By Dr. Robert Norman, Clinical Professor, Dermatology, Nova Southeastern University
I most often write about the inhabitants and history of rivers and uplands and coastal ecosystems. Given the enormous popularity of the octopus, I decided to investigate off-shore into the waters where this amazing creature lives.
According to the National Marine Sanctuary Foundation, “The common octopus (Octopus vulgaris) may be one of the most studied and wide-ranging species of octopus in the ocean, but it is far from being ordinary. It is a skilled hunter, clever hider, master of camouflage, and one of the most intelligent invertebrates of the sea!”
The common octopus has a bulbous mantle or head, two large eyes, and eight flexible arms. The octopus is a marine invertebrate can grow to lengths of about 4.3 feet and weigh as much as 22 pounds. Each one has three hearts, two of which move blood to and from the gills while the third pumps blood to the rest of its body. It is cold blooded; it does not regulate its own body temperature, but matches that of the environment. At the center of its mantle, between its eight arms, is a set of powerful beak-like jaws that can be used to crush its prey.
In addition to a central brain located between the eyes, octopuses have separate “mini-brains” at the base of each of their eight tentacles. Unlike most creatures, octopuses have nine brains, and they put them to incredibly adept use.
Approximately 180 million of the 500 million neurons found in an octopus are concentrated in the central brain. Roughly 40 million or so additional neurons are located in each of the ganglia of each of its eight arms, or tentacles. Therefore, 320 million of an octopus’s neurons – more than two-thirds of them – are found at the bases of its arms rather than in its central brain.
Because each arm has its own ganglia, or cluster of neurons, each arm can act independently of an octopus’s central brain and other arms. The neurons at the base of each arm connect to suckers spread across it; typically, each arm has roughly 250 suckers. Each sucker may have around 10,000 neurons, which it uses to detect physical sensations via touch. These neurons also sense chemicals, allowing each arm to smell and taste objects while exploring them.
As a dermatologist who does research on brain-skin connections, I am particularly interested in the connection between the skin of the octopus and its brain and emotions. The pigment cells covering its body and specialized muscles help to change the animal’s body color and texture to almost instantaneously match the colors, patterns, and even textures of its surroundings.
You most likely have witnessed on a nature show (or in person!) when an octopus blends in with its surrounding environment in reaction to predators and other perceived threats or to appear more threatening.
In the span of a moment, they can change from bright lime to aqua blue to pearly white to an earthy reddish-brown. The texture of the skin texture may also completely transform from smooth to rough and bumpy, providing robust and effective camouflage.
The common octopus is a skilled nocturnal hunter and noted to be among the rare creatures that use objects it finds as tools to help it hide and hunt. This species has been documented picking up empty shells or other debris with their suckered arms and holding them around their body to help them blend in.
It is a strict carnivore that typically eats crustaceans like crabs, clams, and shrimp along with anything it can easily catch. A number of strategies are employed, like ambushing and even injecting a venomous saliva into prey to make them easier to catch.
What about their natural predators? Included are larger animals like sharks, moray eels, seals, sperm whales, and birds. The common octopus uses a wide variety of inventive strategies to defend itself, including expelling ink to help deter attackers, camouflaging to blend into the surrounding environment, compressing its boneless body to fit into the smallest cracks and crevices, and shooting out water jets from its mantle to make for a quick getaway. The common octopus may lose one of its arms to a predator, but it can fully regrow its arms multiple times throughout its life.
It can live at depths of nearly 600 feet but tends to gather near reefs where food is abundant. The common octopus is not migratory but can travel outside of its usual territory to new areas if it needed.
The common octopus has a life span of one to three years. After complex mating rituals where males approach females, it makes dramatic displays with its pigment skills or uses objects to win over a mate. They reproduce internally and females generally lay between 100,000 and 500,000 eggs, all connected in a chain-like fashion. The males die shortly after mating.
Each female chooses when to lay their eggs based on finding a suitable den site, which she then guards until the eggs hatch and the hatchling larvae grow strong enough to swim, eat, and produce ink. Very few common octopus hatchlings survive their first year as they are vulnerable to predation, which is why females lay so many eggs. If they do make it to adulthood, they are generally solitary, territorial, and aggressive toward conspecifics that are not potential mates.
Good news! The common octopus is well-studied, and most populations appear to be healthy and stable for now. No special protections are granted under U.S. laws; they are listed as “Least Concern” on the International Union for the Conservation of Nature (IUCN) Red List. Although not believed to be critically threatened, they are vulnerable to changes like warming oceans, acidification, pollution, habitat degradation, being caught in fishing gear, and prey loss due to overfishing.
Where can you find these amazing creature?
Get out into The Great Florida Outdoors!
Sea Wonder: Common Octopus | National Marine Sanctuary Foundation
How Many Brains Does an Octopus Have? – A-Z Animals (a-z-animals.com)
Dr. Norman is an advanced master naturalist graduate of the FMNP program from UF and a board-certified dermatologist based in Tampa and Riverview. He can be reached at 813-880-7546.
70 books (series editor of 39) ● 300+ articles ● 150 Lectures and Blogs
45 videos and films ● 18 photo calendars and exhibits ● 4 music CDs
Tampa Bay Medical Hero Award (2008)
● Hadassah Humanitarian Award (2012)
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