Maintenance media for the axolotl Ambystoma mexicanum juveniles (Amphibia: Caudata)

Physiological condition and organisms' health which are grown in culture systems depends on several factors including water quality, feeding and density among others. In Mexico, the colonies of the axolotl Ambystoma mexicanum (Shaw), an indigenous amphibian under extinction risk, are maintained under different culture conditions according to the objectives of the colony and the available resources. Particularly, water electrolytic characteristic and ionic and osmotic conditions are the factors with greater variation in the axolotl culture systems. Therefore, it is necessary to standardize the best maintenance conditions to store the germoplasm of the axolotl and to ensure healthy organisms with researching purposes. Thus, the aim of the present study was to evaluate the development and growth of Ambystoma mexicanum larvae reared under different maintenance media, usually used in Mexico for the culture of the species: 1) dechlorinated tap water; 2) dechlorinated tap water enriched with sodium chloride and commercial colloidal solution and 3) Holtfreter's solution reconstructed with dechlorinated tap water. In each experimental condition, 15 larvae on stage 44 (immediately after hatching) were maintained during 21 days and development and growth were weekly recorded. Ionic and osmotic conditions of the external media were routinely registered. The obtained results suggested a better physiological condition of the axolotls maintained on Holtfreter's solution, where the highest growth rate (13 g WW d-1) and the greatest condition factor (0.79) were registered. The use of this solution is recommended due it guarantees the suitable development of early stages of A. mexicanum on culture systems.