FRITZ and HAVEN: HARD CLAM SHELL GROWTH 



FALL-WINTER 

 1979-1980 



FALL-WINTER 

 1979-1980 



FIGURE 2.— Enlargements of acetate peels from five short-term experimental Mercenaria mercenaria showing shell growth from transplanta- 

 tion in October 1 979 to each date of collection (shell margin). Growth disturbance due to transplantation is labelled fall- winter 1979- 1980 in the 

 outer prismatic layer (op) of each. Middle homogenous layer (mh) bands are labelled lb (light band) and db (dark band). Contrast in 

 photographs is due to differences in transparency of portions of the peels. Light regions in photographs correspond to relatively opaque regions 

 on peels, or those which appear dark in polished shell sections. Scale bars represent 1 mm and growth is to the right. 



1 980 to the shell margin in four collections of TI hard 

 clams during summer 1980, 2) the number of 

 increments from the growth disturbance caused by 

 transplantation of short-term hard clams (from the 

 Eastern Shore to the York River) on 16 October 1979 

 to the shell margin in hard clams collected from April 

 1980 (after growth had resumed) to June 1981, and 

 3) the number of increments between MDM formed 1 

 yr apart between 1969 and 1971 by hard clams in 

 lot XI. 



TI Series, From 30 May 1980 



TI hard clams collected in summer 1980 had a 

 strong tendency to form one increment each solar day 

 (Table 6; Fig. 3). Regression of the number of 

 increments formed on days since 30 May 1980 

 yielded a strong linear relationship (F = 156.30, P < 

 0.001) with a regression coefficient (b) not signifi- 

 cantly different from 1.00 (Table 6). Consequently, 

 TI hard clams tended to form one prismatic 



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