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, as well as 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.
Photos courtesy Sandi Strickland (sandandcphotos.com)
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 Hawai‘i 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 Hawai‘i 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 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 number 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 ali‘i 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.
Source: Maui Ocean Center