Elements in the Human Body

The most common elements in the human body (logarithmic scale, data from Wikipedia, chart produced using R). Yes, we are mostly made of air!

---

Rattus norvegicus: the lab rat

The albino Rattus norvegicus used in laboratories (photo above by Sarah Fleming) goes back to the Wistar Institute in Philadelphia. Physiologist Henry H. Donaldson took four pairs of albino rat with him when he joined the Institute in 1906, and work there by Donaldson, Helen Dean King, and others resulted in the development of a standardised “Wistar rat.”

In his 480-page tome The Rat: Data and reference tables for the albino rat (Mus norvegius albinus) and the Norway rat (Mus norvegius) of 1915 (revised in 1924), Donaldson notes: “In enumerating the qualifications of the rat as a laboratory animal, and in pointing out some of its similarities to man, it is not intended to convey the notion that the rat is a bewitched prince or that man is an overgrown rat, but merely to emphasize the accepted view that the similarities between mammals having the same food habits tend to be close, and that in some instances at least, by the use of equivalent ages, the results obtained with one form can be very precisely transferred to the other.”

What Donaldson means by the latter point is: “If the life span of three years in the rat is taken as equivalent to 90 years in man, it is found that the growth changes in the nervous system occur within the same fraction of the life span (i.e., at the equivalent ages) in the two forms.”

Since Rattus norvegicus has adapted to live with people (e.g. in tunnels under our cities), it makes for a perfect laboratory animal. Running rats through mazes of varying kinds has become an established way of studying learning, as in this video from the San Diego News Network:

Circulation: William Harvey’s Revolutionary Idea (a review)

Circulation by Thomas Wright

I recently read Circulation: William Harvey’s Revolutionary Idea by Thomas Wright. This interesting biography of William Harvey concentrates on his discovery of the circulation of the blood through the body, and his publication of Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus in 1628. The historical and social context of Harvey’s work is described particularly well.

William Harvey

Harvey’s idea had the potential to revolutionise medicine, doing for biology what Galileo had done for astronomy. Sadly, although Harvey’s work undermined the basis for pointless treatments like bloodletting, the respect accorded to ancient Greek medicine kept such treatments alive for centuries after they should have ceased.

An illustration from Harvey’s book

This well-written book is well worth reading, and of interest to students of science, history, and medicine (although the descriptions of live dogs being dissected are a little disconcerting). It won the 2012 Wellcome Trust Book Prize.

Circulation by Thomas Wright: 3.5 stars

---

Wellcome Image Awards

Because of a gap in 2013, I had forgotten about the Wellcome Image Awards. This SEM image of a kidney stone by Kevin Mackenzie was one of the winning entries for 2014:

So was this strangely beautiful SEM image of sludge from an industrial farming process by Eberhardt Josué Friedrich Kernahan and Enrique Rodríguez Cañas:

This SEM image of a Purkinje cell by Michael Häusser, Sarah Rieubland, and Arnd Roth was one of this year’s winners:

So was this micro-computed tomography scan of the skull and front legs of a tuatara (a New Zealand reptile) by Sophie Regnault:

And this illustration of pollen grains being released from the anther of a flower by Maurizio De Angelis:

All images used under Creative Commons license (CC BY-NC-ND). Click images to zoom and/or read more about the pictures. They’re lovely, don’t you think?

Hallucigenia

Hallucigenia: as reconstructed in the 1970s (left) and later (right). Images from the Smithsonian.

One of the most interesting of Cambrian fossil creatures is the aptly named Hallucigenia (see above). Famously, Hallucigenia fossils were once reconstructed back to front and upside down, with the spines on the animal’s back seen as bizarre stilt-like legs, and the actual legs seen as strange tentacles. Later reconstructions addressed these errors, but still showed unrealistic stilt-like locomotion.

Hallucigenia is now seen as a close relative of the onychophorans (velvet worms), so that adding spines to the photograph below would give a better indication of appearance. A fascinating recent paper in Nature by researchers at Cambridge clarifies the relationship by showing that a key feature of Hallucigenia’s claws – their construction from stacked elements – resembles that of the jaws and claws of modern onychophorans. This makes Hallucigenia no less nightmarish, but a great deal more comprehensible!

A modern onychophoran (velvet worm). Photo by Martin Smith.

A frog that gives birth to tadpoles!

Limnonectes larvaepartus (adult female)

The Indonesian frog Limnonectes larvaepartus, formally described last year, gives birth to live tadpoles. It is the only frog to do so – the overwhelming majority of frogs lay eggs (and a handful give birth to tiny froglets). A recent paper by Mirza Kusrini, Jodi Rowley, Luna Khairunnisa, Glenn Shea, and Ronald Altig describes the reproductive biology of this unusual frog in more detail (the photos above and below are from the paper). This post from the Australian Museum has more details.

Limnonectes larvaepartus tadpoles

In biology, every rule seems to have exceptions! And the unusual is always waiting around the corner, ready to be discovered – especially in the world’s tropical forests.

The more common reproductive strategy: most other frogs lay eggs like these

Spineless: a book to look out for

Spineless by Susan Middleton (October 2014)

Here is a beautifully illustrated book to look out for: Spineless: Portraits of Marine Invertebrates, the Backbone of Life, by Susan Middleton.

I have no review, but here are some of the lovely images from the book. Wired and the Smithsonian Magazine have more. It looks fantastic!

Society of Biology Photography Competition

The Society of Biology has announced the winners of their 2014 amateur photography competition, which included some fantastic entries by young photographers. Click the camera image below to see the gallery, or read the story in Wired.

Endless Forms Most Beautiful: a book review

Endless Forms Most Beautiful by Sean B. Carroll (2005)

I recently read, somewhat belatedly, Endless Forms Most Beautiful by evolutionary developmental biology pioneer Sean B. Carroll (the title derives from a line in On the Origin of Species: “from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved”).

This well-written book provides an excellent explanation for how a toolkit of genes like the Hox genes (see image below) control embryonic development in animals. The discovery of these genes shows that fruit flies, starfish, and people are more closely related than was once believed.

These genes work by producing proteins which in turn control the expression of other genes, in what is effectively a kind of computer program that can be visualised (and Endless Forms Most Beautiful contains several lovely colour plates which confirm this).

Photo: Caitlin Sedwick (from this paper)

The book includes chapters on the Cambrian explosion, melanic forms (such as black panthers), and the formation of spots on butterfly wings:

Carroll concludes with a plea for teaching more evolutionary biology in schools. Personally, I think a greater priority would be an increased emphasis on teaching ecology, given the serious consequences which human activities (even well-meaning ones) can have for the planet. However, that quibble does not stop me from recommending this book to anyone who has not read it yet.

Endless Forms Most Beautiful by Sean B. Carroll: 3½ stars

Drosophila melanogaster: the legendary “fruit fly”

Drosophila melanogaster, the vinegar fly or “fruit fly” (photo above by André Karwath), has been enormously important as a model organism in genetics and neuroscience, partly because it is so easy to raise in the laboratory (photo below by “Masur”).

Drosophila genes such as fruitless, rutabaga, and white have been enormously important within biology, and flybase.org provides a modern repository of information on such genes. The Hox genes, first found in Drosophila (see below), form part of the complex machinery of embryonic development, which allows protein synthesis to be controlled in both time and space.

Jonathan Weiner’s 1999 book Time, Love, Memory is one of a number of books which explain how valuable this little insect has been.