Since ancient times, people have been fascinated by octopuses. In some cases revered as godlike, and in other cases consumed as an easily captured source of protein, octopuses are both intelligent and behaviorally flexible; characteristics which separate them from almost all other invertebrates. With no internal or external skeletons, four pairs of arms, and two intelligent eyes, they are found in a variety of environments throughout the world. Let’s take a look.
Fascinating to Encounter: Octopus Basics
Inhabiting coral reefs and pelagic waters, as well as the ocean floor, there are about three hundred different octopus species worldwide. All octopuses have a few things in common which differentiate them from the other two-thirds of cephalopod species, which are closely related. First, they are all venomous. Only a single group, though, the blue-ringed octopuses, are known to have caused deadly reactions in human victims. Second, all octopuses have eight arms, usually with suction cups along the undersides. Thirdly, they are equipped with sharp beaks, which are the only hard parts their bodies contain. With the exception of members of the Cirrina suborder, which are equipped with a structured internal shell and a pair of fins, octopuses are capable of squeezing themselves through tiny spaces, particularly while trying to evade capture.
Internally, octopuses are much different than most other creatures. They have three hearts, one for each set of gills, and one which pumps blood throughout the rest of their bodies. To facilitate respiration, they draw water into their mantle cavities, then force it out through their gills, which depending on species, can be located on either the inner or outer portion of the body’s surface.
Only part of the octopus’ nervous system is localized in the brain; two thirds of its neurons are located in the nerve cords found in the arms, which provide for reflex actions even when no brain input is received. Even so, they are capable of solving problems, and are notorious for their ability to escape from aquariums when in captivity. Scientists have proven that they are capable of both long and short term memory, and they are able to find their way through mazes with accuracy. In some cases, octopuses have even broken into fishing boats and entered holds in order to feast on stored crabs.
The octopus is the only invertebrate which has been proven capable of using tools, something even most vertebrate species are incapable of. They have been witnessed finding and retrieving discarded coconut shells, then manipulating them to form shelters. They will often play with small objects, sometimes pushing items that float out into a current, then catching them repetitively. With keen eyesight and the ability to taste items as they touch them, they are amazing to watch.
Often seen crawling at a fairly leisurely pace, octopuses propel themselves through the water by using a swimming method reminiscent of jet propulsion, trailing their arms behind them as they go. When threatened, they can release clouds of ink, and many are masters of disguise, capable of camouflaging themselves against a variety of backgrounds. Some species are able to automatically transform their colors and textures to resemble rocks, coral, and even seaweed.
While some species, such as the Giant Pacific Octopus, can live as long as five years, most species live much shorter lives, sometimes as little as six months. Often, death is associated with reproduction, as males can live for just a few months after mating, and females do not eat while guarding their unhatched eggs, usually dying of starvation shortly after the young emerge. Others will ingest their own arms as they watch over their nests. Some species release eggs in strings, which hang from the ceilings of their lairs, while others release the eggs into the substrate where they nest. Eggs are fertilized internally prior to being released, and some species are capable of storing eggs for a period of time until conditions are favorable for release.
Diving With Octopuses
Depending on where you dive, you’re likely to encounter quite a few different varieties of octopus. Some of the most commonly encountered varieties are also some of the largest. The Giant Pacific Octopus weighs in at an average of about 30 pounds and has an arm span of more than ten feet on average. The largest specimen recorded though, was much larger, weighing in at 600 pounds and having an arm span of 30 feet. Another species, the Seven-arm octopus, which is so named because the males hide their eighth arm, is also quite large, averaging about the same size as the Giant Pacific Octopus.
The Common Atlantic Octopus, which is found in reefs from Mexico to Florida and in the West Indies, can grow to be as large as nine feet across. Usually blending in with their surroundings, they are capable of appearing red, pink, brown, grey, or white with a greenish tinge. Its cousin, the Pacific Red Octopus, is also capable of color change. Identified via the white spots on its mantle and the webbing in front of its eyes, it is one of the longer living species, capable of a life span of up to about 3 years.
Cyane’s Octopus, or the Big Blue Octopus, which is sometimes called the Day octopus, can grow to be almost three feet across, and is found throughout the Indo-Pacific region. The Reef Octopus, which is found in the Caribbean and the Bahamas, is a bluish-green color, and can be nearly three feet across. The Two-Spotted Octopus, which has a distinctive pear shaped body, grows to be a little more than two feet across and has two blue eye spots on its head. Found off the coast of California and into Mexico, it is usually grey to dark brown, although it can be a reddish color.
The Atlantic Longarm Octopus has a tiny body about three inches across, with an arm span that can be as much as thirty-six inches across. Found in Malta, Australia, and even the Florida Keys, these little octopuses are masters of disguise, capable of color change. Caribbean Armstripe Octopuses, sometimes called Brownstripes, have distinctive stripes running the length of each arm. Often hard to find, these octopuses like to bury themselves in the sand for protection.
Blue lined octopuses, which are a tiny, 4.5 centimeter species found in Australia are amazing to see, they’re brown until disturbed, at which point they flash a blue lined pattern while evading predators. This activity is similar to that displayed by blue ringed octopuses, which are often brown and only display their blue rings when disrupted. Most of the blue ringed octopus species live in tidal regions throughout the Pacific Ocean, from Australia to Japan, with high concentrations around South Australia and New South Wales.
These are just a few of the amazing octopus species you may find while diving; there are a variety of different species which are found in waters throughout the world, including some deep ocean dwellers. New species are still being discovered, including one species in the Antarctic with venom that is effective even in sub-zero temperatures. Keep your eyes open, no matter where you dive – you might find some incredible discoveries of your own, and remember never to provoke an octopus; you could be in for an unpleasant surprise.