OPTICAL MALFORMATIONS INDUCED BY 



INSECTICIDES IN EMBRYOS OF THE 

 ATLANTIC SILVERSIDE, MENIDIA MENIDIA 



Since the banning of DDT from use in the United 

 States, other insecticides such as malathion, 

 parathion, and Sevin^ (carbaryl) have come into 

 greater use. Though not persistent like DDT, 

 these insecticides, Uke DDT, find their way into 

 aquatic ecosystems and thus into the spawning 

 grounds of aquatic organisms. Various insec- 

 ticides have been shown to cause developmental 

 abnormalities. Malathion, for example, has been 

 shown to cause skeletal malformations in birds 

 (McLaughlin et al. 1963; Walker 1967; Greenberg 

 and LaHam 1969), mammals (Tanimura et al. 

 1967), and reptiles (Mitchell and Yntema 1973). 

 The experiments described herein were de- 

 signed to study the effects of DDT, malathion, and 

 Sevin on the development of the Atlantic silver- 

 side, Menidia menidia. Since previous studies had 

 all indicated that sensitivity decreases with em- 

 bryonic age, we initiated our treatment early in 

 development. 



Materials and Methods 



Adult M. menidia, from the vicinity of Mon- 

 tauk, N.Y., were collected by a seine during June 

 and July. Eggs and sperm were obtained by 

 stripping the fish, as described by Costello et al. 

 (1957:228-233). The fertilized eggs were sep- 

 arated into small clumps and, after being washed, 

 were placed randomly in glass finger bowls in 100 

 ml of Millipore-filtered seawater (salinity 30%) 

 and incubated at 20°C. The insecticides malath- 

 ion (95% analytical reagent, Supelco Inc., Belle- 

 fonte, Pa.), DDT (p,p'-DDT, 729c technical grade, 

 Montrose Chemical Co., Torrance, Calif., recrys- 

 tallized from ethanol to yield 98% p,p'-DDT), and 

 Sevin (99.2% carbaryl. Union Carbide Corp., New 

 York, N.Y.) were introduced as acetone solutions 

 into experimental dishes during either early 

 cleavage (2-4 cell stage) or late cleavage (about 

 100 cells— see Costello et al. 1957, fig. 104), at 

 concentrations of 10 to 500 parts per billion (ppb). 

 Control dishes received an equivalent amount of 

 acetone (10 /xl). The solutions were not changed; 

 thus we were studying the effect of a single appli- 

 cation of the chemicals (the concentration of 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



which undoubtedly decreased over time due to 

 adsorption). Development was followed with ref- 

 erence to the descriptions of Costello et al. (1957). 

 At appropriate times, eggs were examined to see 

 the percentage which had successfully completed 

 gastrulation and, later, the percentage which had 

 successfully initiated heartbeat. In the first two 

 experiments hatching rates were noted and only 

 the newly hatched fry were examined for mal- 

 formations. Since they appeared normal, in the 

 subsequent experiments embryos were examined 

 for malformations with considerably more suc- 

 cess. Some embryos were preserved in glutaral- 

 dehyde, dechorionated, sectioned, and stained 

 with hematoxylin and eosin. 



A repeat experiment was performed in the fol- 

 lowing summer using the same procedures. 



Results 



In the first experiment, eggs were treated at 

 the late cleavage stage with malathion at 10 and 

 100 ppb and Sevin at 25 and 100 ppb. There were 

 over 200 eggs in each dish. Percents of successful 

 axis formation and heartbeat initiation were 

 lower than controls in most treated groups (Table 

 1) but did not always show a dose-related effect. 

 Hatching commenced 14 days after fertilization 

 and continued for 6 days, at which time the ex- 

 periment was terminated. No difference was 

 noted in hatching times in the various groups and 

 no abnormalities were observed in the fry, al- 

 though some dead ones were seen in each group. 



In the second experiment, eggs at the 2-4 cell 

 stage were exposed to DDT at 25 and 100 ppb and 

 to malathion at 10 and 100 ppb. There were again 

 about 200 eggs in each dish. As in the previous 

 experiment (Table 1) treated groups had lower 

 rates of axis formation and of heartbeat initiation 

 than controls. Hatching commenced 14 days after 

 fertilization and continued for 6 days, at which 

 time the experiment was terminated. No differ- 

 ence was noted in hatching times in the various 

 groups and no abnormalities were noted in the 

 fry, although, as before, some dead ones were 

 noted in each group. 



In the third experiment, eggs at the late cleav- 

 age stage were exposed to DDT at 10, 25, and 100 

 ppb, malathion at 10, 100, and 500 ppb, and Sevin 

 at 25, 100, and 500 ppb. There were about 50 eggs 

 in each dish. When checked for axis formation 

 and heartbeat initiation, the treated eggs were 

 again lower than controls. Embryos were care- 



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