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Octopus briareus

By Lindsey Lee

Geographic Range

Caribbean reef octopuses, Octopus briareus, are predominately found in the Neotropical region of the world in warm waters. The range of this species stretches from southern Florida in North America, through the southeast coast of the Gulf of Mexico, the Bahamas, and the Caribbean, and continues south to the northern coast of South America. Caribbean reef octopuses have also been known to range into the West Indies and off the coast of Curaçao. ("Cephalopods of the world: An annotated and illustrated catalogue of cephalopod species known to date", 2014)

Habitat

Caribbean reef octopuses are primarily found in tropical regions, off the coast, in shallow waters ranging from 3-20 meters. These octopuses predominantly inhabit areas with water temperatures around 20-30°C. Caribbean reef octopuses are normally found in or around coral reefs, which they use for protection and dens. The dens chosen by these octopods are usually dark and exclude other organisms. ("Cephalopods of the world: An annotated and illustrated catalogue of cephalopod species known to date", 2014; Borer and Lane, 1971; Brunt and Davies, 1994; Jordan, 2010)

  • Range depth
    3 to 20 m
    9.84 to 65.62 ft

Physical Description

Caribbean reef octopuses are typically bright green and blue with red-brown specks across their bodies. Chromatophores, which are specialized cells in the skin, allow these octopuses to change colors in order to blend in with their background and disguise themselves from predators and prey. These octopuses have sizable, prominent dark red-brown eyes. Their mantles, the body excluding their arms, are an average of 54 mm long and have been known to grow up to 120 mm. This organism, on average, weighs 1 kg.

At hatching, the young are 15mm, with arms of 7-9mm and a mantle averaging 5.5 mm. These octopuses emerge with the appearance of small adults.

Caribbean reef octopuses have seven rows of teeth. The longest of these octopuses' eight arms, the second and third, grow, on average, five times the length of the mantle. Each arm consists of two rows of suckers, which are connected by loose webs that assist in hunting. In males, the right third arm has a hectocotylus that deposits spermatophores, sacks containing the sperm for mating. ("Cephalopods of the world: An annotated and illustrated catalogue of cephalopod species known to date", 2014; Kaplan, 1982)

  • Sexual Dimorphism
  • sexes shaped differently
  • Average mass
    1 kg
    2.20 lb
  • Range length
    120 (high) mm
    4.72 (high) in
  • Average length
    54 mm
    2.13 in

Development

Caribbean reef octopuses hatch roughly 80 days after the eggs are laid. At hatching, they are 15mm, with arms of 7-9mm and a mantle averaging 5.5 mm. They exit the egg about 15 seconds after they first crack it. These octopuses emerge with the appearance of small adults. Caribbean reef octopuses grow at a rapid rate, increasing their weight by 5 percent a day. Once octopuses have sexually matured at five months, they will continue to grow, and exhibit indeterminate growth. By the time they die they will weigh one-third of the amount of food they have eaten over the course of their life. (Saxena, 2005; Scheel, et al., 2017)

Reproduction

Octopuses are monogamous, meaning one female and male mate. Caribbean reef octopuses do not have a known mating ritual. Because octopuses are solitary, mates are opportunistically chosen. Sexual reproduction can occur in two different ways for Caribbean reef octopuses. Males can either mount the female, reach its hectocotylus, the sperm containing tentacle, into her oviduct, releasing its sperm to cover the eggs, or take off its hectocotylus and give it to the female so that she can store his arm in her mantle and use it when the eggs are ready to be internally fertilized. The males die several months after fertilizing the eggs, while the females die shortly after laying the eggs. (Scheel, et al., 2017)

Octopuses are semelparous, meaning that they only breed once in their lifetime before death, and oviparous, which means they are egg layers. Although octopuses breed year-round, spawning peaks around February-March. Octopuses reach sexual maturity at five months, but may not reproduce for several years. Female octopuses can lay up to 200,000 eggs, each of which take approximately 65 days to hatch. When octopuses hatch, they weigh 0.095g and are 15mm in length on average. Because both the parents are usually deceased by the time the eggs hatch, octopuses emerge from their eggs fully independent. (Aronson, 1986; Hanlon, 1977; Saxena, 2005; Scheel, et al., 2017)

