Excretion in the house cricket (Acheta domesticus): fine structure of the Malpighian tubules.
An ultrastructural analysis of the Malpighian tubules of the cricket, Acheta domesticus, is presented. The excretory system of the cricket is unusual in that the 112 Malpighian tubules do not attach directly to the gut, but fuse to form a bladder-like ampulla which is joined to the colon by a muscular ureter. The tubules have three structurally distinct segments and consist of four cell types. Attached by basal lamina to the outer surface of the distal tip are nodules, consisting of small cells on membranous stalks. These are presumed to serve as attachments to the body wall. The distal 20% of the tubule is hyaline, consisting of a monolayer of squamous cells that appear to be secretory. The mid-tubule comprises 75% of the total length and is the primary region for fluid secretion. It is also characterized by having large numbers of laminate spheres in the cytoplasm of the cells. The proximal 5% of each tubule consists of more columnar cells and may function in fluid resorption. The relationship between structural features and known physiological functions are discussed.
Hazelton
S R
SR
Department of Biology, University of Southwestern Louisiana, Lafayette, Louisiana 70504, USA.
Parker
S W
SW
Spring
J H
JH