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Tuesday, December 01, 2020

After Octopolis, now Octlantis, two undersea ‘cities’ where octopuses live and socialise

Studies on the behaviour of the octopuses on the new site, named Octlantis, corroborated what had been seen during studies on the first site, Octopolis - that octopuses are not as asocial as they were thought to be.

By: Express News Service | September 25, 2017 2:37:37 pm
octopus, indian express An octopus at a den already occupied by another; the intruder eventually evicted the original occupant. © David Scheel et al/Marine and Freshwater Behaviour and Physiology

The sites

In 2009, Matthew Lawrence found an undersea site in Australia’s Jervis Bay that had been occupied by octopuses. Then last December, a second such site was discovered by Martin Hing and Kylie Brown, again in Jervis Bay, and again inhabited by the species gloomy octopus. Studies on the behaviour of the octopuses on the new site, named Octlantis, corroborated what had been seen during studies on the first site, Octopolis — that octopuses are not as asocial as they were thought to be. So far, not much was known about the behaviour of octopuses because they are difficult to study.

Octlantis

Found in December 2016 at depth 10-15 m, 10-15 octopuses between December 17 and January 14, studied by marine and environmental scientist David Scheel of Alaska Pacific University, biological scientist Stephanie Chancellor of University of Illinois and others. Reported in Marine and Freshwater Behaviour and Physiology in September 2017.

Videos showed mating, attempted mating, reaching, signalling. In one instance, an octopus was seen approaching a cluster of dens. Octopus A partially emerged from its den, but returned quickly when octopus B left its den and moved towards the approaching octopus. Octopuses C and D spread their webs, raised their mantles and moved towards the approaching octopus, which eventually retreated.

In another example, an octopus entered a cluster and evicted the occupant of one den. The evicted octopus fled to a den in another cluster, but was evicted from there, too, by the same octopus that had usurped its previous den. Both of these octopuses were presumed to be males.

Octopolis

Found in 2009 at depth 17m, occupied by 2-16 octopuses until December 16. Study on their behaviour by Scheel, Peter Godfrey-Smith and Matthew Lawrence published in Current Biology in January 2016. This study too found mating attempts, reaching without contact, and colour changes. Octopuses sometimes became dark, raised the head on extended arms, spread the arms and web, or raised their mantle. The relative darkness of octopuses correlated with their choice to withdraw or stand their ground, the researchers noted.

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