ANTAGONISTIC FREQUENCY TUNING OF HAIR BUNDLES BY DIFFERENT CHEMORECEPTORS REGULATES NEMATOCYST DISCHARGE

Sea anemones capture prey by discharging nematocysts into them. Chemic al and mechanical cues identify suitable prey to sensory receptor syst ems on the anemone. Conjugated N-acetylated sugars from prey bind to c hemoreceptors on cnidocyte/supporting cell complexes to tune hair bund les on the complexes to lower frequencies matching prey movements. The hair bundles microbasic p-mastigophore nematocysts into vibrating tar gets. Provided that proline receptors are activated after those for N- acetylated sugars, nematocyst discharge is tuned to much higher freque ncies. Thus, anemone hair bundles are tuned to either higher or lower frequencies by antagonistic chemoreceptors. Chemoreceptors for proline can adapt to 10-(8) moll-(1) proline and yet respond to increases in proline concentration of less than 10-(15) moll-(1). Under these condi tions, too few molecules of proline are added to activate chemorecepto rs on all responding cnidocyte/supporting cell complexes. Evidence ind icates that the extreme sensitivity of anemones to proline may be attr ibuted, in part, to intercellular communication.