chemicals tested, at concentrations between 10~ and lCT'molP (final bath concentration or concentration in electrode) were AMP, alanine, arginine,