Adult worms were obtained from Dr. J. Grassle ŽRutgers University. and maintained in our laboratory for multiple generations at about 30‰ salinity on a diet of fine mud J.A. Pechenik et al.rJ. Exp. Mar. Biol. Ecol. 264 (2001) 101–114 103 collected from the Little Sippewissett salt marsh on Cape Cod, Massachusetts, USA, where members of this species occur naturally. The mud was forced through a 1-mm sieve to remove debris and then frozen for at least several days to kill animal residents before use ŽCohen and Pechenik, 1999.. Two experiments ŽCad-1 and Cad-2. were conducted at 23 8C, both using static exposures to toxicant. Approximately 600 larvae released from brood tubes by four females were pooled and subsampled for the first experiment. The larvae were distributed among plastic cups containing 50 ml of either 0.45-mm-filtered seawater or CdCl seawater solution. Seven CdCl concentrations were tested, up to a nominal 2 2
concentration of 1000 mg ly1, plus control seawater, with three replicates per treatment and 12 larvae per replicate. Survival and incidence of metamorphosis were assessed after 24 and 48 h; individuals were observed at 100= using a compound microscope to confirm loss of larval cilia. Metamorphosed individuals were discarded. Remaining larvae were then transferred to cups of seawater with mud to stimulate natural metamorphosis ŽButman et al., 1988; Dubilier, 1988; Pechenik and Cerulli, 1991; Cohen and Pechenik, 1999., and maintained at 20 8C for 2–2.5 weeks to assess juvenile
survival and growth, and adult fecundity. At the end of the experiment we retrieved all surviving juveniles and measured the length and width of each individual at 8–20= using a dissecting microscope equipped with an ocular micrometer. Worms were anesthetized in 0.36 M MgCl before measure- 2 ments were taken. Worm volumes were calculated assuming that each individual was cylindrical. The second experiment was conducted about 1 week later, subsampling from 310
larvae pooled from two females. The experiment was similar to the first one, except that we added one higher nominal CdCl concentration Ž2000 mg ly1 ., and examined larvae 2 only after 48 h. Again, we tested three replicates at each concentration Žincluding seawater controls., with 12 larvae per replicate.
Adult worms were obtained from Dr. J. Grassle ŽRutgers University. and maintained in our laboratory for multiple generations at about 30‰ salinity on a diet of fine mud J.A. Pechenik et al.rJ. Exp. Mar. Biol. Ecol. 264 (2001) 101–114 103 collected from the Little Sippewissett salt marsh on Cape Cod, Massachusetts, USA, where members of this species occur naturally. The mud was forced through a 1-mm sieve to remove debris and then frozen for at least several days to kill animal residents before use ŽCohen and Pechenik, 1999.. Two experiments ŽCad-1 and Cad-2. were conducted at 23 8C, both using static exposures to toxicant. Approximately 600 larvae released from brood tubes by four females were pooled and subsampled for the first experiment. The larvae were distributed among plastic cups containing 50 ml of either 0.45-mm-filtered seawater or CdCl seawater solution. Seven CdCl concentrations were tested, up to a nominal 2 2concentration of 1000 mg ly1, plus control seawater, with three replicates per treatment and 12 larvae per replicate. Survival and incidence of metamorphosis were assessed after 24 and 48 h; individuals were observed at 100= using a compound microscope to confirm loss of larval cilia. Metamorphosed individuals were discarded. Remaining larvae were then transferred to cups of seawater with mud to stimulate natural metamorphosis ŽButman et al., 1988; Dubilier, 1988; Pechenik and Cerulli, 1991; Cohen and Pechenik, 1999., and maintained at 20 8C for 2–2.5 weeks to assess juvenilesurvival and growth, and adult fecundity. At the end of the experiment we retrieved all surviving juveniles and measured the length and width of each individual at 8–20= using a dissecting microscope equipped with an ocular micrometer. Worms were anesthetized in 0.36 M MgCl before measure- 2 ments were taken. Worm volumes were calculated assuming that each individual was cylindrical. The second experiment was conducted about 1 week later, subsampling from 310larvae pooled from two females. The experiment was similar to the first one, except that we added one higher nominal CdCl concentration Ž2000 mg ly1 ., and examined larvae 2 only after 48 h. Again, we tested three replicates at each concentration Žincluding seawater controls., with 12 larvae per replicate.
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