Cuttlefish Husbandry: Part I - What is a Cuttlefish anyway?

<< Cephalopod Articles | Photographs and text by Dr. James B. Wood

About the author: James's first aquariums were jars with tadpoles, and it is rumored that he single handily doubled the frog population of South Florida by the age of 6. James went on to collect his own local minnows and eventually kept marine fish. While in high school, he caught and kept his first octopus. James is working on a book for hobbyists on keeping octopuses and cuttlefish... find out more about Dr. Wood.
Ventral Side of a Cuttlefish

Cephalopoda is the class containing cuttlefish, octopuses, squid and the chambered nautilus. They are a fascinating class of marine invertebrates. Public interest in them is growing and many advanced marine hobbyists have toyed with the idea of keeping them. Unfortunately, there are few articles about keeping cephalopods as pets and many of those that do exist either do not provide useful information, are contradictory, or are incorrect. Cephalopods are invertebrates and as such are very different from us and from other vertebrates; therefore hobbyists can't rely on their past experience and intuition. However, like most creatures, they are not especially hard to keep once you understand their biology and requirements. Octopuses and cuttlefish are the best candidates for advanced hobbyists looking to keep a marine creature that can truly be called a pet. Octopus care has been previously addressed in this publication (see Wood 1994).

Sepia officinalis, the common cuttlefish, is well known to scientists who study cephalopods as it is capable of many advanced color changes, body patterns and other unique and interesting behaviors. Their intelligence and charisma often make it hard for scientists to think of them objectively as research animals instead of as pets. Those that I've been keeping were left over from a research experiment of Dr. Shelly Adamo. Luckily, Sepia officinalis is also one of the easiest cephalopods to keep in captivity and is one of the most common species of cuttlefish available to aquarists.

This is the first part of a four part article on the common cuttlefish, Sepia officinalis. This article will cover what a cuttlefish is and what it is related to. Part two explains how to go about purchasing one. Part three will cover tank size, filtration, lighting, tankmates, feeding and other aspects of setting up a tank to keep cuttlefish. The final part of this article, part four, will describe the reproductive biology of cuttlefish and tips for rearing hatchlings.

Hobbyists invariably regard cephalopods as extremely difficult to keep. Most of the problems that aquarists have or think they have when keeping cephalopods are ultimately caused by bad information or a lack of information. Although cephalopods are active and intelligent, they are very different from mammals and fish in their biology and especially their life history. However, with knowledge and preparation, many species of octopuses and cuttlefish can be successfully kept and bred in captivity. In fact, some of the more common species have been reared for 5 or more generations in the lab.

Cephalopods are a class in the phylum Mollusca which also contains bivalves (scallops, oysters, clams), gastropods (snails, slugs, nudibranchs), scaphopods (tusk shells) and polyplacophorans (chitons). Most relatives of cephalopods, are, well, a bit slow. It doesn't take a head, or even a brain, for a clam to sit around and filter water. So how did cephalopods get to be the fast moving, intelligent animals that they are?

Cephalopods arrived on the scene in the Cambrian period. These early cephalopods had external shells. Scientists believe that the ancestor to modern cephalopods was a mollusk that developed an air space within its shell and a method to regulate the amount of air in it. This allowed early cephalopods to get into the water column and sail around like a hot air balloon. This offered many advantages and the view was great. Predators could be avoided by simply leaving the bottom, and animals could transport themselves over large distances without much energy expenditure. This allowed them to radiate into new areas as well as move to areas with more food and/or less predators. Competition increased and jet propelled locomotion, better nervous systems, improved sense organs, and adaptations for crypsis evolved in a sort of 'evolutionary arms race'. Some species, the ancestors of modern squid, cuttlefish and octopuses abandoned the armor of their heavy shell in favour of a faster, more streamlined form. Cephalopods became one of the dominant groups in the world's oceans. However, jet power is not as energetically efficient as undulation power, and perhaps for this reason, teleosts (bony fish) usurped cephalopods dominant place in the world's seas.

So, why the fascination with cephalopods anyway? Well, after hundreds of millions of years of evolution, cephalopods have developed some pretty neat adaptations. First off, cephalopods are thought to be the most intelligent invertebrates on the planet. Invertebrates make up 95% of all animals. Experiments have shown that cephalopods have fast learning curves and scientists are currently debating whether or not they can learn by observation. Cephalopods can change their color and texture in the blink of an eye and most scientists agree that at least some species use body patterns to communicate. Everyone who has ever seen me feed my cuttlefish has noticed that they beg for food; particularly snarky individuals will occasionally jet water at me. Speaking of which, there is even a scientific paper by Dr. Mather about personality of cephalopods! Other cephalopod abilities include jet power, ink decoys, regeneration, and exponential growth of the young.

So, by now you are saying 'I'm sold! Where can I get one?' How do I keep one in an aquarium? What do I feed them? Hang in there, the answers to these questions are forthcoming in the months to come.

Part II - Where can I get a cuttlefish?

References

Barnes R.D. 1987 Invertebrate zoology, 5th ed. Saunders College Publishing, Fort Worth.
Boyle P.R. (ed) 1987 Cephalopod life cycles, vol 2. Academic Press, London.
Hanlon, R.T., Claes M.F., Ashcraft S.E., and Dunlap P.V. 1997 Laboratory culture of the sepiolid squid Euprymna scolopes: A model system for bacteria-animal symbiosis. Biol. Bull. 192: 364-374.
O'Dor R.K. and Webber D.M. 1986 The constraints on cephalopods; why squid aren't fish. Vie Milieu 35: 267-271.
Wood, J.B. 1994 Don't fear the raptor; an octopus in the home aquarium. Freshwater and Marine Aquarium Magazine. 17(4).

Articles Reference

Wood, J. B. 1998 Cuttlefish Husbandry. Part I; What is a cuttlefish anyway? Freshwater and Marine Aquarium Magazine. vol 21, no 7. Reprinted in: The Cephalopod Page. Wood, J. B. Ed.

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