ROBINSON ET AL: SEASONAL BIOCHEMICAL CHANGES IN PLACOPECTEN MAGELLANICUS 



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MAMJ J AS ONDJ FM 



DIGESTIVE GLAND 



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8 r QUICK ADDUCTOR MUSCLE 



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Figure 6. — Caloric equivalents (lipid + carbohydrate) for 

 major energy storage tissues of the standard deep-sea scallop 

 (120 mm shell height) over the 1-yr study period. • = female; 

 o = male. 



pectinids may occur at times of food shortage 

 (Sastry 1966). Furthermore, neither lipid nor 

 carbohydrate accumulates in the gonad imme- 

 diately following spawning for use as an over- 

 wintering reserve (Thompson 1977; this study). 



Histochemical tests do not reveal significant 

 quantities of lipid in either the quick or catch 

 components of the adductor muscle, whe'-eas a 

 substantial amount is detected biochemically. 

 Quantities of sterols (e.g., 22-dehydrocholesterol, 



cholesterol, brassicasterol, and 24-methylenecho- 

 lesterol) are present in adductor tissue (Idler et al. 

 1964) in addition to structural lipids. These high 

 melting point lipids do not color with Oil red O and 

 other Sudan dyes (Lillie and Fullmer 1976), and, 

 therefore, cannot be localized histochemically. 

 They are, however, readily extracted by the sol- 

 vents used for gravimetric lipid analysis. When 

 addressing the problem of distinguishing struc- 

 tural from reserve lipid, Giese (1966) has con- 

 cluded that lipid levels >b.2'7c dry weight are 

 reserve. Lipid levels in P. magellanicus adductor 

 muscle are never high enough (2.3-4.1% ) to meet 

 this criterion. 



Neither carbohydrate nor lipid concentrations 

 in the quick component of the adductor muscle 

 were significantly different from those in the 

 catch component in the March and April 1979 

 samples. Analysis of the catch component was 

 therefore discontinued. De Zwaan et al. (1980), 

 however, found higher concentrations (2.5 x) of 

 glycogen in the phasic ( = quick) than in the catch 

 adductor of P. magellanicus sampled in July at a 

 time when glycogen levels were at a peak. As with 

 our samples, no difference in lipid concentrations 

 was observed. Taken together, these results may 

 indicate that both components of the adductor 

 contain approximately the same carbohydrate 

 levels during the winter and early spring, but that 

 the quick component rapidly overbalances the 

 catch adductor in importance as a site of carbo- 

 hydrate reserves. 



Gametogenesis is intimately related to energy- 

 reserve fluctuations in P. magellanicus. In Jan- 

 uary, while gametogenesis has already reached 

 the early-development stage (Figure 1), body com- 

 ponent indices (Figure 2), dry weights (Figure 3), 

 and energy reserves (Figures 4, 5) within the 

 gonad, digestive gland and quick component of the 

 adductor muscle have fallen to their lowest values. 

 The initiation of gametogenesis, characterized by 

 increased numbers of gonial cells and an apparent 

 increase in mitotic activity, is first seen in early 

 winter, at a time when energy reserves are de- 

 clining. This initiation thus appears to be depen- 

 dent on the energy reserves accumulated the 

 previous season, although food availability data 

 are not available to substantiate this hypothesis. 

 Following the initiation of gametogenesis, storage 

 products begin to accumulate in the digestive 

 gland, adductor muscle, and gonad in the late 

 winter to early spring (Figure 6). At the same 

 time, gametogenesis proceeds into the middevel- 



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