Ontogeny

Ants on Télé-Québec

Tuesday, April 27th, 2010 | Ants, Ontogeny, Personalities | 1 Comment

Télé-Québec, Canada, aired on March 23 a small documentary of the ant research done by the laboratory of Ehab Abouheif, from McGill University. Abouheif lab looks at ant evolution from a still unusual developmental perspective.

It is worth watching, even thought I can’t embed it here, so you will have to watch it on their site (together with the advertisements, of course). And, if you don’t speak French, don’t worry, you’re not alone…

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WTF?

Friday, September 4th, 2009 | Ontogeny, Phylogeny, Theory | 5 Comments

Can someone please tell me if August 28th is the equivalent of “April’s fool day” somewhere in the world? This paper just published online in the Proceedings of the National Academy of Sciences (USA) reads like something coming out straight from The Onion:

Published online before print August 28, 2009, doi: 10.1073/pnas.0908357106

Caterpillars evolved from onychophorans by hybridogenesis

Donald I. Williamson
Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom

Abstract:
I reject the Darwinian assumption that larvae and their adults evolved from a single common ancestor. Rather I posit that, in animals that metamorphose, the basic types of larvae originated as adults of different lineages, i.e., larvae were transferred when, through hybridization, their genomes were acquired by distantly related animals. “Caterpillars,” the name for eruciforms with thoracic and abdominal legs, are larvae of lepidopterans, hymenopterans, and mecopterans (scorpionflies). Grubs and maggots, including the larvae of beetles, bees, and flies, evolved from caterpillars by loss of legs. Caterpillar larval organs are dismantled and reconstructed in the pupal phase. Such indirect developmental patterns (metamorphoses) did not originate solely by accumulation of random mutations followed by natural selection; rather they are fully consistent with my concept of evolution by hybridogenesis. Members of the phylum Onychophora (velvet worms) are proposed as the evolutionary source of caterpillars and their grub or maggot descendants. I present a molecular biological research proposal to test my thesis. By my hypothesis 2 recognizable sets of genes are detectable in the genomes of all insects with caterpillar grub- or maggot-like larvae: (i) onychophoran genes that code for proteins determining larval morphology/physiology and (ii) sequentially expressed insect genes that code for adult proteins. The genomes of insects and other animals that, by contrast, entirely lack larvae comprise recognizable sets of genes from single animal common ancestors.

I think Lynn Margulis went too far this time…

Homology Weekly: Petiole, Postpetiole and “Tubulation”

The isolated second abdominal segment constitute the characteristic petiole (blue) in ants. <i>Pachycondyla stigma</i> worker (Scanning Electron Micrograph, Roberto Keller/AMNH)

An isolated second abdominal segment constitutes the characteristic petiole (blue) in ants. Pachycondyla stigma worker (Scanning Electron Micrograph, Roberto Keller/AMNH)

The easiest way to know you are looking at an ant is to pay attention to its waist: if it consists of one or two nicely isolated segments you can be sure you made a positive identification. The basal condition for the family, common to all ants, is to have the second abdominal segment in the shape of a node or scale and distinctly isolated from the rest of the abdomen to form a petiole (remember that the first abdominal segment is coupled to the thorax as the propodeum). The functional advantage of such novel architecture seems to be an enhanced articulation between body segments, and thus greater mobility for a posterior part of the body that bears the ant’s weapons in the form of a sting or other specialized chemical producing  organs like the acidopore.1
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  1. This post is dedicated to my long time friend and colleague Francisco Vergara-Silva

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And as we discussed last semester, the Army Ants will leave nothing but your bones.
- Tom Waits

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