CELLULAR IMMUNOSENESCENCEIN ADULT MALE CRICKETS,Gryllus assimilis

摘要

Ecological immunity studies in invertebrates, particularly insects, havegenerated new insights into trade-offs between immune functions andother physiological parameters. These studies document physiologicallydirected reallocations of immune costs to other high-cost areas ofphysiology. Immunosenescence, recognized as the age-related deterioration of immune functions, is another mechanism of radically altering immune systems. We investigated the hypothesis that aging brings onimmunosenescence in adult males of the cricket, Gryllus assimilis. Ourdata show that the intensity of melanotic nodule formation decreased withadult age from after 3-week post-adult emergence. Circulating hemocytepopulations similarly decreased from about 5,000 hemocytes/ml hemolymph to about 1,000 hemocytes/ml hemolymph. The numbers of damaged hemocytes in circulation increased from less than 10% at 1-week postadult emergence to approximately 60% by 3-week post-adult emergence. The composition of hemocyte types changed with age, with increasingproportions of granulocytes and decreasing proportions of plasmatocytes.The declines in nodule formation were not linked to the adult age ofsexual behaviors, which begin shortly after entering adulthood inthis species. We infer that age-related senescence, rather than costreallocations, may account for observed declines in various parameters of immune functions in insects, as seen in other animals.