In 2020, about 600 meters (2,000 feet) deep in an underwater canyon off the coast of Western Australia, scientists encountered a long, gelatinous creature suspended in a giant spiral. “It was like a rope on the horizon. You couldn’t miss it,” says Nerida Wilson of the Western Australian Museum. “It was so huge.”
It was a deep-sea siphonophore, a relative of the Portuguese man-of-war, or blue bottles, which danced like party balloons on the surface of the sea, trailing deadly tentacles through the water. This one was probably a new species of the genus Apolemya group that usually looks like tangled feather boas.
The spiral arrangement is known to be a feeding posture in these types of siphonophores. Numerous stinging tentacles create a wall of death in the water, trapping small prey including crustaceans and fish.
Finding it was one of the chance encounters that are common in deep-sea research. The scientists’ goal was to study life on the deep seabed, and they came across this floating jelly as their submersible made its two-hour transit to ship, the research vessel Falkor, then run by the Schmidt Ocean Institute. .
Screens in different parts of the Falkor transmitted live images from the submersible. Wilson describes how everyone on board was both mesmerized and bewildered when the huge spiral appeared. They all invaded the control room to see better. “It was such a beautiful energy,” Wilson says. “Everyone was like, ‘What is this?'”
Time was already running out because the dive had exceeded the program, and therefore the pilot of the submersible, controlling it from the surface, could only spend a few moments with the animal. “We walked around, took pictures and a little fabric sample,” says Wilson. “Then we just had to continue our merry way.”
Siphonophores look like jellyfish and belong to the same group of animals, but they build their bodies in a unique way – more like hundreds of tiny jellyfish stuck together. Yet, a siphonophore is a single organism. “He had two parents,” Wilson says. “It was a sex product.”
Rather than developing in a more conventional way in a body with organs performing different functions, siphonophores are made up of individual parts called zooids. Some zooids are responsible for feeding, some for reproduction, and others for moving and directing the animal through water. “They’re just an example of doing things a little differently,” Wilson said. “They are one and they are many.”
Based on a rough calculation of the submersible’s trajectory, the spiral-shaped siphonophore is a candidate for the longest specimen ever encountered. At around 45 meters (150 feet), it might even be the longest animal ever measured, far longer than a blue whale.
Reluctant to claim world records just yet, Wilson is working with a photogrammetry specialist to get a more accurate estimate of the size of the siphonophore. It is not easy to extract three-dimensional information from the video, because the siphonophore was moving in the wake of the thrusters of the submersible. “Normally with photogrammetry, you’re going back and forth over a stationary object,” Wilson explains. “It’s technically a bit more difficult.”
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