Dr. Jack J. O'Brien
Assistant Professor, Department of Biological Sciences
University of South Alabama
Ph.D., 1984, University of California, Santa Barbara

Research Description:
Long term research goals are centered upon understanding the ecological and physiological interactions between invertebrates and their parasites.

Current research involves: The rhizocephalan barnacle, Loxothylacus texanus, a parasite of blue crabs. These barnacles are parasitic castrators; reproductive organs of infected crabs do not mature. In addition, crabs bearing the external stage of the parasite do not molt, they acquire the adult morphology at a very small size, and male crabs are feminized. For unknown reasons the parasite is restricted to the Gulf of Mexico as it has not been reported in host populations along the Atlantic Coast.

Ongoing investigations include: Determining the effects of temperature upon parasite fecundity, salinity upon survival of parasite larvae, host molt stage on the ability of the parasite to successfully infect potential hosts, and identifying the chemical cues used by parasite larvae to locate potential hosts.

Representative Publications:
O'Brien, J. 1984. Precocious maturity of the majid crab, Pugettia producta, parasitized by the rhizocephalan barnacle, Heterosaccus californicus. Biol. Bull. 166:384-395.

O'Brien, J., and Van Wyk, P. 1985. Effects of crustacean parasitic castrators (epicaridean isopods and rhizocephalan barnacles) on growth of crustacean hosts. In: "Factors in Adult Growth" A. Wenner, Ed. Crustacean Issues 3. pp 191-218. A.A. Balkema, Rotterdam, Netherlands.

O'Brien, J., and Skinner, D.M. 1988. Characterization of enzymes that degrade crab exoskeleton: II. Two acidic proteinase activities. J. Exp. Zool. 246:124-131.

O'Brien, J., and Skinner, D.M. 1990. Overriding of the molt-inducing stimulus of multiple limb autotomy in the mud crab Rhithropanopeus harrisii by parasitization with a rhizocephalan. J. Crust. Biol. 10:440- 445.

O'Brien, J., Kumari, S., and Skinner, D.M. 1991. Proteins of crustacean exoskeletons: I. Similarities and differences among proteins of the four exoskeletal layers of four brachyurans. Biol. Bull. 181:427-441.

O'Brien, J., Kumari, S.S., and Skinner, D.M. 1993. Differential localization of specific proteins in the exoskeleton of the Bermuda land crab, In: The Crustacean Integument: Morphology and Biochemistry. M.N. Horst and J.A. Freeman, Eds. pp 79-111. CRC Press.