MITCHELL, Jacqueline L.; TAMONE, Sherry L.; University of Alaska Fairbanks, Juneau School of Fisheries and Ocean Sciences: Circulating methyl farnesoate levels in female snow crab Chionoecetes opilio, from the Bering Sea.

The dramatic decline in the Alaskan snow crab fishery prompted investigations into the reproductive biology of this economically important species. Previous studies of snow crab populations in the Gulf of St. Lawrence, Canada indicate that the reproductive output of female snow crab is related to ocean bottom temperatures. In extension of this hypothesis, we designed experiments to determine the effects colder temperatures have on ovarian maturation. To examine this, we analyzed hemolymph extracts for endogenous levels of methyl farnesoate (MF), a crustacean reproductive hormone, by using HPLC methods which have successfully been used to measure levels of MF in the crab Libinia emarginata and the lobster Homarus americanus. MF plays a role in reproduction by inducing vitellogenesis, the uptake of yolk proteins by developing oocytes. Hemolymph samples were collected by, non-lethally removing 1 ml of blood every month from donor crabs held at 3oC, 1oC*, 0oC* and -1oC* (n=15 per tank, (*) = in duplicate) for nine months. Samples were extracted in 75% methanol. The methanol fraction was then added to hexane spiked with an internal non-biological MF standard, and analyzed by HPLC. Endogenous MF peaks were compared to the internal standard peaks for quantification. Currently the areas under these endogenous peaks are being analyzed to determine the effects of these temperature treatments on circulating hormone levels. Changes in circulating MF should lead to a change in ovarian maturation which is evidenced by extrusion. Our extrusion data reveals a 30 day delay in ovarian maturation for every drop in degree of temperature.