Ageing effects on heart rate and heart arrhythmia of the fruit fly, \u3ci\u3eDrosophila melanogaster\u3c/i\u3e

Invertebrate hearts share a common evolutionary origin with hearts of vertebrates. As such, Drosophila melanogaster is a useful model with which to examine genetic and environmental effects on heart function. My project explores the effects of ageing on heart rate and heart arrhythmia of adult fruit flies. Heart rate is influenced by major-effect genes (single gene effects), and by the cumulative effect of many genes (polygenic effects). Most studies have focused on single gene effects; few studies have emphasized the polygeneic basis of heart rate. My project focuses on a polygenic analysis. Polygenic expression is influenced by both the underlying genotype and environment. For this reason, a polygenic approach to the study of heart rate is a useful model of cardio-vascular health in humans. My study of adult heart rate takes a comparative approach by studying four different populations descended from flies collected in the Mississippi River Valley, Minnesota to Mississippi. For each population I determine heart rate and arrhythmia pattern for both male and female adults at ages 1, 10, 20 and 30 days. Adult flies were observed at low power with phase-contrast microscopy, heart contractions recorded on DVD using a video camera, and heart rates analyzed from slow-motion replays. In all populations, heart rates declined significantly with age, but patterns did not differ between males and females except in the LaCrosse population. Significant differences were not found among population. Arrhythmia also exhibits a decline with age, with LaCrosse having a significantly greater amount of heart irregularity while Natchez shows a more uniform heart pattern. No significant differences were observed in the expression of heart irregularity while comparing males and females. This population difference opens the possibility to pursue further genetic analysis as well as other traits influenced by polygenic effects