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Planaria |
Classification:
Kingdom: Animalia
Subkingdom: Eumetazoa Superphylum: Platyzoa Phylum: Platyhelminthes Class: Turbellaria Order: Seriata Suborder: Tricladida Family: Planariidae Genus: Dugesia Species: Dugesia polychroa Planaria chains! How to make them
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Flatworms of the family Planariidae are called "planaria". Most of them live in fresh water, and Dugesia polychroa are a common species in UK lakes and ponds. They're small, but not microscopic— they grow to around two centimetres long, so you can easily see them with your naked eye. These paper ones are even bigger than that to make it a bit easier to cut them out and make paper chains suitable for decorating your house or your tree! Real planaria are predators; they hunt and kill other animals for their food. Having located a tasty insect larvae or a tiny succulent shrimp, a planarian will pin down its prey and squirt some digestive enzymes from its mouth to soften it up. It then happily sucks up its meal. A planarian's mouth is about halfway down its body, and it uses the same opening to excrete waste after digesting its meal. It's pretty gross, really, so maybe it's best not to think about it too much. We apologize if we've put you off your lunch. One of planaria's specialities is regenerating their bodies without a problem if they're damaged. In fact, if they're cut in tiny pieces, each one can regenerate into a whole new worm. Unfortunately for them, this means they get used in biological experiments a lot, since we humans would love to find a way to help people who've been injured re-grow parts of themselves. They were also the subject of a famous experiment in the 1960s to do with how memory works. A biologist named John McConnell trained some planaria to run a maze, then ground them up and fed them to some other ones who'd never even been in the maze before. Incredibly, the untrained planaria who'd eaten the trained ones seemed to know how to navigate the maze! This might mean that their memories of the maze had been stored chemically in a way that could be transferred to other creatures, which would be pretty amazing. Unfortunately, no one else has ever been able to make this experiment work, so most scientists now think that McConnell made a mistake. But wouldn't it be cool if it were true?On the Web:
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