SCALING OF CALCIUM, INORGANIC CONTENTS, AND ORGANIC CONTENTS TO BODY-MASS DURING THE MOLTING CYCLE OF THE FRESH-WATER CRAYFISH PROCAMBARUS-CLARKII (GIRARD)

Allometric relationships were derived for calcium, inorganic contents, and organic contents of the crayfish Procambarus clarkii (0.012-33 g) at various stages in the molting cycle. Whole body parameters were me asured at intermolt, ecdysis, and postmolt (1 week); determinations we re also made on shed exuviae and gastroliths. Significant linear relat ionships on log-transformed data were obtained for all parameters. Sca ling exponents for mineral content varied from 0.93-1.27, agreeing clo sely with scaling of supportive tissue mass in a range of species poss essing both exo- and endoskeletons. Regression relationships were inte rpolated for hypothetical 1-and 30-g crayfish. Larger crayfish deminer alize their cuticle more effectively prior to ecdysis; even so, exuvia e constitute an avenue for significant mineral loss (30 cf. 50%). They also store less mineral between molts, excreting increasing amounts i nto the external water. Gastroliths are the major form of mineral stor age especially in small crayfish (74 cf 57%). Large postmolt crayfish are more mineral deplete (15%) than small crayfish (35%). Within 1 wee k of postmolt, 1-g crayfish have surpassed intermolt mineral content, by branchial uptake from external water. Their rapid rate of remineral ization is commensurate with their increased molting frequency. In the same time period, larger crayfish have recovered only 30% of their in termolt mineral content. Continued branchial uptake, together with ing estion of shed exuviae or other food sources, would restore mineral ba lance. Irrespective of size, crayfish lose 15% organic matter in the e xuviae at ecdysis. In the absence of food, postmolt crayfish draw on o rganic reserves for energy.