THE INTERMOLT CYCLE OF AN ANOMURAN, PETROLISTHES CINCTIPES RANDALL (CRUSTACEA-DECAPODA)

¹ Department of Biology, University of Oregon, Eugene, Oregon

1. The intermolt cycle of Petrolisthes cinctipes is described and morphologic criteria are proposed for designating the physiologic stages of the cycle. The key for staging the animal is provided in Table I.

2. The chronological changes in the derivation of new epidermis and bristles in the uropods furnish a reliable identification of the various stages even without recourse to palpation of the exoskeleton. The characteristics described by Drach (1939, 1944) and Scheer (1960) for certain species of crabs and prawns are found useful in staging a wide variety of Brachyura and Macrura; likewise, the diagnostic features in the stages of the porcellanid might be helpful in staging other Anomura as well.

3. In the porcelain crab the duration between two successive molts is unusually long (about 115 to 130 days), especially in view of the small body size of the animal. This might mean that the growth rate of this crab is relatively higher. It would be equally interesting to know of a possible seasonal shortening or lengthening of the intermolt cycle (see Scheer, 1960) , the molting periodicity and the total number of molts the crab passes through before it enters the terminal anecdysis.