Octopus Feeding, Mating and Development | Sea Life, Islands and Oceania

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FEEDING OCTOPUSES

octopus eating a conch

Octopus are active predators that feed primarily on crustaceans such as crabs and molluscs such as snails (gastropods) and clams (bivalves). They sometimes eat fish and other marine creatures and even other octopuses and cephalopods. Like many spiders and predatory insects, octopuses use toxic saliva to paralyze prey and liquify tissue so they can eat it.

An octopus eating a crab, first bites a hole in the crustacean's shell with its parrot-like beak, then liquefies the crabs flesh with a toxic enzyme in their saliva and finally sucks the meat out of the shell. They use a similar method to eat mollusks. They first balloon their bodies around the shell, injects a neurotoxins into the shell to kill the animal and then liquefies it so the octopus can eats it. Octopuses use 50 percent of the energy from the food the eat (compared to 10 percent with humans).

Reef octopuses on the hunt overturn rocks and search crevasses with their sensitive arms. describing an octopus on the prowl, John Forsysth of the University of Texas told the New York Times, "All eight arms are working at once, investigating every crack and crevice with suction cups and pulling things out from deep inside." Octopuses employ a number of strategies to prey on mollusks.. The can pry open clams, break open thin-shelled mussels and drill into thick-shell clams with their radule. Young octopuses have been observed attaching nibbled-off tentacles of Portuguese man-of-wars to their suckers and using the powerful venom to stun and kill prey.

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Book: “Learning From the Octopus: How Secrets from Nature Can Help Us Fight Terrorist Attacks, Natural Disasters, and Disease” by Rafe Sagarin, Basic Book, 2012.

How Octopuses Open Clams

octopus takes on a clam several times its size

Jennifer A. Mather wrote in Natural History magazine After capturing a clam, an octopus must break through the hard shell to get to the meat inside. To do so, it can deploy a veritable built-in Swiss Army knife of tools . It can pull the shell's halves apart with its arms and suckers, chip at the shell's edge with its beak, or drill a tiny hole in the shell by alternately secreting acid to dissolve it and scraping at it with one of two tooth-covered organs in its mouth. (Which of the two organs it uses remains subject to debate.) If the octopus breaches the shell by chipping or drilling, it secretes a paralytic toxin into the clam's muscles so that it can more easily pull the shell halves apart — and then it's dinnertime. [Source: Jennifer A. Mather, Natural History, February 2007]

We discovered that giant Pacific octopuses apply differing techniques to various clam species: they break fragile mussel shells, probably while pulling on them; they pull apart the stronger Manila clams; and they drill or chip at the strongest clams, the littlenecks. We placed individuals of each species on a device of our own design (which we darkly called the "clam rack"), and measured how much force it took to overcome the clam's muscles and pull the shell halves apart. Intriguingly, octopuses ate plenty of weak-muscled mussels when they had to open dinner by themselves, but they gobbled up littleneck clams — all but ignoring the mussels — when we offered all three species on the half shell. Maybe the mussels were less tasty but easier to get at than the littlenecks.

Octopuses conduct the business of breaking into clams with the clams near their mouths, which are under their arms and so out of sight. There they dexterously manipulate the clams into position by touch. To pull clam shells apart, an octopus holds it with the umbo (the bump near the shell's hinge) toward its mouth. But if it chooses to chip at the shells' edge, it moves the clam's "sides," where the muscle insertions are, toward its mouth. And when it drills, it turns the broad side of the shell toward its mouth.

Predators of Octopus and How Octopus Defend Against Them

Sea creatures that feed on octopus include dolphins, sea birds, sailfish, tuna, sharks and particularly moray eels and conger eels. Octopuses use their ability to change color as camouflage and escape from their enemies under a cloak of ink and mucus. It best method of escape from it nemesis, the moray eel, is to dart into the nearest hole and hope it is to small for the eel to follow.

