ROPES ET AL : SIZE. AGE. AND SEX OF OCEAN QUAHOGS OFF LONG ISLAND. NY 



ous and the first was confounded by a secondary 

 incomplete line that had formed slightly later 

 (Fig. la, b). The formation of secondary lines is not 

 typical at a young age. The formation of a complete 

 line is, however, important in detecting annul i. 



Three clams had shell abnormalities related to 

 an injury An ocean quahog with six bands had a 

 slight depression at the anterior end of the left 

 valve that was not detected as unusual growth 

 lines or increments in the peel of either the valve 

 or tooth; the right valve showed no evidence of an 

 injury (Fig. 2a, b). Another quahog had a deep 

 indentation, and part of the ventral margin was 

 missing in the left valve before band six had been 

 formed, but the right valve showed a slight inden- 

 tation and darkening as evidence of an injury ( Fig. 

 3a, b). The peel of the left valve showed age lines 

 before and immediately after the site of the injury 

 (Fig. 3c). The sixth annuli in the hinge tooth was 

 very prominent (Fig. 3d). The valve of a quahog 

 with seven bands had definite surface indenta- 

 tions associated with annuli, and the hinge tooth 

 showed regularly spaced growth increments (Fig. 



4a, b, c). An injury was not clearly evident. The 

 annuli in peels of all these clams were easily re- 

 lated to bands on the valve surface for mea- 

 surements of growth. 



For 9 clams (47.5-60.4 mm long), all annuli in 

 the peels were counted, but only some bands were 

 measured because those near the ventral margin 

 were too crowded and poorly defined. 



The shells of 3 clams (39.7-64.0 mm long) pro- 

 duced a confused pattern of lines in the ventral 

 third of the peels and extensive ridging and poorly 

 defined bands on the external valve surfaces (Fig. 

 5a, b, c). It was not evident that these clams had 

 been injured, but they were omitted in analyses, 

 since growth appeared to be aberrant. In all, 134 

 clams, 18.7-60.4 mm long and averaging 38.9 mm 

 (S.D. ± 8.65), were used. 



5mm 



i i i i 



5 mm . 



FIGURE 1. — <ai Right valve of a 3-yr-old ocean quahog, 

 Arctica islandica, 20.0 mm shell length, (b) Photomi- 

 crograph of the acetate peel image of the hinge tooth 

 showing three annuli. 



i/. 



~A 







^* 



\ 



, 500>im 



I ' i i i 



FIGURE 2. — (a) Right valve of a 6-yr-old ocean quahog, Arctica islan- 

 dica. 31.1 mm shell length, ibi Photomicrograph of the acetate peel 

 image of the hinge tooth showing six annuli. 



255 



