Embryonic stages: morphology, timing, and variance in the toad Bombina orientalis

Abstract

A Staged series (n = 25–476} with time data for Bombina orientalis embryonic development is presented. Stages for Bombina and Rana pipiens seem identical except that approximately 50% of opercular closures are symmetrical in Bombina. Counting numbers of embryos at a stage at regular intervals allowed mathematical interpolation of the average time of stage change. A single systematic curve fit the average time per stage of embryonic development, while the increase with time in variance per stage of development was primarily linear. It is possible that the increasing complexity of morphological interstage changes causes increases in the interstage interval and variance per stage over time. The reported method of arriving al a staged series for a previously undocumented species seems more efficient than time-lapse photography. The unusually easy maintenance and dependability or Bombina, contrasting with some amphibians, suggest its use where others have been less practical.