Hawaiian Marine Life Profiles: Invertebrates
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Octopus vulgaris (common octopus)
Found in Exhibit:
|When some people in Hawai'i think about octopus, their first thought is "tako poke". Aside from being tasty, the octopus, or he'e in Hawaiian, is possibly the most intelligent of all invertebrates (animals without backbones). He'e have large brains in comparison to their body size, image-forming eyes, a talent for problem solving, and a wide variety of defense mechanisms. Octopuses are classified as cephalopod molluscs, and are closely related to squid, cuttlefish, and nautilus. Cephalopods first appeared in the world's oceans about 500 million years ago, several million years before the first primitive fish evolved! Cephalopods can now be found in just about every habitat possible, from the tropical reef to the deep abyss.
Octopuses all have a funnel, which aids in propulsion, eight arms surrounding a central mouth, three hearts, an ink sac, a hard beak and a toothed tongue. They have no bones or shells, so they are able to swim through very narrow crevices.
Over 70 different types of cephalopods are found in Hawaiian waters. Fishing for and eating he'e were popular activities for the early Hawaiians and continue to be so today. He'e can be caught by hand, speared, or tricked out of their holes with a special lure made with a large cowry shell.
The most frequently seen octopus in Hawaii is the day octopus, or he'e mauli, probably because, as the common name might suggest, they are more active during the daytime and retreat into their lairs (holes in the reef) at night. He'e mauli are found from shallow water to at least 150 feet deep, and geographically span the Tropical Indo-West Pacific region from Hawaii to East Africa. Day octopuses can attain an arm span of 3 feet and weigh up to 4 to 5 pounds. Like many shallow water octopus, they generally live about a year. They have 8 arms with 1,920 muscular suction cups, which are used to cling to the rocks, move around the reef, and find food.
He'e mauli can display a wide variety of colors and textures on its head and arms, which may serve as camouflage as well as a mode of communication. Crabs are a favorite food of the he'e mauli, whose lairs are often identified by the presence of empty shells surrounding the entrance. The octopus can capture prey using its web, and may inject poisonous saliva to weaken or kill the animal. The he'e has a strong beak and radula (a toothy-tongue) to aid in opening up hard shells such as cowries and crabs.
If the day octopuses are harassed, they have a wide range of defense mechanisms, including squirting water at their attacker through their funnel, using their suction cups to hold up a wall of rocks as protection, and as a last defense, they may eject a cloud of ink. The cloud of ink has several different functions, and may take two distinct forms. The ink will generally confuse the predator, and may lead to temporary blindness, or clogging of the gills. The cloud of ink may either create a thick, dark wall to hide the octopus while he escapes, or have a similar size and shape to the octopus to serve as a decoy. Each octopus has a finite supply of ink stored in the ink sac and the octopus can actually control how much ink comes out and what shape it takes.
The day octopus has a short lifespan and reproduces only once. During courtship, the male will slowly approach the female and wave a modified arm, which holds bundles of sperm called spermatores. If the female accepts the male, he will insert the spermatophores into her oviducts. One theory behind the distance that the male keeps during mating is to avoid being eaten by the female after the mating, which has been observed in the wild. After mating, the female produces thousands of eggs and attaches them to solid surfaces. The female tends to the eggs very carefully, fanning them with her arms to oxygenate them. She will not eat or leave her eggs, and eventually her body will begin to decompose, which will serve as food for her developing hatchlings.
In the days of the early Hawaiians, the numbers of octopus in the reefs were far greater than they are today. This was probably due to the strict seasonal regulations on taking he'e that the royalty had in place. The early Hawaiians were excellent conservationists, wisely realizing the importance of reducing their consumption to ensure the sustainability of the food source. Learning from the ways of the early Hawaiians and taking only what we need and appreciating the beauty and wonder of these underwater masters of disguise, we may do our part to ensure their longevity for future generations to come.
Another Octopus Article
Long recognized as one of the most intelligent and elusive of the ocean's inhabitants, the octopus is a cephalopod mollusk, belonging to a family that includes the squid, the chambered nautilus, and the cuttlefish. All are equipped with beaks, sucker-lined tentacles, tubular funnels through which they can squirt water to discourage a diver's curiosity, and the ability to swim backwards. The chambered nautilus and the cuttlefish are not found in Hawaii, but our waters are home to many types of octopuses and squids. Of the nine species of octopuses inhabiting Hawaii's shoreline waters, the most common is the eight-armed day octopus or he'e, who is active during the daylight hours and retreats to its den at night.
Like all octopuses, the he'e is a master of disguise and subterfuge. It can change colors in a heartbeat to blend in with its environment or to confuse an attacker. Its normal color is gray-brown. When startled, it will flush to a reddish brown, and if alarmed, can turn pale as ashes, with a dark circle on either side. To further confuse predators as it jets away from them or disappears into the smallest of spaces, it will produce a variety of textures: bumps, ridges, warts, and puckers that resemble the surrounding reef habitat. Only as a last resort will the octopus eject its ink, or "kukae uli," a phrase that in the old days came to mean the tendency of a person of questionable repute to disappear when called to task for objectionable behavior.
Early Hawaiians relied on the octopus as a food source and either speared it or patiently coaxed it out of hiding with artfully fashioned cowry shell lures that had to be the perfect coloration to interest the wily creature. So wary and selective was the octopus that a man who ogled young women from afar was said to be like the octopus that "notices the little cowries".
For all its defensive ways, the octopus is a formidable predator. The he'e feeds mostly on crabs and other mollusks, along with the occasional fish. Armed with a sharp, parrot-like beak and poisonous saliva, the he'e pounces on its prey with spread arms, totally encloses it, and injects it with saliva to weaken or kill it. The pile of shells typically found outside the lair of an octopus attests to its hunting ability. Though it cannot hear, its sight, smell, and touch capabilities are excellent. Smell and touch sensors on the 1,920 suction cups found on its arms enable the animal to identify even the faintest suggestion of food. Whatever it touches, it can also taste.
The he'e needs fine eyesight not just for hunting but also to keep track of what its arms are doing. It can execute commands from its brain to its arms, but lacking a neurological pathway for feedback from the arms themselves, it must rely on sight to determine if the arms have obeyed the brain's commands. The octopus orients its body by means of two special organs called statocysts attached to its brain. Another physiological oddity: It possesses three hearts, one to pump blood through its large vascular system, and two additional to help oxygenate its blood.
The he'e attains a size of about 4-5 pounds and measures 3 ft. across, from the tip of one arm to another. Its life span is short - only about 12 to 14 months, with the female surviving longer than the male. Mating only once in its lifetime, the male displays black and white stripes to entice the female, then dies soon after transferring its sperm packages during the act of reproduction. The female lays strings of eggs on the ocean floor, fertilizing each one with the male's sperm. She tends and guards them over a 4 to 6 week period until they are ready to hatch. During that time, she does not eat, and her body slowly deteriorates and dies, providing food for her offspring.
It is easy to dismiss the octopus as simply a tasty ingredient in tako poke and other local dishes, but it is actually a beautiful animal that inspired the late Jacques Yves Cousteau to wax poetic. The graceful, elusive movements of the octopus reminded him of an exquisite, ethereal ballet. If you are ever lucky enough to see one undulating across the ocean floor "like a silken scarf", as Cousteau described it, you will not soon forget the encounter.