Amazing new footage shows a pair of blood-sucking parasites attached to the head of a deep-sea ratfish.
In a video posted to Facebook by the Schmidt Ocean Institute, two copepods — tiny crustaceans — are positioned on either side of their host’s head. Long egg sacs attached to the parasites’ backsides create the illusion that the fish is sporting a pair of pig tails.
“They feed on the blood and bodily fluids of their host using their scraping mouthparts, which penetrate the muscle tissue of the fish,” James Bernot, an evolutionary biologist at the Smithsonian’s National Museum of Natural History who was not involved in the expedition, told Live Science in an email.
Scientists captured the footage at a depth of 1,604 feet (489 meters) during an expedition to study the seafloor and biodiversity of the South Sandwich Islands, a chain of 11 subantarctic volcanic islands in the South Atlantic Ocean.
In a Facebook post, representatives said the copepods belong to the species Lophoura szidati and are attached to the head of the ratfish of the genus Macrourus.
Macrourus are commonly called grenadiers or rat tails because of their large heads and thin tails. These common deep-sea fish inhabit the cold waters of the North and South Atlantic Oceans, as well as the Southern Ocean bordering Antarctic waters, and can be found at depths ranging from 1,312 to 10,450 feet (400 to 3,185 meters).
A ratfish has been caught on video swimming off the South Sandwich Islands with a pair of parasites attached to either side of its head.
Information on parasites of deep-sea fishes in Antarctic waters is extremely limited, but L. szidati is one of the most common parasites found on Macrourus species in this region.
L. szidati belongs to the family Sphyriidae. Females of this species have been observed using their mouthparts to penetrate the bodies of various fish, feeding on the muscle tissue of their host.
“These copepods are mesoparasites, meaning they are partly inside and partly outside their host,” Bernoth said, adding that in the video, the middle and back end of the copepods are seen protruding from the fish, while the front, or head, end of their body is embedded in the fish.
Many copepod parasites have multiple stages in their life cycle and usually find their hosts while they are in the larval stage. These tiny larvae burrow into the host's skin and begin feeding. During this time, they undergo metamorphosis and develop anterior claspers that act as anchors to hold them to their hosts as they grow.
In the video, each parasite is carrying a pair of sacs containing hundreds of eggs. “Copepods are amazingly caring mothers to their invertebrates,” said Bernoth. “They carry their eggs in sacs attached to their bodies until the eggs hatch into swimming nauplii, which will go through several larval stages and eventually find their own host.”
According to Bernot, very little is known about the life cycle and lifespan of these parasites, but they are constantly present in the fish's bodies and probably live for several months, growing from almost microscopic sizes.
“Even after the parasite dies, the remains of the embedded head can be found in the host’s body for many years,” Bernot emphasized.
TOPICS parasites
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