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Ashley Berger ’13, Kate Donlon ’13, and Dr. John Pilger of the Biology Department have been working diligently all semester with the species of peanut worms Themiste lageniformis.  Ashley Berger’s SpARC presentation aimed to explain the group’s research findings to the Agnes Scott community as a supplemental talk to the poster of the same topic on display in the Bullock Atrium.

A biological species is a group of organisms able to mate with each other in the wild.  A morphological species has the same characteristics as other members and is classified this way.  Molecular species definitions look at the genetic sequences of the organism and defines species this way.  Berger, Donlon, and Pilger studied Themiste lageniformis this semester to define the species looking at biological, morphological, and molecular species definitions.

It is difficult to define biological species with organisms who reproduce asexually as they do not mate with other organisms.  Homoplasy or convergent evolution is a complication of morphological species definition.

Sipunculans, peanut worms, are marine unsegmented worms that are bilaterally symmetrical, part of a phylum of 200 species.  Themiste lageniformis is a Sipunculan.

Berger introduced the species of peanut worm, a small organism that lives in four regions of the world that are geographically isolated: Hawaii, Florida, Argentina, and India.  The group studied sample populations from Hawaii and Florida.  The organism is the only member in the Sipunculan phylum to use parthenogenesis as a method of reproduction, and the populations have extreme sexual bias with approximately 96% of the population being females.

The group collected genomic DNA from the retractor muscles of the peanut worms and isolated to highly conserved genes with PCR.  They investigated CO1-Cytochrome c oxidase I and 16S-Ribosomal RNA, in order to replicate their sample in order to get enough product to be able to do their study on genes to determine whether or not the Themiste lageniformis is a cryptic species.

There is little sequence variation within or between the populations of Themiste lageniformis, and their data supports the group’s hypothesis that T. lageniformis is a single species with very little genetic variation.

Berger stated that more research is needed to support their findings.  Donlon’s poster shows the specific data collected and can be accessed for further study.

Berger poses future questions for the study of this specific peanut worm:

1) How did T. lageniformis become so widely dispersed?

2) How did parthenogenesis arise?  Is it a plesiomorphic character?  Is it an amorphic character?

Way to go Ashley, Kate, and Dr. John Pilger!

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