Some species of octopus can actually change their shape and imitate the appearance of flounders, shrimp, sea snakes, brittlestars and giant crabs. The also use camouflage and mimicking ability to hunt prey. One species from Indonesia, “ O. marginatus “ has been observed masquerading as a coconut with six of its tentacles while making an escape with its other two tentacles, which walking along the sea floor. A species from Australia, “ O. aculeatis”, uses a similar technique to look like “a clump of algae tiptoeing away.”

evidence of octopus cannibalism

A video shot off the coast of Melbourne, Australia in February 2017, showed an that octopus "blew itself up like a parachute multiple times," turning its body and eight legs into a giant net as it traversed the rocky and coral-filled ocean floor. Live Science reported: One idea is that the octopus was hunting for food, said Kathleen Sullivan Sealey, an associate professor of biology at the University of Miami, who doesn't know the diver but watched the video online.

It makes sense that the octopus was swimming across the ocean floor like a giant parachute, Sullivan Sealey said. Small prey was likely hiding among the coral and rocks along the seafloor. The octopus was likely pushing water downward so it could flush out prey, catch the meal with its net-like body and eat it with its beak, she said. "It's shooting water out of its mantle [head]," Sullivan Sealey told Live Science. "It was using that water to chase little shrimp out from the rocks so that they would get caught in its legs and the webbing between its legs." Another explanation for the behavior was that the octopus was blowing itself up like a blowfish to ward off the threat of a perceived predator.

Octopuses That Change Their Shape and Color

Some species of octopus can change their color and shape so they ressemble a feather star, a flounder, a jawfish, a snake eel, a sea snake, a stingray, a baby cuttlefish, or even a crab. They can also imitate the swimming motion of flounder, bury themselves in the sand with only their eyes exposed like a jawfish and even float with arm looking like the tentacles of a jellyfish. It is believed the adopt the poses to deceive potential prey and ward off predators. [Source: Smithsonian magazine]

Some species of octopus use a hunting strategy called tent-hunting in which they spread their arms and webbing over a patch of a reef and change the color of their skin so that translucent patches appear, Prey view these patches as escape windows. When they try to escape the octopus catches and eats them.

Describing an octopus in Indonesia Les Kaufman wrote in National Geographic: “Just before jumping to a new spot it would darken (except for one bold white stripe), then crash to the ground with arms outstretched, the webbing between them blocking off routes for small creatures...The webbing then would turn nearly transparent white. To us — and perhaps to trapped prey — these white patchs looked like windows of light and escape. We speculate that this color-change act is a ruse to lure, small cowering animals up to the “windows” and thus towards the octopus’s mouth....When at rest, this octopus became camouflaged against the reef, with shifting pasterns of dark and light on its skin that matched the texture and color of the backdrop.”

Octopuses are color blind. Their retina lacks cells that receive and process color. Those that change their colors seem to respond to contrasts in shade and light.

Octopus Mating and Reproduction

Common octopus are oviparous (young are hatched from eggs) and engage in internal reproduction in which sperm from the male parent fertilizes an egg from the female parent. They engage in seasonal breeding and year-round breeding. The number of offspring ranges from 100,000 to 500,000. The duration of embryonic development is related to temperature, as it is in all cephalopods, and it also depends on the size of the egg.[Source: Robin J. Case, Animal Diversity Web (ADW) /=]

Most octopuses are semelparous. This means that offspring are all produced in a single group, after which the parents usually dies Semelparous organisms often only live through a single season or year but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction. /=\

Octopuses mate facing each other. The male ejaculates on to one of its tentacles and then places the sperm on the female’s sex organ. Courting octopuses first approach each other with stylized touching motions. Their skin turns pebbly and changes in color from moldy brown to red to grey. The male uses an arm that is shorter than the others to pull sperm from his mantle and insert it into the female's mantle cavity with a spoon shaped organ called a hectocotylus at the end of one of his tentacles. The octopus mating ritual is often a violent affair with arm wrestling, the flashing of bright colors on their skin and beak thrusting. Mating has been rarely observed. The female sometimes preys on her male suitor.

