. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 ii ill EXTRACT DILUTION Figure 5. Mean percentage of Strongylocentrotus druchaclucnsis lar- vae that metamorphosed in response to serial dilutions of an extract of Lithnthamnion glaciate and to intact L. glacialeCLYTK). Each treatment consists of 5 replicates with 25 larvae per replicate. Error bars indicate standard error. (which would disrupt any such gradient) did not reduce the rate of metamorphosis with L. glaciate (Mann-Whit- ney U-test, P> ) (Fig. 4). This result provides further evidence of contact dependenc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 ii ill EXTRACT DILUTION Figure 5. Mean percentage of Strongylocentrotus druchaclucnsis lar- vae that metamorphosed in response to serial dilutions of an extract of Lithnthamnion glaciate and to intact L. glacialeCLYTK). Each treatment consists of 5 replicates with 25 larvae per replicate. Error bars indicate standard error. (which would disrupt any such gradient) did not reduce the rate of metamorphosis with L. glaciate (Mann-Whit- ney U-test, P> ) (Fig. 4). This result provides further evidence of contact dependence. Induction of larval metamorphosis in S. droebachiensis by a crude extract of L. glaciate in filtered seawater was concentration-dependent (Fig. 5); high rates of metamor- phosis occurred at 1:5 (92%) and 1:10 (78%) dilutions, and these rates did not differ significantly from that with intact L. glaciate (88%) (Mann-Whitney U-test, P > for both comparisons). Metamorphosis was minimal ( 10~3 M; the weakest concentration of GABA that induced metamorphosis in a proportion of larvae T T 80. n Slalic d Ag