... it's not a spit of material inside the body, or a siphon-blast directed on material lying around. The arms play a role.— Peter Godfrey-Smith (@pgodfreysmith) November 10, 2022
So we call it a jet-propelled throw. (Though we say in the paper: could equally be described as an arm-guided release of material propelled by the jet.) 2/ pic.twitter.com/THOGX8caiy
in Jervis Bay, Australia, unusually large numbers of one species — Octopus tetricus, better known as the gloomy octopus — gather...Though the researchers call the octopuses’ actions “throws,” Jervis Bay is not like a dodge ball court populated by eight-armed players; only in one case did an octopus fling a shell by straightening its arm the way a human would. There isn’t really a word for what the gloomy octopus does, Dr. Godfrey-Smith said. For instance, if an animal feels provoked by its neighbor, it will gather silt from the seafloor underneath its body and hold it there. When ready to fire, the thrower positions its siphon — the tubular organ used to pump water for swimming — underneath its body, which the study authors describe as an unusual stance. Then it will violently expel water to push the debris outward.