Male octopuses are the only known nonvertabrae to have an erection. The discovery was made by a scientist watching a male two-pot octopus mate with an unreceptive female. The scientist observed that as the male withdrew his arm it was larger than before. Closer studies revealed that the male had erectile tissues similar to this possessed by male mammals.

Common octopus are polygynandrous (promiscuous), with both males and females having multiple partners and They semelparous, which means that offspring are all produced in a single group, after which the parents usually dies. According to Animal Diversity Web: During mating, the male approaches the female, who fends him off for a while, but then accepts him. He sits next to her or mounts her, inserting the hectocotylus in her mantle cavity to pass the spermatophores. They may copulate for several hours. The same pair often repeat mating over a period of a week or so, but a male copulates with other females and a female accepts other males. Mating often occurs when the females are immature. Only females ready to lay eggs consistently fend off the males. /=\

Females become restless and search for a sheltered place where they can lay and brood the eggs without disturbance. The spermatophores are placed in the oviducts and empty cases are discarded. Fertilization takes place in the oviductal glands as the mature eggs pass through them on thir way out of the oviducts. Two secretions from the oviductal glands, together with the mucus, are used to stick the egg stalks together in strings and attach these to a substrate.

Octopus Brooding and Young

Octopods typically tend their eggs until hatching. The sperm is potent until the female lays her eggs, which is sometimes months later. The female remains in her den and refuses all food during the incubation period, which is typically around 78 days. She stays with her eggs until they hatch and then dies. After mating, the male loses his ability to camouflage and loose his will to live and eventually dies from starvation.

According to Animal Diversity Web: Common octopus Eggs are laid in shallow water. They are always attached to a substrate. On rocky shores, females find a hole, a crevice or sheltered place and they often protect their homes with shells, stones and other solid objects that they gather. Coral reefs provide suitable shelter. On sandy or muddy bottom, eggs are laid in empty mollusc shells or in man-made objects such as cans, tins, bottles, tires, boots, and amphorae [Source: Robin J. Case, Animal Diversity Web (ADW) /=]

In tropical and subtropical waters, eggs are laid throughout the year. The total number of eggs laid by a female varies from 100,000 to 500,000. During egg laying and subsequent brooding, the female rarely leaves the egg mass. She usually does not feed during the entire period of spawning and brooding, which can be as long as 4-5 months at low temperatures. Egg care includes cleaning the eggs with the arm tips and directing jets of water from the funnel through the strings. Intruders, including potential prey, are pushed away, although crabs left overnight may occasionally be eaten. As a rule, females die shortly after the hatching of the last embryos after losing one-third of their pre-spawning weight. /=\

Young octopuses grow in globule-like eggs that become more translucent with time as octopuses become more defined. When baby octopuses burst from their eggs they already can squirt clouds of ink, turn color and propel themselves around. One of the first things they do after hatching is head for cover.

Octopus Broods Its Eggs For 4.5 Years — Longest of Any Animal

Douglas Main wrote in Plos One: In April 2007, Bruce Robison and colleagues happened upon a deep-sea octopus more than 4,500 feet below the sea off California. When they came back about a month later it was guarding a clutch of eggs that appeared quite new and small. So Robison, from the Monterey Bay Aquarium Research Institute, and colleagues decided to take this opportunity to see how long these animals take to brood their eggs, as this hadn’t been investigated before. They came back shortly thereafter to find it was still holding onto the eggs — then back, and back again, a total of 18 times. Every time, the octo-mom was still faithfully clutching her offspring-to-be. [Source: Douglas Main, Plos One, July 30, 2014]

The octopus went about brooding her eggs for a total of 53 months (aka 4.5 years), which is by far the longest on record for any animal and more than twice the lifespan of many shallow-dwelling species. The longest any octopus had previously been known to brood was 14 months. But deep-sea creatures live in much colder waters, and it was previously unknown how long they might take to “raise” their offspring. The authors of the study, published today (July 30) in PLOS ONE, compare it to other known brooding records:

One of the craziest things about this: Octopus mothers aren’t thought to eat when they are raising their young. So how did it survive? The scientists don’t know, but the cold temperatures and slow metabolic rate of deep-sea animals may have helped. But it seemed to take a toll on the octopus, a member of the species Graneledone boreopacifica; over the course of brooding, the scientists observed her turn from a pallid purple to a much paler white, and they noticed the “diminishing size and tumescence [or swollenness] of the mantle, loss of skin texture, cloudy eyes, slack skin, and a loss of pigmentation.”

