Meeting Abstract
Previous studies have demonstrated that hemolymph levels of methyl farnesoate (MF) in the green crab Carcinus maenas increased in response to exposure to dilute (< 27 ppt salinity) seawater (Lovett et al., 2001, 2006). Furthermore, the increase in MF levels did not commence until 8 hr after initial exposure to dilute seawater and acclimation levels of MF were attained within 24-48 hr after exposure. To understand the mechanism by which hemolymph levels of MF increase, the present study examined the effect of hypo-osmotic stress on relative transcript levels for farnesoic acid O-methyltransferase (FAOMeT), the terminal enzyme in the MF synthesis pathway. For crabs acclimated to dilute seawater, transcript levels of FAOMeT in the mandibular organs were higher than those of crabs acclimated to 28 ppt salinity seawater. Other crabs acclimated to 28 ppt salinity were transferred acutely to dilute seawater. In these crabs, transcript levels reached peak values 8 hr after transfer, increasing by almost three-fold from values at t=0. Transcript levels then decreased and by t=48 hr after transfer were not significantly different from those in crabs acclimated to dilute seawater. The timing of peak transcript levels in crabs acutely exposed to dilute seawater corresponds with the observed 8-hr lag in hypo-osmotic increases in hemolymph levels of MF. Hemolymph levels of MF appear to be regulated, at least in part, at the transcriptional level.
