Revisited: Cuttlefishes

Scientific Name: Sepia officinalis; S. atlantica; S. bandensis; S. pharaonis; Metasepia pfefferi; Sepiola rondeletti

Common Name: Cuttlefish

Taxonomy:

Domain: Eukarya

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Decopoda

Family: Sepiidae

Genera: Sepia & Metasepia (most common aquarium genera)

Description:

Looking to do something different with your next marine aquarium? One of the most fascinating and beautiful of all sea creatures, the cuttlefish, may be just the thing to take that same old tank and make it into an extraordinary marine biotope. These colorful, intelligent cephalopods are sure to pique the interest of even the most seasoned saltwater enthusiasts. They have interesting personalities and will quickly learn to recognize you as their keeper5.

The true appeal of these wonderful creatures comes from their beautiful appearance and their engaging personalities. Many specimens will exhibit begging behavior when their aquarists walk past the tank and will unmistakably desire interaction with their owners5. They can even be taught to take food from your hand5.

Cuttlefish are cephalopod mollusks from six different families, including the most common Sepiidae, and are found in all of the worlds seas1. Comprised of 23 genera and 201 individual species, the families are impressive in their variety2. Cuttlefish have some of the same distinguishing features as other cephalopods such as a mantle, advanced eyes, a bird-like beak, eight sucker-lined arms, and two lengthy feeding tentacles2,5. They also possess a hard internal shell, known as the cuttlebone. In living cuttlefish, the cuttlebone is gas-filled and aids in buoyancy control2,4,5. These calcium carbonate (aragonite) cuttlebones are often sold as nutritional supplements for exotic pets and even have uses in the jewelry industry2,4,5. Amazingly, cuttlefish also have skin layers impregnated with color-changing chromatophores, leucophores, and iridophores, which allow them to rapidly change their appearance according to their mood or the look of the background5.

Natural Habitat and Ecology:

Although species are most often found in coastal shallows they exist in every ocean on Earth1. They are primarily bottom dwelling, preferring reef fringes, seagrass beds, and sandy or muddy bottoms2,3,6,7. These areas provide a mottled background against which the cuttlefish can utilize its amazing camouflage skills. Their abilities to blend in with their environment and move with grace and speed make them incredibly stealthy and agile hunters.

It is the camouflage ability of these mollusks that truly separates them from most inhabitants of the typical marine aquarium. As ambush predators, cuttlefish may often be found mimicking the look of the substrate behind them. By creating amorphous skin folds, and changing to mottled or speckled colors, they blend seamlessly into the background and wait for passing fish or crustaceans to wander too close5. Then, with lightning quick reflexes, the predator will snatch the prey and dispatch it quickly with its sharp beak. The fish, shrimp, or crab is grasped by suckers lined with sharp, chitinous rings, positioned at the club ends of the feeding tentacles2. Sharp powerful jaws resembling a birds beak can break through shells and bones, while the tongue-like radula strips the remaining flesh. During more active periods the cuttlefish can be seen wearing vibrant, solid colors. It may also flash or pulse kaleidoscopic patterns with amazing speed3.

Aquarium Care:

Cuttlefish have long been considered to be one of the tougher aquarium species to maintain. Contrary to popular belief, however, their difficulty level does not exceed that of many common marine aquarium inhabitants. If you can maintain coral, you can keep a cuttlefish. In fact, standard reef tank water parameters will also suit cuttlefish quite well (e.g. 1.025 S.G. & 8.1-8.4 pH) 5,6,7.

Several species of cuttlefish make suitable aquarium inhabitants but care must be used in selecting the appropriate size tank. For example, common cuttlefish (Sepia officinalis) can grow to twelve inches or more and will require a minimum of 200 to 300 gallons of water5,6. Though common cuttlefish may be more readily available because they have been successfully cultured for many years5, their size makes them inappropriate for many hobbyists. On the other hand, S. bandensis and Sepiola rondeletti only grow to a maximum of several inches, thus requiring much less space5,6,7.

A cuttlefish tank will require exceptionally clean and well-oxygenated water. It is necessary to have an overflow, heavy protein skimming, and well-maintained mechanical filtration5. The filtration should be augmented with plenty of water-flow throughout the system. Additionally, the aquarium should have well-established biofiltration to accommodate the voracious eating habits of these animals. Cuttles prefer to eat live food but will easily adapt to eating frozen krill or other raw, meaty food such as shrimp or fish5,7.

Most cuttlefish species encountered in the trade will live well in water temperatures in the low to mid 70 Fahrenheit degrees range3,5,7. Interestingly, Sepia officinalis and S. atlantica are actually cold water species that will adapt to warmer aquarium waters if acclimated slowly. They will do especially well in warm water if hatched there from the egg3. It is likely that a healthy looking specimen from the fish store has already undergone the acclimation process. If it will eat at the store, the chances for its survival at home are good. As for lighting, there does not seem to be a consensus though it is likely that trade species will adapt to whatever conditions they are presented.

Perhaps the most critical factors for successful cuttlefish care are selecting the tank mates and aquascaping you will use. Remember that cuttlefish are voracious swimming predators. They will catch and kill any fish small enough for them to grab5. They will also make short work of crabs and shrimp. Other tank inhabitants should be sessile, non-stinging invertebrates which can handle the necessarily-heavy feeding regime. Mushrooms, non-stinging zoanthids, and tree-corals will all make suitable tank-mates. Some people create hanging canopies of macroalgae and/or small islands of live rock5. Seagrass beds also provide good habitat. Usually, a minimalist approach to aquascaping works best if you want to see your cuttlefish often. Their inherent stealth may make them impossible to find in a crowded system.

Housing more than one cuttlefish in a single tank is not recommended, unless you have an exceptionally large aquarium or are attempting to breed them. Sexing individuals can be extremely difficult and male cuttlefish may fight to the death5. Breeding should only be attempted by very experienced cuttlefish aquarists possessing a divided breeding tank. Care must be taken to ensure that males are not mixed and the male and female should be physically and visually separated immediately upon mating5.

Quick Notes:

Do not treat cuttlefish with copper--

Cuttlefish are short-lived--

Cuttlefish can suffocate on their own ink--

Cuttlefish will learn--

References:

1 Anonymous. Current Classification of Recent Cephalopoda. 2001.

2 Cuttlefishes. Amanda Reid, Patrizia Jereb and Clyde F.E. Roper. 2005, FAO Species Catalogue for Fishery Purposes No. 4, Vol. 1, pp. 56-62.

3 Jennings, Greg. The New Encyclopedia of the Saltwater Aquarium. Buffalo : Firefly books Ltd., 2007.

4 Huber, Peter Castro and Michael E. Marine Biology 5th Ed. Boston : McGraw Hill, 2005.

5 Ross, Richard. Feature Article: Keeping and Breeding the dwarf cuttlefish Sepia bandensis . Advanced Aquarist' Online Magazine. [Online] September 2005. [Cited: August 04, 2009.] http://www.advancedaquarist.com/2005/9/aafeature.

6 Shimek, Ronald L. Marine Invertebrates. Neptune City : T.F.H Publications, 2004.

7 Simon & Schuster. Simon & Schuster's Guide to Freshwater and Marine Aquarium Fishes. New York : Fireside Books, 1977.