An 18-foot-long oarfish found dead in Southern California was filled with parasites, according to researchers at UC Santa Barbara who dissected the serpent-like fish last Thursday.
Around two dozen larval tapeworms, two young roundworms, and little pieces of an adult spiny-headed worm were among the specimens found in a small tissue sample of the intestines. Scientists only had a foot of intestine, so it's likely that the whole organ hosted many more parasites, possibly hundreds, zoology professor Armand Kuris said in a video interview.
"Our findings say that these are actually majorly parasites fish," Kuris said in a statement.
The stage of a parasite's life cycle inside its host is important because it helps biologists determine what the oarfish eats and, in turn, what animals eat oarfish.
The larval tapeworms, which hadn't yet developed their telltale segments, for instance, will stay in their larval stage indefinitely until the oarfish gets eaten by a shark, whereupon they resume their maturation inside the shark. The spiny-headed worm, on the other hand, was an adult, indicating that the oarfish ate the organism — probably krill or some deep-water crustacean — that hosted its juvenile form.
The oarfish, believed to be the world's longest bony fish, is not well-studied since it lives in deep waters. Scientists only recently captured the first-ever footage of an oarfish swimming in the Gulf of Mexico, however these fish are rarely seen dead or alive.
On Oct. 13, the well-preserved carcass of an 18-foot-long oarfish — the largest reported in 17 years — was found off Catalina Island.
A second oarfish measuring 14-feet was found on Oct. 18 when it washed up on a Southern California beach. The smaller fish was also in good condition, which suggests it died on the day it was found, according to Russ Vetter, a director at the Southwest Fisheries Science Center who led the dissection of that fish. Aside from some cookiecutter shark wounds, this fish seemed to be perfectly healthy when it died. It was even carrying eggs that were about to be released.
It remains a mystery what killed both fish, but the deaths are probably linked Vetter said. He thinks that an unusual ocean current may have brought the animals close to shore. The fish — believed to be poor swimmers — may have been unable to escape the unfamiliar shallow waters.
The parasite specimens from the larger fish will be sent away for further analysis.
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