A New Way to See the Embryonic Development of Animals

The Daily Mail posted an article today about an upcoming National Geographic special (I first read about it on Propjets and Writings, though it’s since appeared in several other blogs as well). Called In the Womb: Animals, it’s a follow-up to National Geographic’s previous feature on the embryonic development of humans. Using a combination of ultrasound, tiny cameras, and computer graphics, they show the development of a dog, an elephant, and a dolphin in utero.

However, as P. Z. Myers points out in Pharyngula, the images are too “pretty.” The membranes and such appear to be missing, and the uteruses look too spacious. Don’t get me wrong—I strongly support attempts to make science more appealing to the public, and sometimes one has to fill in the details—I’m a big fan of the BBC’s Walking With Dinosaurs series. I’m looking forward to seeing this (it airs on National Geographic on 10 December), but I hope they will make clear just what they could record and what they had to “fill in.”

If you’re interested in learning more, BBC and the Daily Mail both have picture galleries, and additional information and some video clips are available at the National Geographic site.

Cetacean Evolution

Dolphins are my favorite animals, and I’ve always been fascinated by their interesting evolutionary path. Dolphins and whales (that is, cetaceans) are mammals like we are: they breathe air, they give birth to live young, and their spines bend up and down like ours do (not side to side like those of sharks or other fish). And like us, they are descended from four-legged land mammals. It’s quite interesting to examine the sequence of changes that resulted in them more and more adapted to living in water.

Examination of a dolphin skeleton clearly reveals our closely shared ancestry. In addition to the similar spines (vertebral columns), in their flippers, dolphins have the same bones we do in our arms. Connected to the scapula (shoulder bone) is a short humerus (arm bone), then a short radius and ulna (forearm bones), followed by the tarsals (wrist bones), metatarsals (hand bones), and phalanges (finger bones)—dolphins (and whales) have five “fingers” inside their flippers. And often tiny, vestigial hind leg bones are found buried within the animal. In fact, there was a CNN article a couple weeks ago (“Could extra dolphin fins be legs?”) discussing a dolphin with a pair of caudal fins perhaps representing the ancient hind limbs:

TOKYO, Japan (AP) — Japanese researchers said Sunday that a bottlenose dolphin captured last month has an extra set of fins that could be the remains of hind legs, a discovery that may provide further evidence that ocean-dwelling mammals once lived on land.

…

Fossil remains show dolphins and whales were four-footed land animals about 50 million years ago and share the same common ancestor as hippos and deer. Scientists believe they later transitioned to an aquatic lifestyle and their hind limbs disappeared.

Whale and dolphin fetuses also show signs of hind protrusions but these generally disappear before birth.

If you’re interested in more about this fascinating progression, artist Carl Buell has started a series of posts on cetacean evolution at his blog Olduvai George (which I noticed courtesy of Pharyngula). He’s just posted the first in the series, with a nice commentary accompanied by his excellent illustrations. Take a look!

Related posts

• Science News Update (02 Dec 2006)

Research on New Hemostatic Agent

The December issue of Scientific American mentions a new protein solution that, in animal tests, has been able to quickly stop bleeding in a way that’s fundamentally different from previous methods. The research, by Dr. Ellis-Behnke and colleagues, was published online in the journal Nanomedicine on 13 October 2006 (see abstract); the article is still in press.

It’s a solution of peptides (proteins) that is injected over the wound and stops the bleeding in seconds. It’s unclear precisely how it works; the peptides apparently self-assemble into some sort of fibrous network, different from normal blood clots (no platelets are present). No apparent toxic effects have been observed, and the gel is long-lasting. What’s especially neat is that the sustance eventually breaks down into its constituent amino acids, the building blocks of proteins, which can then be used by the body.

Obviously, research is still in the initial stages. Even if it is shown to be safe in humans, its effectiveness will have to be compared to standard methods of stopping bleeding. But it could add to our collection of hemostatic tools, potentially displacing the methods we currently use.

J. R. Minkel discusses the development in an expanded article on Scientific American’s web site. It also features a short clip demonstrating the use of the substance after making an incision in the liver of some type of rodent.