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Octopus bimaculatus

By Brittany Hamilton and Lauren Swope

Geographic Range

Octopus bimaculatus is found off the coast of Northern California south to Baja California, Mexico. There are many observations recorded from the Channel Islands as well. ("Listings and Occurences for Endangered Species in California", 2013)

Habitat

Octopus bimaculatus inhabits rocky reefs in subtidal and intertidal habitats to a depth of 15 m. It prefers to den in abandoned man-made piping or small holes in canyon ledges. ("Two-Spotted Octopus", 2013)

  • Range depth
    0.5 to 18 m
    1.64 to 59.06 ft
  • Average depth
    15 m
    49.21 ft

Physical Description

The California two-spot octopus is usually light brown or mottled in coloration, with two characteristic spots under each eye, hence its name. Its mantle, located in the center of eight tentacles, is pear-shaped with a beak and mouth in the middle. Each of its tentacles grow to a few feet in length, a little more than half of its body size. Its tentacles are each adorned with suction cups used for grasping and holding prey as well as for taste. The octopus can grow to about 18 inches long when fully mature. Like its relatives, Octopus bimaculatus can use the chromatophores in its skin to change its color and texture when hunting for prey or hiding from predators. Octopus bimaculoides is another species of octopus that has the same common name as Octopus bimaculatus because they look so similar, but it is important to know that they are two different species. ("Two-Spotted Octopus", 2013; Foster and Smith, 2013; L. D. Roberts, 2009; Semmens, et al., 2004)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    45 to 60 cm
    17.72 to 23.62 in
  • Average length
    85 cm
    33.46 in

Development

Octopus bimaculatus grows and matures quickly due to its short life span of one to two years. When in the embryo stage, it goes through two different stages of growth: a rapid initial stage and a slower phase in which its beaks, shells, and brain tissue begins to develop. Each individual octopus develops and matures at their own individual rate, resulting in varying growth factors. Once hatched, the young octopuses are completely independent and ready to catch their own prey. Once they reach one to two years of age, they are ready to reproduce. ("Two-Spotted Octopus", 2013; Anderson and James, 2004; Boal, et al., 2000; Marsh and Fox, 2007)

Reproduction

Octopus bimaculatus can reproduce at any time during the year, but most commonly when the water warms during the summer months. The male octopus will use his spermatophores to inseminate the female; the male will die shortly after. ("How Does An Octopus Reproduce?", 2003)

After fertilization, the female will create a den and seal herself in to lay her eggs. A single female can lay thousands of eggs. She will care for her eggs by blowing cool water over them from her siphon to keep them oxygenated. During the process of caring for her eggs, the female often expires due to starvation and exhaustion. After the eggs hatch, which may take 150 to 210 days, the mother will leave the den if she survives and the larval octopus will drift with the tide before settling on the ground to begin developing. ("How Does An Octopus Reproduce?", 2003; Boal, 2006)

  • Breeding interval
    Octopus bimaculatus breeds once in its lifetime.
  • Breeding season
    Mating typically takes place in the summer months, though it can happen year round.
  • Range number of offspring
    20,000 to 100,000
  • Average number of offspring
    70,000
  • Range gestation period
    150 to 210 days
  • Range age at sexual or reproductive maturity (female)
    1 to 2 years
  • Range age at sexual or reproductive maturity (male)
    1 to 2 years

Males die shortly after mating. Females, however, exhibit significant parental care. They remain with the eggs after they are laid, protecting them and siphoning cool water over them. During this time, females do not feed and often die from starvation and exhaustion. Once the eggs hatch, the larvae are independent. ("How Does An Octopus Reproduce?", 2003)

Lifespan/Longevity

Octopus bimaculatus lives between 12 to 18 months in the wild, while some kept as pets have been known to live for up to 2 years. (Forsythe, et al., 1991; Semmens, et al., 2004)

  • Range lifespan
    Status: captivity
    2 (high) years
  • Typical lifespan
    Status: wild
    1 to 1.5 years
  • Typical lifespan
    Status: captivity
    1 to 2 years

Behavior

Many species of octopus are mainly active at night, and the California two spotted octopus is no exception. Octopus bimaculatus leaves the den at night to hunt and mate. Its highly developed eyes make nocturnal behavior possible. Individuals range widely, searching for food, and find temporary burrows for shelter when not hunting. They do not often return to their previous dens and will never construct one of their own. Octopuses will compete for dens, chasing conspecifics out of a den that they desire. They will bring their prey to their dens to consume, creating "middens" of various bivalve shells, crab claws, and other hard parts of their invertebrate prey. (Boal, et al., 2000; Boal, 2006; L. D. Roberts, 2009; Sinn, et al., 2001)

Communication and Perception

Octopus bimaculatus and other cephalopods communicate visually. They manipulate the chromatophores on their bodies to display various signals to conspecifics and to predators as warning signs. They have highly developed eyes. Common visual cues and signs are used to indicate that they are ready to mate, have already mated, are not interested, are expressing dominance, or show relationship to other individuals. Though O. bimaculatus is a solitary creature, it will alert conspecifics to predators or prey in the area. (Boal, et al., 2000)

  • Other Communication Modes
  • mimicry

Food Habits

The main source of food for Octopus bimaculatus is snails, crustaceans, bivalves, and limpets. An octopus may hunt for its prey, or it may lie in wait for food to swim or crawl by its hiding place, while it remains camouflaged in the rocks. Once Octopus bimaculatus has captured its prey with its tentacles, it uses its suckers to hold onto the prey while it is moved towards the beak and radula. The radula can pierce the thick shells of other mollusks and inject a toxin that will affect the prey's nervous system. The beak tears soft tissue, and the radula is then used to scrape the flesh into shreds for consumption. ("Two-Spotted Octopus", 2013; Foster and Smith, 2013)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

