Awww. Baby red panda

It was love at first sight for Shama and Tate, the red pandas at the Smithsonian’s National Zoo, and now, nearly 1½ years after they were introduced, the pair has a cub as evidence of their strong bond. On Wednesday, June 16, Shama gave birth to a single cub—the first for both of the Zoo’s red pandas (Ailurus fulgens) and the first red panda cub born at the National Zoo in Washington, D.C., in 15 years.

Red pandas have a baby. It’s very cute.

The National Zoo is celebrating its first birth of a red panda in 15 years. The history of the red panda–at least, of its classification–is complicated. More on that in a mo. What’s significant here is its current situation. Thanks to habitat loss, the species has declined in the wild to fewer than 2500 individuals, and it is endangered. So a birth–especially between an apparently happy couple with a strong mutual attraction–is a success for the zoo and for red panda conservation, too.

The proud mother was born at the Smithsonian Conservation Biology Institute in Front Royal, Va., and more than 100 surviving cubs have been born at both this research facility and the Washington, D.C., campuses since 1962.

Panda or raccoon?

Taxonomists–the folks who classify organisms by relatedness–have had a conundrum on their hands with the red panda. You’d think that the name says it all: it’s a panda, right?

Well, no. Nothing’s ever that easy in taxonomy. For some time, arguments that it was a relative of the raccoon held weight. But the animal has some strong panda-like traits, including an affinity for bamboo and similar habitats to the giant panda. But they differ in their far more diverse diet and greater habitat distribution.

The panda’s thumb

The giant panda has a faux thumb that’s really just a bone extension of the wrist bones. It’s not an opposable thumb like the one primates have, but the giant panda uses it in a thumb-like way. The red panda happens to share this odd trait. They also share many similarities in their DNA, which ended in the red panda briefly joining the bear family.

So, is it a panda or a raccoon?

The species also has some commonalities with the raccoon, including the ringed tail and more diverse diet compared to the giant panda, one that includes a taste for bird eggs. For these reasons, it also has been classified into the raccoon family. So, which family is it?

It’s neither. While the red panda has now been classified as a distant relative of the giant panda–the bamboo! the “thumb”!–it falls into its very own family, the Ailuridae, of which the red panda, or Ailurus fulgens, is the sole member. Unlike bears, this species arose in Asia and never made the trek to the “new world.”

Interesting note, the snow leopard–another severely endangered species–is their sole wild predator.

Advertisements

Inbreeding in the Darwin dynasty?

Darwin and his wife were first cousins

Charles Darwin married his first cousin, Emma Wedgwood, and his own mother was the product of a marriage between third cousins. Given his insights into the relationship among variation, nature’s choices, and adaptation and his observations of weakening in inbred plants, it is no surprise that Darwin worried about his own family’s consanguinity. Did the inbreeding in the Darwin/Wedgwood families show up in his children?

Is marrying your first cousin really so bad?

Had the Darwin/Wedgwoods only engaged in the first-cousin marriage between Charles and Emma, the outcome would likely not have been serious. A 2002 study reported by the National Society of Genetic Counselors found that having first cousins as parents raises the risk of having a significant genetic defect from 3-4% up to about 4-7%. The group concluded that first cousins planning to reproduce require no more intense genetic counseling than unrelated couples.

Consistent consanguinity, on the other hand

But that study didn’t address serial consanguinity of the kind seen in some European royal houses or in the Darwin/Wedgwood families. And a new analysis reported in BioScience avers that the Darwin offspring did experience the repercussions of such inbreeding. Applying an inbreeding coefficient to calculate whether childhood mortality in the Darwin/Wedgwood family across several generations was related to inbreeding, the authors indeed found an association.

Three of the Darwins’ ten children died at age 10 or younger, one of tuberculosis, one of scarlet fever, and one of an unidentified disease. Studies suggest an association between childhood mortality from bacterial infection and consanguinity, and the Darwin family seems to bear that out. In addition, three of the Darwin children who did live to adulthood experienced lengthy marriages without any children, and such infertility may be another manifestation of homozygous states that interfere with reproduction. A photograph of the youngest Darwin child, Charles, who died in toddlerhood, suggests that the baby had some congenital disorder, although the nature of it remains unclear. Emma Darwin was 48 years old when she gave birth to Charles, so Down Syndrome is one likely explanation.

Successful Darwins

In spite of some of the sad facts of the Darwin family story, a few of his children experienced successes of different kinds. Three of his sons were members of the Royal Society, a long-time Darwin family tradition that skipped over the most famous member of the tribe, Charles himself. And Darwin by any measure of fitness did pretty well: in spite of the loss of three children and the infertility of three children, he nevertheless had several grandchildren.

Did Darwin himself suffer from the effects of inbreeding?

Charles Darwin experienced a variety of chronic health conditions, but they do not necessarily seem to have been related to his family’s consanguineous status. Several theories abound to explain his symptoms, which included digestive and skin problems, but no one knows for certain what afflicted the great naturalist. One of the foremost hypotheses is that he had Chagas disease, occurring after a bug bite on one of his voyages transferred an infectious protozoan that may have permanently damaged the scientist’s gut. Stress seems to have exacerbated the problem, whatever its etiology.

Leeches model reproductive behavior

No, not that kind of modeling.

Leeches have a bad reputation because they dine on blood. Even forgetting for the moment such human-designed culinary delicacies as blood pudding or blood sausage, let’s just say that sucking blood does not necessarily an incubus make.

Not just blood-sucking boneless terrors

In fact, leeches have recently made a comeback in the shape–the slimy, creepy shape–of their use as medical therapy. Their former role was to suck bad humors from the body. Today, with our improved understanding of molecular biology and relegation of humor to Jon Stewart, leeches serve a different purpose. Pracititioners encountering venous insufficiency and premature clotting during certain surgeries can apply leeches–and their salivary anti-clotting factors–locally to address the problem. By the way, the medicinal use of leeches–which has a history stretching back for milliennia–is called hirudotherapy.

Model leeches

And leeches also make an oxytocin-related hormone called hirudotocin that plays a role in their reproductive behavior. A reproductively aroused leech, it seems, undergoes a maneuver that involves a sloooow, five-minute rotation of its body. The rotation results in alignment of reproductive pores with complementary pores on a presumably adjacent partner.

Animal behavior results, at its core, from an interaction of hormones and the nervous system. But linking the two directly and assessing the influence of hormones on nerves has proved elusive in more complex animals. Leeches, though, have a nervous system more basic than a mosquito’s. And an injection of hirudotocin yields leech reproductive rotation within minutes, accompanied by a leechy mouthing of the potential reproductive partner. In the world of animal behavior research, this is exciting stuff.

Sliced leech anyone?

To track the effects of this hormone through the animal’s nervous system, researchers at Caltech and UCSD examined nervous response to hirudotocin in slices of leech. Then, they did the ultimate direct assessment, removing all of the leech except the nervous system. This approach allowed them to trace directly the activation of the nervous sytem that led to the corkscrewing muscle movements of leech reproductive behavior.

Their next step will be to use voltage-sensitive dyes to detect electrical nerve signals along these paths to see which ones are involved in maintaining the behavior. They may not be drawing out bad humors any more, but leeches are certainly doing their part in helping us tease out the links between hormones and behavior.

For your consideration

Why is it so difficult to link a hormone and a behavior, especially in vertebrates?

This article says that animal behavior is a manifestation of the interaction of hormones and the nervous system. Can you think of some other examples of this interaction?

Animals are not the only organisms that use hormones. Plants do, too, but they lack a nervous system. Identify some plant hormones and determine what plant systems they influence.

%d bloggers like this: