New discovery! The blue angel sea slug hunts using the devil’s hand

by Tokai University
March 18, 2025

Blue sea slugs were believed to prey on the Portuguese man-of-war, which contains highly poisonous nematocysts, and uses the nematocysts for defense by incorporating them into the tips of its lateral projections, but the exact way in which it uses these nematocysts remained unclear.

By raising them in an aquarium and observing their behavior, it was discovered that blue sea slugs use their lateral protrusions like hands to capture and eat prey.

It was previously thought that the blue sea slug’s food was cnidarians such as the Portuguese man-of-war, but it has been discovered that it also preys on a variety of other species, including fish.

This suggests that the ingested nematocysts are used not only for defense but also for hunting, and it is hoped that previously unknown hidden food web links will be revealed.

The results of this research were published in Ecology.

Keep reading (in Japanese): https://www.tokai.ac.jp/news/detail/post_573.html

Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70062