Many land-based animals have no lungs. This characteristic often coincides with animals that have an open circulatory system: that is, their blood or other body fluids are not enclosed by vessels. The biggest category of lungless land animals are insects. Instead of lungs, they have spiracles, which are tiny holes in the thorax and abdomen that open deep into the body, letting oxygen in for the cells. The fact that air can only go so far in is one of the things that limits the size of insects.
It is much more rare, but there are actually some amphibians what have no lungs. Since 1995, researchers have discovered three such species; two are caecilians, which are worm-like lizards, and one is a tiny frog. They are thought to have secondarily lost the lungs through evolution, and, like the insects, they can only reach a certain size and still breathe efficiently through their skin.
There are many microorganisms with no lungs that were traditionally considered animals, like amoebas. Many of these are currently classed in a phylum of protists or fungi. One group of species, called myxozoa, is still considered part of the kingdom Animalia.
Click here to cancel reply.
Sorry,At this time user registration is disabled. We will open registration soon!
Don't have an account? Click Here to Signup
© Copyright GreenAnswers.com LLC