by David Braun
SNEAKY SNEAKER SQUID
Small Squid Have Bigger Sperm
Chalk one up for the little guy: Smaller squid males—called “sneakers”—have evolved larger sperm, a perfect match for a female reservoir reserved just for them.
Scrawny spear squid have size where it matters—in their sperm. A new study shows that the smaller males—called sneaker squid—pack heftier sperm than big spear squid. Also, the sneakers’ sperm are tailored for a completely separate sperm reservoir, near the female’s mouth, researchers found.
TRUTH:
THE SPEAR SQUID IS THE FIRST SPECIES KNOWN TO HAVE INDIVIDUALS THAT PRODUCE TWO SEPARATE TYPES OF SPERM.
Large Tactics: Light Show
Female spear squid mate willingly only with big males, which court the females with natural, multicolored, pulsating lights—bioluminescent mating displays that the smaller males don’t exhibit.
Once the female selects a male, he holds her above him and inserts his arm, holding a sperm packet, into her oviduct, a passage through which his sperm travel to her ovaries. He’ll then watch over her until she spawns to try to ensure no other males fertilize her eggs.
Small Tactics: Stealthy & Quick
Yet just as the female begins to lay her eggs on the seabed, a smaller squid, a sneaker, may dart over and mate with her head-to-head.
A female is typically “willing to accept sneaky matings, as she has a specific sperm storage organ near [her] mouth for sneaker males,” study first author Yoko Iwata, a postdoctoral research fellow at the University of Tokyo, said by email.
Though the larger males end up fertilizing most of the eggs, the sneaker males’ behavior ensures that the smaller squid still have a chance at fathering some of the offspring.
“Sperm size is likely to be an adaptation to fertilization environment, either inside the female or externally, rather than competition between sperm, because the fertility and motility of sneaker and consort sperm were the same.”
Yoko Iwata
postdoctoral research fellow, University of Tokyo
Bigger Sperm Matters
For the experiment, Iwata and colleagues dissected commercially fished squid, collecting sperm from the males and from the females’ two sperm storage sites.
The team then measured the sperm cells under the microscope and discovered that the larger males’ sperm—deposited inside the female—were an average of 73 millionths of a meter long. The sneaker male sperm averaged about 99 millionths of a meter. The scientists also collected eggs from live female squid and artificially inseminated the eggs, confirming that both sperm types were fertile.
What’s more, the two types of sperm swam at the same speed, suggesting that the bigger sperm don’t have an edge in competition with the smaller sperm. Rather, the sneakers’ bigger sperm likely evolved to suit the females’ sperm reservoir and the surrounding seawater.
In other words, each of the female’s two sperm receptacles, and waters around these receptacles, may have varying characteristics—such as pH, salinity, or concentration of gases and nutrients—that favor one sperm size over another.
The results are the first evidence of two different-size male types of the same species producing different-size sperm and using different sexual positions, according to the study, published recently in the journal BMC Evolutionary Biology.
And there is likely an evolutionary benefit in all this, Iwata added: The sneaker sperm makes his offspring more genetically variable and thus fitter in the long run.
How Does a Sneaker Become a Sneaker?
Still a mystery, however, is how baby spear squid males become sneakers or bigger males in the first place. Scientists don’t know whether sneaker status is a genetic trait passed down by parents or if environmental factors, such as water temperature or food availability, turn a baby male into a sneaker.
But research on other squid species, at least, suggests the environment may be an influence. William Gilly, a squid expert at Stanford University, said that young jumbo squid—also called Humboldt squid—completely change their life cycles during years of El Niño, a warming of tropical waters in the central and eastern Pacific Ocean.
The warmer water somehow triggers young jumbo squid to begin breeding at six months of age, when their bodies are only about 8 inches (20 centimeters) long, not including arms and tentacles. Usually the squid breed at full maturity, when their bodies are up to 3 feet (1.8 meters) long.
“The whole idea of environmental signals early in life that then cast you on some alternate trajectory,” Gilly said, “may be a very common thing in squid and many animals.”
TRUTH:
SQUIDS SWIM BY SUCKING WATER INTO THEIR MANTLE CAVITY AND QUICKLY EXPELLING IT OUT OF A SIPHON.
UNDER THE SEA
Census Scopes Out
Strange New Sea Species
Beautiful and strange: These new sea creatures came to light during the ten-year Census of Marine Life, and the world is weirder for it.
More than 6,000 new species were discovered during the Census of Marine Life, a ten-year effort to document all sea life. The project’s 500-plus expeditions amassed a visual legacy as unique as the organisms uncovered—from which we selected some of the strangest.
