Neuroendocrine control of nitrogen metabolism in the Indian field crab oziotelphusa s. senex fabricius—I. End-products and elimination

Abstract

The literature concerning nitrogenous components and their metabolism in crustaceans has recently been reviewed by Schoffeniels & GiUes (1970). Their review begins with the words, Little information is available on the biochemistry of nitrogenous compounds in arthropods. One could add that virtually nothing is known of the physiology of nitrogen metabolism in crustaceans. Such information as exists has been obtained incidental to studies of osmotic regulation, events of the intermoult cycle and other aspects of growth and development, and oxidative metabolism and energetics. The relatively large amount of work on the metabolism of carbohydrate in crustaceans, reviewed recently by Hohnke & Scheer (1970), has centered on the control of blood sugar concentration, a matter which is of little intrinsic significance in the physiology of these animals. The processes of growth and development (yamaoka & Scheer, 1970) are regulated by the neuroendocrine system, centered in the eyestalks, and the Y-organ or moult gland. Among these processes is a substantial synthesis of protein during the intermoult period, between ecdyses (Renaud, 1949), and the incorporation of labelled amino acids into protein has been studied by Skinner (1965, 1966a,b), Kurup & Scheer (1966), Yamaoka (1974) and Raghavaiah (1977). Evidence that the eyestalks of crustaceans produce factors influencing incorporation of amino acids into protein has been reported by Gorell & Gilbert (1971), McWhinnie & Mohrherr (1970) and Raghavaiah (1977). The present report concerns the effects of extirpation of the eyestalks (ESX) and of administration of extracts of the eyestalks (ESE) on the concentrations of major nitrogenous components of tissues and on the rates of elimination of end-products. ESX is the classical operation of crustacean endocrinology; it removes the X-organ, a neurohaemal organ containing the neuron endings of the neuroendocrine system. It releases the moult gland (Y-organ) from inhibition and thus initiates processes leading to moulting, and