Plasticity of operculum development in Bombina orientalis (Amphibia, Anura)

Larvae of the fire-bellied toad Bombina orientalis forced to hatch at early Gosner stage 23 completed operculum development much earlier than their si blings, which remained in the egg capsules. However, the development of oth er organs proceeded at similar speed in both groups. Among the characters u sed to define developmental stages in anurans, external gills and operculum exhibit a high level of environmentally inducible plasticity.