Música do BioTerra: Cristina Branco - Tudo isto é fado

Letra: Frederico CarvalhoMúsica: Aníbal NazaréConcerto "Live", gravado no Leidsche Schouwburg Theater, Holanda, Julho de 2006Cristina Branco - vozRicardo Dias - PianoJosé Manuel Neto - guitarra portuguesaAlexandre Silva - guitarraFernando Maia - baixoAntónio do Lago Pinto - guitarra
Tudo isto é fado"Perguntaste-me outro diaSe eu sabia o que era o fadoDisse-te que não sabiaTu ficaste admiradoSem saber o que diziaEu menti naquela horaDisse-te que não sabiaMas vou-te dizer agora
Almas vencidasNoites perdidasSombras bizarrasNa MourariaCanta um rufiaChoram guitarrasAmor ciúmeCinzas e lumeDor e pecadoTudo isto existeTudo isto é tristeTudo isto é fado
Se queres ser o meu senhorE teres-me sempre a teu ladoNão me fales só de amorFala-me também do fadoE o fado é o meu castigoSó nasceu pra me perderO fado é tudo o que digoMais o que eu não sei dizer"

Hidrozoários do Oceano Profundo | Hydrozoa from Deep Ocean

Fotografias por Ph.D.» Kevin Raskoff

Passando o rato pelas imagens pode saber a espécie ou género de cada ser vivo
Ver Publications and Curriculum Vitae

Hoje faço 43 anos - partilho convosco um tema fabuloso de Lisa Gerrard: Space Weaver

Prometo não usar velas: primeiro são menos eficientes que as próprias lâmpadas incandescentes (!) e fluorescentes [ler este artigo com os respectivos cálculos] e segundo já começam a ser muitas para apagar (risos).

Prefiro mesmo ouvir boa música, em boa companhia e estar com amigos e viver um bom dia.

 

Curta-metragem naturalista- Dan Bishop

Maravilhoso, com detalhes magníficos. Muito tocante. O que me atraiu na pesquisa de vídeos youtube foi a fotografia dos frutos brancos do Juniperus e depois ao ver todo o filme, encontrei uma Paz, que sinto também quando estou em Jardins, Parques e em contacto com a Natureza.

Artivismo: Erwin Wurm

Duas reportagens vídeo sobre o artista: aqui (youtube) e aqui (pretty cool people)

Ecologist founder Edward Goldsmith dies at age 81

Fonte: The Ecologist 26th August, 2009

Edward Goldsmith, the founder of the Ecologist and one of the world's foremost green thinkers, has died at the age of 81

Goldsmith ( known almost universally as Teddy) had been suffering from a long-term illness and died peacefully in his sleep on Friday 21st August. He is survived by his second wife, Katherine Goldsmith, and five children.

Teddy's long and eventful life saw him found the Ecologist in 1970 and edit it for twenty years, run as a People Party (later to become the Green Party) political candidate for Suffolk in the general election of 1973, and publish a string of books (the most well known of which is A Blueprint for Survival ), written in collaboration with the first Ecologist editorial team and published in 1972 to great acclaim.

Teddy's signature legacy has been to promote the importance of systems ( and ecological thinking within the environmental movement, and to highlight the importance of learning from indigenous peoples and tribal societies ) ideas that were considered highly heretical when he mooted them in 1970s.

His later books, including what some consider to be his magnum opus, The Way: an Ecological Worldview, attempted to fuse anthropology, religion and science to develop a hybrid understanding of man's relationship to the natural world.

Teddy's nephew and director of the Ecologist, Zac Goldsmith said:
Teddy was a huge figure for me personally, and a key figure historically. A pioneer of the green movement, he was responsible perhaps more than anyone else for waking us up from our collective slumber. He was determined, brave, utterly inspiring, stubborn and more often than not, he was right.

Colin Hines, a contemporary of Teddy and a pioneer of the localisation movement, said:
My abiding memory of Teddy was of his good nature (most of the time!), his wonderful storytelling and the fact that he was innately a ‘gentleman’ in all the best senses of that word - a word of another era - as in a way was he.

