Dear, it’s better under the sea, unless you’re an insect. You may find some bugs that skim the surface of a pond or even create their own scuba bubble to dive beneath the surface of inner lakes. But insects are virtually absent from the open ocean.
However, if you look at the hind flippers of southern elephant seals, you will find some insects that have made their way to a partial aquatic life. Lice of the genus Lepidophthirus macrorhini live on the hind limbs of large aquatic mammals, which spend nearly 10 months of the year in Antarctic waters and dive up to 6,500 feet below the surface in search of food and can stay for almost two hours at a time.
These lice may be the deepest surviving insects in marine ecosystems, according to a study published in July in the Journal of Experimental Biology. By enduring such extreme environments, elephant lice can help scientists discover the mystery of why so few insects have made a home in the vast expanse of the ocean.
L. macrorhini are parasitic, blood-sucking lice that burrow into the seal’s upper skin layer for food. In 2015, María Soledad Leonardi, a marine biologist at the Instituto de Biología de Organismos Marinos in Argentina, found live lice on male elephant seals that came up to breed on King George Island off the coast of Antarctica.
“You can see them with your naked eye,” she said. “They look like miniature crabs.”
For them, the presence of lice on adult seals arising from long coastal excursions suggested that the insects could survive the deep dives and steep climbs of the seals’ water journeys. And that means the lice may be able to withstand the crushing pressure of the depths of the ocean.
Catches of 8,000 pounds at sea are being caught to check if lice hit these extreme conditions would be very troublesome, said Drs. Soledad Leonardi. So, her team decided to bring the lice to the lab.
With tweezers, they lured the insects of the hind flippers of 15 elephant seals born on the beaches of Península Valdés in Argentina. The pups have adult lice that are transmitted from their mother’s body within a few days after birth. The lice reproduce rapidly, and take advantage of the first weeks that the pups are confined to land, as their eggs do not hatch under water.
In the lab, the team deepened the lice into individual rooms with large flash drives filled with seawater that connected to a scuba tank. Then they exposed each louse to a range of water pressure, as much as 200 times greater than that on the surface of the sea and equivalent to depths between 980 and 6500 feet. After 10 minutes of experiencing this deep-sea environment, 69 out of 75 lice emerged.
“It was fascinating to me to see that they survived the high pressure,” said Claudio Lazzari, an insect physiologist at the University of Tours in France and a co-author of the study. “It simply came to our notice then. We can rule out that they just died. ”
The researchers then exposed surviving lice to a water pressure higher than lower than what they had previously been exposed to.
“The idea was to reproduce the situation that lice would experience if their host dived through different pressure levels,” said Drs. Lazzari. All lice were able to tolerate the rapid pressure change, with adults recovering faster and exposing mobility after the experiment, compared to the nymphs.
Stuart Humphries, an evolutionary biophysicist at the University of Lincoln in England, called the study “neat”, but also said that “it would be interesting to know how the lice do it.”
Until now, researchers do not know if seal lice have special adaptations. “My guess is that these guys are just shutting down and shutting down their tracheal system,” Drs. Humphries, which meant that the lice could hold their breath in deep water.
The researchers are now conducting experiments to see if these insects arrest their activity and energy consumption in the deep sea or if they breathe through.
“Understanding how this group of insects manages it underwater will be the key to understanding why other groups could not,” said Drs. Lazzari.
But some scientists think the lice may be a unique case.
“Sail lice are a specialized business; they only live to their host in marine environments and reproduce when the seals are on land, ”said Lanna Cheng, an emeritus marine biologist at Scripps Institution of Oceanography in San Diego. “Whether or not they have the ability to survive as release insects at those depths, we have no idea.”
