California two-spot octopus

Octopus bimaculoides reaches a mantle size of 17.5 cm (7 inches) with arms to 58 cm (23 inches). Not usually heavily textured, it has several common colors, such as grey with yellow splotches, and uses highly developed crypsis (camouflage or color-changing to match the environment).

Octopuses achieve color change in part by chromatophores, iridophores, and leucophores; 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 consequently allow the skin to reflect wavelengths of light which are prevalent in their habitat and produce disruptive patterns. The other aspect to cephalopod 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 also have three hearts, two gills, blue blood, and a donut-shaped brain. [4]

O. bimaculoides can be found in coastal waters from the intertidal down to at least 20 m (65 ft) in the eastern Pacific along mid- and southern-California and the western side of the Baja California Peninsula in Mexico.[1][5]

This species of octopus is found in subtidal to a depth of 20 m (65 ft). It prefers rocky reefs or debris for hiding. It tolerates a wide temperature range 15-26 °C (60-80 °F), though it prefers 18-22 °C (65-72 °F).

Towards the end of their lifespan, they are ready to reproduce. These octopuses will only mate and reproduce one time in their entire life because they are semelparous.[11] While they can mate at any point of the year, it is most common during the summer when the water is warmer. The male will first fertilize the female using its spermatophores. Then the male will die not long after mating.[12] After mating, the female will create a den where she will lay anywhere from around 20,000 to 100,000 eggs. Her work is not done just yet. 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 deteriorates, usually resulting in her death.[13]

In recent years new technology, such as genome sequencing, has provided new information on the large amounts of clustered protocadherins (PCDH) in Octopus 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.[14]

Researchers collected and tagged the octopus species, Octopus bimaculatus, to conduct an acoustic telemetry research on them. They measured the position of the octopuses in the environment over the course of two weeks. They also recorded the movement of each octopus throughout every day of the study. The study showed that the Octopus bimaculatus always moves from one den to another every few days. Moreover, to avoid predation, their daytime movement patterns and the distances they travel vary a lot.[15]

Researchers used Stable Isotope Analysis (SIA) to try and figure out if there is a difference between the Octopus bimaculatus that live in Marine Protected Area (MPA) sites versus non-protected sites. With the SIA, the isotopic composition of the octopus’s prey can be found in their tissues. By analyzing the isotope ratios of carbon to nitrogen in both the octopuses and any nearby prey (from both MPA and non MPA), researchers discovered that the octopuses living in the MPA have a more diverse diet. Due to this result, it can be concluded that because of the MPA the octopuses play a different role than the ones in the non-MPA.[15]

• "CephBase: California two-spot octopus". Archived from the original on 2005-08-17.
• TONMO.com: Octopus bimaculoides Care Sheet
• Video of Octopus bimaculoides (California two-spot octopus)