Mark Anslow, editor of the Ecologist, said:
We live and breathe Teddy's legacy every day. His rigorous thought processes and endlessly interrogative approach to environmental issues help guide the Ecologist's editorial process: never taking developments at face value, and always asking the bigger, wider questions. He will be fondly remembered, and sorely missed.

See also

• An in-depth interview with Teddy, written by former Ecologist deputy editor Paul Kingsnorth in 2007, here.
• The complete Blueprint for Survival online in our archive here.

Mimestismos vegetais e animais -trabalho educativo de Kjell Sandved

Butterfly Alphabet

Sandved and his Snapshots

Na natureza, a camuflagem é uma arte e uma necessidade

Fotografia da Semana

São Pedro de Moel

Dormir Nu É Ecológico

O livro "Dormir Nu É Ecológico" da canadiana Vanessa Farquharson e editado pela Presença este mês de Julho em Portugal, mostra a saga da jornalista que um dia se lembrou de levar a sério a missão de se tornar ecológica num ano.

Resolveu então criar um blogue (Green as a Thistle) e alimentá-lo dia a dia com as suas aventuras e desventuras ambientalistas, num total de 366 medidas a implementar ao longo de um ano que acabou bissexto (desde 1 de Março de 2007 a 29 de Fevereiro de 2008).

Vanessa aplica desde as acções aparentemente mais insignificantes, como deixar de usar cotonetes ou usar apenas uma chávena e um copo por dia, até chegar a vender o seu automóvel, passando por uma panóplia de privações, como desligar o frigorífico e deixar de usar o secador de cabelo, e alterando radicalmente o tipo de alimentação para alimentos exclusivamente naturais, biológicos e frescos, de preferência locais, comendo carne apenas uma vez por semana, bem como passando a usar todo o tipo de produtos de higiene e de limpeza o mais natural e nas menores quantidades possíveis.

Ao fim e ao cabo, a escritora jornalista demonstra que é de facto possível melhorar o nosso comportamento ambiental, com a consciência de que, se há medidas que não são exequíveis ou nem sequer valem a pena, muitas outra há que facilmente se integram no nosso quotidiano, bastando para tal uma pequena dose de imaginação e de boa vontade.

Um livro muito divertido e bem-humorado, fácil de ler, e onde não faltam ideias (embora algumas muito radicais, outras um pouco loucas) para pormos em prática um modo de vida mais sustentável.

Visual Essays por Franke James (My Green Conscience blog)

No One Will Know

"Nature provides a free lunch, but only if we control our appetites." ~William Ruckelshaus, Business Week, 18 June 1990

Is Peak Oil Real? A List of Countries Past Their Peak Oil Production

Posted by Gail the Actuary
in Planet Thoughts

Only 14 of the 54 oil producing nations in the world are still increasing their oil production. The era of cheap oil is definitively over.

This is a guest post by Praveen Ghanta, known on The Oil Drum as "praveen". Praveen is an IT consultant in Atlanta, with degrees in economics and computer science. This was originally posted on Praveen's blog, at truecostblog.com.

Is peak oil real? The BP Statistical Review of World Energy provides the data needed to answer this question. Using the 2009 edition, I have compiled a list of all oil producing countries and regions in the world, along with the production status of each, ordered by year of peak production. BP groups minor producers into categories like "Other Africa", and "Other Middle East", and that notation is used here. All production numbers are quoted in thousands of barrels/day.

