Seaweed crab/Japanese mitten crab. I don't really see the resemblance.
(So Messar's line about being seaweed doesn't make much sense, but in Japanese the crab's name is literally "seaweed scraps" or "seaweed scum." Kani is saying that he looks like scraps ie. an unwanted toy after his seams get ripped apart. Messar responds to that by saying that they're able to protect what's important to them because they're both scraps/scummy/expendable/however you want to put it. It's a callback to the debate about who should go to rescue Tonari and Bon, which was basically an argument about who was the most disposable.)














