RATHBURN, C.K.**; MACEY, B.M.; BURNETT, L.E.; BURNETT, K.G.; College of Charleston: Influence of a Previous Exposure to Vibrio campbellii on the Immune Response of the Blue Crab, Callinectus sapidus
By 1 h following the injection of live Vibrio campbellii into blue crabs, culturable bacteria are eliminated from the hemolymph and circulating hemocyte numbers decline. We hypothesized that crabs with established bacterial infections, as observed in natural populations, may be more susceptible to infection on subsequent exposure to pathogenic bacteria. Blue crabs were injected with either saline or V. campbellii (105 g-1 crab). Both the saline- and Vibrio– treated groups received a second injection containing Vibrio 2 or 24 h after the first injection. Circulating total hemocyte counts (THC) ml-1 and colony forming units (CFU) V. campbellii ml-1 hemolymph were measured immediately before and at selected timepoints following the second injection. By 2 h after the initial injection, but not at 24 h, THC ml-1 was significantly lower (P=0.05) in Vibrio-injected animals than in saline controls. When the second injection containing bacteria was administered 2 h after the first injection of either saline or Vibrio, crabs having received two doses of bacteria had significantly lower CFU ml-1 in the hemolymph at 10, 20, 40 and 120 min after the second injection, compared to crabs first injected with saline (P=0.043). When the second injection containing bacteria was administered 24 h after a first injection of either saline or Vibrio, there was no difference in bacterial CFU ml-1 in hemolymph between the treatment groups at any subsequent timepoint tested. Injection of bacteria had no influence on individual crab weights or hemocyanin concentrations when compared to saline injection. These results suggest that recent exposure to a sub-lethal bacterial infection may improve the short-term immune response of crustaceans to additional infections when environmental conditions are optimal. Supported by NSF DBI-0244007 and IBN-0212921 to KGB and LEB.
