Saturday, July 26, 2008

You're an Ugly Mole: the cryptic lifestyle of Notoryctes typhlops

As we all know, Australian mammals are shameless media tarts. But not marsupial moles. Marsupial moles live in the central Australian desert. Because they are rare and live underground, almost nothing is known about their behaviour or life cycles.

As you can see from the pictures, they look just like Mr. Mole from Wind in the Willows, if he was an albino with a backwards-facing pouch and no eyeballs.

Marsupial moles' underground lifestyles have made sight unnecessary, so over many generations their eyes have degenerated. They have small lenses left in their skin where their eyes would originally have been. They also have no external ears.

Anyone who has ever worn a pair of girls' togs to the beach would know about that annoying pocket-like bit in the groin that seems especially designed to fill up with sand. Marsupial moles don't have this problem. The entrance to a marsupial moles' pouch faces backwards so that when the mole burrows through sand, its pouch is not filled up with grit.

Friday, July 25, 2008

Stop, or my Epitoke Will Shoot!: Polychaete Reproduction

Sexual reproduction can be a bitch. The medical expenses, the ballooning uterus, the risk of disease. When it comes to reproduction without the hazards, polychaete worms have it made.

Polychaetes (pronounced poly-keets) are a type of annelid, and so are related to earthworms and leeches. They live in the ocean, and often have spectacular facial tentacles. Some are free-living, while others live in tubes and have fan-like tentacles to catch food. Ancestral earthworms probably resembled free-living polychaetes, but they lost their tentacles when they moved onto land and started burrowing underground.

If you were one of a few peculiar species of polychaete, having a baby would be a breeze. The hard work would be done for you by a specially adapted clone. At a certain point in your adulthood, you would notice a small version of yourself sprouting from your rear end. This individual would be your 'epitoke'. You would referred to as the 'atoke'.

You may have several epitokes joined in a line behind you. They would be genetically identical to you, but have features that would make them better suited to sexual reproduction. Polychaete epitokes have specialised structures for swimming. Their guts degenerate to make room for vast quantities of eggs or sperm. In human terms, your epitoke would be just like you, but with perkier breasts, a larger penis, wittier conversation and a better car.

When they were large enough, your epitokes would break off from your body and swim up into the ocean. They would brave predation from other animals (or the humiliations of the speed dating scene) in order to release what are genetically your sperm or eggs into the water. You could stay at home watching television and making cups of tea, knowing that a superior version of yourself was out doing all the hard work. With any luck, the ocean would soon be filled with your larvae, even though you had no hand in producing them directly.

And if your epitoke was eaten by a fish (or limped home emotionally crippled from a failed marriage to someone who turned out to be a lady-boy) you could always sprout another one.

Polychaetes are not the only animals to bud off a clone of themselves for sexual reproduction. In some classes of jellyfish, the jellies you see floating in the ocean are only half the story. They have budded off a body form known as a polyp, which is attached to the bottom of the ocean. The floating form of the jellyfish is called a medusa. It's the sexy one. Like the epitoke, it goes around releasing sperm and eggs into the water. Polyps prefer to stay in.

If you want to make this interactive, perhaps we can all take a moment to ask ourselves: in the great ocean of life, am I an atoke or an epitoke? Actually, maybe not. I enjoy anthropomorphism as much as the next person, but sometimes biology hits a little too close to home.

Thursday, July 24, 2008

My Cousin is a Slime Mould OR Phylogenetic Relationships With Particular Attention to Homo Sapiens

The most exciting thing about biology is discovering who you are related to. My human ancestors are a supremely undistinguished bunch of agricultural labourers. My animal, plant, fungal and protistan relatives are a lot more exciting. 

Knowing who your relatives are is useful for serious scientific endeavours like working out how closely you are related to your pet. For example, Romy is more closely related to Coalface (a rabbit) than I am to Gerald (a llama). 

It's also possible to work out how closely you are related to  your meal. Obviously, I am more related to the cheese I ate for lunch (derived from a cow, a fellow mammal), than to the tuna I ate yesterday. I am less related to the mushrooms I will eat tomorrow, but more closely related to them than I am to the seaweed I ate in a noodle soup the other week. I am probably more closely related to the seaweed than to the broccoli I ate the other day. I am only distantly related to the bacteria in yoghurt, which makes me think that moving onto a a high-bacteria diet is the only way to end all this disgusting cannibalism. 

I'd like to show how we are related to everything,  but I'll start close to home. Here's a picture of all the mammals (or maybe not, I can't seem to get pictures to stay up). You can read the tree like you would a human family tree, with the branches representing divergence from a common ancestor. The closer we are on the tree, the more closely we are related. 

Humans are over with the apes and monkeys in PRIMATES. As you can see, our closest relatives are not clever elephants, graceful antelope, or generous organ-donating pigs, but TREE SHREWS. There is a tree shrew in the Melbourne museum. It looks like a rat. Our next closest cousins are bats and gliding lemurs. Thankfully, primates are only distantly related to the CETACEA (whales and dolphins). You already know how I feel about those guys.