CREATURE 1
Yeti Crab
Its fuzzy, winter-white coat might look at home in the Himalaya, but the yeti crab was discovered skittering around hydrothermal vents about a mile and a half (2.4 kilometers) under the South Pacific off Easter Island in March 2005.
The 6-inch (15-centimeter) blind crustacean—officially Kiwa hirsuta—is dubbed the “yeti crab” because its long shaggy arms resemble the mythical yeti, or abominable snowman. It is such an unusual creature that a whole new family of animal had to be created to classify it.
(Photo Credit 11.20)
CREATURE 2
Sea Angel
An expedition to the Arctic Ocean captured a so-called sea angel, Clione limacina, at about 1,148 feet (350 meters) underwater. Despite its nickname, this little angel apparently doesn’t mind showing a little skin: It’s actually a naked snail without a shell, scientists said in December 2009. Such marine snails—most of them the size of a lentil—are widely eaten by many species, making them the “potato chip” of the oceans, biologist Gretchen Hofmann of the University of California said in a 2008 statement.
(Photo Credit 11.21)
CREATURE 3
Squidworm
Squid? Worm? Initially, this new species—with bristle-based “paddles” for swimming and tentacles on its head—so perplexed Census of Marine Life researchers that they threw in the towel and simply called it squidworm.
(Photo Credit 11.22)
Found via a remotely operated vehicle about 1.7 miles (2.8 kilometers) under the Celebes Sea in 2007, the 4-inch-long (10-centimeter-long) creature turned out to be the first member of a new family in the Polychaeta class of segmented worms.
CREATURE 4
Mr. Blobby
Affectionately nicknamed “Mr. Blobby,” this fathead sculpin fish was discovered in 2003 in New Zealand during a Census of Marine Life expedition, according to the Australian Museum in Sydney. Fathead sculpins—named for their large, globelike heads and floppy skin—live in the Atlantic, Indian, and Pacific Oceans at depths of between about 330 feet (100 meters) and 9,200 feet (2,800 meters). Now preserved in 70 percent ethyl alcohol at the Australian Museum, Mr. Blobby’s nose has shrunk—“and he no longer retains his ‘cute’ look,” according to the museum’s website.
(Photo Credit 11.23)
CREATURE 5
Dumbo of the Deep
Found in 2009, a deep-sea “Dumbo octopus” may look like it’s all ears—but the protrusions are actually fins that help propel the animal through the darkness a mile (1.6 kilometers) under the sea. Netted during an expedition to the Mid-Atlantic Ridge, this Dumbo is among the thousands of census-documented creatures that live without ever knowing sunlight. Reaching 6 feet (2 meters) in length and weighing
13 pounds (6 kilograms), the jumbo Dumbo species is the largest of the octopus-like creatures of the mollusk genus Grimpoteuthis.
(Photo Credit 11.24)
(Photo Credit 11.25)
CREATURE 6
Beautiful but Deadly
“Stunningly beautiful but deadly,” the Gulf of Mexico’s Venus flytrap anemone acts much like its terrestrial namesake, stinging its prey with an array of tentacles, according to the U.S. Geological Survey. The species’ native Gulf—along with the Mediterranean Sea, Chinese waters, the Baltic Sea, and the Caribbean Sea—are the ocean regions most under threat from human activities, according to Census of Marine Life scientists. For instance, nutrients in sewage and fertilizer washed from the land are degrading these marine habitats by creating oxygen-free “dead zones,” the report says. What’s more, the Gulf of Mexico oil spill may worsen these dead zones, as well as wield untold damage to the animals at the bottom of the food chain.
OLDEST SHELLFISH
405-Year-Old Clam
Called Longest-Lived Animal
A clam dredged from icy Arctic waters in 2007 is being hailed as the world’s longest-lived animal.
Climate researchers at Bangor University in the United Kingdom recently counted 405 annual growth rings in the shells of a quahog clam. When this animal was young, Shakespeare was writing his greatest plays and the English were establishing their first settlements in the Americas.
Who Wants to Live Forever?
Here are the confirmed record holders for the world’s longest lived …
1. Radiated tortoise—256 years
2. Koi—226 years
3. Bowhead whale—130 years
4. Human being—122 years
5. Macaw—106 years
6. Elephant—86 years
7. Horse—62 years
8. Herring gull—49 years
9. Cat—38 years
10. Dog—29 years
Counting the Rings
The team plucked the mollusk from 262-feet-deep (80-meter-deep) waters off the northern coast of Iceland. The team is studying growth lines in clam shells as part of a project to understand how the climate has changed during the past thousand years.
