Biomedical Ephemera, or: A Frog for Your Boils

Apteryx spp. - The Kiwi

Aside from its obvious qualities, the kiwi bird is surprisingly unique in general. Where flighted birds have hollow bones to conserve weight, kiwis have bone marrow, akin to mammals. They have no keel on the breastbone (to be expected with such nubby wings, as the keel is there to anchor wing muscles), no tail, and a weak gizzard.

Most of the unique traits of the kiwi evolved to allow the bird to fill ecological niches that were open on the New Zealand islands, owing to the lack of mammalian species. The diet, behavior, and even sense of smell are all directly tied to filling in the niche of terrestrial insectivore. Other notable oddities about the kiwi are the cat-like whiskers around their beak and the massive size of their eggs: the bird itself is the size of a chicken, but can lay eggs over six times as large - one quarter the weight of the adult female.

Wild life of the world: a descriptive survey of the geographic distribution of animals. Richard Lydekker, 1915.

Pitohui variable (now Pitohui kirhocephalus) - The Variable Pitohui

Though all pitohuis have been found to have at least some level of toxin in them, the variable pitohui and hooded pitohui have by far the highest and most consistent levels of it, both in their bodies and throughout their feathers.

The toxins carried by the pitohuis aren't actually produced by them - like the Columbian poison dart frog, they acquire the toxin from their food sources. Actually, the chemical makeup of their toxin is almost identical to that of the poison dart frogs. They secrete neurotoxic alkaloid compounds known as batrachotoxins. These toxins are lipophilic, and can permeate unbroken skin. They bind to nerve cells, and basically "break" them - they open up the sodium channels in the cells (permanently depolarizing them) so that the nerves can no longer fire, and a flaccid paralysis ensues.

Bizarrely, the tetrodotoxin of the pufferfish may be a possible "treatment" for batrachotoxin-induced paralysis. Tetrodotoxin is non-competitive with batrachotoxin (meaning it wouldn't be trying to bind to the same part of the cell, and wouldn't have to remove the batrachotoxin first), and causes an extreme tetanic (stiff) paralysis, because it causes nerve cells to enter a state where they're permanently firing and can't stop.

Well, toxin or not, no deaths due to the pitohui have ever been recorded. The Papuan natives see pitohuis as "rubbish birds" because of their toxins, and avoid hunting them. Surely a few natives or explorers have died eating them in the past, but they aren't an active threat to anyone.

The birds of New Guinea and the adjacent Papuan Islands. R. Bowdler Sharpe and John Gould, 1875-1888.

"Faisan Huppe de Cayenne" - aka The Hoatzin

Though being very pheasant-like and looking quite meaty, and being far from an ugly bird, the hoatzin has managed to keep its unique and fascinating lineage alive, much more than the other birds in its territory. While the South American tropical birds are often poached, encroached upon, taken for pets, or used for plumage, these guys are only ever killed in complete desperation.

Why's that? Well, despite looking big and meaty, most of their innards are not at all delicious. The hoatzins eat green leaves and vegetation, and their crop is a giant fermenting chamber! It's much larger than most birds, and the stench of fermentation gives them an overall stank of manure and rot. They're known as "stink birds" by locals (and many biologists who have to study them), and the smell doesn't go away after they're killed and gutted. The meat has a boar-taint kind of taste, and the stink even permeates the feathers.

Well, that's one way to avoid extinction.

Histoire Naturelle des Oiseaux, planches enluminees. Comte de Buffon, 1765-1776.

Opisthocomus hoazin - The Hoatzin

This newly hatched hoatzin chick has something that other birds don't - clawed forefingers, giving it the ability to ascend trees with surprising dexterity, long before it's able to fly.

During breeding season, hoatzin adults are somewhat gregarious, and their nesting areas are prime targets for predators. As the adults don't have any significant defenses other than distraction tactics, when a nest site is attacked, they fly around noisily and try to draw the attention of the predators. Being almost the size of pheasants, they generally aren't attractive targets for eating, but the chicks are.

As the adults distract the predators (or attempt to), the hatchlings dive into the waters of the seasonally-flooded forests below, and scoot beneath the surface to hide. This is when those over-sized feet and clawed forefingers come in handy: after scooting away, when the danger passes, the chicks can climb back up the trees to their nest! The somewhat clumsy flight of the adults is extremely non-conducive to flying down to water-level to rescue offspring, so this trait of the chicks has helped keep the species alive, despite "panic" situations being not uncommon.

It's worth noting that while the bird bears a striking resemblance to Archaeopteryx in its skeletal form, the claws are not a retained trait from its ancestors. In fact, the direct ancestors of all gamebirds had relatively normal wings, and this is a "new" adaptation, probably an atavism from the ancient lizard-like genes still present in its DNA.

[Photograph by J. Arthur Thompson, British Guiana, 1922]