In the depths of the Fram Strait between Greenland and Norway's Svalbard, scientists have been perplexed by a peculiar phenomenon: mysterious octagon-shaped marks imprinted across the seabed. 

These intriguing marks, which IFLScience reports are some as small as a coin and others larger than a basketball, sparked curiosity among marine biologists. 

Thanks to the use of remote-operated vehicles (ROVs), researchers could trace these patterns back to their surprising creators - the deep-sea dwelling "Dumbo" octopuses.

Studying the Depths of the Ocean

The bathypelagic zone, located 1,000 to 4,000 meters deep, is one of Earth's largest and least explored biomes. 

Studying the inhabitants of this extreme environment poses many challenges, especially for the larger species, which often cannot be transported for study without significant damage. 

One such group, the cephalopod mollusks, remains enigmatic, with our understanding of their behaviors primarily based on chance encounters during ROV explorations.

Among these deep-sea dwellers is the Cirrata group of octopuses, also known as "Dumbo octopuses" due to their large, ear-like fins. They are found in the deepest of all Earth's oceans and are believed to feed on worms and crustaceans primarily. 

However, until recently, our knowledge about their feeding habits was limited to observations of a single captive female from the Opisthoteuthis species.

Deep Ocean Discoveries

Defector reports that recent Arctic surveys using ROVs revealed the presence of numerous Cirroteuthis muelleri, a species of Dumbo octopus. These creatures were observed drifting in the water column at depths ranging from 500 to 2,600 meters from the seafloor. 

It was also discovered that C. muelleri were feeding on the seafloor, marking the first recorded instance of a pelagic-benthic feeding migration in cephalopods, a behavior more commonly seen in deep-sea gelatinous fishes and holothurians.

Mysterious Octagon-like Shapes

This discovery not only sheds light on the feeding behaviors of deep-sea cephalopods but also helps explain the mysterious octagonal patterns on the seabed. 

During the high Arctic deployments, researchers noted 106 regular octagonal patterns across the seafloor in 92 out of 5,100 collected images. These patterns often contained indentations from the octopod arms, suggesting that they are the result of C. muelleri feeding events.

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The migratory feeding pattern of C. muelleri, which leaves octagonal imprints on the sludgy seabed, represents an example of convergent evolution in deep-sea megafauna. 

Many experts argue that this behavior is believed to facilitate the vertical transfer of carbon in the water column. The main ecological reasons behind this behavior are likely to avoid predators and save energy using passive transportation with ocean currents.

These findings highlight the ecological connectivity of deep-sea environments and emphasize the need for considering large-scale vertical movements of megafauna in conservation strategies. 

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