Preliminary analysis of spermathecal load of primiparous snow crab (Chionoecetes opilio) from the eastern Bering Sea, 2005-2008
Laura M. Slater, Kirsten A. MacTavish, and Douglas Pengilly
(What can I say? They had me at 'spermathecal load'.)
Their project was a monitoring program measuring spermathecal loads in primiparous female snow crabs from the eastern Bering Sea. They wanted to monitor the loads because a 2005 paper showed this group of females had low sperm reserves, which can mean that they won't have enough sperm stores to fertilize subsequent clutches after their first batch. (And remember, mating can be a dicey thing for female snow crabs!) The goal of the program was to see if large-scale interannual variability exists for female snow crab sperm reserves in the Bering Sea.
So what did they find out? First, clutches were mostly either 3/4 full or full, with healthy, viable eggs. Spermathecal loads in primiparous females had quite the range: from 0.001 g to 0.180 g! These loads are actually pretty low compared to crab stocks on the east coast, but since so many clutches were full of viable eggs it might not be an issue for these ladies.
The eastern Bering Sea was divided into three regions: northwest NW (area closest to Russia), central C (including St. Paul), and southeast SE (an area including St. George and Nunivak Island). Females were smallest in carapace width and had the lowest spermathecal loads in the NW region. There were also variations in loads over the different years of the study (as seen in the graph below), but only region and carapace width had any significant effects on the log-transformed spermathecal loads (ANCOVA, p < 0.05).
average spermathecal loads from the three regions of
the eastern Bering Sea during 2005, 2007, and 2008
What does this mean? Sperm reserves in primiparous females are size-dependent (on the female's carapace width) and show spatial variation (between the different regions of the eastern Bering Sea). Using these differences, sperm reserves may end up being a helpful tool for predicting the presence and fitness of reproductively active males, which, as you know, is my #1 interest!