Table l. — Insecticide effects on percentage of axis formation, heartbeat, optic abnormalities, and hatching. 



Concentrations in parts per billion (ppb). 



fully examined for developmental abnormalities, 

 and various optic malformations were discovered 

 in the insecticide-treated embryos. These took the 

 form of unilateral and bilateral microphthalmia 

 (reduced size of eyes), unilateral and bilateral 

 anophthalmia (absence of eyes), and cyclopia (a 

 single median eye) (Figure 1). Severely retarded 

 embryos were also noted. Percentages of those 

 with successful axis formation which showed op- 

 tical abnormalities were quite high in all treated 

 groups, while none were observed in the control 

 group. Abnormal embryos were fixed prior to 



hatching. (It was assumed that they would die 

 prior to hatching since no abnormal fry had been 

 found in the previous experiments.) At hatching, 

 which commenced 15 days after fertilization and 

 continued for 7 days, one fish with scoliosis was 

 noted in 10 ppb malathion. 



In the fourth experiment, eggs were again ex- 

 posed at the late cleavage stage to DDT at 10, 25, 

 and 100 ppb, malathion at 10, 25, and 100 ppb, 

 and Sevin at 10 and 25 ppb. There were about 200 

 eggs in each dish. When checked for axis forma- 

 tion and heartbeat, treated groups were lower 



t 



|k 



B 



FIGURE 1.— Photomicrographs of whole, fixed, 2-wk-o\d Menidia menidia embryos at approximately 20 x. A is a control embryo, 

 while B is a 10 ppb Sevin-treated embryo with unilateral anophthalmia (the site of the undeveloped eye is marked by X), and C is 

 a cyclopic embryo from a 10 ppb malathion-treated batch (transmitted light illuminates the single lens at L). 



209 



