Seven dwarfs: a cephalopod story

Several months after I predicted his end was near in September, the big European cuttlefish in Discovery Bay went off exhibit after the holidays and completed his lifespan at the usual age of 18 months. I call him the big cuttlefish because, though less than a foot long, he was a giant compared with the seven dwarf cuttlefish that have since taken up residence in his tank. They’re about twice the size of my thumbnail now (here’s one next to a fellow volunteer’s finger for perspective), but they’re also less than four months old and eventually will stretch out to a full four inches.

dwarf cuttlefish and fingerThese tiny cephalopods (or cuttlets, as the Zooborns website cutely calls the babies of their species) are still growing into their final shape, but if you gaze at them long enough, the key features emerge — especially the eight arms and two tentacles sprouting from each tiny head. Their main difference from their European predecessor, size aside, is their habitat: the tropical Indian and Pacific oceans instead of the Atlantic. These seven came from the Monterey Bay Aquarium on the central California coast.

baby dwarf cuttlefishWhen the first four cuttlets entered the tank a few weeks ago, they were kept in a small transparent crate so that aquarist Becky could find them and feed them even tinier mysid shrimp. Last week, we volunteers were told they had the run of the place but that three new cuttlets had joined the crate. But when several of us went to take a look, we saw that the crate was gone and all seven had deployed themselves throughout their aquarium. And indeed, they were big enough to track down. Two or three anchored themselves in this treelike plant. My fellow volunteer Carol, in particular, kept wandering away and then wandering back to see how many had relocated. They were all too relaxed to squirt ink, as stressed cephalopods do, but one showed off his ability to change color, from a milky white to a deep brown. I can’t wait to see what they’re up to this week, and how much bigger they’ve grown.

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Last days of the cuttlefish

After this Dolphin Farewell Week ends (still a difficult thing to think about), my favorite creature in Discovery Bay will officially be the cuttlefish. This cousin of the octopus is a little crazy-looking, which is part of his fascination. The other part, for an interpretive volunteer like me, is the constellation of intriguing facts that apply to him. Like his fellow cephalopods, he can release ink, although that’s escape-level behavior I’ve never seen at the zoo. He can change color, from dark brown to nearly white. He can float aloft, his wraparound fin oscillating to help keep him buoyant. He has three hearts, two of which pump blue-green blood directly to his gills. He can change the shape of his eyeballs. These days, his eyes are a pale milky blue, which means he’s grown quite elderly at more than a year old, and the end may be near.

Like the octopus, he has eight arms — plus two tentacles, all clustered around his head. When I took the photo above, just over a week ago, a boy theorized that this was a female ready to mate, based on a video seen at another zoo and the upraised tentacles (“Hey look, I’m over here!” they seem to say). But when an aquarist stopped by with a serving of shrimp, she confirmed that this guy is male as well as old. The natural lifespan of a European cuttlefish, however well cared for, is six to 18 months; octopuses live about three years.

Some guests come to this tank completely uninitiated (“Is it a squid?” “It’s related to squid.”). Others arrive as experts, like the recent college graduate who’d written a term paper on cuttlefish. My favorite exchange, a couple months ago, involved a little boy and his older, school-age sister. After the three of us had discussed the cuttlefish for several minutes, the boy asked me solemnly, “Does he have feelings?” I hid my smile, paused to think for a minute, then replied that we can’t really know what goes on in the mind (heart? SOUL?) of a cold-blooded invertebrate, but based on his color changes alone, we know that he has simple moods like fear, aggression and hunger. Anything deeper or more complex, such as love or envy or regret, is unlikely, I explained. Children’s animal questions never fail to surprise and entertain me.

In my nearly nine years of zoo-volunteering, we’ve nearly always had a cuttlefish in this tank. They come to us from a Florida aquarium breeder, and when they first go on exhibit, they’re about as big as two human thumbs pressed together. When they get to be more than half a foot long, you know they’re adults and their days are numbered. (Females rarely live long after laying eggs, at any age.) So these days, my first stop in Discovery Bay is always at the cuttlefish tank, to see if he’s still in there. Their lives pass so quickly and so often, it’s hard to say I actually mourn. But soon the tank will be disappointingly empty, for a while, until the cycle starts anew.