Effect Of Salinity On Embryonic Axolotl Development

Kristen Alyssa Meiler

Abstract


The axolotl, Ambystoma mexicanum, is an aquatic salamander native only to Laguna Alchichica in Puebla, Mexico and to the system of water channels and lakes nearby Mexico City. These water systems, under the influence of urbanization, are experiencing adverse effects due to decreasing water levels and increasing salinity. Many species are already unable to survive in these water systems due to this. I questioned the salinity at which axolotl embryos will experience decreased survivorship or increased morphological deformities. I used a freshwater solution as well as increasing saline solutions (with the highest being similar to the current salinity conditions in Laguna Alchichica), in order to determine at what point axolotl embryos cease to develop into viable young. I collected survival rates, developmental stages, number of deformities, and hatching rates as well as measurements of body length, head length, intraocular distance, and gill length of the hatchlings. The embryos reared in the 4 ppt NaCl/L solution showed the greatest amount of abnormalities, including many displaying a very distended, fluid filled abdominal cavity. Generally, embryos reared in the 1 ppt NaCl/L solution grew to be significantly larger than the others, based on the analysis of various two-tailed T-tests. The embryos reared in the saline concentration that was similar to that found in the lakes in central Mexico failed to develop. These results support that there is a threshold salinity at which axolotl embryos may cease to exist in the wild (although wild axolotls may have already developed a higher tolerance than the embryos I tested). These animals are already on the Critically Endangered section of the IUCN Red List so it is important to understand the potentially toxic effects of elevated salinity on embryonic axolotl development in order to be able to slow or reverse the decline of the axolotl.

Keywords


Axolotl, Salinity, Central Mexico

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