The axolotl (Ambystoma mexicanum) is a salamander native to the freshwater lakes and canals of Mexico, primarily Lake Xochimilco. Unlike most other salamanders, axolotls typically do not undergo metamorphosis, retaining their larval features into adulthood. This aquatic creature has a broad head and a long, slender body that can reach up to 10 inches in length.
Aquatic Life: Why Axolotls Stay in Water
Axolotls are obligate aquatic creatures, meaning they are adapted to live exclusively in water and cannot survive on land for extended periods. Their physiology is specialized for an underwater existence, making a terrestrial environment unsuitable.
A primary reason axolotls remain aquatic is their external gills, which are prominent, feathery structures extending from the sides of their heads. These gills are rich in blood vessels and are designed to efficiently extract oxygen directly from the water. While axolotls possess rudimentary lungs and can occasionally gulp air from the surface, their gills are their primary means of respiration. Terrestrial salamanders typically lose their gills and develop lungs as they mature, but axolotls retain this larval trait.
Their skin is another adaptation for aquatic life; it is thin and highly permeable. This permeable skin allows for gas exchange and water absorption, supplementing the oxygen intake from their gills. On land, this delicate skin would quickly dry out, impairing its respiratory function and leading to rapid dehydration and suffocation. A protective layer of mucus covers their skin, helping to maintain moisture and protect against infections while submerged.
Axolotls also have a body structure suited for aquatic movement. Their limbs are relatively weak and structured for crawling along the bottom of their habitat, not for supporting their body weight or moving efficiently on land. They possess a flattened tail, which aids in swimming and navigating their watery environment.
The retention of larval characteristics into adulthood, including external gills and an aquatic lifestyle, is a biological phenomenon called neoteny. Axolotls reach sexual maturity and can reproduce while still in their juvenile, aquatic form. This evolutionary strategy allows them to thrive in their native aquatic habitats where resources are abundant and terrestrial conditions might be less favorable.
Ensuring a Safe Aquatic Environment
Maintaining a suitable aquatic habitat is essential for an axolotl’s well-being and longevity. A fully aquatic tank setup is necessary, with a minimum size of 15 to 20 gallons for a single adult axolotl, though larger tanks are often recommended. The tank should be longer and wider rather than tall, providing ample floor space for the axolotl to move.
Water quality parameters are crucial for axolotl health. The water temperature should be kept cool, ideally between 60-68°F (15-20°C), as warmer temperatures can cause stress and inhibit their ability to absorb oxygen. The pH level should be neutral to slightly basic, ranging from 7.2 to 7.6, though they can tolerate a broader range of 6.5-8.0.
Ammonia and nitrites must be at zero parts per million (ppm), as even small amounts are highly toxic to axolotls. Nitrate levels should be kept below 20 ppm, with an ideal range of 5-10 ppm, to prevent chronic stress and gill damage. Regular water changes, typically 25-50% weekly, and a properly cycled filter are necessary to maintain these parameters.
Regarding substrate, fine sand (less than 1mm grain size) is generally considered safe for axolotls over 6 inches long, as it can pass through their digestive system if accidentally ingested. Bare-bottom tanks or those with large, smooth tiles are also acceptable options, providing ease of cleaning and preventing impaction risks associated with gravel or small rocks. Decorations should be non-abrasive and provide hiding spots, such as PVC pipes or ceramic decorations, to reduce stress.
A secure lid is also important to prevent accidental escapes. Axolotls can sometimes jump out of their tanks, especially if water conditions are poor. If an axolotl is found out of water, it should be gently returned to its tank immediately using wet hands to avoid damaging its sensitive skin. Monitoring the animal for signs of stress or injury, such as labored breathing or skin damage, is recommended after such an event.