Comparative Anatomy

Homology weekly: Prognathy

Tuesday, February 2nd, 2010 | Ants, Comparative Anatomy, Homology Weekly, Morphology | 6 Comments

I am going to take advantage of figures I prepared for a talk I gave recently, where I had to explain a diagnostic characteristic of ants during the introduction. As I have mentioned before, ants are peculiar among wasps and bees in that their mouthparts are directed forward, rather than downward, in a condition known as prognathy (pro-, anterior, projecting; –gnathus, jaw).

Hypognathus condition in insects (left image from Wikimedia commons; right drawing modified after Snodgrass 1935)

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Not yet winter break for me

Friday, December 18th, 2009 | Administrative, Comparative Anatomy | Comments Off on Not yet winter break for me

Forget the Friday winter break parties at the workplace, I’m stuck at home preparing slides for a short talk I’ll be giving on Monday. I’m not complaining though. This is the Portuguese meeting on evolutionary biology I mentioned earlier. The odd date (the 21st of December for the past four years) is to accommodate all the nationals pursuing Ph.D.s and postdocs abroad that come home during the holidays.

The meeting is organized by young researches, and this year will be specially interesting because there will be a discussion about creating a national society of evolutionary biologists.

I will be talking about the evolution of mouthparts within ants, covering some fascinating new discoveries that I haven’t share here yet but will blog about some time in the near future. In the mean time, here are a couple of my slides.

Media sources: antweb.org; Roberto Keller/AMNH.

Media sources: antweb.org; Roberto Keller/AMNH.

Media sources: Wiki Commons; Alex Wild (http://www.alexanderwild.com/); R.E. Snodgrass 1935.

Media sources: Wiki Commons; Alex Wild (http://www.alexanderwild.com/); R.E. Snodgrass 1935.

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The Snodgrass Tapes

Snodgrass Tapes

Here is a hidden treasure in the web.

Robert E. Snodgrass was an American entomologist who published extensively on arthropod anatomy and evolution during the first half of the twentieth century. He was as knowledgeable about arthropod morphology as he was a superb artist– you can see some of his illustrations decorating the banner of this blog. His name is synonymous with insect morphology: his 1935 textbook on the subject (reedited by Cornell University Press in 1993) is still the main reference for any modern course in entomology.

Snodgrass was a lecturer in the University of Maryland for most of his academic life. In 1960, two years before his death, he gave a series of three lectures that were recorded in audio tape. Fortunately for us Jeffrey W. Shultz, professor of entomology at Maryland, has digitized and made these lectures available through a nicely designed page called The Snodgrass Tapes. › Continue reading

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Evolution and development of castes in ants

Thursday, November 12th, 2009 | Ants, Comparative Anatomy, Morphology, Theory | 6 Comments

Manica - castesUp until resuming posting a couple of weeks ago you may had thought I was dead. Well, fear not (nor rejoice just yet). I am now happy to report that those previous months of blogging slowness paid off: I got funding for the project I wrote during the summer.

Starting next year I will be working as a postdoc in the laboratory of Patrícia Beldade at the Instituto Gulbenkian de Ciência in Portugal. This is an evolutionary developmental biology lab, an area of research fondly know as EvoDevo.

EvoDevo ask questions that are of a different nature than the classical Neo-Darwinian ones. For example, in the latter you always presuppose that variation exists in populations and that there is a link between what you see at the level of an organism’s morphology (its phenotype) and the underlying genetics (its genotype), and you study how natural selection then goes to mess things around. In EvoDevo you don’t give these things for granted. Rather, you ask how do new features (novelties and innovations) arise in the first place and exactly how does the link between genotype and phenotype comes about through the developmental process. From there, what you seek is to understand evolution as a process of modification of development.

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More dinosaur than we thought

Thursday, November 5th, 2009 | Comparative Anatomy, Phylogeny | Comments Off on More dinosaur than we thought

Familiar to many, you can know how old a tree is and how fast it has grown by counting the number of rings in a cross section. Well, you can do the same with the long bones of vertebrates.

