RADTKK and DKAN: INCRKMKNT FORMATION OF OTOLITHS OF MUMMICHOO 



resulted in increment formation (Table 2C) in 

 embryos otherwise maintained in constantdark- 

 ness. Increment counts for ED24+L were less 



TABLE 2.— Effect of photoperiod and light stimuli on incre- 

 ment formation in sagittal otoliths of Fundulus heteroclitus 

 embryos. 



A) 

 B) 

 C) 



A 

 B 

 C 



Embryos were incubated in total darkness and sagitta were removed 



3 d after hatching. (ED24) 



Embryos were incubated in constant light and sagitta were removed 



3 d after hatching. (EL24) 



Embryos were incubated in constant darkness with 1 mm of light 



at day 10 of development. Sagitta were removed 3 d after hatching. 



N = 10 in all groups. (ED24+L) 



Sagitta diameter (mm) (X+SD) Increment numbers (X±SD) 



0.071 ±0.008 

 0.177+0.013 

 0.14610012 



0.610.77 

 6.0±0.67 

 4.7±0.48 



than those of the EL24 group and the EL12:D12 

 group at 3 d after hatching, but were very close to 

 the increment counts found at day 2 of the EL12: 

 D12 group. 



The effect of light on larvae which were main- 

 tained under EL12:D12 during embryonic de- 

 velopment and then transferred to constant 

 darkness after hatching was notasevidentasthe 

 effect of light was in the embryos maintained in 

 constant darkness. Larvae raised in constant 

 darkness (LaD24) showed a rapid addition of in- 

 crements between day and day 6 after hatch- 

 ing, but few increments formed after day 6 

 (Table 3). When the LaD24 data were compared 

 with the data from the larvae hatched and raised 





% 



,^•4" 







Figure 5.— Light micrograph of the sagitta from a newly hatched larvae incubated for the total 

 embryonic period in total darkness. Core formation is present but no increments have formed. 

 Bar = 0.02 mm. 



209 



