The giant Pacific octopus (Enteroctopus dofleini) is a fascinating and intelligent marine creature. As the largest octopus species on Earth, it plays a vital role in the biodiversity of deep sea ecosystems. This article delves into the dietary habits of this remarkable cephalopod, exploring what it eats, how it hunts, and the impact of its diet on the environment.
Size and Distribution
The Giant Pacific octopus is the largest species of octopus in the world; average weight is 50 Kg (110 lbs) and length of 5 meters (15 ft). Found throughout the temperate waters of the Pacific, from Southern California to Alaska, west to the Aleutian Islands and Japan.
Physical Characteristics and Adaptations
The octopus has a bulbous mantle where most of its organs are located. Unlike the human head, an octopus head (the dorsal mantle), holds more than just the brain. It also contains the reproductive organs and digestive organs.
The Giant Pacific octopus uses eight strong arms combined with suckers [6] to find and hold prey; it may paralyze prey such as fish with a toxic saliva, then tear into it with its parrot-like beak or simply pull the prey’s defenses apart (as with crab shells) to get at the meal within.
E. dofleini also has the ability to change the texture of its skin allowing it to blend into structural components of the environment. Uses special pigment cells, called chromatophores [6] in its skin to change colors and textures to camouflage very well. With their pigment cells, they can mimic surrounding colors and textures. Chromatophores are sacs of ink in their skin that are colored typically yellow, red and brown. Muscles control their size and shape.
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Oddly enough, an octopus's mouth is actually a beak, very similar to a bird's. This beak is the only hard part of the octopus body and is located on the underside of the dorsal mantle, located in the middle of its arms. The size of the beak determines the size of an opening the octopus can fit through! An octopus can squeeze through any hole large enough to accommodate its beak - A 50-pound octopus can fit through a two-inch hole.
Each arm has two rows of suckers, the largest being close to its mouth/beak and the smallest at the tip of each arm. Each sucker can move and taste independently. They are also very strong! When aquarists interact with our Giant Pacific Octopus the powerful suction of the suckers often leaves small “octohickies” in the shape of the suckers on their forearms.
Dietary Preferences and Hunting Strategies
The Giant Pacific Octopus is carnivorous; its diet includes shrimp, crab, scallop, clam, lobster, fish, and soft bodied prey. The Giant Pacific octopus primarily hunts for food at night, and their diet includes shrimp, clams, lobsters, fish. They have been known to scavenge larger fish and birds. E. dofleini preys on shrimp, crabs, scallops, abalones, cockles, snails, clams, lobsters, fish, squid, and other octopuses.[16][17][18] Food is procured with its suckers and then bitten using its tough beak of chitin.
The Giant Pacific octopus uses eight strong arms combined with suckers [6] to find and hold prey; it may paralyze prey such as fish with a toxic saliva, then tear into it with its parrot-like beak or simply pull the prey’s defenses apart (as with crab shells) to get at the meal within.
After hunting, they bring food back to the den to feed in a safer environment and avoid predators.[31] Shells, bones, and other feeding debris pile up outside of the den, creating "den litter" that is commonly used by scientists and divers to find E.
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Habitat and Den Selection
Lives in dens and caves [15] in intertidal zones to depths of 750 meters (2,500 ft). E. dofleini are den dwellers, which serve as a central point from which they forage while also providing protection, shelter, and privacy.[25] Dens range across depth and substratum type including caves, holes dug beneath rock, and even trash on the ocean floor such as bottles, tires, pipes, and barrels.[25][27][28] Den selection is greatly influenced by foraging behavior and preferred prey. Dens made of soft substrata may be preferred in areas where bivalves are abundant while dens near rocky areas might be chosen in areas with higher crab populations.[28] The size of the den is small, usually being just large enough for the octopus to fit inside and turn around. E. dofleini beak size determines the size of the space it can fit inside, with its body being able to compress through tiny spaces as small as two inches.[25][33] E. dofleini prefer to occupy same shelter for at least one month, often longer if possible. It is common for these octopus to leave their den for short periods of time and eventually return to re-use the same den.[29]
Predators and Defense Mechanisms
Only the largest fish (such as halibut and ling cod) and marine mammals are any threat to adults. Marine mammals, such as harbor seals, sea otters, and sperm whales depend upon the giant Pacific octopus as a source of food. Pacific sleeper sharks are also confirmed predators of this species.[22]
Octopus ink is a sepia color and is used as a defense mechanism. When threatened, E.
