Meeting Abstract
P2.97 Saturday, Jan. 5 Growth and Immune system function in juvenile Franklin\’s gull SNYDER, N. M.*; CLARK, M. E.; REED, W. L.; North Dakota State University, Fargo; North Dakota State University, Fargo; North Dakota State University, Fargo nicole.snyder@my.ndsu.edu
How offspring respond to variation in reproductive timing is not well studied. Evolutionary theory predicts, and empirical evidence indicates, that investments in offspring decline across the reproductive season. Thus, offspring produced later in the season may need to compensate for a poor start in order to survive to breeding age. Franklin’s gull (Leucophaeus pipixcan) eggs laid later in the season are smaller and produce structurally smaller hatchlings than eggs laid early in the season. In a laboratory study with ad libitum feeding, chicks from late season eggs exhibited faster growth rates than chicks from early season eggs, yet their asymptotic masses did not differ. We hypothesized that late season chicks compensate for the initial lower investment at the cost of immune system development, ability to repair DNA damage, and ability to withstand a short-term diet restriction. We tested our hypotheses in a laboratory study of chick growth. We artificially incubated early and late season gull eggs, randomly assigned hatchlings to a diet restriction or control group, measured chicks daily until age 40 days. At age 20 days, we evaluated immune system function with a PHA challenge to the patagium and circulating heterophil: lymphocyte ratios. We evaluated DNA damage at this age with single cell gel electrophoresis (comet assay). We found no differences among groups in patagial swelling, but late season chicks had thinner initial patagia than early season chicks. The comet assay indicated fragmented DNA in cells of late season and diet-restricted chicks. Our findings suggest that late season offspring can compensate for low parental investments without compromising immune function, but may incur costs that inhibit tissue repair or self-maintenance.
