A comparison of rectal pad structure in some terrestrial and intertidal Carabid beetles (Insecta)

Abstract

The structure and ultrastructure of the rectal pads, in two fully terrestrial, and three intertidal species of carabid, were examined. The ultrastructure of the rectal pads is compatible with the theory that they are involved in osmotic regulation. Differences in ultrastructure, particularly the number and structure of the mitochondria, indicate that the intertidal species may be better adapted for osmoregulation in a salt-rich environment. One species, Cillenus laterale (Samouelle) lives near the top of the intertidal zone and its rectal pads display intermediate structural features.