Fig. 6. Hypoxia stimulates embryonic rotation behaviour in three families of freshwater pond snails. H. trivolvis (A), L. stagnalis (B) and Physa gyrina (C), members of the Planorbidae, Lymnaeidae and Physidae families of basommatophoran snails, respectively, demonstrated similar profiles of increased embryonic rotation rates upon prolonged exposure to hypoxia (open bars). Upon return to normoxic conditions (filled bars), an initial inhibition of rotation followed by a return to baseline levels was observed in all three species. Each bar represents mean r.p.m. ± s.e.m. from 22–26 embryos from two stage E25 egg masses (A), 13–17 embryos from one stage E39 egg mass (B) and 23–27 embryos from two stage E35 egg masses (C). Asterisk in B represents loss of a data point due to a corrupted digital file.