Unlike most amphibians that lose their gills as they mature, axolotls keep theirs for life, giving them their unique, otherworldly look. These delicate fronds are not just beautiful—they are essential for survival. Let’s explore axolotl gill anatomy, what makes them so special, and the many questions people often ask about them.
Anatomy of Axolotl Gills
Axolotls have three pairs of external gills or gill stalks, one on each side of their heads. These gill stalks, known as rami, branch out like delicate trees and help move oxygenated water around the axolotl. Each stalk is covered with fine, feathery filaments (also called fimbriae) that greatly increase the surface area for gas exchange.
Inside the filaments are tiny blood vessels that allow oxygen to pass into the bloodstream while removing carbon dioxide. Because the filaments are so thin and numerous, they make oxygen exchange especially efficient.
At the base of the gills, small muscles allow axolotls to wave or “pulse” their gills, circulating water more effectively around the filaments. This constant movement improves oxygen intake, especially in still water.
In addition to their visible external gills, axolotls also have four gill slits hidden underneath the gills, each lined with gill rakers. These gill rakers act like natural filters—preventing food from entering the gill chambers while allowing water and small particles to pass through.
The feathery appearance and bright colors of axolotl gills—often pink, red, or even purple depending on blood flow and individual variation—make them look almost like soft underwater plants.
FAQS
Why Do Axolotls Have Feathery Gills?
The feathery design maximizes the surface area for oxygen exchange. In simple terms, the more “fluffy” and branched the gills, the more oxygen the axolotl can absorb from the water. This design is especially important because axolotls live in still lakes and canals, where water doesn’t always flow quickly. Their gills help them thrive in oxygen-poor environments by pulling in as much oxygen as possible.
Why Are Some Axolotl Gills Fluffy While Others Look Smaller or Thinner?
Gill size and fluffiness can vary based on several factors:
- Oxygen levels in the water: In oxygen-rich water, axolotls don’t need as much surface area, so their gills may shrink or look less fluffy. In low-oxygen environments, the gills grow larger and more branched.
- Genetics: Some axolotls naturally have bigger, showier gills than others.
- Health and stress: Stress or poor water quality may cause gills to appear thin, droopy, or uneven.
So, a fluffy set of gills often means the axolotl is working harder to get oxygen, while smaller gills may reflect healthier, oxygen-rich conditions.
What Does It Mean If an Axolotl’s Gills Are Curled Forward?
When an axolotl’s gills curl forward, it usually indicates stress or discomfort. This can be caused by:
- Poor water quality (high ammonia, nitrite, or nitrate levels).
- Warm water temperatures.
- Overcrowding or aggressive tank mates.
- Illness.
Occasional curling isn’t always a problem, but persistent forward curling should be taken seriously as a sign the axolotl’s environment needs adjusting.
Why Do Axolotls Puff Their Gills Over and Over Again?
Axolotls sometimes “flick” or “puff” their gills to increase water flow around them. This movement helps refresh the water near the filaments, bringing in more oxygen and carrying away waste gases. Think of it as them giving their gills a little shake to “breathe better.” Frequent gill flicking can also signal low oxygen levels or stress, but occasional flicks are perfectly normal.
Do Gills Change Color Depending on the Axolotl’s Health or Environment?
Yes, axolotl gills can change color. The main factor is blood flow:
- Bright pink or red gills usually indicate good circulation and oxygenation.
- Pale or whitish gills may mean low oxygen levels or stress.
- Darker gills can sometimes occur in older axolotls or in specific color morphs.
Temperature, water quality, and even activity levels can affect gill color throughout the day.
Can Axolotls Regrow Damaged Gills?
One of the most incredible things about axolotls is their regenerative ability. If their gills are injured, bitten, or even partially lost, they can regrow them over time. The regenerated gills may not always look exactly the same as before, but they usually function just as well. This regeneration is part of what makes axolotls so valuable to scientific research.
Why Do Some Axolotls Have Shorter Gills in Captivity Than in the Wild?
In captivity, water is often filtered, aerated, and oxygen-rich. Because oxygen is easier to access, axolotls don’t need such large gills, so their gills may appear shorter or less dramatic compared to wild axolotls. In the wild, especially in still or murky water, axolotls rely on bigger gills to survive.
Do Axolotls Ever Lose Their Gills Completely?
Most axolotls keep their gills for life due to a trait called neoteny, which means they stay in their larval form instead of fully maturing like most amphibians. However, in rare cases, an axolotl may metamorphose into a salamander-like form, often triggered by hormonal changes or environmental stress. In that case, they lose their external gills and switch to breathing with lungs.
What Do Healthy Axolotl Gills Look Like?
Healthy axolotl gills are:
- Symmetrical on both sides.
- Feathery with visible, evenly spaced filaments.
- Brightly colored (pink, red, or depending on morph).
- Upright and gently waving in the water.
Unhealthy gills may appear pale, shriveled, droopy, or excessively curled.
Do Gills Help Axolotls Sense Movement in the Water or Are They Only for Breathing?
While the primary function of gills is breathing, they may also play a small role in sensing water flow. The delicate filaments react to movement in the water, which could give the axolotl extra awareness of its surroundings. However, this is not their main sensory organ—axolotls rely more on their lateral line system (like fish do) for detecting vibrations.