Country	Peak Prod.	2008 Prod.	% Off Peak	Peak Year
United States	11297	7337	-35%	1970
Venezuela	3754	2566	-32%	1970
Libya	3357	1846	-45%	1970
Other Middle East	79	33	-58%	1970
Kuwait	3339	2784	-17%	1972
Iran	6060	4325	-29%	1974
Indonesia	1685	1004	-41%	1977
Romania	313	99	-68%	1977
Trinidad & Tobago	230	149	-35%	1978
Iraq	3489	2423	-31%	1979
Brunei	261	175	-33%	1979
Tunisia	118	89	-25%	1980
Peru	196	120	-39%	1982
Cameroon	181	84	-54%	1985
Other Europe & Eurasia	762	427	-44%	1986
Russian Federation	11484	9886	-14%	1987*
Egypt	941	722	-23%	1993
Other Asia Pacific	276	237	-14%	1993
India	774	766	-1%	1995*
Syria	596	398	-33%	1995
Gabon	365	235	-36%	1996
Argentina	890	682	-23%	1998
Colombia	838	618	-26%	1999
United Kingdom	2909	1544	-47%	1999
Rep. of Congo (Brazzaville)	266	249	-6%	1999*
Uzbekistan	191	111	-42%	1999
Australia	809	556	-31%	2000
Norway	3418	2455	-28%	2001
Oman	961	728	-24%	2001
Yemen	457	305	-33%	2002
Other S. & Cent. America	153	138	-10%	2003*
Mexico	3824	3157	-17%	2004
Malaysia	793	754	-5%	2004*
Vietnam	427	317	-26%	2004
Denmark	390	287	-26%	2004
Other Africa	75	54	-28%	2004*
Nigeria	2580	2170	-16%	2005*
Chad	173	127	-27%	2005*
Italy	127	108	-15%	2005*
Ecuador	545	514	-6%	2006*
Saudi Arabia	11114	10846	-2%	2005 / Growing
Canada	3320	3238	-2%	2007 / Growing
Algeria	2016	1993	-1%	2007 / Growing
Equatorial Guinea	368	361	-2%	2007 / Growing
China	3795	3795	-	Growing
United Arab Emirates	2980	2980	-	Growing
Brazil	1899	1899	-	Growing
Angola	1875	1875	-	Growing
Kazakhstan	1554	1554	-	Growing
Qatar	1378	1378	-	Growing
Azerbaijan	914	914	-	Growing
Sudan	480	480	-	Growing
Thailand	325	325	-	Growing
Turkmenistan	205	205	-	Growing
Peaked / Flat Countries Total	-	49597	-	60.6% of world oil production
Growing Countries Total	-	32223	-	39.4% of world oil production

Only 14 out of 54 oil producing countries and regions in the world continue to increase production, while 30 are definitely past their production peak, and the remaining 10 appear to have flat or declining production [1]. Put another way, peak oil is real in 61% of the oil producing world when weighted by production. Since 2008 capped a record run for oil prices, most countries and oil companies were trying all-out to increase production. While a handful of producers (think Iraq) might be limited by above-ground factors, the majority of producers simply couldn't do any better in 2008 [2].

The evidence of the demise of the cheap oil era has become insurmountable. In the face of the highest oil prices on record, the great majority of the world's oil producers were incapable of taking advantage and producing more oil. Many nations including the US saw their oil production peak decades ago - there simply is no turning the clock back. This list shows that we are relying on a small number of countries to keep providing cheap oil. We need to move faster to alternatives and greater energy efficiency, before the last fourteen peak as well.

* More information on these countries:

• Russian Federation - Russia's oil production collapsed by the early 90's as the Soviet Union collapsed, but despite a decade of growth, Russia's own oil execs don't think the old peak can be surpassed.
• India's production appeared to plateau in 1995, and has stayed within a steady range since. The EIA forecasts Indian oil production to remain flat or decline slightly in the near future.
• Republic of Congo (Brazzaville) hit a production plateau in 1998, though current production is still very close to 1999 peak levels.
• Other Central & South America - The remaining countries of the Americas hit a production peak in 2003, though it's still too soon to know if this will be final peak.
• Malaysia has been on a production plateau since 1995, and the EIA projects flat or falling production.
• Other Africa - Oil production in much of Africa is potentially impacted by above-ground constraints, so it's definitely possible that production will rise here. It will rise from a low base of only 50,000 bpd however, and may not have much impact on total world production.
• Nigeria is impacted by domestic insurgencies in its oil-producing regions, and may be able to lift production if the political situation improves.
• Chad's oil production history is too short to definitively identify a peak in production, but the drop-off since 2005 has been dramatic.
• Italy has been on a production plateau for over 10 years, and it's unlikely that a mature economy is significantly under-exploiting its resource potential.
• Ecuador's production grew rapidly until 2004, but has leveled off and declined somewhat since then.

