Researchers studying deep sea life in the southeastern Pacific Ocean saw amphipods riding on giant sea spiders in November 2024. The team published the finding earlier this month in Ecology, giving a direct view of an interaction the authors say is rare to observe.
The scientists used SuBastian to reach life thousands of feet below the surface along the Chilean margin. At roughly 10,000 feet, they saw a Colossendeis colossea carrying at least three Mesopleustes abyssorum amphipods on its body.
November 2024 sightings
Four days later, the team saw another Colossendeis colossea with amphipod passengers about 140 miles from the first sighting. In the paper, the researchers said sea spider hitchhiking among these crustaceans is likely a common occurrence, even though this study appears to be the first direct observation of these two species interacting this way.
That gap between likelihood and proof matters because the report separates a repeated behavior from a documented encounter. The earlier record from 1927 involved a Mesopleustes abyssorum attached to the same species of sea spider, and last year a study reported seeing a Mesopleustes abyssorum on a different kind of sea spider.
Ecology paper
The authors wrote that the interaction could be accidental, a way for a nonmobile species to disperse, or an adaptation to seafloor environments with scarce food resources. Those are three different explanations for the same ride: a stray attachment, a transport method, or a response to hard conditions on the seafloor.
A separate deep-sea species report from Naidely Valeria Vidaurre Quesada shows how limited deep-ocean observations can quickly turn into new species records when researchers get close enough to see them. Here, the key question left by the paper is simpler: why do Mesopleustes abyssorum amphipods ride on Colossendeis colossea sea spiders?
