by David Braun
Shot-in-the-Dark Mating Strategy
Mating with anything with eight arms—male or female—pays off in the dim depths of the ocean, study says.
When it comes to mating, some male squid aren’t very picky: They copulate just as often with other males as with females, a new study says.
That’s because would-be suitors of the hand-size species Octopoteuthis deletron, which live in the murky depths of the eastern Pacific Ocean, can’t easily tell the males from the females, the research shows.
Take a Chance on Me
“They can see each other, but they are not able very well to distinguish between the sexes at the distance at which they decide, ‘I’m going to mate’ or ‘I’m not going to mate,’ ” said study leader Hendrik Hoving, of the Monterey Bay Aquarium Research Institute in California. So “males mate with basically any member of the same species … They just take a chance.”
It’s also hard to tell he from she: A female squid’s defining feature is a patch of wrinkled skin. The result is a strategy that the study authors call “a shot in the dark”—it’s just not worth it to males to make sure their partner is the right gender.
TRUTH:
MOST SQUID HAVE THREE HEARTS.
Slap Happy
For the study, Hoving and colleagues recorded squid via robotic submarines in the dark—1,300 to 2,600 feet (400 to 800 meters) underwater. The scientists observed more than a hundred male and female squid, and they found that just as many male squids as female squids bore sperm packets on their bodies—showing that males slap a sperm packet on just about anything with eight arms.
When he finds a suitable partner, the male uses his large penis to transfer multiple sperm packets to the male or female. These break open into smaller sperm sacs that attach to his partner’s mantle, fins, and arms. But the “love affair” ends there: The squid, which lead a solitary existence, die shortly after mating.
Homosexual Animals
There are a number of well-documented instances of homosexual or bisexual behavior among animals:
1. Roy and Silo are two male chinstrap penguins at New York’s Central Park Zoo who were together for six years, from 1999 until 2005.
2. Some male ostriches court only their own gender, and there are pairs of males flamingos that mate, build nests, and even raise foster chicks.
3. Japanese female macaques were recently discovered engaging in intimate acts.
4. Studies suggest that 75 percent of bonobo sex is nonreproductive and that nearly all bonobos are bisexual.
5. Other animals appear to go through a homosexual phase before they fully mature—male dolphin calves often form temporary sexual partnerships.
Same Sex Mating Is Rare
Nathan Bailey, of the U.K.’s University of St. Andrews, said the study team “makes a pretty good case” for their claims about the male squid’s lack of choosiness. Very few species show such high levels of what biologists call same-sex sexual behavior, Bailey, who wasn’t involved in the research, said by email. “Some primates or dolphins do, but this study puts O. deletron on the higher end of the scale.”
Hoving acknowledged that his research results can become fodder for jokes. “But I don’t really care,” he said. “I’m interested in deep-sea animals and how they’re capable of living in that environment, and one of the challenges is finding the opposite sex.”
HIGH FLYING
Great White Shark Jumps on Boat, Stressing Everyone
Most fish stories sound too good to be true, but this one sounds just plain scary. You decide.
Marine researchers chumming the ocean to lure sharks closer to their vessel off South Africa’s southwestern Cape coast got more than they bargained for when a half-ton (500-kilogram) great white shark leaped into their boat. It happened in July 2011, near Seal Island, off Mossel Bay, in a part of the ocean famous for its “flying” sharks.
“We go out into the bay everyday to get data on the shark population,” said Enrico Gennari, director of Oceans Research, an independent research organization that works with universities and runs public awareness programs to teach people about sharks. Oceans Research has also collaborated with National Geographic to produce television documentaries about sharks and other predators.
“Our team was chumming to attract sharks to the boat so that we could photograph their fins, which, like human fingerprints, are a way to identify individual animals,” Gennari said. “They waited for four or five minutes, but nothing happened until there was an enormous splash and a shark landed in the boat.”
History Lesson
According to the International Shark Attack File, which has attack data going back to 1580, the deadliest sharks to humans are:
1. Great white shark: 431 attacks
2. Tiger shark: 169 attacks
3. Bull shark: 139 attacks
Off the coast of South Africa, great white sharks are known for their leaping abilities. (Photo Credit 11.8)
The team’s first thought was to make sure everyone was well clear of the giant predator, which was thrashing around on the deck. “They moved everyone out of the way then radioed us,” Gennari said. He and a colleague arrived at the boat within minutes. It was not possible to push the flailing animal back into the sea by hand, and an attempt to pull it off the vessel with a rope attached to the second boat also failed.
Shark Overboard
“We radioed the harbor and said we were on the way, and that we needed a crane. It took about 20 minutes, and the whole time we were splashing water on the shark’s gills, trying to help it breathe,” Gennari said. “At the harbor, a pipe was placed into the shark’s mouth to pump water over its gills to keep it alive. The crane was used to hoist the animal by its tail, a risky maneuver because its great weight out of the water could have damaged its spine and internal organs. But the only other option we had was to let it die on the boat.”
