RICE ET AL.: EFFECTS OF COPPER ON NORTHERN ANCHOVY 



I 



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o 



E 



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3 

 E 



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Figure 3. — Percentage cumulative mortality of northern an- 

 chovy embryos continuously exposed to copper during test II: 

 numbers next to curves are the exposure concentrations in /xg 

 Cu/1. 



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^ 80 



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^ 60 



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 E 



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£ 

 o 



40 



20 



10 



20 



Time 



30 



h 



40 



50 



Figure 4. — Percentage cumulative mortality of northern an- 

 chovy embryos continuously exposed to copper during test III: 

 numbers next to curves are the exposure concentrations in /xg 

 Cu/1. 



Table 3. — Types of mortality and the percentage hatching of 

 northern anchovy embryos exposed to different concentrations of 

 copper. 



bryos with either type of mortality the chorion was 

 clear at the time the embryos were removed from 

 the exposure chambers. However, during prelimi- 

 nary testing, we noted that the chorion became 

 opaque when dead embryos were allowed to re- 

 main in copper concentrations as low as 100 /u.g 

 Cu/1 for a period of time. Embryo mortalities of 

 both types were found at the bottom of the expo- 

 sure chambers whereas normal embryos were 

 found at or near the surface of the water, except 

 just before hatching when they tended to sink. The 

 estimated mean hatching time from the start of 

 copper exposure was 32, 33, and 37 h for embryo 

 tests I, II, and III, indicating that in each test the 

 embryos were exposed during similar devel- 

 opmental periods. Hatching success was high for 

 controls and decreased with increases in copper 

 exposure concentration. 



Larval control mortalities were high, but fol- 

 lowed the general pattern for larvae not fed during 

 yolk-sac absorption (O'Connell and Raymond 

 1970; Lasker et al. 1970). Northern anchovy larvae 

 continuously exposed to concentrations <200 /xg 

 Cu/1 consistently showed better survival than did 

 the controls (Table 3) (Figures 5, 6). Though he 

 offered no explanation, Benoit (1975) found 

 bluegill, Lepomis macrochirus, larval survival 

 greater at 12 /xg Cu/1 than in the controls. It is 

 possible that low levels of copper exposure in- 

 creased survival of both the northern anchovy and 

 bluegill larvae by inhibiting harmful microbial 

 populations. The period of yolk absorption was 

 estimated to be between 24 and 30 h from the start 



100 



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'Epiboly disrupted, the yolk naked and a deformed opaque mass of proto- 

 plasm at the animal pole. 

 ^Dead after epiboly, embryo appears normally developed. 



100 



Figure 5. — Percentage cumulative mortality of northern an- 

 chovy larvae continuously exposed to copper during test I: num- 

 bers next to curves are the exposure concentrations in fig Cu/1. 



679 



