B.S. City College of New York, (Biology) 1963

PhD Univ. of Rhode Island, (Biol. Oceanography - Marine Ecology) 1970

 

TEACHING AND RESEARCH AREAS

Optimal Foraging Theory predicts that an organism should maximize its rate of energy intake per unit time. A major focus of my research is the foraging habits of crustaceans, effective predators on bivalves in marine and estuarine habitats. Studies involve prey size selection, diet selectivity, cost/benefit analysis and the effects of risk and predation on foraging behavior in the blue crab (Callinectes sapidus), the rock crab (Cancer irroratus) and the Jonah crab (Cancer borealis).

These studies also involve mechanisms used for prey detection and factors that elicit foraging responses. Odor is important in prey detection, location and identification. We have shown that crabs will recognize and approach food odors at concentrations of 1 part in 100 billion but we have not been able to determine a significant role for vision as a means of identifying or selecting prey. Recent studies have examined the role of tactile cues in prey selection.

Other investigations involve the mechanical and biological performance of rock and Jonah crab claws. We have measured the mechanical advantage (efficiency) of rock crab claws from populations along the Atlantic coast and found significant variation by location. Claws from the northern most sites generally had larger mechanical advantages than those in southern locations, although there was not a smooth gradient. Mechanical advantage is a simple measurement of how much force the crab can apply to hard shelled prey, but it is not as good a predictor as claw strength. We have also measured actual claw strength and have found several morphological claw attributes that are highly correlated to strength.

The second focus of my research has been on the effects of Dimilin (diflubenzuron) on molt in the blue crab. Dimilin is an insect growth inhibitor used to control gypsy moth populations by interrupting the formation of chitin in arthropods when they molt. Areas where Dimilin is sprayed constitute a major portion of the drainage area for the Chesapeake Bay. In a U.S. Forest Service funded project, we have determined the levels of Dimilin lethal to juvenile blue crabs. We have also found that the presence of organic sediments can intensify this reaction because Dimilin adsorbs to these sediments. Since the blue crab is a benthic organism, it is in direct contact with the sediments and much of it diet is obtained from benthic prey. We have also investigated the effects of exposure to sublethal concentrations of Dimilin on blue crabs.

Other studies include: control of molt in Crustacea, crustacean aquaculture, crustacean artificial diets, orientation, migration and biological rhythms in marine organisms, and the effects of Permethrin on juvenile striped bass.

SELECTED PUBLICATIONS:

Ristvey, A. and Rebach, S. 1999. Enhancement of the response of rock crabs, Cancer irroratus, to prey odors. Biol. Bull. 197(3): 361-368.

Rebach, S. 1999. Acute toxicity of permethrin/piperonyl butoxide on hybrid striped bass. Bull. Environ. Contam. Toxicol 62:448-454. Zhou, T. and Rebach, S. 1999 Chemosensory orientation of the rock crab Cancer irroratus. J. Chem. Ecology. 25(2): 315.329.

Block, J. and Rebach, S. 1998. Correlates of claw strength in the rock crab, Cancer irroratus. Crustaceana. 71(4): 468-473.

Rebach, S. and D. Wowor. 1997. Geographic variation of claw attributes in east coast cancrids. J. Crust. Biol. 17(2): 234-242.

Rebach, S. 1996. The role of odor in prey recognition by rock crabs, Cancer irroratus Say. J. Chem. Ecology. 22(12): 2197-2207. Rebach, S. and D.P. French. 1996. Effects of Dimilin on the blue crab, Callinectes sapidus, in shallow water habitats. Estuaries. 19: 279-287.