Nervous control of egg progression into the common oviduct and genital chamber of the stick-insect Carausius morosus

Abstract

In Carausius morosus, egg-laying activity is nocturnal. When an oöcyte leaves the ovariole (ovulation) during the day, it remains in a chamber which is located between the genital valves until the evening. The admission of another egg into the common oviduct is possible only when the egg chamber is empty. Nerve cord transection between the 7th and 8th abdominal ganglia interrupts the reflex which controls the progression of the egg through the common oviduct. Sensory hairs on the walls of the egg chamber, which is innervated by the 8th abdominal ganglion, are described. The information perceived by these sensory hairs enters the 8th ganglion, then travels to the 7th which innervates the oviducts. Present experimental results together with the observed existence of numerous anastomoses between the segmental nerves from different ganglia, suggest that though the normal reflex travels via the nerve cord, a lateral pathway is also possible. The effector is the common oviduct. The muscular sheath of this organ shows a special feature which is related to the control of egg passage: the muscle fibres no longer form a complete layer as they do in the lateral oviducts but rather form a half-sleeve of circular fibres around the dorsal face. The contraction of this half-cylindrical muscle prevents the progression of eggs.