The shark was lowered into the water, but it stranded itself on a harbor beach. Attempts to push it back into the water by hand failed, so the Oceans Research team lashed the animal to the side of a boat and drove it out to sea. After half an hour of the assisted swim through the ocean the shark seemed to recover, slapping its tail strongly, Gennari said. The shark was released and it swam away, he added.
“We don’t know whether it’s still alive; we hope to see it again soon,” Gennari said. The specimen is well known to the Oceans Research team because it had been photographed regularly, and it is readily identified by its unique dorsal fin.
“This was the first, and hopefully last, time a shark has jumped into our boat,” Gennari said. “It was quite stressful for everyone, both for the shark and the humans. But the people were safe and apparently the shark survived, so it really could not have ended better.”
TRUTH:
THE WORLD’S LARGEST SHARKS ARE TYPICALLY FEMALE, NOT MALE.
White Sharks Can Jump
This is not the first time a shark has jumped into a boat in this part of South Africa’s coastal waters. “There have been several incidents of leaping great white sharks in the past,” Chris Fallows of Apex Shark Expeditions told National Geographic. Fallows has been monitoring and photographing breaching great white sharks for 20 years. “In 1976 in False Bay, it happened on two different occasions,” Fallows wrote. “One of the incidents resulted in a very badly injured fisherman. Sadly in both cases, the shark died.”
Apex Shark Expeditions records around 600 to 700 predatory events every year at Seal Island. “Often during these events we see spectacular breaches. It is thus inevitable that over the years we have had a few sharks jump close to the boat, but due to a huge emphasis being placed on safety, good fortune, as well as a fairly large boat, we have thankfully not had a shark land in [our] boat.”
So what could cause a shark to jump on a boat? “There can be several things,” Fallows explained. “In most cases the sharks breach while in pursuit of something, be it a seal, or fish, or a decoy. Occasionally however, great white
s and some other species perform what is known as a natural breach. This type of breach takes place for no apparent reason, although it is speculated that it could have some form of social function of communication or dominance. These breaches are often very high, the mouth of the shark is closed, and it is often when there are several sharks in the immediate vicinity.”
Big Boy
In fall 2009, researchers landed the largest shark ever—a two-ton-plus, 17.9-foot-long male. After fitting the fish with a satellite-tracking tag and taking a blood sample, they released him back into the waters off Mexico’s Guadalupe Island.
AWESOME AMOEBAS
Giant “Amoebas”
Found in Deepest Place on Earth
When scientists venture to Earth’s most extreme places, they are often surprised by the life-forms they find. This time, they traveled to the deepest place on Earth and found a giant one-celled creature.
Huge “amoebas” have been spotted in the Mariana Trench, the deepest part of the world’s oceans.
The giants of the deep are so-called xenophyophores, sponge-like animals that—like amoebas—are made of just one cell. They were found during a July 2011 research expedition run by the Scripps Institution of Oceanography in La Jolla, California.
TRUTH:
XENOPHYOPHORES CAN CONCENTRATE HIGH LEVELS OF LEAD, URANIUM, AND MERCURY AND ARE THUS LIKELY RESISTANT TO LARGE DOSES OF HEAVY METALS.
Attack of the 4-inch Amoeba
The animals are about 4 inches (10 centimeters) long—among the largest single-celled organisms known to exist. The creatures were discovered at depths of 6.6 miles (10.6 kilometers). That breaks a previous record for xenophyophores found in the New Hebrides Trench at 4.7 miles (7.6 kilometers).
Xenophyophores represent “one of the few groups of organisms found exclusively in the deep sea,” said Lisa Levin, a Scripps oceanographer who studied the expedition’s data. “If any creatures should be able to live at the ocean’s greatest depth, then xenophyophores certainly should be among them.”
Lower the Drop-cams
The Mariana xenophyophores were seen in footage from Drop-cams, free-falling devices equipped with lights and digital video that were developed by the National Geographic Society. Protected by thick walls of pressure-resistant glass, the Drop-cams were baited to attract whatever marine life might be lurking in the deep. Expedition scientists also saw, for instance, the deepest-swimming jellyfish to date.
“The deep sea is the largest biome on Earth and holds much of the diversity on the planet—[yet it’s still] largely undescribed,” Levin said in an email to National Geographic News.
According to Jon Copley, a marine biologist at the United Kingdom’s University of Southampton, “many of the major discoveries in deep-sea biology have come from making direct observations at the seafloor.”
“The Drop-cam is a great tool for the future because it can help us see more of what’s down there for less cost than using ROVs or submersibles,” he said via email. For instance, “finding xenophyophores far deeper than before shows how much we still have to learn about our ocean’s depths and their inhabitants.”
Tullis Onstott, an expert in deep-sea microorganisms at Princeton University, also called the xenophyophore discovery “fantastic.” “Who knows what’s next, behemoth nematodes?” he said by email.
“The xenophyophores are … fascinating giants that are highly adapted to extreme conditions but at the same time are very fragile … These and many other structurally important organisms in the deep sea need our stewardship as human activities move to deeper waters.”
