Worm Salad

December 7, 2008, 6:25 pm
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Sorry about not blogging. I know I made a promise to post, and broke it just as quickly, but real life has a habit of interfering with my best intentions. Expect the next post in my awesome reptiles series later today, but, in the mean time, I offer you this picture of my baaaaaby blood python as a way to make things right.

Branwen, originally uploaded by Lady Shmee.

Remarkable Reptile #7
December 4, 2008, 9:02 pm
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I will admit that I am a sucker for snakes. They’re fascinating, they’re venomous (at least some), they’re beautiful, they’re diverse, they’ve invaded a huge variety of habitats and occupy a surprisingly large niche space, they have a great mythological association; basically, snakes are pretty darned cool animals, and they managed this huge extent of awesome all without legs. I actually gave a presentation in my evolutionary developmental biology class yesterday on how snakes lost their legs, and while I might blog that later, this post is yet another entry in my remarkable reptiles countdown.

And so, today’s post starts with a reminder that snakes aren’t the only lizards that have lost their legs. In fact, leg loss seems to be a common thing in lizards, from the very primitive to the derived. From amphisbaenians to blind lizards to skinks, legless lizards come in all shapes, sizes and phylogenetic contexts. Really, it’s pretty amazing that this trait has evolved so many times over so many groups. It’s a trait that, in legless lizards, at least, seems to have evolved in conjunction with a burrowing lifestyle, although there’s still some pretty heated scientific controversy over whether the earliest snakes lost their limbs in order to become better swimmers or better burrowers (although the developmental and genetic context for that loss is actually pretty well understood; ask me about that sometime).

Ophisaurus apodus by brian.gratwicke on flickr

Ophisaurus apodus, the scheltopusik

The lizard above is one of my favorite legless lizards, and it’s a pretty good representative of what a standard-issue legless lizard looks like. He has eyelids and ear openings, unlike a snake, and is a substrate-burrowing insect-eater. (I have to admit, though, his scientific name does tickle my fancy: it literally translates to ‘snake-lizard without legs.’) So, if this boy is ordinary what kind of a legless monster would earn his place on my countdown? Read on to find out about a different kind of legless lizard… Continue reading

Remarkable Reptile #9
December 2, 2008, 7:58 pm
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Today, we’re staying in snakes, but we’re going to look at the evolution of a really hot-sauce characteristic in the group: venom. Venom is probably the reason that people have such an irrational fear of snakes, and is also one of the most intriguing of the features found in snakes. Of course, there are other venomous reptiles — the beaded lizards and gila monsters are the best-known venomous lizards, and venom has been implicated as one of the reasons, in addition to massive bacterial load, that the bite of komodo dragons is so devastating (Incidentally, if anyone wants to buy me a pet gila monster, I wouldn’t say no.)

Snakes use their venom for both prey capture and defense — it’s utility in each is fairly obvious: as a defensive mechanism, it is enormously effective in deterring a would-be attacker by killing them or causing fairly excruciating pain, while in prey capture, venom subdues the prey and begins the digestion process in the snake. Both uses are very well-documented in venomous snakes, but the question remains: which came first, the chicken or the egg? Or, in this case, what is the primary purpose of venom? What did it evolve for? And if one of those functions disappears, will there still be selection pressure to produce venom?

To answer this question, we’re turning to a fascinating group of snakes: the sea snakes. Snakes make up about eighty percent of marine reptile life (the other twenty percent consists of sea turtles and the saltwater crocodile). The true sea snakes, or Hydrophines, make up the majority of that salt-water snake diversity. These animals are highly specialized, with salt-excreting glands, paddle tails, and, most importantly for our purposes, an incredibly strong neurotoxic venom. The vast majority of these snakes are fish hunters, which accounts for the potency of their venom — in order to subdue fish prey, and to keep it from being stolen or swimming away, their venom has to be very fast-acting indeed. So, while these snakes are, for the most part docile, they are far from harmless and can easily kill an adult human.

Photo by richard ling on flickr, used under a CC license

A close-up of the olive sea snake.

The olive sea snake, shown above, is a pretty typical Hydrophine snake. So, why do sea snakes make my remarkable reptiles list? And what do they have to do with venom evolution? To find out the answer to that question, read on. Continue reading

Remarkable Reptile #10
December 2, 2008, 5:01 am
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I have always been a fan of island  biogeography and one of my big passions in biology are the weird things that animals do on islands. From giant flightless birds to enormous tortoises to pygmy elephants, the variety of life on islands never ceases to amaze me. And while the science has its practical uses, beyond initial wonderment and amazement, from predicting alpine responses to climate change to managing wildlife preserves, my fascination with islands still stems primarily from their wondrous diversity of life.

(Incidentally, if this description of a fascinating science has piqued your interest at all, may I recommend David Quammen’s The Song of the Dodo to you?¬† It’s a really remarkable, well-written look at the scope of the science, and its practical implications, and while I may hold reservations about some of his assertions, it’s still a very good book.)

And so, we start my look at remarkable reptiles with one species that really exemplifies the magnificent and diverse beauty of islands — the common boa, Boa constrictor.

The subspecies that you’re probably familiar with is the one sold in pet stores across the world; the Colombian red-tailed boa, a locality specimen of B. c. imperator. With their charming disposition and fairly impressive size of up to about nine feet, they are an instantly recognizable snake. But, just in case you’ve never seen one, here’s a picture of one of these mainland beauties:

Mainland Colombian Boa, showing typical coloration

Mainland Colombian Boa, showing typical coloration

So, if you’re interested in what these beauties do when they get onto islands, read more after the jump. Continue reading