Why are there no crocoduck fossils?

March 31, 2009

This is a nice video explaining some basics of evolutionary theory around transitional forms, like why fossils of a “crocoduck” have never been found. 

There are some other videos in this series here. Interestingly, the guy who made this video is a Christian biology teacher (and evolutionist) who is an advocate for teaching science, not religion, in science classes.


Hox genes rap & reptiles

March 28, 2009

I found this rap video on Hox genes (yes really) on a couple of other blogs over the past week.  Its so good I thought I’d post it here.

And now that you’re all familiar with the basics of Hox genes…   a recent study in Genome Research has found some rather unusual features of this gene family in lizards.  Hox genes play an important role in specifying the anterior-posterior body plan in the developing embryo, and are found in ordered clusters in the genome.  Vertebrates have 4 clusters (A, B, C, and D), with each cluster containing multiple Hox genes.  

This figure shows the 4 Hox clusters in mammals, colour-coded according to where they are expressed in the developing embryo

This figure shows the 4 Hox clusters in mammals, colour-coded according to where they are expressed in the developing embryo

Hox clusters are unusual in that there is very little repetitive DNA  between the genes (repetitive elements being a large fraction of most eukaryotic genomes).  Thus, in most vertebrates Hox genes are located close together, in a tightly ordered sequence.  

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Funky fungus

March 26, 2009

I saw this Stinkhorn fungus Aseroe rubra on a walk up Mt Kapakapanui in the Tararuas. It may look pretty, but apparently the spores smell like rotting meat.

Chemical attraction?

March 24, 2009

Research published in last month’s Chemistry and Biodiversity journal heralded the discovery of a new compound “tuataric acid”. Yes, isolated from our very own tuatara.

Stefan Schulz and his colleagues at University of Braunschweig, and collaborator Paul Weldon at the Smithsonian Institution, have analysed the constituents of the cloacal secretions in tuatara and found an unexpectedly diverse array of compounds. As tuatara have no external sexual organs, the cloaca is the “one stop shop” opening at their posterior end, with prominent skin glands on either side of the opening that secrete a greasy white substance. When the tuatara secretions were analysed, Schulz and colleagues found over 150 different types of glyceride-based molecules, including one never-before seen compound, which they dubbed “tuataric acid”.

Perhaps even more excitingly though (for me at least), was the finding that individual tuatara secrete specific mixtures of these glycerides and that the makeup of these individual profiles remains stable over years. This could provide a mechanism for chemical recognition of individual tuatara, a finding which ties in nicely with some behavioural work we have recently been doing on tuatara.

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