Post-Ovipositional Developmental Stages of the Japanese Grass Lizard, Takydromus tachydromoides (Squamata: Lacertidae)

Abstract

The Japanese grass lizard, Takydromus tachydromoides, is a species endemic to Japan. While several studies have investigated the reproductive ecology of T. tachydromoides, the embryogenesis of this species has not been reported in detail. In the current study, we observed the external morphological characteristics of 247 embryo specimens that developed under a constant temperature (28°C) throughout the duration from oviposition to hatching. We identified 17 consecutive developmental stages for the post-ovipositional developmental process of this species based on the staging criteria that have been widely used for the description of embryogenesis of lizards. The youngest embryos on the day of oviposition corresponded to stage 26, which is a relatively early period in pharyngula stages, and juveniles hatched at stage 42, approximately 30 days after oviposition. The entire developmental sequence of key morphological features was shared with other species of Lacertidae, except for the timing of the beginning of the first body pigmentation. This is the first description of the complete sequence of post-ovipositional developmental stages for the oviparous species of Lacertidae, providing valuable information for further evolutionary developmental studies.