[1] To be considered past-peak, a producer's current (2008) production has to be at least 10% less than its best year, and the best year must have occurred prior to 2005. Some countries' production has been artificially constrained by political and other non-geological considerations. But in some of these cases, it will be difficult to pass an old peak because decades of depletion have occurred since that peak. Iraq peaked in 1979, making it all the more difficult to pass that now.

[2] While OPEC maintains formal production quotas, it is widely believed that only Saudi Arabia had true spare capacity in 2008, while all other OPEC nations were producing at capacity. The truth is unclear, since OPEC nations do not provide detailed reserve statistics for their oil fields.

Total [oil company] has created its own short list of oil producers past peak, and Wikipedia has a list here.

Source: The Oil Drum

Música do BioTerra: Machine Gun (Slowdive Trip Hop Cover)

Original
[Verse: Rachel Goswell]See you walking and I know she's my friend againJust the weight of the water drags me down againGuess I'll think of the water, it's my friend, oh yeahIt's just the way that the water makes me feel again
[Chorus: Neil Halstead]Son of Sheba, I saw him drownSon of yellow, I saw him downIt's all I need, yeah
[Verse: Rachel Goswell]
[Chorus: Neil Halstead]

Velas e Carbono* Candles and Carbon

The widespread practice of misguided eco-Luddites turning off their lights for Earth Hour and burning candles as a source of light is grossly misguided and actually contributes to increased carbon dioxide emissions. [reading more here: Physical Insights] 

In a society where 94 percent of the electrical energy generated is generated using fossil fuels, ordinary citizens using electricity are not to blame for anthropogenic greenhouse gas emissions.

* Ref: Relatório Estatístico dos Consumos Energéticos 2009 da IEA 

Ideia entretanto também referida em Calor: Como Impedir o Planeta de Arder, de George Monbiot  

Como evoluiu a vagina? Vagina Evolution

                                                 

Do mesmo autor da postagem anterior PZ Myers

Resumo do artigo
Em praticamente todos os seres vivos, à excepção dos Mamíferos, o sistema reprodutor combinado com o sistema digestivo e urinário, desembocam todos num único tubo com contacto para o exterior, a cloaca. Há cerca de 150 milhões de anos, contudo, uma provável alteração nas funções do oviducto (aparecimento do útero, com funções de desenvolvimento interno do embrião) devido, muito provavelmente, a modificações epigenéticas, terá levado ao aparecimento de toda uma nova estrutura: a vagina.

Evolution of the mammalian vagina [originalmente https://scienceblogs.com/pharyngula/2007/01/14/evolution-of-the-mammalian-vag]

Q: What unique organ is found only in mammals, but not in fish, amphibians, reptiles, or birds?

The title and that little picture to the left ought to be hint enough, but if not, read on.

A: The vagina. Aren't we lucky?

There's an old joke going around about poor design: what kind of designer would route the sewer pipes right through the center of the entertainment center? It's a good point. It doesn't make sense from a design standpoint to have our reproductive and excretory systems so intimately intermingled, but it does make a heck of a lot of sense from a purely historical point of view. In a sense, reproduction is an excretory function: we are shedding gametes produced internally, and we already have a perfectly good set of pipes running from our insides to the outside, so why not use them? It's just that in our lineage, which has specialized in giving great care to our gametes and zygotes, that plumbing has become increasingly elaborate, and that part of the system that was once just a convenient throughway has become a destination and a long-term residence in its own right.

Formation of the Müllerian ducts

Development tells us part of the story. The reproductive and urinary tracts are all tangled together in early development, arising together from two pairs of ducts, the Müllerian and Wolffian ducts, which are modified in complex ways to form a series of kidneys (we keep only the last one, the metanephros), one set of pathways for the male testes, and yet another set for the female ovaries.

