Quarterly Journal of Microscopical Science, Vol s3-97, 465-480, Copyright © 1956 by Company of Biologists

Formation and Involution of Striated Muscle Fibres during the Growth and Moulting Cycles of Rhodnius prolixus (Hemiptera)

¹ Department of Zoology, University of cambridge

The ventral intersegmental muscles of the abdomen in Rhodnius undergo a cycle of development and involution during each larval stage. They are fully developed only at the time of moulting or hatching from the egg. Within 3 or 4 days after moulting the fibrils have disappeared; but the nuclei, with a little cytoplasm containing mitochondria, survive within the highly folded muscle-sheath.

The formation of fibrils begins between 2 and 3 days after feeding. At first they are uniformly birefringent. The striations appear later, and the muscles will then contract after transection. The fibrils are 0.1-0.2 µ thick when first formed; they grow by intussusception and splitting to a thickness of about 0.8 µ.

Succinoxidase first appears in quantity in the mitochondria at the time when striation and contractility develop. It disappears within 3 days after moulting, during the involution of the fibrils. The distribution of ribonucleic acid in the developing muscle is described.

Involution results from autolysis which begins around the nuclei in the centre of the uscle. The phagocytic blood-cellsplay no part in the break-down.

The rich nerve-supply to the muscles persists apparently unchanged throughout the cycle of involution; and the cycle of growth occurs normally after section of the nerves.