Innate Cross Immunity of Host Fish to the Parasitic Larvae of Unionoid Mussels

Date of Graduation

Fall 2006


Master of Science in Biology



Committee Chair

M. Chris Barnhart


Most parasitic organisms are host-specific, meaning that the parasite is able to parasitize only one or a few compatible host species while other species are innately immune. The mechanisms of this innate immunity are poorly understood and are less studied than the adaptive (antibody-based) immune system. I used the glochidia larvae of freshwater mussels to investigate innate immunity in fish. Glochidia are briefly parasitic on the gills or skin of fish, where they complete their transformation to the juvenile stage. Mussel communities are diverse, so that fish may often encounter multiple species of glochidia. I used infections of compatible and incompatible mussel species on the same host fish to determine whether incompatible parasites can prime innate immunity in a way that affects the success of compatible species. Largemouth bass were infected (primed) with incompatible glochidia of Fusconaia or Potamilus. Simultaneously or shortly after priming the fish were infected with compatible glochidia of Lampsilis. I recorded the time course of release of glochidia and juveniles and quantified transformation success, the percent of attached glochidia that were recovered as live juveniles. Success of the compatible Lampsilis glochidia was lower when fish were primed with incompatible glochidia. The effects of priming lasted at least four days; even after all incompatible glochidia were gone from the fish. The effects of priming were diminished by administration of acetylsalicylic acid (ASA) to the fish. ASA is a potent anti-inflammatory specific to the prostaglandin-producing cyclooxygenase pathway. Therefore, the inflammatory response appears to be involved in these effects. Cross immunity may help explain the evolution of species diversity in mussels. Glochidia infections may also be a useful model for investigating the innate immune system.


fish immunity, Unionoida, glochidia, parasite, cross immunity, innate

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© Jolene R. Bowers