Meeting Abstract

P2.139  Saturday, Jan. 5  Expression of molt-inhibiting hormone in brain and thoracic ganglion of green shore crab, Carcinus maenas ZANDER, I. A.*; ABUHAGR, A. M.; CHANG, E. S.; CHANG, S. A.; MYKLES, D. L. ; Colorado State University iazander@rams.colostate.edu

Molt inhibiting hormone (MIH), a neuropeptide hormone produced in the eyestalks of decapod crustaceans, regulates molting by suppressing the synthesis of ecdysteriods (molting hormones) by the Y-organ. Typically, molting can be induced by eyestalk ablation (ESA). However, adult green shore crab (Carcinus maenas) is refractory to ESA. ESA causes a small increase in hemolymph ecdysteroid titers, but animals do not immediately enter premolt. Some ES-ablated animals molt after many months, but most fail to molt at all. We therefore hypothesized that other regions of the nervous system, specifically brain and/or thoracic ganglion, were secondary source(s) of MIH. Nested endpoint RT-PCR showed that MIH transcript is present in brain and thoracic ganglion of intermolt crabs. Sequencing of the PCR product confirmed its identity as MIH. Quantitative PCR was used to determine the effects of ESA on MIH expression. Both green and red color morphs were ES-ablated and brain and thoracic ganglion were harvested at 7 days and 14 days post-ESA. Tissues from intact animals served as controls. MIH expression was similar between the color morphs and ESA had little effect on MIH transcript levels, indicating that the MIH gene was not regulated transcriptionally by the loss of the eyestalks. The data suggest that MIH secreted by neurons in the brain and thoracic ganglion is sufficient to prevent molt induction when the primary source of MIH is removed by ESA. Supported by NSF (IOS-0745224).