Octopus are found in both temperate and tropical oceans. Many have a short life span, less than two years. They only mate once, then die. The male dies shortly after depositing his sperm into the mantle cavity of the female. The female is capable of storing the sperm for a few months, but after depositing the fertilized eggs and caring for them until they hatch, the female then dies.
They have the most well developed eyes of any aquatic invertebrate. Even though they can not hear, they have an excellent sense of touch and smell. They crawl and swim by drawing water into the mantle cavity and forcibly expelling it through their siphon tube. Similar to how a jet engine works. They are also excellent at changing their skin color as a means of passive defense. At time of real danger, they eject an inky secretion that forms a dark cloud allowing for escape.
As for strength, they are extremely strong for their size. A small 5 inch (12 cm) octopus could lift an aquarium cover that is weighted down with a brick! Then crawl out and wander around your home! I know - been there, done that! They are also highly intelligent and make good but short-term pets. The ones I've maintained appear to be quite ammonia sensitive and require very good water quality and excellent water movement. They like to hide during the day, as they are nocturnal creatures. A bite from the tiny, 1 inch (2.5 cm) Blue Ringed octopus mentioned below can be fatal.
Note: Even though Cuttlefishes are invertebrates, they have the word "fishes" included in their common name. Therefore many hobbyists think of them as a fish instead of an invertebrate. Because of that I have included these interesting creatures in the "Fish" section of this Animal Library. Simply click on the underlined word above, which will take you directly to these fascinating creatures.
These are small rounded body squid with two large rounded fins. They have tentacles similar to cuttlefish. They are vicious predators, and will attack anything eatable.
These are elongated squid, or what could be called torpedo-shaped, and have two triangular or slightly rounded fins. They have tentacles similar to cuttlefish. They are vicious predators, and will attack anything eatable.
This strange snail-like animal, about 8 inches (20 cm), is a relative of the octopus, cuttlefish, and squid. It has changed little over the past 500 million years and is considered by some to be a living fossil. It is a deep living species, capable of migrating from about 1500 feet (450 m) to approximately fairly shallow waters at about 300 feet (90 m) without internal damage or being effected by temperature changes. This seems to occur daily when they feed upon shrimps, crabs and other small invertebrates during evening hours.
Its shell is divided into a various number of compartments depending upon its age - about 4 as a newly hatched specimen and about 30 compartments in an adult stage. As it ages, its body moves to the outer compartment areas, leaving the most inner areas/compartments vacant, except for a gas, which serves as means to control its buoyancy. They swim by pulling water into the mantel cavity within the shell and forcing it out a muscular siphon under its tentacles. By controlling the direction of the outflow, it can swim in any direction. Its darker top shell makes it more difficult to see from above, and its lighter bottom shell makes it more difficult to see from below. Nautilus belauensis, N. macromphalus, N. pompilius and N. stenomphalus are among the known existing species.
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