Top billing for platypus at end of evolution tree (Nature)

[jpak]

http://www.nature.com/news/2008/080507/full/453138a.html

Monotreme's genome shares features with mammals, birds and reptiles.

A draft sequence of the platypus genome reveals reptilian and mammalian elements and provides more evidence for its place in the ancestral line of animal evolution.

The platypus (Ornithorhynchus anatinus ) is endemic to Australia and one of nature's oddest creatures, seemingly assembled from the spare parts of other animals. The semi-aquatic monotreme is a venomous, duck-billed mammal that lays eggs, nurses its young and occupies a lonely twig at the end of a sparse branch of the vertebrate evolutionary tree.

Now, the structure of its genome has revealed new clues to how mammals evolved. “The analysis is beginning to align these strange features with genetic innovation,” says Wesley Warren of Washington University in St Louis, Missouri, the lead author of the genome analysis — a huge international project (see page 175). Comparisons with the genomes of other mammals will help to date the emergence of the platypus's distinguishing characteristics and reveal the genetic events that underlie them.

For example, mammals are defined by their possession of mammary glands, which in females can produce milk. Although the platypus doesn't have nipples, it produces true milk — full of fats, sugars and proteins — which the young suck through a glandular patch on its skin. The analysis shows that the platypus has genes for the family of milk proteins called caseins, which map together in a cluster that matches that of humans. This is a sign that one of the genetic innovations that led to the development of milk occurred more than 166 million years ago, and after mammals first split from the lizard-like sauropsids that gave rise to modern reptiles and birds.

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[PetrusMonsFormicarum]

1. Quite a ladder

that we have climbed.



or maybe not . . .

[Glorfindel]

2. Aw, the platypus is cute - it's not fair to compare it to B*shit...

or "homo imbecilis vulgaris repugnans" to use the precise, correct, scientific Latin terminology for this lowest form of life. :evilgrin:

[and-justice-for-all]

5. Dont be mean to The platypus please...nt

[struggle4progress]

3. Platypus genome as distinctive as its owner (ArsTechnica)

By John Timmer | Published: May 07, 2008 - 12:01PM CT

... The platypus has a whopping 52 chromosomes, many of them quite small, a configuration that looks like those of birds and reptiles. Its sex chromosomes are inherited like the mammalian X/Y system, but share sequence homology to the birds' Z/W chromosomes and, in a uniquely platypusian twist on things, the animals run around with ten sex chromosomes (males have five each of the X and Y). Incidentally, birds, being derived from dinosaurs, are used as a reptilian reference genome in the absence of having sequenced anything that's commonly thought of as a modern reptile.

Platypuses have an extensive collection of non-coding RNAs. Many of their microRNAs are shared with birds and mammals, and only small fractions are shared with only one or the other of these groups. But roughly half of the microRNAs found were specific to monotremes, and many of these appear to be involved in reproduction in some way. All eukaryotes also make a class of non-coding RNA called snoRNA that helps in the processing of ribosomal RNAs. In the platypus, however, snoRNAs have somehow latched on to a reverse-transcription based transposase, and have hopped all over the genome, resulting in a gross overabundance of these sequences. Actual transposons account for roughly half the genome, and it appears that some of these may still be active.

At the gene level, the platypus appears to have about 18,500 protein coding regions, roughly in line with the count in other mammals, but a bit higher than the chicken; 82 percent of these appear in one of the other species of mammals or birds. The genes involved in fertilization are a mix of those found only in mammals and those found only in birds and fish. The platypus also has only a single gene for egg yolk protein, in contrast to the three in the chicken genome. Like the rest of the mammals, the genes for platypus milk proteins are clustered together and reside next to the tooth enamel genes that they arose from via duplication.

The genome also sheds light on some of the unique platypus features. Like other mammals, the platypus has expanded their sensory abilities by duplicating many of the genes involved in smell. Oddly, in the platypus, the family undergoing the largest duplication is exclusively used for pheromone sensing in the mice. The authors suggest that these were adapted for use by the electrosensing system of the animal. The platypus' venom appears to be derived by duplication of many of the same genes that have given rise to components of reptilian venom. Most of these genes have been duplicated anyway on the mammalian lineage, but a separate duplication event created a side branch of genes that were exapted into the venom system ...

http://arstechnica.com/journals/science.ars/2008/05/07/platypus-genome-as-distinctive-as-its-owner

[eppur_se_muova]

4. A new word to add to my vocabulary -- 'platypusian'. I plan to use it frequently. nt