Figure l. — Photograph of regener- 

 ating caudal fin, 1 wk after amputa- 

 tion. Measurements were made at A 

 toB. 



mm _ 



dard length (SL) to 0.05 ppm methylmercury, 1.0, 

 3.0, or 10.0 ppm zinc or combinations of 0.05 ppm 

 methylmercury with 1.0, 3.0, or 10.0 ppm zinc. 

 Experiment II was similar, but used 0.025 ppm 

 methylmercury and fish 4.1-5.2 cm SL. Experi- 

 ment III used 0.05 ppm methylmercury and the 

 same concentrations of zinc, but was performed in 

 water of reduced salinity (10%o) on fish 4.3-5.1 

 cm SL. 



Fish were frozen at the end of some experi- 

 ments and later analyzed for metal uptake by 

 atomic absorption spectrophotometry (cold vapor 

 technique for mercury, flameless atomic absorp- 

 tion spectrophotometry for zinc). These analyses 

 can be considered accurate within 10%. 



Results 



Table l. — Analysis of variance on effects of methylmercury 

 and zinc on fin regeneration in Fundulus heteroclitus. 



Source of variation 



df 



SS 



MS 



Hg 



Zn 



Hg X Zn 



24.778 

 2.200 

 0.411 



24.778 

 0.733 

 0.137 



173.671 

 5.139 

 0.960 



0.001 

 0.003 

 0.416 



Table 2. — Growth of tail regenerates in Fundulus heteroclitus 

 e5q)osed to methylmercury and zinc for 14 days in Experiment II 

 and 11 days in Experiment III. 



*Significantly different from controls (P<0.05) by (-test. 



In Experiment I, caudal fin regeneration was 

 retarded by methylmercury and was accelerated 

 by zinc in a dose-dependent fashion. The retarda- 

 tion produced by the mercury could be partially 

 counteracted by the zinc (Figure 2). Analysis of 

 variance of day 14 (Table 1) showed significant 

 effects of mercury, and of zinc, but not of interac- 

 tion. 



Experiment II, using 0.025 ppm methylmer- 

 cury, produced similar results (Table 2). It can be 

 seen that zinc again accelerated growth in a 

 dose-dependent manner and counteracted the 

 methylmercury-caused depression of growth. 

 Only the group in methylmercury alone and the 



group in 10 ppm zinc were significantly different 

 from controls (P^0.05) as determined by the 

 ^-test. 



In Experiment III (10%o salinity) a similar pat- 

 tern was seen (Table 2). High mortality due to 

 interruption in air supply caused the experiment 

 to be terminated early. The groups in methylmer- 

 cury, methylmercury + 1 ppm zinc, and in 10 

 ppm zinc were significantly different from con- 

 trols, as seen by the ^-test. 



Analysis of mercury uptake revealed consider- 

 able variation (Table 3). However, it seems likely 

 that the tissue residues are dose dependent and 

 that zinc does not change the uptake of mercury 



164 



