Research Training Program

Smithsonian Institution
National Museum of Natural History

PROJECT SUMMARY
1997

Christopher T. Richards
Oberlin College
Oberlin, Ohio
Jon L. Norenburg, Ph.D
Supervising Scientist
Department of Invertebrate Zoology
"Working with Jon Norenburg, I learned many laboratory and analytical techniques that I will continue to apply throughout my educational and professional career."

New species from Florida sheds light on Pantinonemertes phylogeny

ABSTRACT
A nemertean is an unsegmented worm with an eversible proboscis. Although most nemerteans are marine, terrestrial species occur in many different parts of the world. As a consequence of terrestrial habitat, this group has become ecologically, morphologically and behaviorally distinct from all marine groups. How did nemerteans make this transition from sea to land? In the past, terrestrial nemerteans were thought to have derived from a common marine ancestor. More recently, comparative morphology has suggested that these adaptations occurred independently in several groups. Unfortunately, it is still undetermined how land nemerteans evolved because many species are poorly known and inadequately described, if known at all. In order to help unravel this mystery, marine ancestors and transitional groups must be identified from which fully terrestrial forms could have evolved. Genus Pantinonemertes is an ideal group to study because it represents a range of terrestrial and transitional species. Cladistic analysis of this group, using morphological, ecological and behavioral data from many different species theoretically will allow scientists to trace the evolution from sea to land. Past attempts at such analysis, however, have produced uncertain phylogenies, because there are relatively few species and because previous descriptions have been inadequate. Describing a new Pantinonemertean from Florida, using thin cross-sections of specimens under light microscopy, determined that it is distinct from P. agricola by gonochorism, oviparity and a supra-littoral habitat. This new species was used in a re-analysis of the Pantinonemertes which improved resolution, but still left an uncertain phylogeny.

Funding for this research was awarded through the National Science Foundation's Research Experience for Undergraduate Projects Award number DBI-9531331.

Letter of Gratitude