“On a side note, we discovered this very old clam,” said Al Wanamaker, a postdoctoral researcher at the university.
Some protest the “oldest animal” designation, saying it should go to certain corals that grow together to form colonies. By this reckoning, the clam would be only the oldest non-colonial animal.
Slow Aging
Quahog clams are known for their longevity. A 220-year-old clam taken from American waters in 1982 holds the official Guinness World Records oldest animal title. Unofficially, the record belongs to a 374-year-old Icelandic clam housed in a German museum.
The new clam is at least 30 years older, according to the Bangor University team. The animal died when the researchers counted its rings.
“There’s probably many others that are actually quite older—we just haven’t found them yet,” Wanamaker said. “I think in my stomach if you start getting up around 600, then maybe that would be the maximum—but that’s just pure speculation,” he added.
Scientists believe the secret to the clams’ longevity is a slowed cell-replacement process. But why they age so slowly is unknown. “It is possible that an investigation of the tissues of these real-life Methuselahs might help us to understand the process of aging,” team member Chris Richardson said in a media statement.
Wanamaker added that several research teams want to study the tissue of living quahog clams to tease out the secret.
TRUTH:
THE 405-YEAR-OLD CLAM IS NAMED MING, AFTER THE CHINESE DYNASTY.
Climate Records
The researchers hope to use their shell studies to reconstruct a record of environmental changes during the past several centuries. “Just like tree rings, those growth lines vary in accordance with the environment,” Wanamaker said.
Shell growth is related to water temperature, salinity, and food availability for example. A main goal, Wanamaker said, is to determine if the climate of the last half century “is extraordinary compared to the last thousand years.”
Photo Credits
FRONT MATTER
tp, Joel Sartore/National Geographic Stock; col.1, Everett Collection/Shutterstock.
CHAPTER 1
1.1, Travis Dove/National Geographic Stock; 1.2, Simon Hartshorne/Shutterstock; 1.3, Bart Acke/Shutterstock; 20, Richard Barnes/National Geographic Stock; 1.4, P. T. Nicholson; 1.5, siloto/Shutterstock; 1.6, Imaginechina/Corbis; 1.7, Photograph courtesy Stuttgart Regional Council; 28, Photograph courtesy Stuttgart Regional Council; 28–9, Courtesy Stuttgart Regional Council; 29, Courtesy Stuttgart Regional Council; 1.8, Courtesy Stuttgart Regional Council; 1.9, Illustration by Greg Harlin; 1.10, Illustrated by P. Groszman; 36, Hein Nouwens/Shutterstock; 1.11, Barcroft/Fame Pictures; 40–1, Barcroft/Fame Pictures; 41 (UP), XinHua News Agency/Newscom; 41 (LO), imago stock&people/Newscom; 1.12, Cory Richards; 1.13, jumpingsack/Shutterstock; 1.14, Ho New/Reuters; 50–1, Bambuh/Shutterstock; 1.15, Chris Brooks; 1.16, Courtesy York Archaeological Trust; 55, Makc/Shutterstock.com.
CHAPTER 2
2.1, Anatomical Travelogue/Photo Researchers, Inc.; 59, dodoimages/Shutterstock; 63, dodoimages/Shutterstock; 2.2, Courtesy Michael Miyamoto; 2.3, Hein Nouwens/Shutterstock; 2.4, Oskin Pavel/Shutterstock; 70, Morphart Creations Inc./Shutterstock; 73, dodoimages/Shutterstock; 2.5, Joel Sartore/National Geographic Stock; 2.6, Pete Oxford/Minden Pictures/National Geographic Stock; 2.7, Hasloo Group Production Studio/Shutterstock; 2.8, Steve Gschmeissner/Photo Researchers, Inc.; 84, Germán Ariel Berra/Shutterstock; 2.9, Pete Ryan/National Geographic Stock; 90, Courtesy University of Bradford; 90–1, Courtesy University of Bradford; 91, Courtesy York Archaeological Trust; 2.10, Courtesy York Archaeological Trust; 2.11, Bianca Lavies/National Geographic Stock; 95, red rose/Shutterstock; 2.12, NASA; 98, paulart/Shutterstock; 2.13, Mary Evans Picture Library/Alamy; 2.14, Everett Collection/Shutterstock.
