The Art of Science exhibition has many lovely pictures in the galleries, but I think my favorite is this image of Nodal expression in zebrafish.
After writing about the dilution of those “dangerous” kids’ chemistry sets, I find that Nature has just published a news article wondering how dangerous chemistry actually is.
Fellow scienceblogger Evolgen has seen the light—evo-devo is wonderful. He’s attending a meeting and listening to some of the bigwigs in the field talk about their work, in particular some research on the evolution of gene regulation. While noting that this is clearly important stuff, he also mentions some of the bickering going on about the relative importance of changes in cis regulatory elements (CREs) vs. trans acting elements, transcription factors. I’ve got a longer write-up of the subject, but if you don’t want to read all of that, the issue is about where the cool stuff in the evolution of morphology is going on. Transcription factors are gene products that bind to regulatory regions of other genes, and change their pattern of expression. The things they bind to are the CREs, which are non-coding regions of DNA associated with particular genes.
One of the most evocative creatures of the Cambrian is Anomalocaris, an arthropod with a pair of prominent, articulated appendages at the front of its head. Those things are called great appendages, and they were thought to be unique to certain groups of arthropods that are now extinct. A while back, I reported on a study of pycnogonids, the sea spiders, that appeared to show that that might not be the case: on the basis of neural organization and innervation, that study showed that the way pycnogonid chelifores (a pair of large, fang-like structures at the front of the head) were innervated suggested that they were homologous to great appendages. I thought that was pretty darned cool; a relic of a grand Cambrian clade was swimming around in our modern oceans.
However, a new report by Jager et al. suggests that that interpretation may be flawed, and that sea spider chelifores are actually homologous to the chelicerae of spiders.
I’m going to introduce you to either a fascinating question or a throbbing headache in evolution, depending on how interested you are in peculiar details of arthropod anatomy (Mrs Tilton may have just perked up, but the rest of you may resume napping). The issue is tagmosis.
This story bugs me. It’s a heartwarming tale of an inspiring teacher in an inner city school, who gets young kids motivated to learn science. Or does he?
I have another short piece commissioned by Forbes magazine in one of their special reports. The section is called “Work Is…”, and there are some provocative ideas in there. My own article is answering the question, “Do Animals Work?” and as you might guess, the answer is yes. I think I got one of the easier topics, actually.
I saw it first at Virge’s place, but Mike Snider is also on the blogroll and I would have gotten to it eventually…but hey, if you’re a fan of fossil tetrapods and poetry, here’s a treat: a Tiktaalik sonnet. You can also view some drafts of its construction, which is developmentally interesting, I think, and not quite as messy as chopping up embryos.
I think my title reveals why I’ll leave the poesy to the pros.
I just learned (via John Lynch) about a paper on cetacean limbs that combines developmental biology and paleontology, and makes a lovely argument about the mechanisms behind the evolution of whale morphology. It is an analysis of the molecular determinants of limb formation in modern dolphins, coupled to a comparison of fossil whale limbs, and a reasonable inference about the pattern of change that was responsible for their evolution.
One important point I’d like to make is that even though what we see in the morphology is a pattern of loss—whale hindlimbs show a historical progression over tens of millions of years of steady loss, followed by a near-complete disappearance—the molecular story is very different. The main players in limb formation, the genes Sonic hedgehog (Shh), the Fgfs, and the transcription factor Hand2, are all still present and fully functional in these animals. What has happened, though, is that there have been novel changes to their regulation. Even loss of structures is a consequence of changes and additions to regulatory pathways.
