Collaborative Research: Life History Variation in Copepods: Modulation through Chromatin Diminution and Endoreduplication

East Tennessee State University, Johnson City TN

Investigators

Abstract

0080921 Rasch This research investigates responses of aquatic microcrustaceans to massive losses, gains, and reorganizations of genomic DNA. The focus is on embryonic chromatin diminution - reduction in size and reorganization of the genome, with additional exploratory research on endoreduplication - the amplification of nuclear DNA without subsequent mitosis. The PI's will investigate whether variation in DNA content in somatic and germ cell lineages can explain variation in developmental time and embryonic and adult body sizes through effects on bulk size of the genome. Research will include reconstruction of a phylogeny of the Cyclopidae and use of phylogenetically-independent contrasts to test for correlated evolution of adult somatic DNA content with developmental rate and adult body size. The PIs will investigate whether large amounts of germline DNA in embryos make possible higher rates of protein transcription at times during development when there is greatest need for such transcripts. Quantitative changes in DNA will be measured using cytophotometry and isotopically labeled DNA and RNA precursors. Copepods are ideal for examining evolution of large-scale changes in the genome because their genome size varies greatly among species, mechanisms that modulate their DNA contents are known, their life history variation and population biology are well studied, and their chromosomes are amenable to quantitative and comparative analyses. Copepods may be the most abundant multicellular organisms in the oceans, are a primary diet item of many fish, and thus play a major role in global ecology.