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Sidney K. Pierce

Sidney K. Pierce

Sidney K. Pierce
Professor Emeritus


Office: SCA 126
Phone: 813/974-4494
Lab: SCA 125
Fax: 974-3263


Personal Bio



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

Recent Journal Articles


Honors and Award






Recent Publications


Pierce, S. K., M. L. Middlebrooks and N. E. Curtis. 2015. Sacoglossan sea slugs make routine use of photosynthesis by a variety of species-specific adaptations. Invert. Biol. 134: 103-115.

Curtis, N. E., M. L. Middlebrooks, J. A Schwartz, and S. K. Pierce. 2015. Kleptoplastic sacoglossan species have very different capacities for plastid maintenance despite utilizing the same algal donors. Symbiosis. 65: 23-31.

Schwartz, J.A., N. E. Curtis and S. K. Pierce. 2014. FISH labelling reveals a horizontally transferred algal (Vaucheria litorea) nuclear gene on a sea slug (Elysia chlorotica) chromosome. Biol. Bull. 227: 300-312.

Middlebrooks, M. L., S. S. Bell, N. E. Curtis, and S. K. Pierce. 2014. Atypical plant-herbivore association of algal food and a kleptoplastic sea slug (Elysia clarki) revealed by DNA barcoding and field surveys. Mar. Biol. 14: 1429-1440.

Middlebrooks, M. L., S. S. Bell and S. K. Pierce. 2012. The kleptoplastic sea slug Elysia clarki prolongs photosynthesis by synthesizing chlorophyll a and b. Symbiosis. 57: 127-132.

Pierce, S. K. and N. E. Curtis. 2012. The cell biology of the chloroplast symbiosis in sacoglossan sea slugs. Int. Rev. Cell Mol. Biol. 293: 123-148.

Pierce, S. K., Fang, X., Schwartz, J. A., Jiang, X., Zhao, W., Curtis, N. E., Kocot, K., Yang, B., Wang, J., 2012. Transcriptomic evidence for the expression of horizontally transferred algal nuclear genes in the photosynthetic sea slug, Elysia chlorotica. Mol. Biol. Evol. 29: 1549-1556.

Middlebrooks, M., S. K. Pierce, S. S. Bell. 2011. Foraging behavior under starvation conditions is altered via photosynthesis by the marine gastropod, Elysia clarki. PLoS. 6(7): e22162.

Curtis, N. E., J. A. Schwartz and S. K. Pierce. 2010. An Ultrastructural comparison of chloroplast containing cells in the digestive diverticulum of four sacoglossan sea slugs of differing kleptoplastic abilities. J. Invert. Biol. 129: 297-308.

Schwartz, J. A., N. E. Curtis and S. K. Pierce. 2010. Using algal transcriptome sequences to identify transferred genes in the sea slug, Elysia chlorotica. Evol. Biol. 37: 29-37.

Pierce, S. K., N. E. Curtis, and J. A. Schwartz. 2009. Chlorophyll a synthesis by an animal using transferred algal nuclear genes. Symbiosis 49: 121-131.

Curtis, N.E., C. J. Dawes and S.K. Pierce. 2008. Phylogenetic analysis of the large subunit RUBISCO gene supports the exclusion of Avrainvillea and Cladocephalus from the Udoteaceae (Bryopsidales, Chlorophyta) J. Phycol. 44(3):761-767.

Pierce. S. K., N. E. Curtis, J. J. Hanten, S. L. Boerner and J. A. Schwartz. 2007. Transfer, integration and expression of functional nuclear genes between multicellular species. Symbiosis 43:57-64.

Hubert, M. D., E. Indyk, C. Pena-Rasgado, S. K. Pierce, H. Rasgado-Flores, S. S. Garber. 2007. Effect of extracellular glucose and K+ on intracellular osmolytes in a human kidney cell line. Front. Biosci. 12:4352-4363.

Curtis, N. E.,S. K. Pierce, S. E. Massey, J. A. Schwartz and T. K. Maugel. 2007. The intracellular, functional chloroplasts in adult sea slugs (Elysia clarki) come from several algal species, and are also different from those in juvenile slugs. Mar. Biol. 150:797-806.

Curtis, N. E., S. E. Massey and S. K. Pierce. 2006. The symbiotic chloroplasts in the sacoglossan Elysia clarki are from several algal species. J. Invert. Biol. 125:336-345.

Pierce, S. K., N. E. Curtis, S. E. Massey, A L. Bass, S. A. Karl and C. Finney. 2006. A morphological and molecular comparison between Elysia crispata and a new species of kleptoplastic sacoglossan sea slug (Gastropoda: Opisthobranchia) from the Florida Keys USA. Molluscan Res. 26:23-38.

Pierce, S. K., S. E. Massey, N. E. Curtis, G. N. Smith, Jr., C. Olavarria and T. K. Maugel. 2004. Microscopic, biochemical and molecular characteristics of the Chilean Blob and a comparison with the remains of other sea monsters: Nothing but whales. Biol. Bull. 206:125-133.

McCoy, E. D. and S. K. Pierce. 2004. The function of course pre-requisites in Biology: Comparing student driven and faculty driven models. Action Bioscience. A reviewed Web publication of the AIBS) .

Pierce, S. K, S. E. Massey, J. J. Hanten and N. Curtis. 2003. Horizontal of functional nuclear genes between multicellular organisms. Biol. Bull. 204:237-240.

Mondy, W. L. and S. K. Pierce. 2003. Apoptotic-like morphology is associated with the annual synchronized death of a population of kleptoplastic sea slugs (Elysia chlorotica). J. Invert. Biol. 122:126-137.

Peña-Rasgado C., S.K. Pierce and H. Rasgado-Flores. 2001. Osmolytes responsible for volume reduction under isosmotic or hypoosmotic conditions in barnacle muscle cells. J. Cell Molec. Biol. 47:841-853.

Hanten, J.J. and S.K. Pierce. 2001. Synthesis of several light-harvesting complex I polypeptides is blocked by cycloheximide in symbiotic chloroplasts in the sea slug, Elysia chlorotica (Gould): A case for horizontal gene transfer between alga and animal? Biol. Bull. 201:33-44.

Pierce, S. K., Maugel, T. K., Rumpho, M. E., Hanten, J. J., Mondy, W. L. 1999. Annual viral expression in a sea slug population: Life cycle control and symbiotic chloroplast maintenance. Bio. Bull. 196: 197:1-6.

Pierce. S. K., Smith, G. N., Clark, E. and Maugel, T. 1995. On the giant octopus (Octopus giganteus) and the Bermuda Blob: Homage to A. E. Verrill. Biol. Bull. 188:219-230.