RADTKE and DKAN: INCREMENT FORMATION OF OTOLITHS OF MUMMICHOG 





m 



.02 mm 



Figure 3.— Light micrograph of the core of the sagitta of Fundulus heteroclitus taken on day 10 of 

 embryo formation. No increments have yet formed. Bar = 0.02 mm. 



diameter (Table 2A, Fig. 5). The embryos incu- 

 bated in constant light (EL24) hatched at 15 d 

 postfertilization and showed 6.0+0.67 incre- 

 ments when sampled 3 d after hatching (Table 

 2B). Constant light conditions did not signifi- 

 cantly alter increment formation; the constant 



light group (EL24) showed the same number of 

 increments as in the EL12:D12 group at 3 d of 

 age. Thus, the effect of light on embryonic incre- 

 ment formation and otolith diameters was the 

 same for the EL24 and EL12:D12 groups. 

 A 1-min light stimulus on day 10 of ED24+L 



207 



