Session 4, Abstract 20

MORPHOLOGICAL ASYMMETRY AS AN INDICATOR OF STRESS IN RODENTS, A COMPARATIVE STUDY OF RODENT SPECIES IN SOUTHERN CALIFORNIA

Joshua Ramsey* and Rachel Para*(Wendy Binder), Department of Biology Loyola Marymount University

Vertebrates generally develop in a bilaterally symmetrical manner, but it is hypothesized that this pattern may be disrupted by stressors, one of which is pollutants in their environments. Pollutants, absorbed during nutrient uptake, can make their way into the food chain through plants, and may be concentrated in higher trophic levels—omnivores, for example. As they develop, vertebrates exposed to pollutants may be unable to develop symmetrically, and fluctuating asymmetry (FA) may be introduced. FA is a random deviation from bilateral symmetry toward either the right or left side. While a variety of methods to measure bilateral symmetry have previously been used including rulers and calipers, more modern equipment may gather higher quality data. A three-dimensional digitizer accurately collects points in a three-plane coordinate system. This tool was used to collect measurements from rodent skulls to compare the degree of bilateral symmetry of the specimens. By measuring distances between landmarks - identifiable locations on the skull (e.g. sutures) - and between endpoints on the limbs, differences between left and right sides were calculated, and differences within and between species were compared. Preliminary results were inconclusive but with larger sample sizes, correlations between pollution levels and symmetry may emerge. This data will then be compared to individuals from less polluted regions to determine the difference in degree of asymmetry between rodents due to environmental pollutants.

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