In non-therian mammals, all of these complicated pipes have one common destination, a single outlet to the external world: the cloaca. Cloaca is Latin for sewer, and it is appropriately named. The terminus of the large intestine is here, as well as the ends of the ureters from the kidneys and the ducts from the ovaries or testes. Everything gets dumped in to the cavity of the cloaca, making a nice stew of feces, urine, and sperm or eggs. Mmm-mmm. The cloaca is the grey cylinder at the bottom of figure A, below, in the first three organisms, amphibians, birds/reptiles, and monotremes (my apologies for the murkiness of the image; it's the best copy I have).

The fundamental organization of the reproductive part of the vertebrate urogenital tract is straightforward: it's a tube with a funnel at one end that captures eggs released by the ovary, and conducts them to an external orifice. Along the way, cells lining the tube secrete useful products like albumin and yolk, and deposit a shell, and may act to temporarily store the egg before its final release.

Marsupial and placental mammals have dispensed with most of those functions, and expanded on others. One part of the oviduct has acquired a richly vascularized epithelium and specializations for investing and nurturing a resident embryo, becoming a uterus. That's an amazing and innovative function in itself, but in addition, it has formed a new, separate channel, the vagina. The vagina is an entirely new structure, which has no homolog in amphibians or reptiles.

That is an interesting observation. It's a wholly original structure that arose sometime after the monotreme-marsupial split, an evolutionary novelty. How did that happen? How can we study a unique event that occurred over 150 million years ago?

Wagner and Lynch have a proposal to answer both questions. The general mechanism for generating novel structures is evo-devo orthodoxy:

1. An epigenetic side effect of other evolutionary changes in the body leading to a novel physical structure in the organisms.
2. The genetic consolidation and individuation of the novel structure.

(Note that this proposes phenotype before genotype, which is somewhat heretical for neodarwinism. It shouldn't trouble the evo-devo gang in the slightest, of course.)

How to study such a process from the past?

The basic assumption of a molecular evolutionary approach to the study of evolutionary novelties is that changes in developmental regulation have left traces in the molecular structure of the genome and a comparative study of genomic structures should be able to identify genetic changes coincidental with a phenotypic novelty. (emphasis mine)

That process of consolidation and individuation would have left detectable scars in the genome—the genes involved would have acquired changes necessary to fix the phenotype in the population. Again, as we'd expect from the evo-devo perspective, those changes would have been made to the regulatory genes that control tissue-specific gene expression. What genes should we examine? Let's look at the therian organs of interest, and here are some likely candidates: the HoxA genes that have region-specific domains in the female reproductive tract.

  

The HoxA-9 through HoxA-13 genes are expressed in order along the length of the embryonic Müllerian duct, and also continue to be expressed in adulthood; so the cells of the vagina are all expressing HoxA-13, while the cells of the cervix all have HoxA-11 turned on (for some reason, I find that to be a wonderful piece of knowledge, and I just have to say…Hooray for HoxA-13! It has just become my favorite Hox gene.)

So the question is whether there is any evidence that these particular Hox genes have signs of any set of changes that are associated with particular transitions in vertebrate evolution—in particular, are there differences that can be traced to the transition between monotremes and the theria, and between the placentals and marsupials. The answer seems to be yes: the diagram to the right is a measure of the number of synonymous to nonsynonymous changes in HoxA-11, which is an indicator of the selective pressures that have shaped the gene.

Furthermore, they've identified where these changes have occurred, and they are not in the homeodomain (the part of the protein that binds to specific sequences in the DNA, but in the amino terminal end.

The 3-D models below show where the relevant amino acids (in yellow) end up in the folded protein. The interesting thing here is that regulatory proteins don't just interact with each other, but also with other regulatory proteins that are simultaneously binding. It's a whole chain of interactions—regulatory proteins binding to the DNA, and also binding between each other in a complex called the enhancersome—that determines the level of expression of a particular gene.

There is a great deal left to be done. Hox genes are rather high up the chain of regulatory genes, so there are many more genes downstream that have to be puzzled out. We also are a long ways from figuring out how these patterns of gene expression define the morphogenetic processes that create this lovely novel structure, the vagina. The important thing, though, is that there are these questions waiting to be answered—the investigators have a research program.