Lifespan and Reproductive Behavior
Unlike most other octopus species, whose lifespans normally span only one year, the giant Pacific octopus has a lifespan of three to five years.[3] They reach sexual maturity at one to two years of age.[34]
Females lay 20,000 to 100,000 eggs in a den and tend to them throughout incubation (5-7 months). The female Giant Pacific octopus lay around 74,000 eggs secured in a deep den or cave. After laying those eggs, the female spends seven months looking after the eggs. She will guard the eggs and use her arms and siphon to circulate water around the eggs. During this time, the female enters a period known as senescence - the end of her life. She does not eat, and her only focus is protecting and supporting the eggs.
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After mating, both the males and females stop eating and ultimately die.[39][34][25] After reproduction, they enter senescence, which involves obvious changes in behavior and appearance, including a reduced appetite, retraction of skin around the eyes giving them a more pronounced appearance, increased activity in uncoordinated patterns, and white lesions all over the body. While the duration of this stage is variable, it typically lasts about one to two months.
Intelligence and Behavior in Captivity
Octopuses are ranked as the most intelligent invertebrates.[44] Giant Pacific octopuses are commonly kept on display at aquariums due to their size and interesting physiology, and have demonstrated the ability to recognize humans with whom they frequently come in contact. These responses include jetting water, changing body texture, and other behaviors that are consistently demonstrated to specific individuals.[45] They have the ability to solve simple puzzles, open childproof bottles, and use tools.[23] The octopus brain has folded lobes (a distinct characteristic of complexity) and visual and tactile memory centers.
Captivity research has helped to link feeding, prey preference, and habitat selection to behavioral responses. Identified behaviors include shooting water and moving towards caretakers, changing body texture, as well as other consistent behaviors regarding diet preference. There is evidence that captive octopus recognize individual people and treat different people differently. They have the ability to solve simple puzzles, open childproof bottles and use shells and stones as tools. They are known to escape tanks and aquariums, and also to return after forays.
Human Interaction and Consumption
Humans use it as food, aquarium pets, and bait. The Giant Pacific Octopus is considered a delicacy and is also used as fishing bait.
Octopus will go from tender, to tough, then back to tender again during cooking. Has a slightly sweet flavor and smooth, slimy texture when eaten raw. When cooked, it retains some of its sweetness and has a meaty, crunchy texture. If undercooked or overcooked, it will be rubbery. Sold in a variety of forms, including fresh, frozen, dried, salted, and brined. When prepared fresh, it is often served alongside other seafood in stews, paella, and pasta dishes, but can also be prepared on its own (usually roasted or grilled). If bought live, gloves are recommended since it can bite. Long, slow cooking should always deliver tender results. The average simmering time should be about an hour for a 1lb (450g) octopus, two hours for a 4 lb (1.8kg) octopus, but that will vary. Octopus is lean and low in calories.
Environmental Concerns and Conservation
While they are not believed to be threatened, they are sensitive to pollutants. The burning of fossil fuels, deforestation, industrialization, and other land-use changes cause increased carbon dioxide levels in the atmosphere. The ocean absorbs an estimated 30% of emitted anthropogenic CO2.[57] As the ocean absorbs CO2, it becomes more acidic and lowers in pH. Ocean acidification lowers available carbonate ions, which is a building block for calcium carbonate (CaCO3). Calcifying organisms use calcium carbonate to produce shells, skeletons, and tests.[58] The prey base that octopuses prefer (crab, clams, scallops, mussels, etc.) are negatively impacted by ocean acidification, and may decrease in abundance. Because octopuses have hemocyanin as copper-based blood, a small change in pH can reduce oxygen-carrying capacity. Potential changes in octopus populations will affect upper and lower trophic levels.[54] Lower trophic levels include all prey items, and may fluctuate inversely with octopus abundance. Higher trophic levels include all predators of octopuses, and may fluctuate with octopus abundance, although many may prey upon a variety of organisms.
One way is to establish underwater reserves or Marine Protected Areas (MPAs), like the Olympic Coast National Marine Sanctuary. This 2,400 square mile sanctuary in Washington State was established to preserve one of the most productive, healthy ecosystems in North America.