Reference : Biol. Bull, 155: 627-639. (December, 1978) COMPARISON OF THE GRADIENT OF SETAL DEVELOPMENT OF UROPODS AND OF SCAPHOGNATHITES IN ASTACUS LEPTODACTYLUS 1 ROGER VRANCKX AND MICHELE DURLIAT Laboratoirc Biologic ct PJiysiologic dcs Organismes Marins, Universite P. & M. Curie, 4 Place Jnssicu, 75230-PARIS 05, France The intermolt stages of decapod crustaceans are usually defined according to the criteria of Drach (1939; 1944). Many authors subsequently adapted this method to their own material for treating diverse physiological problems. Drach and Tchernigovtzeff (1967) then generalized this technique for application to all crustaceans. The original method allowed rigorous classification, but required injury to the animal due to the extraction of appendages used for microscopic observation. In order to choose from the tremendous number of crayfish available in populations, it was necessary to find criteria for stages within the cycle that would allow a quick and simple identification of molt stages without damage. The observation of more easily accessible appendages was suggested by several authors: the pleopods of the macruran, Homarus aniericamis, (Aiken, 1973) or of some Stomatopoda (Reaka, 1975) ; the antenna scales of a natantian, Palaetnon pancidcns, (Kamiguchi, 1968) ; the uropods of three natantians ( Scheer, 1960) ; or appendages of an anomouran, Petrolisthes cinctipes (Kurup, 1964) ; or of the macrurans, Homarus amcricanus, (Donahue, 1954; Rao, Fingerman and Finger-man, 1973) ; Orconectes sanborni ("Stevenson, Guckert and Cohen, 1968) and Parastacoides tastnanicus (Mills and Lake, 1975). The need to keep the animals uninjured together with the fact that they possess neither bladed pleopods nor antenna scales, brought us to use the uropodal blades in crayfish to determine molting stages as well as to predict ecdysis. The data obtained from uropods is set out, and the validity of our method has been tested by a comparative study of the scaphognathites. MATERIALS AND METHODS Hardness of the shell The hardness of different parts of the cephalothorax and the appendages can be estimated by palpation following the classical sequence set out by Drach (1939). Examination of the uropods After apolysis, two methods can be used to predict the duration of premolt stages. The first, worked out on Jasus paulensis (Vranckx, in preparation), measures the retraction of epidermis which has pulled away from the old cuticle. 1 This paper is dedicated in homage to Professor Pierre Drach on his jubilee, and the authors also wish to thank him for critical review of this manuscript. 627
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