Platypus Update

RD notes that today it's been announced that the Platypus genome has been sequenced. In keeping with our tradition of Platypus coverage, we thought we'd pass the news along.

Read all about it here: Platypus Genes Hold Keys to Animal Evolution

Some snippets:

One of the more surprising elements was the animal's system for sex determination. Most mammals have two sex chromosomes, either two "X" chromosomes (to make a female) or an "X" and a "Y" (to make a male). Not only do platypuses have ten instead of two, but some of those resemble the "Z" and "W" chromosomes of birds more than standard-issue "Xs" and "Ys."

Moreover, the key gene on the Y chromosome that confers maleness in most mammals is not present on any of the platypus's sex chromosomes. It is on another chromosome, where it seems to have nothing to do with sex. In its place, another gene seems to be central to sex determination in platypuses -- evidence of a shakeout of various evolutionary efforts to settle on a system of sex determination in early mammals.

[...]

Platypus milk appears to be a modified version of a moisturizing fluid that ancestral platypuses once used to keep their leathery, lizard-like eggs from drying out during incubation. It is secreted from "milk patches" on the mother's abdomen.