Life history and immune defense in two garter snake ecotypes I - A field study.

SPARKMAN, A. M.; PALACIOS, M. G.; BRONIKOWSKI, A. M.

Seattle, Washington, EEUU

Congreso; Annual Meeting of the Society for Integrative and Comparative Biology.; 2010

Society for Integrative and Comparative Biology.

Life-history theorists have long observed that fast growth and high reproduction tend to be associated with short lifespan, suggesting that greater investment in such traits may trade off with self-maintenance. The immune system plays an integral role in self-maintenance, by defending organisms from pathogens which may reduce survivorship. Recent ecoimmunological theory predicts that fast-living organisms should rely more heavily on constitutive innate immunity than slow-living organisms, given that these defenses tend to be cheaper to develop, become functionally mature earlier during ontogeny, and act more rapidly and generally against pathogens than acquired defenses. We conducted the first study to test this hypothesis in an ectothermic vertebrate using replicate populations of two life-history ecotypes of the garter snake, Thamnophis elegans, one fast-living and one slow-living. We tested for differences in three aspects of constitutive innate immunity—natural antibodies, complement-mediated lysis, and bactericidal competence—between fast-living and slow-living ecotypes. As predicted, free-ranging snakes from the fast-living ecotype had significantly higher levels of all three measures of immunity than the slow-living ecotype. This difference may reflect an immunological trade-off in life-history strategy, differences in resource availability between the two ecotypes, or both.  Ecotype differences were not explained by parasite loads measured. Finally, both ecotypes also exhibited a positive relationship between innate immunity and age/body size in the field, with fast-living snakes showing faster rates of increase in innate immunity with age in association with their faster growth rates.