Lisa Levin
deep-sea biologist, Scripps Institution of Oceanography
SENSITIVE SNIFFERS
Sawfish Snout Has Sixth Sense
Splits Prey in Half
The sawfish has a nose like a Swiss Army knife—it can slice up prey, probe the bottom for food, and serve as an “antenna” to detect electric fields of prey.
They may not see dead people, but sawfish use a sixth sense based in their long snouts to hunt and dismember prey, new research shows for the first time.
Previously, scientists had suspected that sawfish—large ocean and freshwater fish found throughout the tropics—use the saw, a cartilaginous extension of the skull, to probe sand or mud for prey. The saw also serves as a weapon, the new research suggests. Lateral swipes, observed during experiments in the lab, can split smaller fish in half.
Ovo-What?
Sawfish are ovoviviparous, meaning their offspring are in eggs, but the eggs develop inside the mother’s body. The young are nourished by a yolk sac. Depending on the species, gestation may last from several months to a year. Sawfish pups are born with their saw fully developed, but it is sheathed and flexible to avoid injuring the mother at birth.
Invisible Touch
Now, preliminary experiments also suggest that the fish’s long, tooth-lined saw is full of pores that can detect movements or electric fields of passing prey—acting as a sort of “distant touch,” Barbara Wueringer, a sensory neurobiologist at the University of Queensland in Australia, said by email. This skill is especially handy for nosing out dinner in murky or dark waters, Wueringer said.
“We know so little about sawfish, even though these animals can grow really big”—up to 16 feet (5 meters). “To know that the saw acts like an antenna that can sense prey is amazing.”
TRUTH:
THE “TEETH” ON THE SAWFISH’S SNOUT ARE NOT TRUE TEETH, BUT MODIFIED SCALES. ITS REAL TEETH ARE LOCATED INSIDE ITS MOUTH, WHICH IS ON THE FISH’S UNDERSIDE.
Making Sense of Sawfish
In addition to observing the animals, Wueringer dissected several sawfish that had been accidentally caught or died naturally. She found that the sawfish’s saws were full of tiny pores that signal the ability of an animal to detect the electric fields present in all living animals. Sharks and rays have these pores, as do some fish such as lungfish and even some mammals such as the echidna.
By making “maps” of the skin of four species of rare sawfish, Wueringer pieced together where the pores are distributed on the saws. She then compared this data with pore placement on two species of shovelnose rays.
This fish’s saws are lined with pores that detect electric fields. (Photo Credit 11.9)
Determining where pores are most concentrated gives clues about animals’ feeding behaviors, she said. “For example, rays have their eyes on the upper side of their head, but the mouth is on the lower side. Pores that can detect electric fields around the mouth allow these animals to sense a fish when they are trying to ingest it—but cannot see it,” she said.
In the sawfish, the pores were most concentrated on the upper sides of their saws, which should enable the predators to stalk fish in the space above their saws.
Research May Help Rare Species
Overall, Wueringer hopes the research will help conservationists learn more about sawfish, especially the four species she studied, whose last stronghold is a remote bay of northern Australia.
In general, sawfish have dwindled dramatically in recent years, largely due to overfishing, both intentional and accidental—the sawfish’s serrated snouts make the animals especially vulnerable to entanglement in fishing nets, according to the International Union for Conservation of Nature.
“In order to protect endangered species, we need to know as much as we can about them,” she said. “How a species catches its prey, and also which senses are involved in detecting the prey, is part of the basic understanding of a species.”
MAGIC ACT
“Bizarre” Octopuses
Carry Coconuts as Instant Shelters
Coming soon to an ocean near you—the amazing disappearing octopuses! A new study shows that these smart creatures are using coconut shells as portable places to hide.
Octopuses have been discovered tiptoeing with coconut-shell halves suctioned to their undersides, then reassembling the halves and disappearing inside for protection or deception
, a new study says.
Peek-a-boo! A veined octopus hides in coconut shells. (Photo Credit 11.10)
“We were blown away,” said biologist Mark Norman of discovering the octopus behavior off Indonesia. “It was hard not to laugh underwater and flood your [scuba] mask.”
The coconut-carrying behavior makes the veined octopus the newest member of the elite club of tool-using animals—and the first member without a backbone, researchers say.
Coconuts to Go
A team led by biologist Julian Finn of Museum Victoria in Melbourne, Australia, was observing 20 veined octopuses (Amphioctopus marginatus) on a regular basis. The researchers noticed that the animals were frequently using their approximately 6-inch-long (15-centimeter-long) tentacles to carry coconut shells bigger than their roughly 3-inch-wide (8-centimeter-wide) bodies.
An octopus would dig up the two halves of a coconut shell, then use them as protective shielding when stopping in exposed areas or when resting in sediment. This action, on its own, astonished the team. Then they noticed that the octopuses, after using the coconut shells, would arrange them neatly below the centers of their bodies and “walk” around with the shells—awkwardly.
“I’ve always been impressed by what octopuses can do, but this was bizarre,” said study co-author Norman, senior curator for mollusks at Museum Victoria.
To carry the shells, a veined octopus has to stick its arms out and over the edges of the coconut and walk around as if on stilts—making the octopus, while in motion, more vulnerable to predators—study leader Finn explained.
