The Repository Abyss Report: Into the Dark

The Viral Deep-Sea Jellyfish Still Has No Species

September 30, 2026 · Runtime 22:22 · Watch on YouTube

In April 2016 a NOAA robot filmed a jellyfish hanging motionless at 3,750 metres on an unofficially named seamount south of Guam, and the video went around the world. It has a genus, Crossota. Ten years later it has no species. We ran the published species key on the footage itself, question by question.

Chapters

  1. 0:00 A jellyfish at 3,750 metres
  2. 0:43 The second jellyfish, and the dive
  3. 1:28 Enigma Seamount, and the rock it was sent for
  4. 2:09 Down to 3,778 metres
  5. 2:47 Balls of mud nobody could name
  6. 4:01 Gromia, a guess with no sample
  7. 5:39 22:49 UTC: what is that?
  8. 6:40 A jelly standing on the floor
  9. 8:14 The first rock, and a family name
  10. 8:51 The things with a name
  11. 9:52 Up the valley
  12. 10:29 00:16 UTC: the jellyfish that went viral
  13. 11:40 An ambush pose, seen from above
  14. 13:01 Four records, four levels
  15. 13:38 Never-before-seen, and a family that is gone
  16. 14:14 What makes a Crossota
  17. 14:53 Five species, and Crossota species A
  18. 15:29 A type specimen without tentacles
  19. 16:10 The key, question one
  20. 16:47 Our measurement: where the gonads sit
  21. 17:19 Colour under the robot's lights
  22. 18:01 Counting tentacles
  23. 18:38 Why a video cannot finish the key
  24. 19:32 What the robot did collect
  25. 20:26 Sixteen hours back up
  26. 21:03 What would close the case
  27. 21:40 The record, and next time

Transcript

A jellyfish at 3,750 metres 0:00

Thirty-seven hundred and fifty metres down, south of Guam, a jellyfish hangs perfectly still. Its long tentacles are spread out like the spokes of a wheel. In twenty sixteen, this video went around the world. Ten years later, the animal in it still has no species name. It has a genus. NOAA called it Crossota. The coverage called it never-before-seen. In this episode we take the published key to the species of Crossota, and we run it on the video itself, question by question. Every moving picture is NOAA footage from that one dive. Every number comes from the dive record, a paper, or our own measurement.

The second jellyfish, and the dive 0:43

And there is a second jellyfish. The same robot filmed it on the same dive, eighty-six minutes earlier, sitting on the mud. It is in the public archive, under a family name that is no longer used. The ship's daily update mentions one beautiful jellyfish. The archive has two. The dive is EX sixteen-oh-five, leg one, dive four. NOAA Ship Okeanos Explorer puts two vehicles in the water together. Deep Discoverer is the robot, with the arms and the main camera. Seirios hangs above it, lights it, and films it from above. The expedition is exploring the Mariana Trench Marine National Monument and the waters around it.

Enigma Seamount, and the rock it was sent for 1:28

The site is about two hundred and twenty kilometres south of Guam. On the chart it is Enigma Seamount, and the name is not official. The ship's own daily update explains it. It was given that name because we don't know much about it. Its shape is rounder and rougher than the flat-topped seamounts around it. The reason for the dive is rock. The sea floor to the north-east is Pacific Plate, from the Jurassic. This seamount may sit on the boundary with a much younger plate. Rocks from its flanks can be dated. So the plan is simple. Land near the base, drive eight hundred metres up the slope, and bring back rock.

Down to 3,778 metres 2:09

The robot goes in at twenty twenty-six UTC on the twenty-third, which is early morning on the twenty-fourth in Guam. The archive files everything under UTC, so that is the date on every clip you will see. The descent takes two hours and seventeen minutes, through open water full of salps. At twenty-two forty-three the robot touches down, at the foot of the seamount. Sediment, and loose volcanic rocks, many of them dark with manganese. The temperature is one and a half degrees. Almost at once, the cameras pick up something that nobody on the ship can name.

Balls of mud nobody could name 2:47

Small round balls, the colour of the mud, lying everywhere, in large numbers, between the rocks and under them. The dive summary says the team kept seeing them for at least an hour and a half before anyone offered a name. The name was a guess. Gromia sphaerica, or a close relative.

