Join the Seattle Aquarium for Winter Fishtival, where we’ll feature different sea animals and fun activities each day. December 28 is all about cephalopods (meaning “head-foot”), a group that includes octopus, squid and cuttlefish. Seattle Aquarium intern Paul Ehlen is a devoted cuttlefish fan—read on as he shares his knowledge and enthusiasm for these fascinating creatures.
All about Sepia bandensis: the dwarf cuttlefish
Despite its common name, this little critter is not a fish at all but a cephalopod. These visually stunning animals have the ability to change color, pattern and texture in the blink of an eye. Cuttles are perfect predators, like tiny raptors of the sea they swoop down and snag their prey with their lightning-fast feeding tentacles. Dwarf cuttlefish are intelligent, interacting with people and each other in subtle and dramatic ways. And a breeding population is currently on display in the Ocean Oddities section of the Seattle Aquarium!
Sepia bandensis possess an array of amazing physical adaptions. Perhaps most notably, they can change color and pattern in the blink of an eye: from a blanched white resting color to near jet black when they’re excited and every shade and pattern in between. They can even scroll bands of color across their bodies, an effect which some have suggested is used to mesmerize prey as well for intraspecies (within the species) communication. Dwarf cuttlefish achieve these amazing effects through the use of several types of specialized pigment cells, commonly referred to as chromatophores. In addition to color and pattern changes, cuttles can produce a texture like tags of skin which further aids their ability to camouflage as they seek to avoid predators or ambush their prey. Like the color changes, these textural changes happen in an instant. The speed and complexity of the color and texture changes of cephalopods and especially cuttlefish like Sepia bandensis surpass those of any other animal group, including some fish like flasher wrasses and even chameleons, the archetypal color change experts in the animal world.
Beyond their amazing skin, S. bandensis have a number of other unique physical attributes that they share with their cephalopod cousins including three hearts, a ring-shaped brain, copper-based blood (it’s blue!), jet propulsion, 360° vision and the ability to squirt ink. They also have mouths with a sharp beak and a rasping radula for a tongue, both of which they share with octopus and squid. They have eight arms arranged around their mouth as well as two feeding tentacles which they can fire with amazing speed and accuracy. These animals are about the size of a pea when they hatch and are fully grown at 3–4” in length. In addition to their ability to swim with jet propulsion via their excurrent syphon, they can cruise around more slowly and nimbly using undulations of a lateral fin that girds their mantle. Inside this mantle is their cuttle bone, an incredibly light and porous calcium structure used to regulate buoyancy. Finally, these crazy critters can actually walk across the bottom using two of their arms and two skin flaps on the bottom of their mantles.
Here we see a pair of Sepia bandensis displaying two of the most recognizable of their myriad awesome behaviors; "walking" and scrolling bands of color across their bodies.