Jellyfish Found by Team Aboard NOAA Ship Okeanos Explorer Shatters Range Assumptions
In a new study, scientists examining a deep-sea jellyfish collected by a team aboard NOAA Ship Okeanos Explorer have changed what we know about the animal’s habitat and relatives.
Download largest version (jpg, 930 KB)
The story of this discovery begins with the deep-sea jellyfish genus Botrynema, whose shape some have compared to a swimming lampshade. Since the 1940s, it was generally believed that Botrynema could be divided into two species: One with a large “knob” on top of its body (Botrynema brucei) and one with no knob (Botrynema ellinorae). B. brucei was held to live in deep waters all around the world, while the knobless B. ellinorae was thought to be restricted to waters near the arctic. That distinction was clear and simple, but was ultimately shown to be incorrect. Recent work by scientists arrived at two findings that challenged the knob/no knob species division:
-
- Genetic testing showed no clear species distinction between B. brucei and B. ellinorae, causing the researchers to suggest reclassifying B. ellinorae as the subspecies B. brucei ellinorae.
- Some specimens that genetically belonged to B. brucei ellinorae had knobs on top of their bodies, just like other B. brucei. Therefore, the presence of a knob could not be used to tell the northern subspecies apart from its relatives.
These discoveries naturally led to an opportunity: Since it had long been assumed that the ellinorae subspecies had no knobs, ellinorae with knobs could easily have been seen outside of the arctic in the past and mistaken for B. brucei. If an ellinorae could now be found and confirmed with molecular analysis further south, it could massively expand the known range of this strange subspecies.
Download largest version (jpg, 930 KB)
That opportunity arrived in the form of NOAA Ocean Exploration’s Windows to the Deep 2019 expedition. Using remotely operated vehicle Deep Discoverer, the exploration team aboard NOAA Ship Okeanos Explorer was able to collect a jellyfish with a knob at 999 meters (3,300 feet) below the ocean surface near Florida. As revealed in the new paper by Montenegro et al., that specimen was discovered to belong to B. brucei ellinorae– thousands of miles from its previously known arctic and subarctic habitat.
How did this northern subspecies make it so far south? More research is needed, but the authors suggest that B. brucei ellinorae with knobs may have been carried away from high latitudes by the Atlantic Ocean’s Deep Western Boundary Current. Running down the coast of North America, this deep-ocean water mass could have helped B. brucei ellinorae slowly drift to new habitats.
Other intriguing questions remain: Why is the knobless form of B. brucei ellinorae found only in the far north, while those with knobs are found both in the arctic and around the world? What evolutionary purpose does the knob serve in the first place? Montenegro et al. suggest a couple of ideas. A current called the North Atlantic Drift may block ellinorae without knobs from exiting subarctic waters while letting those with knobs through. Knobs may also serve a defensive purpose against predatory jellyfish like those in the genus Solmissus, which are more commonly found further south.
Finding conclusive answers to these questions will require scientists to learn more about B. brucei. In the meantime, this latest discovery by Montenegro et al. is a valuable reminder that the simplest answer to a question isn’t always the right one– and that challenging assumptions in science can lead to unexpected discoveries.
This new study was led by Javier Montenegro of the Minderoo-UWA Deep-Sea Research Centre of the University of Western Australia. It was co-authored by Jessica Kolbusz, Yakufu Niyazi, and Alan J. Jamieson (all also from the Minderoo-UWA Deep-Sea Research Centre) as well as Joan J. Soto-Angel and Aino Hosia of the University Museum of Bergen, Allen G. Collins of the National Systematics Lab of the NOAA Fisheries Office of Science and Technology, and Dhugal J. Lindsay from the Institute for eXtra-cutting-edge Science and Technology Avant-garde Research (X-STAR) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
Montenegro et al (2025) An unexpected journey – the arctic deep-sea halicreatid trachymedusa Botrynema brucei ellinorae off Florida: a reassessment under an integrative taxonomic approach. Deep Sea Research Part I: Oceanographic Research Papers 223. Access the full article online.