Gromia, a guess with no sample 4:01

Gromia sphaerica is a single cell, up to the size of a grape. In twenty oh eight, a team found it off the Bahamas, collected it, and confirmed it by DNA. The cells were rolling across the mud and leaving tracks up to half a metre long. On this dive, the summary still hedges. It might be an amoeba. It might be a sponge. None of those balls came up. The sample list for this dive has five lines, and none of them is a ball of mud. So the first unnamed thing on Enigma Seamount stays a guess, written down with the word tentatively in front of it. It will not be the last.

22:49 UTC: what is that? 5:39

Six minutes after touchdown, twenty-two forty-nine and thirty-five. Thirty-seven hundred and eighty-three metres. The camera is looking for a rock, and a small orange dome comes into the frame, sitting on the mud. Listen to the room.

A jelly standing on the floor 6:40

The jellyfish is not swimming. Its bell is lifted off the sediment, and its long tentacles reach down and out, touching the floor like the legs of a stool. The bell is striped with dark lines, which are its radial canals. The robot moves closer, and it does not react. The biologist on the line goes through a field guide, and then says where the guess came from. A similar animal, at about the same depth, in the eastern Pacific. And a family name, borrowed from a jellyfish specialist. Here is the whole thought, as it was said.

The first rock, and a family name 8:14

And then the dive moves on, because the dive is about rock. Seventeen minutes later the arm closes on the first sample, a manganese-coated stone at thirty-seven hundred and eighty-one metres. It gets a sample number, a time, a depth, and a temperature. The jellyfish gets a line in the annotation log. In the archive, that line is still the only written identification this animal has. Trachymedusae, which is the order. And Aglanthidae, which was meant as the family. Keep that second word in mind. It turns out to matter.

The things with a name 8:51

Here is what the robot did find with a name. A drinks can, lying on the sediment at thirty-seven hundred and eighty metres. A plastic bag near it. The dive summary's photo caption puts it better than we could. Unknown spheres on the seafloor, as well as a can. Two of the most definitive objects observed.

Up the valley 9:52

The robot drives on, up the centre of a small valley. Scree, pebbles, fine sediment swept away in places by a current. The summary notes that animals were scarce, and offers a reason. Low currents mean little food arriving for the things that filter it from the water. What there is, is strange enough. Polychaete worms swimming above the floor. A glass sponge on a stalk. A squat lobster in a crack in the rock. Deep red shrimp standing on long thin legs. Each one annotated by the room, with a name to the level the video allows.

00:16 UTC: the jellyfish that went viral 10:29

At six minutes past midnight, the second rock. Thirty-seven hundred and fifty-four metres, a rounded stone with a manganese crust. Sample number two. The robot keeps climbing, and ten minutes later, over broken rock, something comes down into the lights from above. Zero sixteen and sixteen UTC. Thirty-seven hundred and fifty metres. A second jellyfish, and a completely different one. It is not on the floor. It is hanging in open water over the rocks, and it is not moving at all.

An ambush pose, seen from above 11:40

NOAA's caption describes what you are looking at. The long tentacles are even, extended outward, and the bell is motionless. That suggests an ambush predator, waiting for something to swim into its net. Then the camera closes in above it, and looks straight down through the bell. The bell is clear, so from above you can see its plumbing. Red radial canals run out from the centre. The same caption says the bright yellow bodies along them look like the gonads. Around the rim, two kinds of tentacle, short and long. Every detail you need for the rest of this episode is in this one view.

Four records, four levels 13:01

The next day NOAA posted forty-two seconds of this, edited, in full high definition. That is the clip the world saw. The raw file in the archive is a hundred and ninety seconds, at lower resolution, and the animal is in frame for almost three minutes. So this animal has four written records, and they do not agree on how far the name goes. The archive annotation says Crossota, a genus. The dive summary says Rhopalonematidae, a family. The public caption says genus Crossota. And the coverage said never-before-seen.