  • Breeding interval
    Octopuses breed once in their lifetime.
  • Breeding season
    Although octopuses breed year-round, spawning peaks around February-March. Most breed between six months to a few years after they reach maturity.
  • Range number of offspring
    200,000 (high)
  • Average gestation period
    65 days
  • Average time to independence
    0 minutes
  • Average age at sexual or reproductive maturity (female)
    5 months
  • Average age at sexual or reproductive maturity (male)
    5 months

Male Caribbean reef octopuses do not have any parental involvement other than providing sperm to fertilize the eggs. The male octopuses are dead by the time the eggs have hatched. The females protect the eggs pre-fertilization by keeping them inside of their body cavities. Once the females lay the eggs in crevices, they do not leave them alone, not even to feed. The female octopuses protect the eggs from predators and keep them clean by pushing water past them. The females usually die before the eggs hatch. (Saxena, 2005; Scheel, et al., 2017)

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

Lifespan/Longevity

Caribbean reef octopuses live 10-12 months, on average, in the wild. The sporadic feeding habits of these octopuses will decrease their lifespan in the wild. When kept in captivity, these octopuses live 10-17 months on average. In captivity, their lifespan can be decreased by cannibalism, disease, laboratory accidents, and escapes. Male Caribbean reef octopuses die a few months after they give their hectocotylus to the females for reproduction. The females usually die shortly after laying the eggs and ensuring the eggs are well hidden to maximize chance of survival. (Hanlon and Forsythe, 1985; Saxena, 2005)

  • Average lifespan
    Status: wild
    10-12 months
  • Average lifespan
    Status: captivity
    10-17 months

Behavior

Caribbean reef octopuses are solitary. They live alone in dens along coral reefs, only interacting with others for mating purposes. These octopuses are territorial and defend their den, along with the surrounding area, from other octopuses and predators. They can kill other octopuses within their territory and then eat them.

Caribbean reef octopuses are nocturnal, and the night protects them from predators and makes it easier to sneak up on prey.

Octopuses are monogamous, meaning one female and male mate. Caribbean reef octopuses do not have a known mating ritual. The male either mounts the female, or take off its hectocotylus and give it to the female so that she can store it and use the sperm when the eggs are ready to be internally fertilized.

Caribbean reef octopuses have many ways to communicate with other octopuses. These organisms have a sender-receiver match (a species-specific vocalization) that allows them to communicate with each other. Octopuses use a complex skin display, using the chromatophores, to form patterns that other octopuses are able to comprehend. These octopuses also use their layers of iridocytes deep in the dermis of their skin, which produce reflections off the skin, signaling to other octopuses. (Aronson, 1991; Hanlon and Messenger, 1996; Iglesias, et al., 2014; Snyderman and Wiseman, 1996)

Home Range

Caribbean reef octopuses are sedentary. They mainly stay around the same reef, and even the same den, for the majority of their lives. These octopuses are known to only change dens a few times over their lifetimes. They almost always return to their dens after hunting. Caribbean reef octopuses change their dens when they are disturbed by an intruder. Home range and territory sizes have not been reported in literature. (Aronson, 1991; Iglesias, et al., 2014; Snyderman and Wiseman, 1996)

Communication and Perception

In general, all octopuses have high-acuity-lens eyes on the sides of their heads. This placement forces them to use monocular vision, which means they only use one eye at a time. They are also color blind, but are able to distinguish between different hues and brightnesses. Octopuses respond to sound and use it as a way to find prey. Octopuses have various ways of communicating among themselves. These organisms have a sender-receiver match (a species-specific vocalization) that allows them to communicate with each other. Octopuses use a complex skin display, using the chromatophores, to form patterns that other octopuses are able to comprehend. Another form of communication for these species are using their layers of iridocytes in the dermis of their skin, which produce reflections off the skin, signaling to other octopuses. Octopuses can also change the appearance of their skin and their posture, shaping their bodies into different patterns. These organisms use their advanced eyesight and tentacles, loaded with nerve endings, to perceive their environment. (Bouwma and Herrnkind, 2010; Byrne, et al., 2002; Shashar and Cronin, 1996)