We propose that a research program to explain evolutionary novelties has to focus on the question of whether novel characters arise through the evolution of novel regulatory links among developmental genes. We further propose that a detailed analysis of the evolution of developmental genes involved in the development of a derived, novel character can reveal molecular changes that could be causally involved in the origin of evolutionary novelties. The case study presented here suggests that the statistical methods of molecular evolution are strong enough to provide specific hypothesis for experimental test. The success of this research program will depend on the ability to connect the patterns of molecular evolution with the functional role of these molecular changes.

That's the cool thing about evolutionary biology: exciting questions, titillating ancestors, and the promise of tools to answer more.

---

• Lynch VJ, Roth JJ, Takahashi K, Dunn CW, Nonaka DF, Stopper GF, Wagner GP (2004) Adaptive evolution of HoxA-11 and HoxA-13 at the origin of the uterus in mammals. Proc Biol Sci. 271(1554):2201-7. [pdf]
• Wagner GP, Lynch VJ (2005) Molecular evolution of evolutionary novelties: the vagina and uterus of therian mammals. J Exp Zoolog B Mol Dev Evol. [Epub ahead of print]
• Cifelli RL, Davis BM (2003) Marsupial Origins. Science 302:1899-1900.
• The evolution of female genitalia

Como evoluiu o pénis? Penis evolution

Quem está na blogosfera (e não só) procura ou é insistentemente convidado a aumentar o tráfego de visitantes do seu blogue ou página. Toda a gente sabe que o sexo é um tema que tem muita procura. Bom mas podemos falar dele de uma forma séria e interessante. Porque não uma abordagem sobre a evolução dos principais órgãos sexuais: o pénis e a vagina?
Embora em inglês, quem melhor para abordar a evolução do pénis por PZ Myers (biólogo e Professor Associado da Universidade de Minnesota, Morris).

Resumo do artigo Penis Evolution ( originalmente em inglês: mais abaixo)
Os pénis embrionários tiveram uma história complexa. Eles evoluíram independentemente várias vezes, e talvez o mais preocupante para o ego masculino, que tenham sido perdidos secundariamente, pelo menos, algumas vezes. E cada vez que eles têm evoluído, as evoluções convergem numa solução morfológica notavelmente semelhante.

So I was just browsing through some fun journals (Integrative and Comparative Biology, always good for some unusual stuff) and ran across a paper with a wonderful title: "The Functional Morphology of Penile Erection: Tissue Designs for Increasing and Maintaining Stiffness." If that kind of thing will sell commercial air time during the Super Bowl, it's got to be popular.

As is typical, though, while the promise of salaciousness drew me in, it was the science and the evolutionary story that kept me interested. Amniote penises have had a complex history. They have evolved independently multiple times, and perhaps most troubling to the male ego, they have been secondarily lost at least a few times. And every time they have evolved, they converge on a remarkably similar morphological solution.

That last observation is perhaps not very surprising. The penis has a very simple job to do: to maintain sufficient stiffness to enter an orifice in the mate, and to deliver sperm. That's it. Every amniote settles on a similar solution, forming a hydrostat, a tube containing a pressurized incompressible fluid surrounded by a membrane under tension. It's a kind of glorified water balloon.

Where different amniote lineages differ is in how they build their penis. Mammals have a medial penis containing two inflatable, vascular erectile bodies, and the tissue used for it embryonically is gathered from non-cloacal epithelia and connective tissue. Crocodile and turtle penises contain a single erectile body, and they form their penises from tissues on the ventral cloacal wall. Squamates (lizards and snakes) have paired penises built from lateral cloacal wall tissue. Birds, like crocodiles, assemble a penis (when they have one) from the ventral wall of the cloaca, but they use the lymphatic system as a pump, rather than the blood system.

In these cross-sections through the penises of a turtle, bird, mammal, and snake, you can see that while each is different in its organization, all contain the same kind of functional core: a vascular space (VS) surrounded by a tensile membrane (TM).

Diagrams illustrating transverse sections of amniote intromittent organs. A turtle penis is at the upper left, a bird penis is at the upper right, a mammalian penis is at the lower left, and a snake hemipene is at the lower right. All the structures are hydrostatic: each contains a central vascular space (VS) and surrounding tensile membrane (TM) characteristic of hydrostats.

