LEE, Kara J.*; YU, Xiaoli; CHANG, Ernest S.; MYKLES, Donald L.; Colorado State University, Ft. Collins; Colorado State University, Ft. Collins; Bodega Marine Lab, Bodega Bay, CA; Colorado State University, Ft. Collins: A Molt-Inhibiting Hormone (MIH)-like Factor in Secondary Limb Buds that Lowers Hemolymph Ecdysteroid Levels in the Land Crab Gecarcinus lateralis.

Molting in crustaceans is regulated in part by a molt-inhibiting hormone (MIH) produced in the eyestalk neural ganglia Xorgan/sinus gland complex. MIH acts at the crustacean Y-organ (YO) to inhibit the synthesis of ecdysteroid molting hormones. In land crabs undergoing limb regeneration, there appears to be another factor, termed limb autotomy factor – proecdysis (LAF_pro) that also inhibits molting. This factor is located in secondary limb buds (2^o LB), which are formed when primary limb regenerates, grown after multiple leg removal, are autotomized. Partial characterization of this factor has previously revealed it is, like MIH, a heat stable peptide. As part of our studies investigating the control of crustacean molting, our objective is to further characterize and determine the specific role of LAF_pro in regulating molting and ecdysteroidogenesis. Western blot analysis (using a Callinectes sapidus MIH antiserum) indicates that 2^o LBs contain an MIH-immunoreactive protein not present in primary limb buds (1^o LB); this protein has the same electrophoretic mobility as MIH in sinus gland extracts. In injection experiments, 2^o LB extracts resulted in a decrease in hemolymph ecdysteroid levels in premolt animals. To investigate a possible direct effect on ecdysteroid synthesis, future experiments will include exposing YO’s in vitro to 1^o and 2^o LB extracts to test for their ability to suppress ecdysteroid synthesis. Characterization of this molt-inhibiting factor in limb regenerates is essential for a more complete understanding of the complex hormonal regulation of molting in crustaceans. Supported by NSF IBN-9904528 and IBN-0342982.