Creatures from the deep

Bone-eating worm: A female Osedax, below, and under magnification at right, with tiny males clinging to its body

Enthusiasm reigns among the scientists working in biologist Paulo Sumida’s laboratory at the Oceanographic Institute of the University of São Paulo (IO-USP). On the afternoon of April 1, 2014, seated in front of a computer at a table surrounded by shelves holding books, as well as marine organisms kept in alcohol in plastic jars, Olívia Soares Pereira, an undergraduate and newest member of the group, was as excited as a soccer fan as she watched a high-definition film shot on the ocean floor. Viewed on one of the lab’s computers, the film featured peculiar animals such as an octopus with membranes between its tentacles, a red starfish, and elongated corals that grow on mounds covered with asphalt that has seeped out of the earth. The film, similar to those seen on National Geographic TV, recorded an April 2013 trip in a Japanese submarine to previously unexplored regions at depths of over 4,000 meters off the Brazilian coast, between the states of Espírito Santo and Rio Grande do Sul.

As Pereira and her colleagues began to watch the films—100 hours of footage were taken—they wondered how, and ultimately why, these organisms were structured in that way. One of the organisms they have already examined, which offers an example of the peculiar life forms on the ocean floor, is a bone-eating marine worm, or polychaete, of the genus Osedax. “The females have a harem of dwarf males, sometimes more than 100, clinging to their body,” says Sumida, who adds the curious fact that these polychaetes are also called zombie worms, because they colonize carcasses and live among dead animals. The body of the female consists of a red tentacle four to five centimeters long. On one end of the tentacle, which remains outside the bone it is digesting, are palps, ridge-like structures that serve as gills to filter oxygen from the water. The other end branches out and attaches to the inside of bones, like the root of a plant. The ovaries, located near that base, are quite large, and the males, just a few millimeters in length, live in the female’s gelatinous tube, very close to the oviduct through which the eggs pass.

A female Osedax

The females dictate the destiny of the males from early on. Upon leaving an egg, a larva can grow and become another female if it attaches to a bone. If it comes into contact with the body of the female, however, it will fail to grow and will become only a dwarf male, probably through the action of chemicals released through contact with the female’s body. “It’s a very interesting evolutionary adaptation,” Sumida comments.

If males and females were the same size, he says, there would be greater competition for food and it would be harder to find a sexual partner. The current situation—probably the only one to survive over the course of millions of years—enables the female to produce thousands of eggs and, at the same time, avoid competition for food with the tiny males. “The ova are larger and could not be produced by small females, whereas the spermatozoon can be produced in large numbers by small animals,” the biologist observes. According to Sumida, another example of this phenomenon is the devil fish, another deep-sea creature. The male is miniscule and attaches itself to the body of the female, which is much larger. “When a male comes across a female, it latches on and remains there. It becomes a parasite of the female, to the extent that its tissues fuse with those of the female.”

The submarine Shinkai, prior to one more expedition to the ocean floor

Sumida was able to study this worm—a previously undescribed species of polychaete and the first in the Atlantic—because he and colleagues from Japan and the Brazilian states of São Paulo, Santa Catarina, Rio Grande do Sul, Rio de Janeiro and Espírito Santo spent time in a submarine at the so-called São Paulo Ridge, about 700 kilometers off the coast of São Paulo State. There, they were lucky enough to find the tailbones of a whale, later identified as an Antarctic minke whale about eight meters long, that had probably died on the ocean floor five to ten years earlier. It was the first whale carcass found in the deep ocean (4,200 meters down, in this case) off the South American coast. They collected nine vertebrae, already degraded, that had been taken over by those polychaetes. “We’ve now found three different morphotypes [morphological variations] of Osedax, but all of them are genetically identical,” Sumida says. “Associated with the bones we found 25 species of marine organisms and several others inside the bones, mainly polychaetes, all of them probably not yet described.” After two years of planning and obtaining authorizations, the submarine Shinkai 6500, operated from the Japanese oceanographic vesselYokosuka, explored the Brazilian waters as part of an around-the-world voyage. The submarine takes two hours to descend to the ocean floor 4,000 meters down and can remain there for up to eight hours.

In June 2013, two months after the trip to the ocean floor, Sumida, this time aboard theAlpha-Crucis—the oceanographic vessel owned by USP—took part in another unusual operation: the launching of metal structures containing whale bones and wood and plastic panels at depths of 1,500 and 3,300 meters. Their objective was to learn what organisms would colonize them and thus gain a better understanding of the processes involved in the transformation of organic matter in the cold, dark waters of the ocean floor. The materials are expected to be recovered in October 2014, and the findings are to be compared with the bones and wood deposited off the coast of the state Washington in the US by researchers from the University of Hawaii.

“We know little about the deep seas,” says Sumida, who completed his master’s degree 20 years ago with a focus on deep-sea organisms and has subsequently descended six times to the ocean floor. His record descent prior to 2013 was in 1999 when he descended to 1,200 meters off the coast of California in the US submarine Alvin. One of the most comprehensive surveys of Brazilian marine biodiversity was the Program to Evaluate the Sustainable Potential of Living Resources in the Exclusive Economic Zone (Revizee). Completed in 2003, Revizee brought together 150 specialists from 40 Brazilian research institutions who assessed the stocks of 50 species of fish and crustaceans, including deep-water species, within 350 kilometers from the coast (see Pesquisa FAPESP Issue No. 83). In 2010, Brazil—a leader in terrestrial biodiversity, inasmuch as it is home to about 20% of the life forms found on the planet—was in a modest position with 9,101 species of marine organisms, equivalent to 4% of the total species catalogued in the Census of Marine Life, which involved 2,700 specialists from 80 countries over a 10-year period (see Pesquisa FAPESP Issue No. 176). As a physical indicator that much remains to be done, boxes of alcohol-filled jars kept in another room contain the red starfish, a crab and other creatures from the deep, awaiting their turn to be examined.

Read the HCSM new issue in English: Oceans and Seas: history, science, policy.