Figure 2
From: Mechanisms underlying dual effects of serotonin during development of Helisoma trivolvis(Mollusca)
Effects of different agonists of 5-HT receptors on embryonic development of H. trivolvis. (A) The length of embryos during the development under control conditions (control, n = 80) and after incubation with 5-HT4R agonist RS67333 (2.5 μM, n = 80), 5-HT7R agonist 8-OH-DPAT (5 μM, n = 80) and 5-HT1R agonist 5-CT (1 μM, n = 80). Development is significantly retarded after RS67333 and 8-OH-DPAT, and accelerated after 5-CT treatment. Linear fitting slope coefficient (k) is 0.068 for control (R2 = 0.99), 0.031 for RS67333 (R2 = 0.98), 0.052 for 8-OH-DPAT (R2 = 0.99), and 0.075 for 5-CT (R2 = 0.99). (B) Overview of representative larvae after 84 h of incubation in the above mentioned drugs, equal magnification. The size of embryos strongly corresponds to certain developmental stages. At the time when the control animal is in the end of metamorphosis and represents a miniature snail, the embryos incubated with RS67333 and 8-OH-DPAT are still at the premetamorphic stage. On the contrary, the embryo incubated with 5-CT reaches the postmetamorphic adult-like stage and is bigger than the control. (See also supplementary materials Movies 1 to 3). f – foot, ll – lung lobe, mm – mantle margin, t – tentacle, e – eye, sh – shell. (C) Incubation with RS67333 (2.5 μM) and 8-OH-DPAT (5 μM) results in significant increase of both total duration of development and duration of metamorphosis. Retardation effect of RS67333 is more pronounced, when treatment starts at stage 19. Incubation with 5-CT (1 μM) reduces developmental time and duration of metamorphosis with the strongest effect at stage 23 (n = 60 for each group). Data are shown as mean ± s.d. (*, p <0.05; **, p <0.01).