Octopus briareus

Geographic Range

Octopus briareus are found in relatively warm, shallow water, including the tropical waters of the western Atlantic, the southeastern U.S., the Bahamas, the Caribbean islands, northern South America, and western Central America (Nauen 1984).

Habitat

They inhabit shallow waters around coral reefs as well as well as rocks and seagrass beds. They are usually hidden in their lairs, which are very difficult to locate. The lairs can be within a coral reef or among plants and rocks on the ocean floor. These lairs are in the relatively shallow waters of the littoral zone of the oceans (Nauen 1984).

Physical Description

Octopus briareus have chunky bodies with eight arms that vary in length and diameter. In comparison to their bodies, their arms are relatively thin. They are able to change colors and textures in order to blend in to their surroundings. They can be brownish and even iridescent red to green. They do not demonstrate much sexual dimorphism. Males and females are similar in size, color, and demeanor. Also, the ovaries and testies are hidden. The only real noticeable differences are the presence of hectocotylus in males. This is a ventral crest formed by the fusion of a protective membrane with a ventral row of papillae so that the original form of conical papillae is hidden. Males also have at least one suction disc that is much larger than the rest as well and whiter in color. Octopus briareus are usually between 40cm and 60cm long, though they can get up to 100cm long. They can get up to 1.5kg in weight (Boyle 1983).

  • Range mass
    0 to 1.5 kg
    0.00 to 3.30 lb
  • Average mass
    0 kg
    0.00 lb

Reproduction

When it is time to mate, the male initiates the process. This usually happens during the day. He approaches the female, mounts her, perches on top of the mantle, and wraps his arms around her head and mantle. He then transfers two spermatophores with the hectocotylus into the oviduct. This process lasts between 30 and 80 minutes. Though the female may struggle, the male is the one that terminates the process when he swims away. Suction marks present on the female's mantle are evidence of mating. After they have sperm in their Females can store sperm in their oviducts for up to 100 days. Before they lay their eggs, they find a suitable site that will provide protection. They sometimes even close themselves inside their lair and seal off the opening. Females contain 100-500 eggs. The eggs are 10-14mm long and 4-5mm wide with a 5-10mm long stalk. These stalks hold together clusters of eggs, each made up of around 25 eggs. The female sits with her eggs and broods them until they are ready to hatch. The process takes 50-80 days for the eggs to mature enough to hatch; however, it can be much faster in warmer waters. When they emerge, the babies are small versions of adults and are able to swim, consume food, produce ink, and change color as soon as they are born. Growth is very quick, and after 17 weeks, young will be 75% of adult size. Males are sexually mature after just 140 days and females at 150 days (Boyle 1983).

Behavior

These animals are not social. A number of them may inhabit the same vicinity, but they live separately except during mating. Usually, one octopus does not even attempt to go near another's den. If two octopi do come in contact at a den, there is inevitably a fight. The acceptable distance between living spaces is a minimum of around 60ft., depending on the density of octopi inhabiting the area. They are not sedentary animals. They don't live in the same den for life, instead moving around in search of a suitable shelter. Octopus briareus are free moving animals, but when nesting they become sessile until their eggs hatch.

To escape predators, octopi suck water into the mantle and expel it for a quick getaway, along with a cloud of ink.

Also, some of the smaller animals on which they usually prey become a threat to their eggs when octopi are nesting. At that time, females may kill these animals but do not eat them. (Boyle 1987).

Food Habits

Octopus briareus eat a wide variety of animals, but their diet consists primarily of crabs and shrimp. Crabs are preferred because shrimp are much faster and more difficult to catch. Lobsters, polychaetes and a wide variety of fish are also consumed. Octopus briareus are known to hunt at dawn or dusk. They usually hunt by lying and waiting in their lairs, but if prey does not come around, they may leave to pursue it (Boyle 1983)

Economic Importance for Humans: Positive

None.

Economic Importance for Humans: Negative

None. They are not particularly aggressive and their bites are not deadly.

Conservation Status

Octopus briareus are not in any danger so far due to humans. They are not sought after for any particular characteristics nor do they have any specific predators that are a major threat.

Other Comments

Octopus briareus are interesting specimens of marine life. They can be easily studied and bred in laboratories, which allows scientists to continue to gain knowledge of them.

Contributors

Amanda Robinson (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, 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

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

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

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

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.

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

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

native range

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

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

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.

References

Boyle, P. 1983. Cephlapod Life Cycles Vol. I Species Accounts. London: Academic Press.

Boyle, P. 1987. Cephlapod Life Cycles Vol. II Comparative Reviews. London: Academic Press.

Cousteau, J. 1973. Octopus and Squid: The Soft Intelligence. Garden City, New York: Doubleday & Co..

Ingrao, D. N/A. "Octopuses" (On-line). Accessed March 19, 2000 at http://www.marinelab.sarasota.fl.us/OCTOPI.HTM.

Nauen, C., C. Roper, M. Sweeny. 1984. FAO Species Catalogue. N/A: United Nations Development Program.

Wood, J. N/A. "Raising and Rearing Octopus Briareus" (On-line). Accessed March 19, 2000 at http://www.nhm.ac.uk/hosted_sites/tcp/rearing.html.