glucose-6-phosphate . Glucose-6-phosphatase was not assayed in starved 

 quahogs, but perhaps it may be activated under such conditions. Partially 

 starved quahogs showed changes in glycogen, glucose-6-phosphate dehydrogenase, 

 and fructose diphosphatase levels similar to those observed in mammalian 

 tissue. - J.L.M. 



544 



Engel, Robert H ., and Marilynn J. Neat. 1974. 



Occurrence of specific and non-specific cholinesterases in the quahog, 

 Mercenaria mercenaria. Comp. Biochem. Physiol. 48A(3): 407-410. 



Cholinesterase activity was measured in foot, gill, and mantle tissue. 

 Substrate saturation and specificity studies showed that gill enzyme was a 

 specific cholinesterase, while mantle activity was ascribed to a non-specific 

 cholinesterase. Quahogs were obtained from Duxbury Bay, Mass. - J.L.M. 



545 



Engel, R. H., M. J. Neat, and R. E. Hillman. 1972. 



Sublethal chronic effects of DDT and Lindane on glycolytic and gluconeogenic 

 enzymes of the quahog, Mercenaria mercenaria. In Marine Pollution and Sea 

 Life. M. Ruivo (ed.) . Fishing News (Books) Ltd., London, p. 257-260. 



The study was made to determine if sublethal chronic doses of insecticides, 

 at concentrations currently existing in estuarine waters, could alter 

 activity of key regulatory enzymes and thus effect intermediary metabolism. 

 It was clear that overall catalytic capacity of Mercenaria mercenaria was 

 well below that of mammalian tissue. The most striking effect of DDT and 

 lindane on hard clams appeared to be a consistent decrease in fructose 

 diphosphatase activity as compared to controls. This suggested that 

 chlorinated hydrocarbons may interfere with gluconeogenesis . Quahogs used 

 in the study were under metabolic stress from partial starvation. Normal 

 environmental variations which create similar stress might be exacerbated 

 in presence of DDT or lindane. Exposure to chlorinated hydrocarbons also 

 gave a slight but significant decrease in mantle lactic dehydrogenase. DDT 

 reduced glucose-6-phosphate dehydrogenase content of gill tissue to almost 

 nothing. Lindane gave a significant increase in foot glucose-6-phosphate 

 dehydrogenase activity. It was concluded that glycolysis is an operative 

 metabolic pathway in quahog tissue, and that it responds to stress such as 

 starvation with compensating mechanisms analogous to those identified in 

 mammalian tissue. Chronic exposure to sublethal doses of chlorinated 

 hydrocarbons could lead to an increase in glucose degradation and 

 suppression of gluconeogenesis. - J.L.M. 



546 



Engle, James B. 1964. 



A brief history of Federal shellfish investigations in Chesapeake Bay. 

 In The Bureau of Commercial Fisheries Biological Laboratory-Oxford, 

 Maryland: Programs .and Perspectives. U.S. Dept. Interior, Fish Wildl. 

 Serv., Circ. 200, p. 1-7. 



547 



Engle, James B. 1966. 



The molluscan shellfish industry, current status and trends. Proc. Natl. 

 Shellf. Assn. 56: 13-21. 



Hard clam, Mercenaria mercenaria, has filled an important role in the 

 economy of the Mid-Atlantic and lower New England areas of the U.S. coast. 

 Many oyster growers have turned to hard clam harvesting as a significant 

 adjunct to the declining oyster business. About 50% of hard clam production 

 comes from the Mid-Atlantic area, about 95% from Narragansett Bay, Long Island 

 Sound, Long Island bays, Maryland and Virginia coastal bays, and lower Chesa- 

 peake Bay. A great natural expansion of the clam population has occurred in 

 bays of Long Island. In New York State a minimum size law and selective 

 harvesting with hydraulic dredges (on private grounds) have greatly assisted 

 in cultivation, recruitment, and conservation of the resource. - J.L.M. 



152 



