Meeting Abstract

P3.86  Wednesday, Jan. 6  Characterization of the Genome of Triops longicaudatus HEAD, Jennifer M.*; REIBER, Carl L.; Univ. of Nevada, Las Vegas; Univ. of Nevada, Las Vegas jennifer.head@unlv.edu

Triops longicaudatus is a branchiopod crustacean that has remained virtually unchanged in the fossil record for approximately 250 million years. Triops generally inhabits shallow, ephemeral bodies of fresh water, tolerates extreme conditions, and forms cysts during periods of desiccation. Despite many studies, reproduction in branchiopods is poorly understood. Many populations of Triops are female-biased and are thought to employ parthenogenic, hermaphroditic, and sexual modes of reproduction. In an attempt to elucidate the reproductive strategy and complex genome of T. longicaudatus, we analyzed the nuclear content of hemocytes in both male and female individuals to obtain an estimate of both the total genome size and ploidy using flow cytometry. Eukaryotic genomes range in size from 20Mb in the nematode Pratylenchus coffeae to 670 Gb in Amoeba dubia. Using Chicken Erythrocyte Nuclei as a control, we estimate the total haploid content of Triops hemocytes to be 131.0 ± 0.6 pg in males and 130.0 ± 0.8 pg in females, translating into a genome size of approximately 1.27 Gb. A more in depth analysis and comparison of the male and female hemocytes resulted in very different DNA profiles for male and female cell populations. While the female individuals consistently had histograms resembling those of diploid organisms, the males have what appears to be an additional haploid population of cells. The difference in ploidy between males and females could be a result of different modes of reproduction in each gender or due to a cytoplasmic endosymbiont-based reproductive strategy. Ongoing karyotyping studies will help to further clarify the reproductive biology of Triops as well as the size and structure of the Triops genome.