FREQUENCY SPECIFICITY OF VIBRATION DEPENDENT DISCHARGE OF NEMATOCYSTSIN SEA-ANEMONES

Hair bundles on tentacles of sea anemones are similar to vertebrate ha ir bundles in terms of structure and function. Anemone hair bundles ar e involved in regulating discharge of nematocysts, ''stinging capsules ,'' used to capture prey. N-acetylated sugars from the prey including N-acetylneuraminic acid (NANA) induce hair bundles to elongate while s hifting vibration dependent discharge of nematocysts to lower frequenc ies matching prey movements. In the present study, we find that vibrat ion dependent discharge of nematocysts exhibits sharp frequency discri mination to within one Hz. Testing at one-Hz intervals over the range of frequencies spanning 1-75 Hz, we find that seven of these are stimu latory in seawater alone. A total of twenty-six frequencies are stimul atory in the presence of NANA. Stimulatory frequencies in NANA are low er than those in seawater alone. We find that antagonists of ryanodine receptors including ryanodine, procaine and tetracaine shift discharg e to lower frequencies. Fluorescently tagged ryanodine labels numerous small loci in the apical cytoplasm of supporting cells. We propose th at calcium induced calcium release (CICR) via ryanodine receptors may sharpen frequency specificity and/or cause shortening of hair bundles to shift frequency specificity to higher frequencies. (C) 1998 Wiley-L iss, Inc.