One advantage to investing so much maternal care is that when these species’ eggs hatch, they emerge like miniature adults and can therefore skip the juvenile stage that other octopuses have to pass through. Scientists think this gives them a better chance of surviving in the dark, mysterious world of the deep sea.

Why Octopuses Torture and Eat Themselves after Mating

Some female octopuses torture themselves and sometimes even eat themselves when their eggs are close to hatching. Scientists have long wondered why octopuses did this. A study published in the journal Current Biology in May 2022 offered an explanation — female octopuses do it because of chemical changes that occur around the time the mother lays her eggs. [Source: Joshua Hawkins, BGR, May 20, 2022]

tudy in 1977 found that a set of glands near the octopus’s eyes was responsible for the mechanism that caused the self-destruction. Researchers involved with the 2022 study found that these glands produce steroid hormones in the octopus. According to BGR: When the mother has laid her eggs, these glands go into overdrive. It is these steroids that are believed to push octopuses to torture themselves. Altogether, the researchers found three separate chemical shifts that occur at the same time the octopus mother lays her eggs. First, there’s a rise in pregnenolone and progesterone. These two hormones are usually associated with reproduction in a host of creatures. So, it isn’t surprising to see them here.

Next, they saw a second shift as the octopus began producing higher levels of 7-dehydrocholesterol, or 7-DHC. This is a building block of cholesterol, and humans also produce it in the process of making cholesterol, as well. However, it may be one of the chemical changes causing octopuses to torture themselves after mating. 7-DHC can be a toxic compound. That’s why humans don’t keep it in their systems long. The researchers also noted that the optic glands began producing more of the components used in bile acids. Octopuses don’t utilize the same kind of bile acids as humans and other animals, but they do make the building blocks for those acids.

The researchers believe that these chemical changes all come together and cause octopuses to torture themselves. The exact reasoning for why these changes occur, though, or why the octopus’s body is designed this way is still unclear. Z. Yan Wang, an assistant professor at the University of Washington, told Live Science that it could be a way to protect the younger octopuses.

Octopus Development

Octopuses are a fast-growing, highly-fecund, short-lived creatures Because big blue octopuses lack larva, they instead have large yolk-filled eggs. In the case of big blue octopuses, according to Animal Diversity Web: Egg development requires about 20 to 30 days and eggs are 3 millimeters long when laid. Their growth rate post-hatching ranges from 5.6 to 5.8 percent per day. Male big blue octopuses start developing larger suckers on their seventh or eighth pair of suckers when they are seven to nine months old. [Source: Heidi Chicas, Animal Diversity Web (ADW) /=]

At 10-12 months males and females become sexually mature. Males are sexually mature at the weight of 320 grams, and females 600 grams. Males will start developing a larger arm on their third right arm during this time. These arms will be used during reproduction to be inserted into females’ mantle cavity, where the sperm are unleashed. As for females, their eggs become fertile during this time. /=\

Big blue octopuses reach their full sizes between 13 to 15 months right before reproduction. Size variation depends on food availability. Adult females range from 600 grams — 4800 grams and males reach 400 grams — 6600 grams. Once the suckers have fully enlarged (at about 15 to 18 months), males start eating less, lose weight, and slowly lose their ability to change color, and die. As for females, they stop eating and lose weight after spawning. They die 60 days after they lay their eggs. This happens because females don’t eat while protecting their eggs from predators.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023