They are the best of beings; they are the worst of beings. They are animals; they are plants. They are saviors; they are killers. They are predators; they are parasites. They are, in short, dinoflagellates — a large, diverse and eccentric group of (usually) single-celled organisms that are as celebrated as they are feared. And I hereby nominate them for Life-form of the Month: January.
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Some dinoflagellates have eyes. Others give off light. Some, like plants, make energy from the sun; others, like animals, capture and eat their prey. Some do both. Funky.
But even if you’ve never seen a dinoflagellate and wouldn’t recognize one if it waved its flagella at you, you’ve probably come across them, for they impinge on our lives in two important ways, one good, one bad.
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Most dinoflagellates are small — you need a microscope to see them — and even the biggest ones are no bigger than a piece of caviar. But they have gigantic genomes. Some dinoflagellates have genomes containing around 67 times more DNA than the human genome, and 10 times more than the most extravagantly endowed plants. That’s colossal. (Note that lots of DNA doesn’t necessarily mean lots of genes; in terms of gene numbers, it remains to be seen if dinoflagellates are exceptional.)
Even more peculiar is the way they store their DNA. The usual way is to wrap it around molecular spools known as histones. Dinoflagellates don’t have histones. Instead, their genome appears to exist as a liquid crystal matrix. Wackier still: dinoflagellates have unconventional DNA. In most organisms, DNA is composed of the molecules adenine, guanine, cytosine and thymine. Dinoflagellates often replace thymine with something called hydroxymethyluracil. It’s all most bizarre.
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