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Weird Gramma here with “WeirdFins,” all about strange stuff in the sea, and brought to you by the National Oceanic and Atmospheric Administration. And, boy, how strange is this: Sponges that are carnivores, that is, they eat meat! Most of these sponges were only recently discovered in deep oceans and off Alaska’s Aleutian Islands, but some live in shallow underwater caves in the Mediterranean Sea. These are habitats that don’t have many nutrients in the water, so this adaptation is a pretty nifty way of making sure to get lunch.
Now, sponges can be really colorful and pretty, but they’re quite primitive animals and don’t have a stomach or digestive system like most other animals. So most sponges feed by sifting bacteria and other tiny particles in the water through many tiny openings. The particles break down into molecules which are then just absorbed into the sponge’s cells. But not carnivorous sponges! When a tiny shrimp or other invertebrate (the animals without backbones) swims by a carnivorous sponge, the meat-eater throws out teensy fishing lines with hooks that act like Velcro to entangle the prey. Then new sponge tissue grows around the lunch item, which is broken down by bacteria and chemicals called enzymes, and the nutritious particles are absorbed by the individual cells of these Spongezillas.
All the meat-eating sponge species are pretty small, most of them about the size of your pencil eraser, but the things they eat are often twice their own size and can take awhile to digest. It usually takes you a couple of hours to digest your cheeseburger and fries—a little longer if you throw in a shake—but it can take carnivorous sponges 8 to 10 days to finish off a shrimp dinner!
You can see these sponges on the National Marine Fisheries Service WeirdFins link at www.nmfs.noaa.gov.