An analysis of sea urchin metamorphosis

Metamorphosis of sea urchin larvae is initiated by one or more cues from the environment. The cues can be from bacterial films (Cameron & Hinegardner, 1974), algae (Kitamura et al., 1993) or sand and seawater from adult habitats (Highsmith, 1982). The substances from sand are peptides (Burke, 1984), and those from red algae are free fatty acids (Kitamura et al., 1993) and dibromomethane (Taniguchi et al., 1994). Burke (1983a) suggested that chemical and physical stimuli were received by sensory receptors, probably podia of the adult rudiment, and transmitted to effectors of metamorphosis such as larval and adult tissues. Morpho-genetic, histolytic and histogenic processes progress during metamorphosis to create a juvenile, though direct evidence for the mechanism of induction has not been shown. Glutamine (Gin) induces metamorphosis in larvae of many sea urchin species (Strongylocentrotus intermedius: Naidenko, 1991; Pseudocentrotus depressus: Yazaki & Harashima, 1994; Hemicentrotus pulcherrimus: Yazaki, 1995). We have analysed the metamorphosis of sea urchin larvae using Gln, neurotransmitters and a natural cue (green algae).