Embryo development in Mexican axolotl (Ambystoma mexicanum): a stage morphological study

Ambystoma mexicanum is an amphibian critically endangered, however is an important model for regeneration research. In this work we analyze axolotl embryo development, identifying and describing the stages from zygote until hatching with high quality images. The embryos were maintained in natural conditions at 16°C, inside their jelly layers the whole study period to take images that show the natural development from oviposition to hatching We analyzed and described a total of 49 development stages that were grouped in 5 phases: (1) fertilized oocyte, (2) cleavage, (3) gastrulation, (4) neurulation, and (5) organogenesis. Time from fertilization to hatching took about 350 hours under the management conditions set up in laboratory; it can be considered that the complete development of the axolotl embryo until hatching takes two weeks approximately. Results of this work may allow researchers in developmental biology, as well as those working on the conservation of the species including assisted reproduction techniques, to have recent material to carry out studies that favor the understanding and conservation of this mexican species.