Acquired and Cross Immunity of Largemouth Bass (Micropterus Salmoides) to the Glochidia Larvae of Unionid Mussels
The glochidia larvae of freshwater mussels (family Unionidae) are temporary parasites of host fish, where they are contained within dermal cysts. The immune responses of largemouth bass (Micropterus salmoides) to glochidia of the broken rays mussel (Mapsilis reeveiana) were investigated to determine 1) the persistence of acquired immunity to glochidia 2) whether antibody production is correlated with immunity, and 3) whether cross immunity to other mussel species occurs. Transformation success, defined as the present of attached glochidia that were recovered as live juveniles, as used to quantify resistance to glochidia. Fish exposed to successive glochidia infections (priming) acquired significant immunity, which diminished over time but remained significant for at least 12 months after priming. Immunoblotting was used to show that serum antibodies to glochidia proteins were present after priming, but diminished and were difficult to detect 7 months later. However, primed fish produced antibodies more quickly during re-infection 7 months after priming than control fish, suggesting that memory B cells were present. Transformation success of Lampsilis abrupta, Villosa iris, and Utterbackia imbecillis was significantly reduced on fish primed with L. reeveiana, indicating cross immunity across genera and subfamilies. Antibodies from primed fish recognized proteins of similar molecular weight from L. reeveiana and L. abrupta, and proteins of different molecular weight from V. iris. However, no proteins from U. imbecillis were bound, suggesting that responses not mediated by antibodies may also be involved. Acquired immunity and cross immunity to glochidia are significant to mussel propagation and may influence mussel evolution by creating competition for naïve host fish.
antibodies, immunity, unionid, glochidia, cross immunity, parasite, Biology
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