In the lab of Wes Brown, I worked on sequences of small subunit (18S) RNA and the gene order of the mitochondrial genome of sipunculan worms, a phylum of marine, non-segmented worms, to elucidate higher-level systematic relationships of these worms among other spiralian phyla.

    I also generated sequences from representatives of 11 genera of sipunculans for a 710 bp fragment of the cytochrome c oxidase subunit I gene (Staton, in press). The data, when combined with sequence data from 18S rDNA genes may resolve otherwise confounded parts of the evolutionary hierarchy.

    It proved impossible to isolate purified mitochondrial DNA from a sipunculan by standard methods, but I used new PCR technology to amplify this DNA. From data I gathered for the 710 bp CO-I fragment, I designed species-specific primers for one species, Phascolopsis gouldii, which amplified the entire mitochondrial genome (Turbeville et al. 1997).

    Second, I completed enough sequence of the mitochondrial DNA of the horseshoe crab, Limulus polyphemus, to estimate gene order rearrangements within the genome of this relict species. Such rearrangements are crucial to our understanding of rare molecular evolutionary events within the mitochondrial genome of Limulus, a chelicerate, and among it and other arthropod groups. Interestingly, Limulus mtDNA differs little in gene order, except for the translocation of a single tRNA, from that of Drosophila-- even though the last common ancestor for the group was probably pre-Cambrian (> 600 mybp) (Staton et al 1997).

    I also participated in a collaborative effort with Dr. Craig M. Young of the Harbor Branch Oceanographic Institution to examine mtDNA variation within the species Phormosoma placenta, a species of deep-sea urchin belonging to the family Echinothuriidae which are noted to have development of short duration. Despite the species hypothesized short development, P. placenta have a much wider biogeographic distribution than do many echinoid species that possess long development times, and therefore are enigmatic with respect to proposed theories that correlate overall larval development with biogeographic range and potential gene flow between geographically isolated marine populations. Preliminary results from individuals collected in the Bahamas and the Rockall Trough demonstrate that the individuals within each habitat were homogeneous for a portion of their CO-I gene, whereas individuals between sites were roughly 3.6% divergent in their mitochondrial sequences, suggesting an estimated genetic isolation of 2.4-3.6 million years for the two groups Staton and Young.

Staton JL. In Press. Phylogenetic analysis of a 654-bp portion of the mitochondrial cytochrome c oxidase subunit I gene from 13 sipunculan genera: intra- and interphylum relationships. Invertebrate Biology

Staton JL, Daehler LL, Brown WM (1997) Mitochondrial gene arrangement of the horseshoe crab Limulus polyphemus L.: Conservation of major features among arthropod classes. Molecular Biology and Evolution 14(8): 867-874.    Article in PDF format (194 kb)

Staton JL, Young CM (1994) "Genetic divergence between two populations of the bathyl echinoid Phormosoma placenta." 7th Deep-Sea Biology Symposium, Crete, Greece.

Turbeville JM, Staton JL, Brown WM (1997) Amplification of the complete mitochondrial genome of two protostome worms: a useful technique for comparative studies of metazoan mitochondrial DNA. Molecular Marine Biology & Biotechnology 6(2): 141-143.    Article in PDF format (33 kb)