Broadclub cuttlefish

At the Aquarium

How do you incubate cuttlefish eggs behind the scenes? You could, at a cost of hundreds of dollars, buy commercial incubators. But that would be too easy. Plus, our aquarists figured they could create something just as good as the store-bought jobs.

For $2.50 and "a day in the life of one volunteer," we make a better bubbler out of soda bottles, plastic tubing and silicone glue. It looks like mad science, but it works. To date, we've produced hundreds of baby cuttlefish for exhibit using the system.

Natural History

One of the hypnotic heavyweights in the cuttlefish family, the broadclub cuttlefish is the second-largest cuttlefish species, with eight arms and two feeding tentacles. This cunning predator hypnotizes prey with flashing, colored bands that ripple along its skin. The two largest clubbed arms fan out at angles from the body while the two feeding tentacles do the striking and initial grabbing of prey.

Broadclub cuttlefish are cephalopods related to squid, octopus and chambered nautilus. The cuttlefish's flat body allows it to live and hover near the ocean bottom where it finds its favorite food. An outer shell once covered the cuttlefish's body but has since evolved into a porous internal shell called a cuttlebone. The cuttlefish varies its buoyancy by varying the amount gas and liquid held in the holes of the shell.

A cuttlefish moves by undulating a delicate fringe that runs along its entire body, but for a quick getaway it expels a forceful stream of water through its siphon. When threatened, cuttlefish can produce a covering cloud of ink called sepia. Long ago, this dark-brown ink was used for writing and drawing.

Conservation

As with other sea life, pollution, overfishing and habitat destruction pose serious threats to cephalopods. Habitat destruction, bottom trawling, pollution by runoff and saltation threaten cuttlefishes' environments.

Cool Facts

Males fight for choice mating dens. Most fights end without major injuries. After the males win their territory, female cuttlefish appear at the dens and mate with resident males. Fertilization is internal.

Face to face the cuttlefish embrace and the male uses a special arm to transfer a sperm packet into the female's mantle cavity. After mating, the female retreats deep within the den where she lays her eggs one at a time. She coats the eggs with a protective sheath and carefully cements them to the roof of the den. She leaves the eggs unattended to develop and to hatch on their own. The female dies shortly thereafter.

Like their fellow cephalopods, broadclub cuttlefish are master color changers. Known for their bright coloration, they can rapidly change to ornate colors. Cuttlefish and other cephalopods use color to communicate warnings, mood changes, courtship displays or for camouflage.

Cuttlebone is composed of calcium. This calcareous cuttlebone is often fed to birds to whet their beaks or as calcium supplements.