Suspected chemoreceptors in coelenterates and ctenophores

Chemoreceptors in coelenterates and ctenophores have not been identified with certainty. Among prospective chemoreceptive cells are the sensory nerve cells, the cnidocyst-bearing cnidocytes, and the epitheliomuscular cells that are likely to be involved in feeding or aggression. Both behaviors are mediated by coordinated chemical and mechanical reception. This is reflected in the close apposition of putative chemo- and mechanoreceptors. Among the structures that have been designated as likely chemo- and/or mechanoreceptors are stereocilia, kinocilia, and/or microvilli which are universally present on all the putative chemoreceptor complexes, while gland cells and mucous secretions are prevalent. Evidence that the actin-containing stereocilia are chemically modulated mechanoreceptors is presented for several forms.