In March 2021, a photograph started circulating on social media that supposedly showed an octopus with an abnormal number of tentacles:
This is a genuine photograph of a 96-armed octopus and is on display at Shima Marineland in Japan. It appears that the octopus has about eight "main" tentacles that branch off into several smaller tentacles.
Pinktentacle.com reports that the octopus was discovered in Matoya Bay in December 1998. It was brought to Shima Marineland but died a few months after arrival. Since then, this unusual specimen has been on display at the aquarium.
In November 2020, after a nine-armed octopus was found by a fisherman in Japan, the Shima Marineland flexed its tentacle muscle and noted that it had a specimen that topped the recent discovery by more than 80 arms.
Shima Marineland wrote on Twitter (translated via Google):
The news is the nine-armed octopus found in Miyagi prefecture. As mentioned in the article, the museum has a specimen of a octopus with 96 branches. It is still on display at the Sunfish Hall, so please take a look.
The aquarium also posted several additional photos of this specimen (including the viral image shown above).
While octopuses normally have eight arms, this isn't the first time one with numerous additional tentacles has been discovered. An article published in a 1965 issue of the Proceedings of the Japan Academy described several "octopuses with branched arms" that had been discovered since 1884, including one specimen with 90 arms.
Japan's Toba Aquarium also has a few Octopi specimen on display with far more than the expected eight tentacles.
The Toba Aquarium writes that the octopus on the left has 56 tentacles while the octopus on the right has 85. While the aquarium noted that there was "no established theory" to explain why these two animals developed multiple extra limbs, the organization believes these octopi may have regenerated extra tentacles after an injury.
The Toba Aquarium writes (loosely translated via Google):
The 85-legged octopus was collected in Toshijima, Toba City in 1957, and the 56-legged octopus was collected in Kaisan-cho, Kitamuro-gun in 1964. These octopuses have eight tentacles at the base, which is the same as ordinary octopuses, and they are branched from the middle, and each number is the same. At present, there is no established theory that can accurately explain the cause of these octopus "myriapoda", but it seems that it is a peculiar regeneration abnormality when some kind of damage is caused.