Recently scientists have discovered a bustling community of approximately 15 gloomy octopi, also known as the Common Sydney Octopus, and scientifically identified as Octopus tetricus. The discovery was made in the waters of Jervis Bay, located off the eastern coast of Australia. This is of particular interests because scientists have long believed that the gloomy octopus was an antisocial creature that spent most of its time alone. Let us review what scientists already know about the gloomy octopus.
About the Gloomy Octopus
The gloomy octopus is an invertebrate of the class Mollusca, which includes squid, clams, and snails. They are typically grey to mottled brown in color with rust-red along the inside of each arm that taper to the tip of their tentacles. They have eight arms attached to a rounded head and body, characteristic of most species of octopi. The arms are uneven in length with two rows of suckers that are equipped with chemoreceptors. These receptors are what the octopus uses to taste with when it is touching things.
Their eyes are typically white and the skin has many patches and large papillae that they are able to raise over their body to produce a spike-like appearance, commonly seen when they are imitating seaweed. Gloomy octopi are among the largest of octopus, having a body size of about 80 cm with a tentacle span that can reach up to 2 meters. They have three hearts, two that pump copper-rich blood through each of the gills and one that pumps blood throughout its entire body.
The gloomy octopus has the largest brain in comparison to its body weight of any known invertebrate. Like other octopus the gloomy octopi are incredibly intelligent, a result of hundreds of millions of years of evolution. They have evolved to address new situations through a combination of behaviors. Scientists have employed maze and problem-solving experiments that show octopus to have incredible short and long-term memory and are capable of learning geography. They are also masters of deceit through mimicry.
Like the cuttlefish, gloomy octopi are able to rapidly change their display patterns, color, and alter skin sculpture to mimic seaweed. This enables them to merge into the background to avoid predators, ambush prey, or to lure a potential mate for reproduction. Gloomy octopi are able to change their colors through contraction of specialized skin cells. Chromatophores are the specialized skin cells that contain the yellow, orange, red, brown, and black pigments. Iridophores are the skin cells that give the octopus its iridescent green and blue hues, and leucophores are the skin cells that create the white pattern.
The gloomy octopus can be found on intertidal rocky shores and in the ocean along the subtropical east coast of Australia and northern New Zealand, including the island of Lord Howe. While they have been found in a range of ocean habitats, the gloomy octopus is most commonly found in rocky reef habitats during the breeding season, and most the rest of their life they can be found in soft-sediment habitats.
The gloomy octopus usually feeds at night and is an opportunistic predator. Ambushing prey and using its sharp beak, the gloomy octopus feeds on crabs and a variety of other mollusk species, such as snails and bivalves. They have also been known to feed on small fish and on others of their species.
The male is equipped with a specialized are that it uses to transfer spermatophore into the females mantle cavity. Once the eggs are fertilized, the female lays thousands of eggs in hanging chains from the ceiling of her den. The female does not feed during the time the eggs are developing. She will fan water over them to reduce algal growth and guard them against predators.
Mating is the end of life for the gloomy octopus. Males will live for only a few short months after mating, while the female will die shortly after the hatching of her eggs. The average lifespan of the gloomy octopi is about 3 years. The female gloomy octopus has been observed engaging in reproductive cannibalism, in which the female eats the male after the act of mating is complete.
The Mystery of Octlantis
One other community of gloomy octopus was found in 2009 not too far away from Jervis Bay. Scientists named this community of gloomy octopi, Octopolis. At the time scientists believed this community to be a complete anomaly and believed that the cephalopods had gathered there because of an unidentifiable human object created a central point that the gloomy octopi surrounded with dens.
The unidentifiable object is around 30 cm in length and is heavily encrusted, possibly being made of metal. Octopolis has been observed for seven going on eight years, and at any given time anywhere between 2 and 16 gloomy octopi can be found. Octlantis, however, has no human object that would explain the congregation of gloomy octopi.
In a statement given to UIC Today, co-author and doctoral student in biological science at the University of Illinois-Chicago, Stephanie Chancellor gives a likely explanation.
“At both sites, there were features that we think may have made the congregation possible — namely several seafloor rock outcroppings dotting an otherwise flat and featureless area. In addition to the rock outcroppings, octopuses who had been inhabiting the area had built up piles of shells left over from creatures they ate, most notably clams and scallops. These shell piles, or middens, were further sculpted to create dens, making these octopuses true environmental engineers.”
Over the eight days that scientists observed Octlantis, the scientists witnessed the octopi communicating, fighting, and mating. The gloomy octopi were even observed evicting each other from dens.
These new findings are giving insights into the lives of this mysterious octopus once thought to be a solitary animal. The gloomy octopus is notoriously hard to study and even harder to keep in the lab due to their particular water chemistry and ability to escape. This elusive master of disguise is difficult and extremely expensive to track in the wild. Despite these challenges, scientists have managed to study this magical creature, but are just beginning to understand their social complexity.