Enteroctopus megalocyathus

Geographic Range

The Patagonian giant octopus or southern red octopus, Enteroctopus megalocyathus , is limited to the Neotropical region of southern South America. This species is found as far south as the southeastern Pacific coast of Chile, as far north as Rio de la Plata in Argentina, and around the coast of the Falkland Islands.

• Biogeographic Regions
• neotropical neotropical
  • native native
• atlantic ocean atlantic ocean
  • native native

Habitat

Southern red octopuses inhabit shallow sub-tidal zones of the Patagonian coast. They live in small caves and crevices at a depth of 5 to 140 m. The area around the den of the animals are usually littered by crab shells and occasionally the shells of bivalve mollusks.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• coastal coastal

Physical Description

Southern red octopuses vary in color from bright red to rust and have whitish suckers under their arms. Their mantle is about 20 cm wide and has a rough appearance. The arm length for this species is approximately 60 cm. Each arm has numerous suckers (180 to 210) that occur in two rows, arms also have enlarged suckers closer to the mantle. The total body length from mantle to arm tip, on average, is 1 m. Average body mass of southern red octopuses is approximately 4 kg. The eyes of the adults are highly developed and large, 2.32 to 9.82 mm in diameter.

Hatchlings of the southern red octopus are 14.8 to 21.5 mm in total body length. Arm length ranges from 5.8 to 9.2mm, mantle size is 7 to 9.5 mm in length, and 5.3 to 8.8mm in width. Newly-hatched young are mostly colorless apart from the chromatophores on the mantel and arms. Along the arms the chromatophores are arranged in a linear fashion. On the mantel, the chromatophores are more spaced out.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Eggs are laid in clutches and individual eggs are pear-shaped and 2 mm in length. The eggs have posterior string that is connected to many other eggs from the same clutch. There are multiple strings from a single clutch of eggs and range from 1.5 to 2 m in length. The total number of eggs laid per clutch varies but is typically over 1000. During development, the embryos show exponential growth through the metabolism of the external yolk-sac. It takes about five months (168 days) for the eggs to hatch into paralarvae that lack the yolk-sac. The paralarvae, once hatched, move to the surface of the water and continue life as a planktonic species. There is no set time until sexual maturation of this species. Instead, sexual maturity is determined by the size of the reproductive organs and total body size.

Reproduction

Southern red octopuses are a seasonally breeding species. Mating is random and occurs when males opportunistically encounter females. When mating, males mount the females in a courtship dance, similar to that of Enteroctopus dofleini . Males assume an erect position using all of their arms to support them over their surroundings. Males will then slowly move towards a female and insert his hectocotylus arm into the female. Females will only mate with one male, whereas the males will attempt to mate with all the females that they encounter.

• Mating System
• polygynous polygynous

Age is not a factor when determining the sexual maturity of southern red octopuses. The best indicator of sexual maturity is the size and weight of the animals and their reproductive organ size. Males at sexual maturity weigh 667 to 1553 g, females weigh 1157 to 2448 g. The average gonad weight for males and females are 64.7 g and 153 g respectively for sexual maturity. The breeding season takes place from late summer through late winter. Females will store the sperm received by the males in their mantel next to their ovaries. Females will lay on average between 1000 and 5000 eggs. Time to hatching is at least 187 days.

• Key Reproductive Features
• semelparous semelparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous
• sperm-storing sperm-storing

Southern red octopuses, like other octopuses, are cared for by the female parent. After mating the female is the sole provider of care for the eggs while they are developing. Females blow water over the eggs to clean them and to ensure proper oxygenation. Females never leave the eggs to ensure that they are always protected not even leaving to eat. Once the eggs hatch, the female dies shortly afterwards.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • protecting
• pre-hatching/birth
• pre-independence
  • protecting
    • female

Lifespan/Longevity

Lifespan of southern red octopuses is primarily determined by when this species mates. The average lifespan of this species in the wild is similar to that of Enteroctopus dofleini , giant Pacific octopus, that live 3 to 5 years. Because southern red octopuses are cultured in captivity for food, the maximum lifespan of this species is never fully achieved in captivity.

