Octopus joubini

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Geographic Range

Tropical Western Atlantic:

Florida, Gulf of Mexico, Caribbean Sea to Guyanas, Bahamas, West Indies.

Habitat

Inhabit empty shells among coral, near low tide line and below in shallow water. They use crevices, empty clam shells, or spaces in a reef face to eat and rest.

Physical Description

Small; maximum length (including arms) approximately 15 cm. Like all octopuses, Joubin's octopus has 8 arms. One arm, the ligula, is modified in males to form a sex organ. Octopus joubini has smooth skin with small pimples scattered at intervals.

Reproduction

Actual mating time is usually brief, about 5 minutes, as compared with other species like the Octopus dofleini, which mates for 2-3 hours. Amount of contact and sex of the initiator seems to vary. As a result of its small size, the animal is vulnerable to many predators. A shorter mating time shortens the period of vulnerability to these predators. It can occasionally cause problems, however. The sperm is passed to the female through a spermatophore that the males, using a special arm, place in the female's mantle cavity. The spermatophore evaginates in the female's oviduct, releasing sperm. Usually males would hold the spermatophore in the female until this process is complete, but in this case the male cannot because the fertilization takes too long. The eggs produced are usually fairly large, 6-8 mm in length. The females begin spawning from 4-5 months after hatching, with death shortly after 30-45 day brooding period.

Behavior

Octopus are usually considered solitary animals. They seem to show preferences for the same areas of residence. In tank experiments, O. joubini move to the corners of the tank for safety and more "cover." They form hierarchies, with dominance usually based on size. The bigger octopus routinely wins a dispute, and thus gains better access to food, homes, etc. When there is a tremendous difference in size between two animals, they tend to ignore each other. They make their social arrangements using space, although they seem to have no natural social spacing.

Food Habits

Mainly feed on crabs, e.g., Uca fiddler crabs, but also consume snails. Prefer crabs, possibly because they come into more contact with them, and crabs are more active than snails. The octopus seems to spend long periods of time pulling snails out of their shells before consuming them, but they can kill and eat a crab in one minute or less.

Economic Importance for Humans: Positive

Used in research, both behavioral and biomedical.

Economic Importance for Humans: Negative

Possible effect on crab populations in the area.

Conservation Status

At present there is an argument over whether the Octopus joubini is a synonym of either O. mercatoris or an as-yet undescribed species. Possible differences between the two supposed species include coloration, egg size, and hatchling ecology.

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

While small in size, Octopus joubini has a rapid growth over a relatively short life span (4-8 months). Their small size seems to be due to their small hatching size and the short duration of their rapid growth. They have keen senses. Their vision is so good that they are able to see a diver at least when he sees them, if not before.

Contributors

Nichole Rudolph (author), 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.

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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.

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

Abbot, R. T. 1954. American Seashells. D. Van Nostrand Co., Inc.

Forsythe, John.1984. Journal of Zoology, 202, 393-417.

Forsythe, John and Toll, Ronald B. 1991. Bulletin of Marine Science, 49(1-2), 88-97.

Mather, Jennifer. 1978. The Veliger, 21(2), 265-267.

Mather, Jennifer. 1980. Bulletin of Marine Science, 30(4), 848-857.

Mather, Jennier. 1980. The Veliger, 22(3), 286-290.

Mather, Jennifer. 1982. Animal Behavior, 30(4), 1166-1170.

McKinsky, Donald. 1988. The Nautilus, 102(3), 127-128.

McLean, Richard. 1983. Journal of Experimental Marine Biology and Ecology, 69.