Predators of Octopus bimaculatus include moray eels, sea lions, harbor seals, and humans. To scare off predators, O. bimaculatus can change its skin by manipulating its chromatophores and flashing warning signals. (Kier and Smith, 2002)

  • Anti-predator Adaptations
  • mimic
  • cryptic

Ecosystem Roles

California two-spot octopuses are both primary and secondary consumers. They help maintain the population of smaller mollusks as well as serve as food for larger predatory animals. They are also known to be hosts for ectoparasitic flagellates and ciliate protozoans, which live on the octopuses' gills. (Forsythe, et al., 1991)

Commensal/Parasitic Species
  • flagellates
  • ciliate protozoans, Ciliophora

Economic Importance for Humans: Positive

This species of octopus is not hunted by humans as a main source of food, however it is caught in traps and nets and can be sold. As of 2013 in California, the daily bag limit is 35 specimens, and there are no size limits. There is a market in the pet supply trade. Because two spotted octopuses are small (up to 45 cm), they are welcome aquarium pets. Aquarium websites list them from US $30 to $40 depending on size. ("Listings and Occurences for Endangered Species in California", 2013; Foster and Smith, 2013)

Economic Importance for Humans: Negative

There are no known adverse effects of Octopus bimaculatus on humans.

Conservation Status

Octopus bimaculatus has no special conservation status. ("Listings and Occurences for Endangered Species in California", 2013; Marsh and Fox, 2007)

Contributors

Brittany Hamilton (author), San Diego Mesa College, Lauren Swope (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Angela Miner (editor), Animal Diversity Web Staff.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

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.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

internal fertilization

fertilization takes place within the female's body

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

mimicry

imitates a communication signal or appearance of another kind of organism

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.

natatorial

specialized for swimming

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.

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

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

2003. "How Does An Octopus Reproduce?" (On-line). Accessed May 13, 2013 at http://wildwetcoast.wordpress.com/2012/03/10/how-does-an-octopus-reproduce/.

2013. "Listings and Occurences for Endangered Species in California" (On-line). Accessed March 11, 2013 at http://www.fws.gov/endangered/.

2013. "Two-Spotted Octopus" (On-line). PBS Online. Accessed May 13, 2013 at http://www.pbs.org/oceanrealm/seadwellers/survivaldwellers/octopus.html.

Anderson, R., W. James. 2004. Interspecific Evaluation of Octopus. Journal of Applied Animal Welfare Science, 7: 95–106. Accessed February 20, 2013 at http://www.tandfonline.com/doi/pdf/10.1207/s15327604jaws0702_2.

Boal, J. 2006. Vie Et Milieu. Social Recognition: A Top Down View of Cephalopod Behavior, 56: 69-79. Accessed April 23, 2013 at http://millersville.edu/academics/scma/biology/faculty/boal-pdf/5.boal_vie_milieu_2006.pdf.

Boal, J., A. Dunham, K. Williams, R. Hanlon. 2000. Experimental Evidence for Spatial Learning in Octopuses. Journal of Comparative Psychology, Vol. 114/No. 3,: 246-252. Accessed February 15, 2013 at http://psycnet.apa.org/journals/com/114/3/246.pdf.

Forsythe, J., R. Hanlon, R. Bullis, E. Noga. 1991. Octopus bimaculoides (Pickford & McConnaughey,. Journal of Fish Diseases, 14: 431-442. Accessed February 16, 2013 at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2761.1991.tb00595.x/pdf.

Foster, , Smith. 2013. "Two-Spot Octopus" (On-line). Pet Education. Accessed May 13, 2013 at http://www.peteducation.com/article.cfm?c=0&aid=2112.

Kier, W., A. Smith. 2002. The Structure and Adhesive Mechanism of Octopus Suckers. Integr. Comp. Biol, 42: 1146–1153. Accessed February 20, 2013 at http://icb.oxfordjournals.org/content/42/6/1146.full.pdf+html.

L. D. Roberts, P. 2009. "Two-Spotted Octopus" (On-line). Accessed March 13, 2013 at http://jaffeweb.ucsd.edu/node/twospottedoctopus.

Marsh, J., M. Fox. 2007. Seafood Watch. Seafood Report, 1: 24-35. Accessed May 13, 2013 at http://www.montereybayaquarium.org/cr/cr_seafoodwatch/content/media/MBA_SeafoodWatch_GulfofCalifornia_Guide.pdf.

Semmens, J., G. Pecl, R. Villanueva, D. Jouffre, I. Sobrino, J. Wood, P. Rigby. 2004. Understanding octopus growth: patterns, variability and physiology.. Review: Marine and Freshwater Research, 55: 367-377. Accessed April 23, 2013 at http://digital.csic.es/bitstream/10261/30661/1/Semmens%20et%20al%202004.pdf.

Sinn, D., J. Mather, R. Anderson. 2001. Early Temperamental Traits in an Octopus (Octopus bimaculoides). Journal of Comparative Psychology, Vol. 115/No. 4: 351-364. Accessed February 15, 2013 at http://psycnet.apa.org/journals/com/115/4/351.pdf.

Stoskopf, M., B. Oppenheim. 1996. Anatomic Features of Octopus bimaculoies and Octopus digueti. Journal of Zoo and Wildlife Medicine, 27: 1-18. Accessed February 20, 2013 at http://www.jstor.org/stable/pdfplus/20095538.pdf.

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