The complex sex chromosomes in monotremes display unusual interactions during and after meiosis, which is a type of cell division. Guojie Zhang, the corresponding author on the study and a professor in the biology department at the University of Copenhagen, tells Inverse, 'From the genome sequencing, we found these 10 sex chromosomes do not have any homolog with the X/Y chromosomes in human, but they are more similar with the ZW chromosome of birds in the genomic sequencing structure.' Through their analysis, researchers found similarities between platypus and birds, but not so much between platypus and humans. Humans, meanwhile, have two sex chromosomes. The monotreme has 10 sex chromosomes: five X chromosomes and five Y chromosomes. This genetic data confirms the semi-aquatic lifestyle of the platypus, which closes its nasal cavity and eyes when in the water, relying instead on other senses - like electric stimuli - to detect prey.īut given the monotreme's unique reproductive strategy, the researchers focused specifically on its unique sex chromosomes. For example, the scientists found that the water-based platypus possesses far fewer 'olfactory' or smelling genes compared to the terrestrial echidna. The scientists used genetic data to analyze everything from the platypus' eating habits to its swimming routine. What was discovered - For the first time, the new research provides a complete chromosome map of the platypus genome, along with a less-complete map of the echidna genome. Both share in common one habit unique to monotremes: egg-laying. Platypus are semi-aquatic creatures and echidna are land dwellers. Monotremes include only two animals that survive today: the platypus and the echidna.

Marsupials and eutherians are often lumped together into a subclass known as therian mammals, but monotremes are so distinct from other mammals that they deserve their own separate category.

The largest group by far are eutherians, which include animals that nurture their young in the mother's placenta (accordingly, the infraclass is sometimes referred to as ' placentals'). Necessary background - The three main groups of mammals are: monotremes, eutherians, and marsupials. Echidna, along with platypus, compose a unique group of mammals known as monotremes. An echidna walking in a coastal wilderness area in Victoria, Australia.

Platypus lay eggs