Image from William Warby on Flickr.

The term “cuttlefish” does not refer to a single species, but rather all animals belonging to the order Sepiida. To make matters just a bit more misleading, cuttlefish aren’t even fish, much like how the ghost shark[1] is not a shark or how the pelican gulper eel[2] is neither an eel nor a pelican. These creatures actually belong to the phylum Mollusca, a large phylum that includes land snails and clams, and the order Cephalopoda, which also contains squids and octopuses.

Yes, believe it or not, these are distant cousins of the land snail. Photo by DAVID ILIFF. License: CC-BY-SA 3.0

These cute little guys are curious creatures that are well known for both their high intelligence and advanced camouflaging capabilities[3]. Their large, sophisticated brains that allow them to possess high intelligence for invertebrates. Like other cephalopods, cuttlefish can alter the pigments in their skin to camouflage themselves, ward off predators, and even win mates[4]. These creatures’ camouflaging capabilities is impressive not just for how rapidly they can change colors but also because they are technically colorblind. Scientists believe[5] that their well-developed eyes can better perceive contrast (through light polarization sensitivity), aiding them in camouflaging themselves.

Other prominent features of these animals include their w-shaped eyes (with wide-ranging vision capabilities) and cuttlebones. Unique to these animals, cuttlebones[6] are internal structures that are used for buoyancy. Because of the delicate nature of these structures, cuttlefish will typically remain in shallow waters to avoid excess pressure, although scientists have recorded them reaching depths down to 600 m beneath the surface of the ocean[7].

A cuttlebone, an internal shell that cuttlefish use for buoyancy. (Image: Mariko GODA by CC-BY-SA 3.0)

While typically small animals, the largest[8] individual species, the Australian giant cuttlefish (Sepia apama), reaches up to nearly 20 in (50 cm) and weighs 23 lbs (10.5 kg). Typical diets for these creatures includes small fishes and crustaceans[3]. Many animals prey on them, including other cuttlefish!

There’s a significant imbalance in males to females of these animals, with there being many more males than females. As such, males have had to adapt some extraordinary features to court potential mates. One of their more incredible mating techniques is to use their camouflage in a rather sneaky manner. Smaller males won’t show off flashy colors to woo mates (like birds, for example) but rather disguise themselves as females to swim past larger, more aggressive males in order to get closer to females. Unfortunately, cuttlefish die after mating once, so typically they only live between one to two years[3].

Giant cuttlefish with an Eastern Blue Groper fish in its mouth
Cuttlefish consuming an Eastern Blue Groper. Image credit: Elaine de Jager by CC-BY-SA 4.0

How many cuttlefish are there in the world?

While the exact number is unknown, the scientific community does not consider these animals to be endangered. They have wide-reaching habitats and are found in various temperate or tropical oceans around the world.

How many eggs do cuttlefish lay?

They can lay hundreds[9] of eggs at once (usually 100 to 300).

How many hearts do cuttlefish have?

Like squids and octopuses, they have three hearts.

 

References:

[1]“Getting to Know the Ghost Shark, Which Is Neither a Ghost Nor a Shark.” Out of the Box Science, Out of the Box Science, 12 Jun 2018, https://outoftheboxscience.com/living-world/getting-to-know-the-ghost-shark-which-is-neither-a-ghost-nor-a-shark/.

[2]“‘That looks nothing like a pelican’: Getting to Know the Elusive Pelican Gulper Eel.” Out of the Box Science, Out of the Box Science, 1 June 2018, https://outoftheboxscience.com/living-world/that-looks-nothing-like-a-pelican-getting-to-know-the-elusive-pelican-gulper-eel/.

[3]Kaufmann, Gisela, et al. “King Camouflage.” NOVA, season 34, episode 2, 3 April 2007.

[4]Norman, M D, et al. “Female Impersonation as an Alternative Reproductive Strategy in Giant Cuttlefish.” Proceedings of the Royal Society B: Biological Sciences, vol. 266, 1999, pp. 1347-1349. PubMed Central, www.ncbi.nlm.nih.gov/pmc/articles/PMC1690068/.

[5]Shashar N, et al. “Polarization vision in cuttlefish in a concealed communication channel?” Journal of Experimental Biology, vol. 199, 1996, pp. 2077-2084. PubMed Central, https://www.ncbi.nlm.nih.gov/pubmed/9319987.

[6]Checa, Antonio G, et al. “The Cuttlefish Sepia Officinalis (Sepiidae, Cephalopoda) Constructs Cuttlebone from a Liquid-Crystal Precursor.” Scientific Reports, vol. 5, 2015, pp. 11513. PubMed Central, www.ncbi.nlm.nih.gov/pmc/articles/PMC4471886/.

[7]Lu, C C, and C F E Roper. “Aspects of the biology of Sepia cultrata from southeastern Australia.” La Seiche, The Cuttlefish, edited by E Coucaud-Camou. Centre De Publications De l’Université De Caen, 1991, p. 192.

[8]Aglibot, D, “Sepia apama.” Animal Diversity Web, University of Michigan, 2014, http://animaldiversity.org/accounts/Sepia_apama/.

[9]“Cuttlefish.” Encyclopaedia Britannica, Edited by editors of Encyclopaedia Britannica, Encyclopaedia Britannica, Inc., 4 February 2018, www.britannica.com/animal/cuttlefish.

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