Deepest ctenophore

Two ctenophores were observed at a depth of 10,040 m (33,939 ft) by the submersible DSV Limiting Factor in the south-west Pacific’s Kermadec Trench in February 2022, as part of the “Ring of Fire” scientific expedition. This increases the previous known depth for a ctenophore by 2,823 m (9,261 ft). It was not possible to fully identify the specimens, which were globular with lengthy, filamentous tentacles. The findings were reported in a comprehensive study into extreme depths of marine species in all five oceans, based on hundreds of observations that took place between 2021 and 2022. It was published in the journal Marine Biology in March 2023.

Sometimes known as "comb jellies", ctenophores have eight rows of fused cilia (slender sensory organs) arranged along their sides. Although their jelly-like mass makes them superficially similar to jellyfish, the two are not closely related and belong to separate phyla: Ctenophora and Cnidaria.

The revelation of a new deeper extent for a ctenophore appeared in the study Maximum depth extensions for Hydrozoa, Tunicata and Ctenophora. Its authors are deep-sea marine biologists Alan J Jamieson, Dhugal J Lindsay and Hiroshi Kitazato.