抄録
Hydra, a member of phylum Cnidaria, undergoes three types of digestive movements (Shimizu et al., 1984), esophagal reflex-like, peristaltic reflex-like and defecation reflex-like movements. Since Hydra belongs to Hydrozoa, the most latent class of Cnidaria, we extended our analysis to a more ancestral class of the phylum, the class Anthozoa that includes popular organisms e.g. corals and sea anemone. Nematostella vectensis is a well studied Anthozoa. We found no movements related to digestion. Instead, we find from archival sources that peristalsis unrelated to digestion occurs in this organism. Unlike peristalsis in Hydra, peristalsis in Nematostella was characterized by (1) very narrow bands of constriction of the tissue, (2) very drastic constriction of the tissue which can never be seen in intestinal tissue. Also, we find from recent development in genome project in Hydra and Nematostella that Hydra has gap junction communication and related genes whrereas Nematostella has no gap junction communication or related genes. To examine the effect of gap junction communication in Hydra, we tried to block the communication by treatment with heptanol. We found that the digestive movements are all blocked by the treatment. From this and other observations, we propose a possibility that the gain of gap junction communication was an evolutionary cue for the appearance of digestion related peristaltic movements. [J Physiol Sci. 2007;57 Suppl:S218]
