How Would a Filter-Feeding Marine Turtle Feed?
Back home, many large planktivores have ingenious ways to trap food and not water. For sharks like the basking and the megamouth, that is no problem, as they have modified their gills into rakers to separate food from water. But whales, being air-breathing mammals, have to be more innovative. That is where this neat little piece of cetacean anatomy called "baleen" comes into play. It works by a whale opening its mouth underwater and taking in water. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food source for the whale.
Now in this alternate Earth, there are no mysticete whales, whale sharks, basking sharks or megamouth sharks. In their place are large, completely marine turtles. They are still reptiles, which breathe air, so they can't have gill rakers like sharks. Nor, for that matter, could they swallow saltwater. And being turtles, they don't have teeth, so they can't have anything to modify into baleen. So in an alternate Earth where turtles take on the niche of oceanic ram feeders, how would they collect food without choking on seawater in the process?
This post was sourced from https://worldbuilding.stackexchange.com/q/136897. It is licensed under CC BY-SA 4.0.
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Real World (TM) sea turtles might not have teeth, but they do have esophageal papillae that are quite gruesome to look at, but help the turtle snare and consume jelly fish. These hard, spiky projections are made of keratin, similar to baleen. As the link mentions, the turtle does ingest a little water with its jellyfish diner, and uses these projections to keep the jelly in place "as the turtle uses the muscles in its throat to expel excess salt water."
Modifying these papillae into plankton filters is an evolutionary no-brainer.
This post was sourced from https://worldbuilding.stackexchange.com/a/136902. It is licensed under CC BY-SA 4.0.
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