Date of Completion

Spring 5-1-2014

Project Advisor(s)

Spencer Nyholm

University Scholar Major

Biological Sciences


Biology | Other Immunology and Infectious Disease | Other Microbiology


Many organisms have beneficial microbial symbionts, and complex interactions between the immune system and the bacteria must occur to allow these symbioses to persist. The host immune system must recognize and preferentially tolerate the beneficial microorganisms, while simultaneously eliminating harmful pathogens. The Hawaiian bobtail squid, Euprymna scolopes, is a model organism for host-microbe interactions because of the unique light organ symbiosis. Hemocytes, the squid’s primary immune cell, infiltrate and patrol the light organ and continuously interact with the symbiont Vibrio fischeri. Using this model, several innate immunity genes have been shown to be differentially expressed in the hemocytes of animals with or without V. fischeri. One such differentially produced protein is a putative cephalotoxin. Cephalotoxin has never before been found outside of the posterior salivary gland in cephalopods, where it normally plays a role in paralyzing their crustacean prey. This research used sequencing methods and a tissue survey to characterize this putative cephalotoxin and understand whether it plays a role in the symbiosis. A cephalotoxin contig was obtained that contained 3050 bases out of the possible 3402 bases sequenced from Sepia esculenta cephalotoxin. Cephalotoxin was also found to be expressed in the hemocytes and the gills of adult E. scolopes, and the gills of juveniles. Cephalotoxin’s presence in the gills is most likely due to the high concentration of hemocytes within the gills because of its vascular nature. The salivary gland of adult squid did not contain cephalotoxin, which further indicates the novel role that it is likely playing in E. scolopes.