The team of veterinarians at the Charleston Veterinary Referral Center doesn't see a lot of eels. So when Dr. Jason King deduced that a green moray eel from the South Carolina Aquarium had a slipped invertebral disc, he drew on his knowledge of house pets.
"We see it fairly often in dachshunds," says King, a neurologist at the 24-hour clinic who saw the six-foot-long patient on Sept. 22. In both eels and wiener dogs, he reasoned, an out-of-place disk can pinch nerves in the spine and lead to weakness or even paralysis. Jason Cassell, an aquarist at the S.C. Aquarium who is in charge of day-to-day care for the snakelike creature, had been the first to notice problems. He says he has never named the fish (only the more popular animals get nicknames) and does not know whether it is male or female (eels have no external sex organs), but in conversation he refers to it as a male.
"His posture was different from how he normally sits," Cassell says. Ordinarily, the eel could often be seen at the bottom of the Great Ocean tank with its back half resting in the gravel and its front half elevated. But starting in September, it became less active and tended to contort itself sideways at a 90-degree angle. It also had a hard time turning right.
So Cassell, along with the aquarium's Dr. Shane Boylan, loaded the eel into a tank on the back of a flatbed truck and drove it to the referral center in West Ashley. There, Dr. King dissolved a powder anesthetic in the tank that would knock the fish out long enough to run a CAT scan. The fish would only last about seven minutes out of water, so he had to move quickly.
King and Cassell both say that moray eels tend to be docile; they just don't like it when you mess with their burrows, and sometimes they confuse human fingers for food. Their first row of teeth is curved backward, so their jaws have to be forcibly pried open once they latch on to something. Meanwhile, a second set of pharyngeal jaws in the back of the throat sets to work pulling the food down like an alien monster in the movies, King says.
Today, after spending some time resting in a PVC pipe — something like a cast for an eel — the creature has perked up a bit, but it isn't taking food. Cassell says that when he feeds fish to the eel, it shows an interest but ultimately regurgitates it, possibly because of an inflamed esophagus. This species can go three or four months without eating, though, so Cassell isn't too concerned yet. If the recovery takes a few months, he can purée a fish and tube-feed it to the eel.
The next step is to move the eel into a narrower PVC pipe, where it is less free to wiggle around. If it is a good patient and sits still for the majority of the next six to eight weeks, Cassell reckons, the disc should have time to heal. The animal is probably 15 to 20 years old; this species has a life span of 30 to 40 years in the wild.
So how does a captive eel injure its back? It doesn't look like a fight, says Cassell. There are no scrapes or bruises.
"He was probably moving around the tank quickly and hit the acrylic side of the tank," he says. "He probably did it commonly, but because he's getting a little more up in age, he might have hurt himself this time."