Never-before-seen, and a family that is gone 13:38

Australian Geographic called it a strange, glowing jellyfish, never seen before. The ship's caption never used either word. There is no glow in this footage. Every photon in it comes from the robot's own lights. Now back to that word from the first jellyfish. Aglanthidae. In the World Register of Marine Species, Aglanthidae is listed as unaccepted. It is an old family name, from eighteen seventy-nine, and it is filed today under Rhopalonematidae. The same family as Crossota.

What makes a Crossota 14:14

So the dive filmed two jellyfish, eighty-six minutes apart. One went viral with a genus. One went into the archive under a name the register no longer uses. Both belong to the same family, and neither of them has a species. The question is why a camera cannot finish the job. Start with what the genus means. In the paper we are about to use, a jellyfish is Crossota if its gonads hang down like pendants, its bell has furrows on the outside, it has no stalk under the bell, and its ring canal has no branches running inward. Those are features you can see.

Five species, and Crossota species A 14:53

The World Register lists five accepted species of Crossota. Two were named in nineteen oh two. Two in nineteen thirteen. And one in two thousand and three, which is the one that tells us how a new species of this genus actually gets made. It started as Crossota species A. That is what it was called in a paper in nineteen ninety-two, and it kept that letter for eleven years. It was a deep-water animal, caught in trawls off California and Hawaii, below a thousand metres. Everyone who worked on it knew it was new.

A type specimen without tentacles 15:29

It became Crossota millsae in two thousand and three, in the journal Zootaxa, described by Erik Thuesen. The type specimen is a female, seventeen millimetres tall, collected by the robot Tiburon at twenty-five hundred and forty metres off Monterey. It is kept at the Santa Barbara Museum of Natural History, under a catalogue number. And the paper says something that matters here. All adult specimens lost their tentacles in the net. The trawl brought up bodies without tentacles. One animal collected by the robot shed its tentacles in the sample chamber while the scientists watched. The tentacles sank to the bottom.

The key, question one 16:10

The paper also prints a key to the four species of Crossota found in the Pacific. A key is a list of questions, answered in order, each one splitting what is left in two. It is the tool a taxonomist uses to decide. We are going to put our jellyfish through it. Question one. Are the gonads nearer the ring canal, at the rim of the bell, than the manubrium, the mouth tube in the centre? And is the umbrella colourless? If both are yes, it is Crossota alba. If the gonads sit close to the centre and the umbrella is pigmented, go on.

Our measurement: where the gonads sit 16:47

The camera can try the first half of that. We took two frames from NOAA's high definition clip, where the camera looks straight down through the bell, and marked the rim, the base of the manubrium, and each yellow gonad. In both frames the gonads sit about sixty percent of the way out, from the base of the manubrium toward the ring canal. Nearer the rim than the centre. By the first half of question one, that points to alba. It is a rough reading, from video, of a bell seen at an angle.

Colour under the robot's lights 17:19

The second half is colour, and alba's umbrella is colourless. This bell reads orange and amber, with red canals. But the only light at this depth is the robot's own. Colour on video is a property of the lamps and the camera as much as of the animal. So question one comes back with two answers. Question two. Are the gonads about halfway between the manubrium and the middle of the radial canal, with a burnt tangerine umbrella? That is Crossota millsae. Its canals and gonads are pink to lavender. Ours are red and yellow, and our gonads sit further out. It does not read as millsae either.

Counting tentacles 18:01

Question three splits the last two by counting. Two hundred to two hundred and fifty tentacles in one row is Crossota rufobrunnea. Six hundred or more, apparently in several rows, is Crossota brunnea. So we counted what the video lets us count. Around the bell, in three frames, we can count between about twenty and thirty long tentacles. NOAA's caption says there are two sets, short and long. The short ones are a fringe at the rim, and at this range they cannot be separated. The key wants hundreds. The camera sees thirty.

Why a video cannot finish the key 18:38

And that is the trap in one sentence. The net brings up the body without the tentacles. The camera shows the tentacles, and cannot count them, and cannot turn the body over under white light. Each method answers the questions the other one cannot. One line in the paper shows what a new species looks like inside a key. Crossota millsae, it says, fails at the second couplet, and falls between the two options. Failing the key is how Thuesen knew. But he was failing it with specimens in a dish. Our jellyfish fails at the first question. That could mean it is a species nobody has described. It could equally mean the video is misleading us, on colour, or on where the gonads sit in a bell that is tilted and contracting. A video cannot tell those two apart. A specimen can.