Similar in function, but different in embryonic origin—this all suggests that these organs evolved independently. There are multiple hypotheses about the exact order and pattern of descent of the penis—the diagrams below illustrate two—but one of the striking things about this pattern is how lineages, such as the birds, can so blithely lose their intromittent organ. Most birds lack penises altogether, and they are found mainly in ratites and ducks, yet both of the cladograms below show that the ancestral bird most likely had one. Think about that… it hasn't been at all uncommon for female vertebrates to be untroubled by the absence of a penis in their mates, and apparently have preferred it that way.

Phylogeny of extant amniotes illustrating alternate hypotheses for the distribution of intromittent organs in amniotes. A. The penis is an amniote synapomorphy. B. The penis as a convergent trait. The position of the Testudines is disputed; alternate hypotheses increase the possible number of independent penile origins, as does the patchy distribution of the organ within Aves.

This paper presents the evolutionary history of the penis as background to its primary focus, which is on the bioengineering of a rigid hydrostat. All of the organisms converge on an exceedingly similar solution. The tensile membrane of the hydrostat consists of alternating layers of collagen fibers, each oriented at 90° to one another. This is the same principle used to give plywood its rigidity, by having fibers oriented to oppose bending along their least extensible axis at every angle. In addition, the fibers in the rest state are crimped, allowing them to stretch during extension, but then become straight and resistent to further extension when the organ is fully inflated.

Diagram of collagen fiber arrangement in the wall tissue of a flaccid mammalian penis. There are two layers forming an axial orthogonal array: an outer layer with fibers at 0° to the long axis of the penis and an inner layer with fibers at 90° to the long axis. Collagen fibers are highly crimped in the flaccid penis, but straighten upon erection.

The paper also describes some experimental measures of stiffness. The author extracts the penis of the nine-banded armadillo, and can then pump it up by inflating it with known volumes of fluid, whele measuring its resistance to bending (reported as values of E, or Young's modulus of elasticity.) I confess to having the odd thought that locker-room bragging ought to supplement reports of inches/centimeters of length with E values in 10^-5Nm². Imagine all the insecure jocks reporting to their local physiologist for a three-point bending test!

Change in the average flexural stiffness of mammalian penile erectile tissue (corpus cavernosum) during inflation, as measured by three-point bending tests in the nine-banded armadillo (Dasypus novemcinctus). Flexural stiffness increases as internal volume increases, and is highest when the corpus cavernosum reaches maximum volume. There is not a statistically significant difference in the flexural stiffness of the corpus cavernosum when the structure is bent laterally or dorsoventrally (n=4; F-ratio=2.70; 0.05

The author concludes from the degree of convergence seen in the species studied that there must be adaptive significance to the arrangement.

What, then, can we conclude if we observe convergence at more than one anatomical or functional level? Multiple levels of convergence could imply that there are more constraints on the system—that there are fewer possible anatomical designs that successfully meet the selective regime. Therefore, if there is only one way to solve the problem imposed by the selective regime, we will see convergence at more levels than if many equally successful anatomies can evolve.
If this hypothesis is true, the evidence from mammals and turtles suggests that the amniotes that have evolved inflatable penises have been subjected to an extremely restrictive selective regime. Penile convergence in mammals and turtles does not stop at gross functional similarity; they have converged on a single anatomical design down to the level of specific collagen fiber arrangements. The differences in penile collagen fiber layering that exist between mammals and turtles do not, as of yet, seem to have any functional effect on penile stiffness. It may be that the way the axial orthogonal array is put together is less critical to the problem of increasing penile flexural stiffness than the presence of the array itself.

I agree in part, but it also seems to me that contingency is equally significant. The reason that all of these animals have converged on the same solution is that they've begun with similar raw materials: a high-pressure circulatory system and a tissue bed rich in the protein collagen.

There was no mention of the adaptive significance of this organ to weblogging or to administering Harvard, to my disappointment.

---

Kelly DA (2002) The Functional Morphology of Penile Erection: Tissue Designs for Increasing and Maintaining Stiffness. Integ. and Comp. Biol. 42:216–221.