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Rare Seven-Arm Octopus Spotted in Monterey Bay

12/17/2025

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Summary

Story summary

Monterey Bay Aquarium Research Institute (MBARI) scientists observed a seven-arm octopus, Haliphron atlanticus, in Monterey Bay on November 6, 2025.
The sighting marks the fourth observation of Haliphron atlanticus in 35 years.
The octopus was filmed at a depth of 2,300 feet while feeding on a helmet jelly.
Haliphron atlanticus can grow up to 13.1 feet long.
The species has a specialized mating arm that is often tucked away.

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Story summary

Monterey Bay Aquarium Research Institute (MBARI) scientists observed a seven-arm octopus, Haliphron atlanticus, in Monterey Bay on November 6, 2025.
The sighting marks the fourth observation of Haliphron atlanticus in 35 years.
The octopus was filmed at a depth of 2,300 feet while feeding on a helmet jelly.
Haliphron atlanticus can grow up to 13.1 feet long.
The species has a specialized mating arm that is often tucked away.