What the robot did collect 19:32

The robot did collect animals that day. At zero thirty-six, a primnoid coral, at thirty-seven hundred and thirty-six metres. At two sixteen, a second one, higher on the slope. Corals are fixed to the rock. You can cut them with an arm and put them in a box. Later in the dive the pilots filmed tracks in the sediment, and someone on the ship labelled that clip with a single word. Tracks. Nothing in the record says what made them. We are not going to say it either. It is a picture of a question, and it goes into the archive as one. The geology got its material too. Near the end, the robot found pillow mounds at least ten metres high, and took a fresh piece of pillow basalt from right beside them. Three rocks and two corals. Five samples, five numbers, in the summary.

Sixteen hours back up 20:26

Then the robot left the bottom, at two twenty-seven. After the dive, a mechanical problem with the sheave on deck meant it had to be reeled in at about fifteen percent of the normal speed. It came out of the water at eighteen sixteen. The dive lasted twenty-one hours and fifty minutes. So the robot spent almost sixteen hours hanging in open water, filming all the way up. Salps, squid, and more jellyfish, annotated clip by clip with the same code. JFH. Jellyfish. None of them more precise than that.

What would close the case 21:03

Here is exactly what would close the case. One specimen of this jellyfish, from anywhere it lives. Lay it flat and measure where the gonads are. See the umbrella under white light. Count every tentacle, including the stumps. Take a small piece for DNA. Then run the key again. Ten years on, NOAA's page for this video still says what it said in twenty sixteen. Scientists identified this hydromedusa as belonging to the genus Crossota. That sentence is accurate, and it is the honest limit of what a camera could say.

The record, and next time 21:40

What the record holds is two jellyfish, one family, one genus, and no species. It holds a room saying out loud that it had never seen a jelly sit on the floor like that. And it holds a can, with a sample list that never had room for the most famous animal on the dive. Next time, a limit. No fish has ever been seen in the deepest quarter of the ocean. In twenty fourteen, two of the scientists listed on this dive helped measure a molecule inside fish muscle that may explain why. It predicts a floor, at about eighty-two hundred metres. Next episode, the depth where fish run out.

Description and sources

EX1605 leg 1 dive 04 was a geology dive to Enigma Seamount, sent to bring back rock that could be dated. It brought back three rocks and two corals. It also filmed two jellyfish, 86 minutes apart: one sitting on the mud at 3,783 m, annotated live under Aglanthidae, a family name the World Register now files under Rhopalonematidae; and the famous one at 3,750 m, which the room called a rhopalonematid and NOAA's caption placed in the genus Crossota. The key to the Pacific species of Crossota (Thuesen 2003, after Kramp 1968) asks where the gonads sit, what colour the umbrella is, and how many tentacles there are. On two frames of NOAA's HD clip, our reading puts the gonads about 60% of the way out toward the rim, which points one way, while the colour under the robot's lights points the other; and the camera can count about thirty long tentacles where the key needs hundreds. C. millsae was recognised as new by failing that key, with specimens in hand; a video cannot tell a new species from a misleading picture.

PRINT-READY, FROM THIS CHANNEL

Read This Dive, Vol. 01 — the method, and five dives read with it

https://therepository.gumroad.com/l/read-this-dive

PRIMARY SOURCES

Abyss Report reads the deep ocean through the record that resolved it -- instrument, date, position and the primary sources above.

About the material. Every moving frame is NOAA Ocean Exploration video from EX1605 leg 1 dive 04 (23-24 April 2016 UTC), public domain, credited on screen with dive, depth and position; the high-definition shots come from NOAA's own edited release of the same encounter. Credits use the vehicle track's longitude, 144.78E, not the catalogue's 144.45E. Seven cuts drop the narration and play the original control room audio; each window was re-transcribed in isolation twice and used only where both passes matched. In one of them the first 23 seconds are muted: the recording there carries a faint tonal sound we could not rule out as music. Gonad position and tentacle count are our own rough readings. Every diagram is drawn in code from the sources listed.

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