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.

1 comment:

Romy said...

Oh, it's so exciting! I'm learning and laughing at the same time! I've seen these little guys with their facial tentacles in the sea and never thought they would be participating in such shady activity! The lazy buggers.