Cephalopods are highly evolved molluscs characterized by bilateral body symmetry, a prominent head, and a modification of the molluscan foot into the form of arms and/or tentacles that surround the mouth. They have well developed brains and eyes, a hard and chitinous beak, and in many cases complex defense mechanisms and/or ways to subdue prey such as “ink,†potent venoms, and color changing chromatophore cells. Due to the similarity of the name, they are sometimes confused with amphipods or copepods which are small shrimp-like crustaceans. The class cephalopoda is supertended by the phylum Mollusca and it contains two subclasses, Coleoidea which contains the
octopus, squid, and cuttlefish and Nautiloidea which only contains the few species of
nautilus.
There are around 700 species of cephalopods worldwide in all undersea habitats, and surprisingly few inhabiting the coral reefs. Most cephalopods have a short life span with fast growth rates and only a life expectancy of one to three years. Cephalopods are the most active of the molluscs and some squids rival fishes in their swimming speed. Cephalopods are an ancient group that appeared some time in the late Cambrian several million years before the first primitive fish began swimming in the ocean. By the time the Coleoidea separated from the Nautiloidea, vascular plants and vertebrates had still not reached land. Some of the most spectacular cephalopods are the giant squid such as
Architeuthis dux, whose body length (not including arms and tentacles) can grow in excess of 18 feet. They are the largest known invertebrates. Based on analysis of stomach content, these squid eat fish and other small squid.
In the home aquarium only small species are appropriate and these amazing creatures demand a great degree of planning and care.
Octopus bimaculoides is one species of octopus commonly kept in captivity. This octopus can be fed meaty foods like shrimp, crab, and bivalve meat. They should be kept in aquariums with tight fitting lids that cannot be easily propped up from the inside and the rockwork in the aquarium should be extremely stable so that it cannot topple down onto the octopus that may enjoy digging and rearranging his habitat. It is also important to make sure powerhead strainers and other intake covers cannot be pulled off by these inquisitive cephalopods as they can be sucked in and irreparably injured or killed.
Southern Calamari Squid
Sepioteuthis australis
Mourning Cuttlefish
Sepia plangon
Giant Cuttlefish
Sepia apama
Chambered Nautilus
Nautilus pompilius
Blue-lined Octopus
Hapalochlaena fasciata
Common Sydney Octopus
Octopus tetricus
Courtesy of ATJ