A Very Rare Octopus With Seven Arms Was Caught In Sweden

In late October, a fishing boat in the western Skagerrak Strait accidentally caught an extremely rare seven-armed octopus, Haliphron atlanticus. The animal had no commercial value, but attracted the attention of scientists. They decided to study the octopus in University of Gothenburg.

“The other day I got a call from the Gothenburg fish auction and asked if I would like to bring an unusual octopus to the laboratory. I immediately found it interesting to study it and take samples,” says marine biologist Kristin Appelqvist from the University of Gothenburg.

A rarity for science

This species is pelagic, which means that it isfloats freely in the water column, does not bury itself in silt and does not attach to stones.Typically, Haliphron atlanticus is found at depths of several hundred to several thousand meters in the Atlantic, but isolated observations have been recorded in other oceans.Until 2025, it was seen only five times in Scandinavian waters.

Interestingly, Haliphron atlanticus has been nicknamed the “ghost octopus” due to its translucent, slightly pale appearance. In the summer of 2025, a similar specimen was found on a beach in California, and its shape and translucent body immediately gave the visual impression of a “ghost.” The name in Swedish, spökkrake, also reflects this ephemeral, almost invisible appearance of the animal.

The sample weighed 25 kilograms and had a length of 1.25 meters. According to Christine, the octopus turned out to be bycatch from a trawler that was fishing for shrimp at a depth of 200 meters.

“Bycatch is a fish or animal that is not harvested and is often discarded. For researchers, such a case is a real success,” she notes.

Features of the seven-armed

Haliphron atlanticus has eight limbs like other octopuses, but in males the eighth becomes a mating organ that attaches to the female and then separates. After mating, the male usually dies, and females often die after laying eggs or giving birth to young.

“This individual ate shrimp, which is likely what brought it into the trawl,” adds Christine.

Scientific study

In the laboratory, Christine took DNA samples and saved one eye and mouthparts for later comparison with other specimens. These parts help explore species characteristics, evolutionary relationships and feeding habits. Internal organs were also examined and stomach contents were examined to understand the animal’s diet and behavior.

Scientists note that it is almost impossible to find such a specimen on your own.

“Sometimes attempts are made to film the animals using remotely operated underwater vehicles or test trawling, but the discovery of this octopus was purely an accident. Such finds provide a unique chance to study the life of pelagic giants,” says the biologist.

Size and sexual dimorphism

Haliphron atlanticus is one of the two largest known species of octopus (the other being Enteroctopus dofleini).Females can reach almost four meters in tentacle span and weigh up to 75 kgwhile the males remain tiny,about 30 cmwhich demonstrates clear sexual dimorphism. The seven-armed tentacles havewider suction cupsthan other octopuses, which helps to hold prey and move through the water column.

Contribution to science

The sample is now frozen at the Tjarne Marine Laboratory. Christine is looking for colleagues and research groups who would like to study the animal further.

“I plan to write a short scientific report so that the find will be included in international databases,” says the biologist.

These data will help to better understand Swedish deep-sea ecosystems and contribute to fundamental marine biology, including evolutionary and ecological aspects of this rare species.