Caribbean Dwarf Octopus

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Species group:

Other common names:

Scientific name: Octopus mercatoris

The basics:
The Caribbean Dwarf Octopus is a good choice for those new to the fascinating world of Cephalopod care, and one of the few Octopuses that may thrive in a relatively small aquarium.

The Caribbean Dwarf Octopus is found in the Caribbean Sea, Gulf of Mexico, and many Florida bays.

It inhabits shallow water, seeking shelter in rock caves, empty shells, and bottom refuse such as bottles, cans and shoes.

Appearance / health:
The mantle (head and body) tops out at 2.54 cm (1 in) or less in length, and the highly-changeable skin color is most often reddish to dark brown.

In common with related species, the Caribbean Dwarf Octopus’s natural life span is only 8-12 months, 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 invertebrate rules, being intelligent, and often very responsive to careful owners. Many learn to open jars in order to obtain food, and seem to enjoy playing with plastic blocks and other toys. Nocturnal and extremely shy, most will eventually accept food from tongs…sometimes even engaging in a spirited tug-of-war with their owner. 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 Caribbean Dwarf Octopus requires a well-filtered 30 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 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 Caribbean Dwarf 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 23-25.5 C (74-78 F).

Youngsters and newly-acquired adults often refuse all but live shrimp and crabs; small 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, but possible, as the Caribbean Dwarf Octopus seems somewhat more sociable than other species. Females guard their eggs, 50-350 in number, within shelters. They generally do not feed during the incubation period, and usually expire shortly after the young hatch.

Written by Frank Indiviglio

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