Now Gregory M. Erickson and co-workers published a paper in which they did just that to a specimen of one of the most famous fossil forms around: Archaeopterix. Watch Mark Norell, paleontologist from the American Museum of Natural History and co-author of the paper, explain the results:

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Eickwort’s Manual of Insect Morphology

Tuesday, November 3rd, 2009 | Comparative Anatomy, Education, Personalities, Science | 1 Comment
GeorgeEickwort

George Campbell Eickwort (1949–1994)

The Department of Entomology at Cornell University saw a time of great research and teaching in insect morphology at the end of the Twentieth Century, most of which came from the efforts by two extraordinary systematists: William L. Brown Jr. and George Campbell Eickwort.

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Homology Weekly: Compound Eyes

Wednesday, October 28th, 2009 | Ants, Comparative Anatomy, Homology Weekly, Morphology | 9 Comments

iGigantiops destructor/i (Michael Branstetter - www.antweb.org)

Gigantiops destructor (via Michael Branstetter - www.antweb.org)

The lateral eyes of adult insects (and most Arthropods) known as compound eyes, are like no other visual organs found in animals. You can think of our vertebrate eye as a simplified, one-lens photographic camera with a sensor composed of millions of light sensitive cells (and a blind spot, mind you). Well, that’s nothing. Each insects eye is composed of several small photographic cameras, each with its own lens and light sensitive cells (albeit, commonly only six of these). These units are called ommatidia (sing. ommatidium), and the image if formed by the combined information from all of them.1

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  1. To be honest, I have never know if this visual organ is called compound eye because it is composed of several ommatidia or because each ommatidium is composed of several elements. This has never disturb my sleep though.

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Homology Weekly: Mandible Adductor Apodemes

Thursday, September 24th, 2009 | Ants, Comparative Anatomy, Homology Weekly, Morphology | 7 Comments
The unusual mandible closer apodeme (left one in the pair) of species in the Odontomachini genus group. Disected out and cleared from all muscles (Scanning Electron Micrograph, Roberto Keller/AMNH)

The unusual hook-shaped mandible closer apodeme (left one in the pair) of species in the Odontomachini genus group (Anochetus emarginatus pictured here). Piece dissected out and cleared from all muscles (Scanning Electron Micrograph, Roberto Keller/AMNH)

Last August, before taking a break from blogging, I posted an impossible-to-answer trivia. It consisted of the image above depicting an unidentified mysterious skeletal piece (sclerite) in the shape of a hook, together with two key pieces of information: a) it is entirely internal; b) it comes in pairs. › Continue reading

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Blogging will resume in early September

Saturday, August 22nd, 2009 | Administrative, Comparative Anatomy | 5 Comments

Archetype is about to get even quieter.

Grant proposals have been dealt with (more or less), and next week I will be in Turin, Italy, for the congress of the European Society for Evolutionary Biology. I just don’t want to won’t have time to blog during the congress, unfortunately.

But do not fear, for I leave you with a very tough quiz. Let see if someone knows what’s depicted below. A couple of tips:

– It is one of the few sclerites (skeletal pieces) in adult workers that is completely internal.

– It comes in pairs (left one pictured).

The answer will be revealed upon my return.

The mysterious sclerite X (Scanning Electron Micrograph, Roberto Keller/AMNH)

The mysterious sclerite X (Scanning Electron Micrograph, Roberto Keller/AMNH)

Nineteenth century figure found to be wrong about something, kind of

Friday, August 21st, 2009 | Comparative Anatomy, History of Science | 1 Comment

appendixI have Google Alerts set for the term “cladistics” so I will receive a feed every time Google indexes that word. Now, in the last couple of days those feeds have catch a story circulating in the news media regarding a recently published study looking at the appendix from a comparative and phylogenetic perspective, pretty cool if you ask me.

I can only access the abstract of the original publication unfortunately, but it does seems to be a well done and thorough study. The problem is the way the report gets increasingly hyped by the news media. I first got this: Evolution of the appendix: A biological ‘remnant’ no more. OK, that’s not bad. I then got this: Appendix redux. Yeah, sure, succinct and clever. But today I got this: Darwin wrongly called the appendix a biological ‘remnant’, say researchers:

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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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