CHAPTER 3
3.1, Joel Sartore/National Geographic Stock; 3.2, Piotr Naskrecki/iLCP/Supplied by WENN.com, via Newscom; 3.3, Photograph courtesy Robin Moore, ILCP; 3.4, L. Lee Grismer/AFP/Getty Images, photo via Newscom; 3.5, Courtesy Gabor Csorba, HNHM; 3.6, Gregory Guida/Durrell Wildlife Conservation Trust/PA Wire URN6726800 (Press Association via AP Images); 118, Courtesy Martin Nyfeler; 118–9, Courtesy Martin Nyfeler; 119, Courtesy Martin Nyfeler; 121 (up), Julie de Leseleuc/Shutterstock; 3.7, Courtesy Susannah Rouse, Oxford; 3.8, Bruce Dale/National Geographic Stock; 124, Vule/Shutterstock; 3.9, Adriano Migliorati/Caters News Agency; 126 (INSET), Adriano Migliorati/Caters News Agency; 3.10, Michael Nichols, NGP; 3.11, Heidi & Hans-Jurgen Koch/Minden Pictures; 3.12, Steve & Dave Maslowski/Photo Researchers, Inc.; 3.13, Courtesy Arthur D. Cha; 3.14, Alaska Stock Images/National Geographic Stock; 3.15, Chris Johns/National Geographic Stock; 136, AKaiser/Shutterstock; 138, Iozas/Shutterstock; 3.16, Julie Ng/National Geographic My Shot; 140, mariait/Shutterstock; 3.17, Courtesy Jodi Rowley, Australian Museum; 143, Ultrashock/Shutterstock; 3.18, Courtesy Foerder/Reiss, CUNY; 3.19, AP Images; 3.20, Jeoffrey Maitem/Getty Images; 152, Nebojsa S/Shutterstock; 3.21, worldswildlifewonders/Shutterstock.
CHAPTER 4
4.1, Eye of Science/Photo Researchers, Inc.; 4.2, Science/AAAS; 160, Hein Nouwens/Shutterstock; 162, Eric Isselée/Shutterstock; 166, Courtesy David Hughes; 166–7, Courtesy David Hughes; 167 (UP), Courtesy David Hughes; 167 (LO), Courtesy David Hughes; 170, Hein Nouwens/Shutterstock; 4.3, Photograph courtesy David Hu and Nathan J. Mlot; 4.4, Photograph courtesy David Hu and Nathan J. Mlot; 4.5, Photograph courtesy David Hu and Nathan J. Mlot; 179, Mur34/Shutterstock; 4.6, Caters News Agency Ltd/Newscom; 4.7, Photograph by Valter Jacinto; 4.8, Peter Koomen/AFP/Getty Images/Newscom; 4.9, Photograph courtesy Jerome Sueur, MNHN; 4.10, Courtesy Mike Picker, University of Cape Town; 184–5, John McQueen/Shutterstock; 188, kirian/Shutterstock; 4.11, Kees van der Krieke, Stippen.nl; 4.12, Mathieu B. Morin; 4.13, Ke
es van der Krieke, Stippen.nl; 4.14, K van der Krieke; 4.15, Millard H. Sharp/Photo Researchers, Inc.; 196–7, Pitroviz/Shutterstock.
CHAPTER 5
5.1, Smithsonian Institution, via NASA; 5.2, Emory Kristof/National Geographic Stock; 202, Ozger Aybike Sarikaya/Shutterstock; 203, 6259040374/Shutterstock; 5.3, AP Images/Eric Gay; 209, LeCire/Wikimedia Commons; 5.4, Photograph from Roadrunners Internationale via Pangloss Films; 212–3, Photograph from Roadrunners Internationale via Pangloss Films; 213 (UP), Photograph from CIA via Pangloss Films; 213 (CTR), Photograph from CIA via Pangloss Films; 213 (LO), Photograph from CIA via Pangloss Films; 217, lantapix/Shutterstock; 5.5, Kenneth Garrett/National Geographic Stock; 5.6, AP Images/Matteo Borrini of Florence University, HO; 224, Steve Mann/Shutterstock; 5.7, James P. Blair/National Geographic Stock; 232, Oxlock/Shutterstock; 235, Oxlock/Shutterstock; 5.8, Adam Woolfitt/Robert Harding/Robert Harding World Imagery/Getty Images; 238–9, John Young/Shutterstock; 5.9, NASA; 5.10, NASA; 5.11, NASA; 5.12, NASA; 5.13, NASA; 5.14, NASA; 5.15, NASA; 5.16, Reuters/Corbis; 248–9, R. Formidable/Shutterstock.
