Axolotl Biology – Page 3

Axolotls are a mystery to many of us. It can be easy to dismiss the axolotl as just any other member of the amphibian family, like newts, frogs, or toads. But, that would be a mistake! Unlike other amphibians, axolotls don't undergo metamorphosis. As a result, they retain their juvenile features into adulthood, such as their long dorsal fin, webbed feet, or feathery external gills. They don't evolve into land-dwelling adults either but instead live exclusively underwater. As you can see, axolotls are quite unique. These particularities lead us to question how the axolotl’s body actually works. For example, do they have lungs? Here's what you need to know: Axolotls have rudimentary lungs. However, axolotls rely predominantly on other organs to breathe. These organs include their external gills, their skin, and the buccopharyngeal membrane at the back of their throats. Carry on reading to find out more about how axolotls breathe! How Do Axolotls Breathe? Axolotls can breathe via 4 different organs or mechanisms: Through their gills. Through their skin. Through their mouths. Through their lungs. Below, we'll take a look at each one in more detail. Breathing Through Their Gills Since axolotls are 100% aquatic animals, they are able to breathe through their gills. These gills are very thin and feather-like, and while they are a beautiful feature that makes the axolotl very distinguishable, they are also great for getting oxygen into their blood. Feathers The ‘feathers’ on their gills actually increase the surface area of these organs, which allows them to undertake faster diffusion rates because there is space for a larger volume of oxygen and carbon dioxide to be exchanged. Rakers As well as the feathers, the gills also have a feature called ‘rakers’. Rakers work in the way that eyelashes or nostril hairs do – they remove any impurities from the water before the axolotl receives oxygen, which effectively removes the risk of parasites or other harmful substances making their way into the bloodstream. Breathing Through The Skin (Cutaneous Respiration) This is a useful way for all types of salamanders to oxygenate their blood. As axolotls have incredibly thin skin that has a moist coating covering them (slime coat), oxygen and other gases can easily diffuse through to the surface-level blood vessels. It is a very efficient process, and the simplest to complete. Interestingly, you will find much higher levels of carbon dioxide (compared to oxygen) closer to the axolotl’s skin surface. This is because gas diffusion encourages carbon dioxide to be expelled through the skin, rather than the gills or mouths. While all members of the salamander family can breathe through their skin, they can also breathe on land – which axolotls are unable to do. This is because they are still in the pre-metamorphosis stage, so they haven’t evolved to function out of the water. Breathing Through Mouth (Buccal Respiration) Buccal respiration is mainly a form of breathing for amphibious animals. Through this type of respiration, the axolotl will use their buccopharyngeal membrane (found at the back of the throat) to breathe. Breathing Through Lungs (Pulmonary Breathing) Now, we finally come to the lungs! Axolotls receive the smallest amount of oxygen through their lungs. This is because their lungs are very small and underdeveloped, which means that there isn’t enough capacity to carry all the oxygen they need around their body in order to survive. Axolotl lungs have an incredibly simple, sac-like structure, with little folded pockets. These pockets are surrounded by a huge number of blood vessels, and also a very thin membrane. Axolotl lungs are effectively very primitive. Axolotls mainly use their lungs when there isn’t enough oxygen in their water to survive using only their skin and gills. This is particularly apparent when they are in polluted and/or stagnant water. This simplicity of the lung structure isn’t a problem for the axolotl, however, because it has so many ways of getting oxygen into its bloodstream. Considering that their gills and skin absorbing oxygen is so passive, breathing through their lungs must be a strange phenomenon for them – and they rarely do it. The only time you may notice them doing it is when they pop up to the water's surface to capture some air bubbles! Interestingly, this is also a fun activity for axolotls to take part in. Because swallowing air bubbles fills their bodies up so much, the trapped air in their lungs can actually allow them to float around their water environments, rather than swim around. However, if they seem to be using this method a lot, you will need to take a look at the water levels and parameters of the conditions the axolotl is in – particularly if they are in a tank. This is because the water could be low in oxygen, and it is struggling to passively ‘breathe’ through its skin and gills. Do Axolotls Have Ribs? If an axolotl has lungs (even if the lungs are incredibly underdeveloped), you would think that it would make sense for them to also have a rib cage, so they can protect their lungs. While they do look like they have a rib cage in their chest, these lines along their body are actually known as coastal grooves. The coastal grooves are there simply in a protective capacity, and they ensure that the intercostal neurovascular bundle doesn’t come to any home. Conclusion Axolotls do have lungs. While they are very small and don’t have much capacity to pass a lot of oxygen around their body, the lungs are present and can be used in extenuating circumstances. This kind of circumstance would be when the water conditions they are living in don’t have enough oxygen, particularly if it is polluted and/or stagnant. Otherwise, axolotls prefer to breathe through their gills are their skin. https://www.youtube.com/watch?v=bFkIG9S2Mmg