Meeting Abstract
19.1 Tuesday, Jan. 4 Ontogenetic changes in immunity in Mormon crickets SRYGLEY, R.B.**; , ; USDA-Agricultural Research Service robert.srygley@ars.usda.gov
Immune defenses confer protection from wounding and invasion. A trade-off between allocation of resources to growth or defense is well known in many plants, but it is much less explored in insects. Mormon crickets (a katydid) form large migratory bands that march over rangeland in the western United States. They begin to migrate as early as the 4th nymphal instar and continue through their adult lives. Immune defense is particularly relevant to survival in migratory bands, but little is known about whether Mormon cricket immunity changes with age. Mormon crickets were collected in Lodgegrass, Montana and fed ad lib in the laboratory. We recorded molt dates; and as an indicator of their capacity to defend against invasion and heal wounds, we measured phenoloxidase (PO) and prophenoloxidase (proPO) activity and total protein in late instar nymphs (5th, 6th, and 7th) and teneral adults. We also measured the rate that they encapsulated glass rods introduced into their abdomens. PO, proPO and total circulating protein did not differ significantly between nymphal instars, but PO and total protein increased significantly with time post molt. Comparing nymphs and adults between 0-5 days post molt, total protein did not change with age in adults, whereas it increased in nymphs. PO and proPO also increased with age but did not differ significantly between adults and nymphal stages in these first few days of adulthood. The rate of encapsulation was not significantly different between nymphs and adults within one day of molting. Adults do not mature until 10-12 days post molting, and PO and proPO activity and rate of encapsulaton continued to increase between 0-13 days, independent of sex. I conclude that very young adults are much like nymphs in enzymatic immunity. Each molt sets the insects back in terms of circulating PO, proPO, and rate of encapsulation.
