. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 5-HT INJECTIONS INDUCE METAMORPHOSIS 181 siphon ,,-eyespot. r ciliated cells Figure 2. (a) Diagram of a larva at the beginning ofmetamorphosis. Ciliated cells are being individually dropped from the velum, (h) Drawing of a newly metamorphosed juvenile. The velum has been lost in large pieces (modified from Fretter and Graham. 1962). formation before analysis (Rohlf and Sokal, 1981), but were transformed back to percentages for graphing. Er- ror bars are standard deviations of the mean. Graphs were produced with the Statgraph
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 5-HT INJECTIONS INDUCE METAMORPHOSIS 181 siphon ,,-eyespot. r ciliated cells Figure 2. (a) Diagram of a larva at the beginning ofmetamorphosis. Ciliated cells are being individually dropped from the velum, (h) Drawing of a newly metamorphosed juvenile. The velum has been lost in large pieces (modified from Fretter and Graham. 1962). formation before analysis (Rohlf and Sokal, 1981), but were transformed back to percentages for graphing. Er- ror bars are standard deviations of the mean. Graphs were produced with the Statgraphics software program (Manugistics, Inc.). Results Injection and bath-application of 5-HT induced sig- nificantly more metamorphosis than did FIO controls (Fig. 3). The results of 5-HT injections were also statisti- cally different from those produced by bath-application of 5-HT. Fluoxetine, a 5-HT reuptake inhibitor (Kandel. 1991; Frazer and Hensler, 1994; Ramamoorthy el 1993), and «m5-HT, a 5-HT agonist (Walker, 1986; Chaouche-Teyara et al., 1993), also induced significant levels of metamorphosis compared to controls (Figs. 4, 5). The results of 10 6 M fluoxetine injections did not differ statistically from those seen in the 5-HT bath con- dition. Injections of 10~4A/ fluoxetine induced less metamorphosis than injections of 10 6 A/ fluoxetine (cf. Figs. 4. 6). When 1(T4A/ fluoxetine and 5-HT are in- jected together there is an additive effect (Fig. 6). Gram- ine, a 5-HT antagonist (Zhang and Harris-Warrick, 1994), did not promote metamorphosis when injected alone, and when injected along with 5-HT it resulted in decreased rates ofmetamorphosis (Fig. 7). To determine if these results were indeed specific to serotonergic neu- rons and their influence on larval physiology, GABA was injected as a negative control. Injections of this neuro- transmitter did not induce significant levels of metamor- phosis (Fig. 8). CTJ o & a in O e CD e 60 40 (5 20 in Q) a 0 5-HT Injection
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