Food Habits

Caribbean reef octopuses are carnivores. Their primary prey are Caribbean spiny lobsters (Panulirus argus). These octopuses have also been known to eat other aquatic crustaceans (i.e., crabs and shrimp), small fish, and small mollusks. They are also known to eat other Caribbean reef octopuses, making the smaller ones vulnerable. Caribbean reef octopuses use their seven rows of teeth, suckers on their arms, and the web-like structures that connect the tops of their arms together to capture and eat prey. These octopuses are known to hurdle themselves over reefs, surprising their prey, and capturing them in their web. Then, the octopuses reach underneath, grabbing their prey, and guide it towards their mouths. They also snatch their prey with an arm and roll it up underneath of them, after which they eat the prey. Less frequently, Caribbean reef octopuses have been known to lurk behind their prey and grab it with their front arms. Octopuses' food intake depends on the amount of food available, the water temperature (higher temperatures favor more food eaten), and whether or not the female is pregnant (two weeks before laying the eggs, the female reduces her food intake by 50 percent). ("Scientists in the Sea", 1972; Borer and Lane, 1971; Borer, 1971; Brunt and Davies, 1994; Hanlon and Messenger, 1996)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

The known predators of octopuses are sharks, large fish, birds, eels, humans (Homo sapiens), other octopuses (feeding on smaller individuals), and some dolphins and whales. Octopuses have numerous anti-predator adaptations. They have an instinct to flee when they feel threatened, and they are able to squeeze into smaller spaces, giving them an advantage over their bigger predators. Octopuses release ink from a gland which creates a black cloud and allows them to escape under the darkness. Octopuses also are able to change the color of their skin, which is a cryptic adaptation, camouflaging them into their background and hiding them from predators. Lastly, octopuses are known to mimic larger animals by configuring their bodies into different shapes to scare off predators. (Aronson, 1991; Saxena, 2005; Aronson, 1991; Saxena, 2005)

  • Anti-predator Adaptations
  • mimic
  • cryptic

Ecosystem Roles

Caribbean reef octopuses are the hosts for Aggregata octopiana, which are parasitic alveolates mainly associated with inflammation, ulceration, and the destruction of the host's organs, and Digenetic trematodes. These octopuses are affected by ectoparasitic protozoans, Ichthyobodo necator, and metazoan parasites in the phylum Dicyemida. Caribbean reef octopuses primarily prey on Caribbean spiny lobsters, Panulirus argus, but are also known to eat aquatic crustaceans, such as crabs and shrimp, small fish, and small mollusks, and other Caribbean reef octopuses. These octopuses are prey for sharks, large fish, birds, eels, humans, Homo sapiens, other octopuses, and some dolphins and whales. (Castellanos-Martínez and Gestal, 2013; Gestal, et al., 1999; Glynn and Enochs, 2011; Hanlon and Forsythe, 1985; Hanlon, et al., 1984; Overstreet and Hochberg, 1975)

Commensal/Parasitic Species
  • Parasites alveolates (Aggregata octopiana)
  • Digenetic trematodes
  • Ectoparasitic protozoans (Ichthyobodo necator)
  • Metazoan parasites (Phylum Dicyemida)

Economic Importance for Humans: Positive

Caribbean reef octopuses are mainly captured by artisanal fishermen who end up selling them for pet trade, and, rarely, sold to fish markets for people to consume. These octopuses are used in biomedical research, particularly when relating the nervous system to behavior, because of their similar behavior to vertebrates. Octopuses have been used to study blood-brain barriers, blood pigments, immune mechanisms, neurotransmitters, environmental toxicology, and hormonal control of reproduction and aging. (Hanlon and Forsythe, 1985; Hanlon, 1977)

Economic Importance for Humans: Negative

There are no known negative economic impacts of Caribbean reef octopuses on humans.

Conservation Status

Caribbean reef octopuses have not been evaluated by the IUCN Red List. These octopuses have no special status on the U.S. Federal List, the State of Michigan List, nor the international list (CITES). Granted there are no major threats to Caribbean reef octopuses, but minor threats include their harvesting by humans for research, food, and pet trade. Additional threats include bacterial infections, Vibrio parahaemolyticus, Vibrio damsela, and Pseudomonas stutzeri; all cause ulcers that are common when these octopuses are kept close in captivity. (Hanlon and Forsythe, 1985; Hanlon, 1977)

Contributors

Lindsey Lee (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.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

internal fertilization

fertilization takes place within the female's body

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

piscivore

an animal that mainly eats fish

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) 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.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

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Aronson, R. 1986. Life history and den ecology of Octopus briareus Robson in a marine lake. Journal of Experimental Marine Biology and Ecology, 95/1: 37-56.

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