Monotreme Reproductive Biology and Behavior :: Mammals Wildlife Essays

Monotreme Reproductive Biology and Behavior Monotremes are mammals that are oviparous, or egg-laying. There are only 3 extant species of monotremes: the playtpus and two species of echidna. Their reproductive systems are highly specialized to facilitate both the production of eggs and milk. The male tract is quite simple. The female tract has qualities similar to those of birds, though female echidnas also possess pouches. The monotreme egg is also very specialized and somewhat similar to a reptile egg. Platypuses and echidnas have very different behaviors when it comes to mating, but their genetics are quite similar. Monotremes possess a few large chromosomes and several unpaired microchromosomes. The descendants of the first radiation of mammals, monotremes have characteristics of both placentals and marsupials, while still retaining characteristics of reptiles and birds in a combination all their own. Introduction At first glance platypuses seem to be an amalgamation of mammals, birds, and everything in between. In fact, their reproduction biology also has much in common with a variety of animals—reptiles, birds, placentals and marsupial mammals. Platypuses belong to a group of animals called monotremes. These egg-laying mammals have been a mystery to researchers since their discovery by Westerners over 200 years ago. The first specimens of platypuses brought back to England were thought to be hoaxes similar to mermaids (Moyal, 2001). Found only in and around Australia, there are only three living species of monotremes: the platypus (Ornithorhynchus anatinus) and two species of echidnas (Tachyglossus aculeatus, and Zaglossus bruijni). The word â€Å"monotreme† is Greek for â€Å"one-hole,† referring to the cloaca that is the exit for the urinary, reproductive, and excretory systems (Dawson, 1983). The creatures are oviparous--the females lay eggs that develop outside of her body. This paper will explain the background of the animals, the anatomy of the tract and egg, breeding behavior, and genetics behind this unique reproductive system. It will pay special attention to the similarities of the monotreme reproductive system to those of animals we are more familiar with. Background Monotremes are crepuscular animals only found in Australia and New Guinea.