Effect of water quality on the feeding ecology of axolotl Ambystoma mexicanum

• Main Authors: Diego de Jesus Chaparro-Herrera, Sarma Nandini, S.S.S. Sarma
• Format: Article
• Language: English
• Published: PAGEPress Publications 2013-10-01
• Series: Journal of Limnology
• Subjects: Ambystoma mexicanum, Oreochromis niloticus, invasive species, zooplankton, water pollution.
• Online Access: http://www.jlimnol.it/index.php/jlimnol/article/view/676

<p class="p1">Ambystoma mexicanum<em>, a highly endangered species, is endemic to lake Xochimilco (Mexico City, Mexico) which currently is being </em><em>negatively affected by the introduction of </em>Oreochromis niloticus <em>(Tilapia) and water pollution. During the first weeks of development, when </em><em>mortality is the highest, </em>Ambystoma mexicanum<em>depends on a diet of zooplankton. The aim of this study was to check whether contamination </em><em>levels in lake Xochimilco influence zooplankton consumption by similar size classes of </em>A. mexicanum <em>and </em>Oreochromis niloticus<em>. In this </em><em>study, we analysed changes in the functional responses and prey preference </em>of A. mexicanum <em>and larval Tilapia in two media, one with filtered </em><em>lake Xochimilco water and another one with reconstituted water. As prey we used cladocerans </em>(Moina macrocopa<em>, </em>Alona glabra<em>, </em>Macrothrix triserialis <em>and </em>Simocephalus vetulus) <em>and ostracods </em>(Heterocypris incongruens)<em>. Zooplankton was offered in 5 different densities, </em><em>10, 20, 40, 80, 160 ind./mL. Prey consumption by </em>A. mexicanum <em>varied in relation to the species offered and age of the larvae. From the </em><em>first week to the eighth week prey consumption by </em>A. mexicanum <em>increased by 57%. Our functional response tests showed that regardless </em><em>of the prey type, prey consumption by </em>A. mexicanum <em>was lower in the contaminated water from lake Xochimilco. Among the zooplankton </em><em>offered in the contaminated environment predators preferred smaller and slower moving microcrustaceans such as </em>Alona glabra <em>and </em>Heterocypris incongruens<em>. Furthermore, </em>O. niloticus <em>preferred prey such as </em>Moina macrocopa <em>and </em>Macrothrix triserialis <em>in the contaminated </em><em>medium and was more voracious than the axolotl. Our results indicate that both water quality of the lake and the presence of the more resistant </em><em>exotic fish adversely impact the survival of this endangered amphibian.</em></p>