The Physiology and Ultrastructure of the excretory system of the New Zealand Earwig, Anisolabis Littorea (White)

Abstract

Studies on the excretory capacity of insect Malpighian tubule/hindgut complex have focused mainly on a few, relatively specialised species. Certain aspects of the excretory physiology of the endemic New Zealand earwig, Anisolabis littorea, a seashore dwelling member of the primitive order Dermaptera, were studied, as were the histology and ultrastructure of the Malpighian tubules and hindgut, in order to determine the nature of the excretory process and to compare it with other insects studied. The physiology and ultrastructure of the Malpighian tubule of Anisolabis, with a few minor exceptions, were found to closely parallel those of the less specialised insects studied; the rectal pouch was shown to concentrate material in the lumen, principally by absorption of water without net movement of ions (in the course of these experiments a new method was devised for measuring changes in concentrations of amaranth in small volumes (0.1μ1) by microdensitometry); electron micrographs of the rectal pads indicated that the ultra-structure was compatible with this function; the rectal pouch was shown to be impermeable to labeled trehalose and glucose, while the colon and ileum were relatively permeable to these molecules.