About Us


Sidney K. Pierce

Sidney K. Pierce

Sidney K. Pierce
Professor Emeritus (Tampa)


Office: SCA 126
Phone: 813/974-4494
Lab: SCA 125
Fax: 974-3263
Email: pierce@usf.edu


Ph. D., 1970, Florida State University


Cellular physiology and biochemistry
Symbiosis, gene transfer, osmoregulation, marine invertebrate biology and sea monsters


E. clarki

Three main research projects are underway in Dr. Pierce's laboratory. First, we are investigating the molecular biology of an intracellular symbiosis between the digestive cells of a sea slug (Elysia chlorotica) and algal (Vaucheria litorea) chloroplasts. The plastids, once incorporated into the molluscan cell, continue to photosynthesize, even after several months separation from the rest of the plant and provide sufficient energy to sustain the slug in the absence of any additional food. Several plastid proteins are synthesized during this amazingly long period, including some that seem to be coded for in the slug genome. Complicating this remarkable association further is the presence of one or more endogenous retroviruses. We are investigating the role the viruses may have in synchronizing the life cycle of the slug population as well as providing the means by which algal genes have been moved into the slug DNA. Since moving to Tampa, we have expanded these investigations to include another sea slug, Tridachia (=Elysia) crispata, which lives in the Keys. This slug also steals pastids from algae and may also have genes for plastid proteins in the molluscan DNA. Transfer of genes between multicellular organisms has never been demonstrated before, so these species of sea slug may be a very useful model system to understand how such an important phenomenon could occur.

Second, we are continuing a decades-long investigation of the biochemical and molecular mechanisms regulating cell volume recovery from osmotic stress, with a particular interest in the salinity tolerance mechanism of marine organisms. Osmotic change toleration depends upon the ability of the cells within an organism to regulate the amount of cellular water. This regulation is accomplished by cellular mechanisms that control the permeability of membrane channels to certain intracellular solutes-ions, certain amino acids such as taurine, and certain quaternary ammonium compounds such as glycine betaine. Currently, the role of membrane protein phosphorylation in the regulation of membrane permeability changes to taurine that occur following a hypoosmotic stress (low salinity) are being studied. All work on these projects has been done on the cells and tissues of a variety of marine invertebrates. Currently, red blood cells from the bivalve, Noetia ponderosa, are being studied.

Third, on occasion we investigate sea monsters. Of particular local interest, we determined by biochemical and microscopical analyses on pieces of the 100 year old carcass, that the St. Augustine (FL) giant octopus was in fact merely a piece of whale skin. Similar analyses on pieces of the Bermuda Blob and the Tasmanian West Coast Monster, and most recently on the Chilean Blob, produced similar results. We are collaborating with monster investigators around the world.

Specialty Area

Cellular Physiology and Biochemistry