The California two-spot octopus (''Octopus bimaculoides''), often simply called a "bimac", is an

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

species native to many parts of the Pacific Ocean including the coast of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. One can identify the species by the circular blue eyespots on each side of its head. Bimacs usually live to be about two years old. They are closely related to Verrill's two-spot octopus ('' Octopus bimaculatus''). In 2015, ''O. bimaculoides'' became the first octopus to have a fully sequenced

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

Description

''Octopus bimaculoides'' reaches a mantle size of with arms to . Not usually heavily textured, it has several common colors, such as grey with yellow splotches, and uses highly developed

crypsis In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be part of a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean life ...

, which is camouflage or color-changing to match the environment. Octopuses achieve color change in part by

chromatophores Chromatophores are cells that produce color, of which many types are Biological pigment, pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals an ...

iridophores Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast ...

, and

leucophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast ...

s. All are structures of the skin in increasing depth. Chromatophores are elastic pigment sacs with muscle fibers attached by which they can expand and contract. The leucophores are important because they allow for the reflection of white light, and allow the skin to reflect wavelengths of light which are prevalent in their habitat, and produce disruptive patterns. The other aspect to

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

camouflage is the brain, which contains nerves coated in chromatophore fibers, controlling coloration patterning. This octopus is named for the false eye spot (ocellus) under each real eye. These ocelli are an iridescent blue, chain-link circle, set in a circle of black. On its arms, the octopus possesses many "suckers" that it uses to taste. They have three hearts, two gills, blue blood, and a donut-shaped brain.

Distribution and habitat

''O. bimaculoides'' are found in coastal waters, in the eastern

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

along mid- and southern-California and the western side of the Baja California Peninsula in Mexico. They live at depths from the

intertidal The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various sp ...

, down to at least . It prefers rocky reefs or debris for hiding, and tolerates a wide temperature range , though prefers .

Ecology and behavior

Lifespan

These octopuses live around one to one and a half years in their natural habitat, but can live for up to two years in captivity. The end is signaled by egg-laying in the female and

senescence Senescence () or biological aging is the gradual deterioration of Function (biology), functional characteristics in living organisms. Whole organism senescence involves an increase in mortality rate, death rates or a decrease in fecundity with ...

in both males and females.

Diet

Since these octopuses do not live for long, they mature rapidly and can hunt for food to feed themselves right after hatching. Hatchlings feed on

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

mysid Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in thi ...

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

. As they grow, the list of what they eat grows with them. California two-spot octopuses eat anything they can find, like fish and crustaceans. They are nocturnal, and hunt at night. Their camouflage abilities give them an advantage while hunting.

Reproduction

Towards the end of their lifespan, they are ready to reproduce. These octopuses are

semelparous Semelparity and iteroparity are two contrasting reproductive strategies available to living organisms. A species is considered ''semelparous'' if it is characterized by a single reproduction, reproductive episode before death, and ''iteroparous ...

: they mate and reproduce only once in their lives. They can mate at any point of the year. It is most common during the summer when the water is warmer. Using its

spermatophores A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially ...

, the male fertilizes the female. The male dies soon after the reproductive act. After mating, the female creates a den, where she will lay 20 to 100 eggs. After laying her eggs, she must keep them alive and well. She blows cool water through her siphon so that the eggs receive oxygen. This will go on until the eggs hatch, which ranges from 150 to 210 days. During this process, the female does not eat, and her condition deteriorates, usually culminating in death.

Genetics

In recent years new technology, such as genome sequencing, has provided new information on the large amounts of clustered

protocadherin Protocadherins (Pcdhs) are the largest mammalian subgroup of the cadherin superfamily of homophilic cell-adhesion proteins. They were discovered by Shintaro Suzuki's group, when they used PCR to find new members of the cadherin family. The PCR fra ...

s (PCDH) in ''O. bimaculoides''. The octopus was found to have 168 PCDH genes, about 120 clustered and 50 non-clustered PCDH. Unlike what has been documented about mammalian clustered PCDH, octopus PCDH are clustered around the genome in an organized manner, creating a head-to-tail arrangement.

Studies

Researchers collected and tagged the octopus species, ''O. bimaculatus'', to conduct acoustic telemetry research. They measured the position of the octopuses in the environment over the course of two weeks, recording the daily movement of each octopus. The study showed that ''O. bimaculatus'' always moves from one den to another every few days, and likely to avoid predation, the octopuses varied their daytime movement patterns and the distances they travel. From

stable isotope analysis Isotope analysis is the identification of isotopic signature, abundance of certain stable isotopes of chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web ...

to look at the variation in diets of octopuses living in

marine protected areas A marine protected area (MPA) is a protected area of the world's seas, oceans, estuary, estuaries or in the US, the Great Lakes. These marine areas can come in many forms ranging from wildlife refuges to research facilities. MPAs restrict human ...

, versus non-protected sites. The researchers discovered that the octopuses living in protected areas have more diverse diets.

References

External links

TONMO.com: Octopus bimaculoides Care Sheet

Video of ''Octopus bimaculoides'' (California two-spot octopus)
{{Taxonbar, from=Q2616929 Octopuses Molluscs of the Pacific Ocean Cephalopods of North America Western North American coastal fauna Fauna of California Molluscs of Oceania Cephalopods described in 1949