Effects of Bitter Crab Disease on gene expression in Alaska Tanner Crabs

Alaska Tanner crabs (Chionoecetes bairdi) are a coldwater crab species found in the Bering Sea, along the Gulf of Alaska, and southeastern Alaska. The southern stocks supported a $21 million fishery in 2014, but warming waters and disease have been threatening their numbers as well as the industry’s profits. Bitter crab disease is caused by a parasitic dinoflagellate of the genus Hematodinium, and is considered to be the “principal threat” to crab stocks by the Alaska Department of Fish and Game. Aside from its causing the crabs to become lethargic, among other signs, it renders their meat bitter and chalky. Due to this, the crab industry has been suffering from the loss of marketable product. It is not known how the disease is transmitted, or if it is fatal. It would be useful to have a better grasp of how the parasite affects its host on a molecular level, which is what our study set out to do. We held infected and uninfected crabs in tanks over the course of 2.5 weeks at ambient (6˚C), cold (4˚C), and warm (10˚C) temperatures, sampling their hemolymph at three time points. From a pooled sample, we identified crab genes involved in immune response and temperature response. For this presentation, we shared new data on differential gene expression between infected and uninfected crabs.