2 – Molting and Regeneration

Chapter 2 – Molting and Growth

A rapid technique for molt staging in live Macrobrachium rosenbergii

1 – Dynamics of the Integument

The epidermis-exoskeleton complex in the fiddler crab is an organ consisting of cellular elements and a secreted cuticle. The epidermis is composed of a basement membrane, pigment cells, intraepidermal connective tissue and cuticled secreting cells. The latter two tissues undergo a morphologic cycle of decline and recrudescence correlated to the molt cycle. The cuticle consists of an inner membranous layer and endocuticle, both deposited after molting, and a more distal exocuticle and epicuticle, formed before ecdysis occurs. All layers except the epicuticle are constructed of helicoidally-oriented lamellae of chitin-protein microfibrils, and are cellularized by pore canals, which are extensions of the cuticle-secreting cells.

A survey of the fine structure of the integument of the fiddler crab.

1. New setae can be seen in the process of development in the uropods and telson of living specimens of Orconectes sanborni. The setae form by secretion of a tube within a tube. Three stages in the formation of the new setae can be used to subdivide intermolt stage D1 into three substages.2. The beginning of seta formation defines the beginning of stage D1. Before beginning this stage, the membranous layer of the cuticle begins to be reabsorbed the epidermis separates from the old cuticle, gastroliths begin to be formed, and the rate of regenerating limb growth increases sharply except in individuals which do not display such increase at all.3. The membranous layer had been completely reabsorbed in about half the specimens examined in each D1 substage. Therefore, the rate of reabsorption of the membranous layer is not correlated with the rate of seta formation.4. Ratios of gastrolith length to carapace length and of regenerating limb bud length to carapace length varied in different specimens, but the var...

Lack of correlation of some proecdysial growth and developmental processes in the crayfish

1.Criteria are presented for distinguishing the molting stages of Armadillidium vulgare.2. An oxidase is present in secretory droplets in the tegumental glands of the legs throughout the entire molting cycle.3. This oxidase seems to be the polyphenol oxidase involved in sclerotization of the cuticle.

J. Ross Stevenson

Papers

Lack of correlation of some proecdysial growth and developmental processes in the crayfish

Polyphenol oxidase in the tegumental glands in relation to the molting cycle of the isopod crustacean armadillidium vulgare