SEASONAL CHANGES IN SOFT-BODY COMPONENT INDICES AND 



ENERGY RESERVES IN THE ATLANTIC DEEP-SEA SCALLOP, 



PLACOPECTEN MAGELLANICUS^ 



William E. Robinson^ William E. Wehling,'' M. Patricia Morse,^ and Guy C. McLeod'' 



ABSTRACT 



The relationship between the energy storage cycle and gametogenesis was investigated over a 1-year 

 period (March 1979-March 1980) in a population of the Atlantic deep-sea scallop, Placopecten 

 magellanicus , from Boothbay, Maine. Soft body component indices, dry weights, lipid, and carbo- 

 hydrate levels were measured in digestive gland, adductor muscle components, and gonadal tissue. 

 In addition, mantle, mantle edge, foot, and kidney tissues were examined histochemically for 

 glycogen and lipid content. Gametogenesis began in early winter ( December- January ) during a period 

 when energy reserves and tissue indices were falling. Gonadal growth occurred concurrently with 

 increases in body component indices, dry weights, and replenishment of lipid and carbohydrate levels 

 in the digestive gland and adductor muscle (January-March). The accumulated springtime energy 

 reserves in somatic tissues were lost in the late spring-summer, as maturation of gametes was 

 completed. Following spawning in mid-September, a slight recovery of energy reserve levels and body 

 component index values was evident for the digestive gland and quick component of the adductor 

 muscle. Recovery did not occur in the gonad. Energy reserves, body component indices, and dry weights 

 all declined throughout the late fall and early winter months. A buildup of energy reserves in the early 

 spring appears essential for the later completion of gonadal maturation. Similarly, the autumn 

 recovery of energy reserves within the somatic tissue may be important for the subsequent initiation 

 of gametogenesis in early winter, as well as for meeting metabolic demands during the period of 

 low food-availability. 



The Atlantic deep-sea scallop, Placopecten magel- 

 lanicus (Gmelin), supports an extensive com- 

 mercial fishery throughout most of its western 

 Atlantic range from the Strait of Belle Isle, 

 Newfoundland, to Cape Hatteras, N.C. (Posgay 

 1957; Altobello et al. 1977; Serchuk et al. 1979). 

 In spite of its economic importance, the under- 

 lying factors which affect reproductive success are 

 poorly understood although the basic reproductive 

 biology is well documented. The annual cycle of 

 gametogenesis has been described both macro- 

 scopically (Coe 1945) and microscopically (Naidu 

 1970). Spawning seasons have been identified 

 throughout most of the scallop's geographical 

 range (Dickie 1955; Posgay and Norman 1958; 

 Naidu 1970; Merrill and Edwards 1976). Larval 



'Contribution No. 97, Marine Science Institute, Northeastern 

 University. 



^Marine Science Institute, Northeastern University, Nahant, 

 Mass., and Department of Biology, Northeastern University, 

 Boston, Mass.; present address: New England Aquarium, Re- 

 search Department, Central Wharf, Boston, MA 02110. 



^Marine Science Institute, Northeastern University, Nahant, 

 MA 01908 and Department of Biology, Northeastern University, 

 Boston, MA 02115. 



"New England Aquarium, Central Wharf, Boston, MA 02110. 



Manuscript accepted April 1981. 



FISHERY BULLETIN: VOL. 79, NO. 3, 1981. 



development has been followed in the laboratory 

 through settlement (Baird 1953; Culliney 1974; 

 Drew 1906) and temperature and salinity effects 

 on development have been investigated (Culliney 

 1974). The lack of consistent year-class recruit- 

 ment, however, probably reflects the importance 

 of environmental influences on reproductive suc- 

 cess (Dickie 1955; Serchuk et al. 1979). 



As an initial step toward a better understanding 

 of reproductive success in any invertebrate spe- 

 cies, the relationship between the buildup and 

 utilization of energy reserves and the annual cycle 

 of gametogenesis and spawning should be investi- 

 gated (Giese and Pearse 1974). Thompson (1977) 

 undertook such an approach using Atlantic deep- 

 sea scallops collected from three populations 

 in southeast Newfoundland. Although his main 

 emphasis was on the seasonal changes in blood 

 chemistry, biochemical analyses for glycogen, 

 lipid, and protein levels were conducted on both 

 gonadal and somatic tissues. Other contributions 

 to an understanding of the energy reserve-repro- 

 ductive cycle relationship have been made. Naidu 

 (1970) presented gonad wet weight data, broken 



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