California Two-spot Octopus

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Species group:

Other common names: “Bimac”

Scientific name: Octopus bimaculoides

The Basics:
Although not recommended for beginners, the California Two-spot Octopus is one of the hardier species – “hardy”, that is, by Octopus standards! Still, it is a complex, fascinating creature, well-worth the consideration of serious aquarists interested in delicate marine invertebrates.

The California Two-spot Octopus is found in the Eastern and Indo-Pacific Ocean, from central California to Mexico and from East Africa to Japan and northern Australia.

It inhabits rocky coastlines, tide pools, wrecks, and coral reefs.

Appearance / health:
The mantle (head and body) is 12.7-17.5 cm (5-7 in) in length, the arms span 51-58 cm (20-23 in), and the highly-changeable skin color is most often gray or yellowish-brown with yellow blotches. The two blue-ringed ocelli, or false eye-spots, are very distinctive.

In common with related species, the California Two-spot Octopus’s natural life span is only 1-2 years, and it is extremely sensitive to copper, ammonia and nitrates in the water. When startled or stressed, Octopuses release a black, inky liquid designed to confuse predators. In the confines of an aquarium, however, ink can prove fatal to an Octopus.

Behavior / temperament:
Octopuses break all preconceptions about invertebrates. They are quite intelligent, learning to open jars in order to obtain food, and seem to enjoy playing with Frisbees and other items. Nocturnal and extremely shy, some will eventually accept food from tongs. No Octopus, however calm, should be handled or hand-fed, as all produce venom and can deliver a painful bite with their hard, curved beaks. While fatalities from the commonly-sold species are unknown, the possibility of a serious allergic reaction to their venom must be considered.

The California Two-spot Octopus requires a well-filtered 55 gallon or larger aquarium that has been cycled for 2-3 months and is provisioned with a thin layer of sand. They are consummate escape artists, putting snakes to shame, so the filter canopy must be weighted or secured with clips, and all hose/wire openings must be sealed. Wet/dry and other out-of-tank filters are the best options, and a protein skimmer is advisable.

Lighting should be subdued; a red night-viewing bulb will allow you to observe your pat’s nocturnal wanderings. Caves, preferably of live rock, are essential. All rockwork must be secured, using silicone if necessary, as Octopus are incredibly strong – and they seem to delight in trashing whatever homes we provide for them!

The California Two-spot Octopus should be maintained at a specific gravity (salinity) of 1.025-1.026 and a pH of 8-8.4. They fare best at 18-22 C (65-72 F) but can adjust to cooler and warmer temperatures.

Youngsters and newly-acquired adults often refuse all but live shrimp and crabs; green, fiddler, calico and other crabs may be collected or purchased at bait shops. In time, most pets can be weaned to non-living foods. The diet should be varied, and include crabs, clams, mussels, scallops, snails, abalone, and other marine invertebrates. Some will also accept spearing and other fishes.

Captive breeding is rare, with fights and/or predation being the usual result when two individuals are introduced. Female California Two-spot Octopuses guard their eggs, up to 150,000 in number, within caves. They generally do not feed during the 2-4 month incubation period, and usually expire shortly after the young hatch.

Written by Frank Indiviglio

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