143 



Bayne, B. L. 1976. 



Aspects of reproduction in bivalve molluscs. In Estuarine Processes. Vol. 

 1. Uses, Stresses, and Adaptation to the Estuary. Martin VJiley (edj . 

 Academic Press, New York, p. 432-448. 



Mercenaria mercenaria , among other mollusks, has a swimming larva that feeds 

 on suspended particulate matter. About 52% of the energy available for 

 production, once the demands of maintenance have been met, is eventually 

 utilized in gametogenesis . This value probably increases with age. It is 

 consistent with a planktotrophic "strategy" characterized by high fecundity 

 and high metabolic cost. Mercenaria mercenaria in a mixed estuary usually 

 spawned at or just after low tide, which coincided with maximum water 

 temperature caused by heat brought down the estuary during ebb tide. 

 Discussion of energy (=nutrient) reserves, other seasonal physiological 

 changes, and relationships between adult condition and larval vigor do not 

 refer specifically to hard clam, but the following processes apply generally: 

 use of energy resources for reproduction takes the form of storage and 

 utilization of glycogen, coupled with an annual gametogenic cycle that 

 probably is synchronized with a variety of environmental factors. Details 

 vary between species, but all involved accumulation of energy when food is 

 abundant, for use in maintenance and gametogenesis. A mutual control of the 

 storage cycle between glycogen synthesis in the adult and lipid synthesis in 

 the developing oocyte may exist, based on neurosecretory hormones and blood 

 glucose levels. Physiological factors buffer gametogenic events from 

 environmental disturbance, although not always with 100% efficiency. 

 Included are acclimation of metabolic rate with changes in temperature, and 

 a switch mechanism that lets gametogenesis proceed to completion once 

 sufficient nutrient reserve has accumulated, even with short-term environ- 

 mental deterioration. Despite the buffering effects, stress on the adult 

 affects fecundity and vigor of larvae. Successful embryogenesis depends on 

 lipid reserves in the egg to bring the larva to the feeding stage. Lipids 

 also seem to play a role in larval growth. - J.L.M. 



144 



Bayne, B. L. (edj . 197 6. 



Marine Mussels: Their ecology and physiology. Internatl . Biol. Progr. 10, 

 Cambridge Univ. Press, xvii + 506 p. 



This useful book, as its title implies, deals primarily with mussels, but 

 other bivalves, including Mercenaria (Venus) mercenaria , have been considered 

 when appropriate to avoid superficial discussion of certain subjects. All 

 references to M. mercenaria are from published papers abstracted elsewhere 

 in this bibliography. - J.L.M. 



145 



Bear, Richard S., and Cecily Cannan Selby. 1956. 



The structure of paramyosin fibrils according to X-ray diffraction. J. 

 Biophys. and Biochem. Cytol. 2(1): 55-69. 



Various molluscan sources have been used, but that preferred for extraction 

 of paramyosin is the "white" portion of the adductor muscle of Venus 

 mercenaria, because the protein is so highly concentrated there. The small- 

 angle pattern then is overlaid only weakly with actin diffraction. The 

 wide-angle diffraction of paramyosin probably is of a-type, and supercoiled 

 a-helices must be involved. Cables of this type, about 1,400 A long, may 

 extend over 2 cells. Other considerations suggest that the cable units may 

 be aggregated into supercables essentially forming rather solid rods of about 

 100 A diameter. An alternative interpretation of the small-angle diffraction 

 would conclude that large particles are arranged helically, with minimum 

 helix diam about 150 A. The simplest particle connection would have 5 

 particles in 2 coil turns along 720 A of fibril or helix axis. This view is 

 distinctly different from the suggested arrangement of "rods" in net-like 

 layers. The authors prefer the net-of-rods model over the particulate-helix 

 model and give technical reasons for the preference. - J.L.M. 



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