Behavior

Southern red octopuses are motile and solitary creatures that spend most of their time in their dens and only leave to avoid predation, hunt for food, or mate. Unless mating, members of the same species are hostile towards each other and cannibalism can occur. This species exhibits timid behavior and as a result rarely interacts with humans. Southern red octopuses like other cephalopods have an ink sac that is used to avoid predators. They also have chromatophores that allow them to change their color to avoid predators by blending in with their environment. The chromatophores are also used to communicate with other members of this species over territory and mating.

• Key Behaviors
• natatorial natatorial
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

Southern red octopuses have a small home range due to their solitary lifestyle and hermit-like behavior. However, quantitative estimates of home range have not been reported.

Communication and Perception

Each arm of southern red octopuses has anywhere from 180 to 210 suckers. These suckers have large chemical receptors on their surface giving the animal a very acute sense of taste and touch which helps the octopus detect its prey. Southern red octopuses have very developed eyes which it uses to learn through observation of its surroundings and its immediate environment. Cephalopods have some of the most developed eyes of all members of this phylum. These highly developed eyes give southern red octopuses an advantage when it comes to defense. This allows for the southern red octopus to use its chromatophores to become perfectly camouflaged with its surroundings. The chromatophores have a elastic sac that is filled with a pigment. The pigment is controlled by contraction of muscles that allow for the sac itself to expand or contract. Another feature of southern red octopuses, like other cephalopods, is the ability to spray ink for defense to avoid predators.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• mimicry mimicry

• Perception Channels
• visual visual
• polarized light polarized light
• chemical chemical

Food Habits

Southern red octopuses are considered generalist foragers. Like most cephalopods, they are predators feeding primarily on brachyuran and anomuran crustaceans, fish, mollusks and other cephalopods (with cases of cannibalism). There is no difference in diet composition between males and females. Individuals returns to their dens to consume prey and then deposit the remains around the entrance of the den. The skeletal remains of the prey are known as middens. Examination of the middens shows the main dietary components of this species. The diet of this species varies on location and mantel size. Larger octopuses near Ancud, Chile feed on large crabs, smaller octopuses in Melinka and Quellón, Chile feed on small crustaceans. Using their arms, octopuses attack prey and brings it close to their beaks to penetrate the prey's shell. Once penetrated, octopuses inject digestive enzymes from salivary glands into the shell of prey to dissolve the flesh. The digested prey is then removed by using a 7-toothed radula to scrape up food.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Southern red octopuses have a number of adaptations to help them avoid predation. Southern red octopuses are a prime target for many predators that are larger than them. This species is an important part of the diets for beaked skates ( Dipturus chilensis ), South American sea lions ( Otaria flavescens ), and spiny dogfishes ( Squalus acanthias ). Humans ( Homo sapiens ) also prey upon southern red octopuses.

Like other cephalopods, they have chromatophores and dermal papillary muscles to camouflage them to match their surroundings color and texture. Along with these defenses, southern red octopuses have an ink sac to confuse predators if they get too close. One of their defense mechanisms is the ability to regenerate arms lost due to predation.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Parasites of southern red octopuses include the apicomplexan, Aggregata patagonica . Their ecosystem roles are fairly unremarkable. They are not top predators, nor are they the basis of a food chain.

Economic Importance for Humans: Positive

Southern red octopuses are one of two octopuses fit for the international market. Southern red octopuses are currently harvested and exported all around the world for food. Current research is investigating the cultivation of this species for the international market.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no negative economic impacts of southern red octopuses on humans.

Conservation Status

Southern red octopuses are not a protected species. There was a ban on commercial fishing of this species from 2009 to 2011 in Chilean waters. However, Uriate and Farias (2014) did not give a reason as to why the ban was in place, and why it was short-term. Southern red octopuses are not evaluated on the IUCN Red List and have no special status on the US Federal List, or through CITES.

Additional Links

Encyclopedia of Life

Contributors

Kristopher Moore (author), Radford University, Alex Atwood (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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