Discovery about dolphins is not a total shock
Newborn bottlenose dolphins sport a row of hairs along the tops of their jaws. But once the animals are weaned, the whiskers fall out. “Everybody thought these structures are vestigial — so without any function,” said Guido Dehnhardt, a marine mammal zoologist at the University of Rostock in Germany.
But Dehnhardt and his colleagues reported in The Journal of Experimental Biology that the pits left by those hairs can perceive electricity with enough sensitivity that they may help the dolphins snag fish or navigate the ocean.
The researchers trained two bottlenose dolphins to rest their jaws, or rostrums, on a platform and swim away anytime they experienced a sensory cue like a sound or a flash of light. If they didn’t detect one of these signals, the dolphins were to stay put.
Once trained, the dolphins also received electrical signals. “The dolphins responded correctly on the first trial,” said Tim Hüttner, a biologist at the Nuremberg Zoo in Germany and a study co-author. The animals were able to transfer what they had learned, revealing that they could also detect electric fields.
Sharks are far more sensitive to electric fields, which they use up close after they have chased down prey by smell from a distance. But the electrosense might also aid dolphins for a close grab at fish while they’re hunting. Dolphins spot prey with their eyes and by sending clicking sounds that bounce off prey, known as echolocation. But fish bodies also produce electrical fields through the activity of their muscles and gills.
Such signals could help the dolphins home in on prey hiding on the seafloor. Bottlenose dolphins perform what’s called crater feeding, said Denise Herzing, a marine mammalogist at the Wild Dolphin Project in Florida who wasn’t involved with the study. “They dig,” she said. “They put their beaks down into the sand, almost up to the eyeballs, and pull out these eels.”
— Carolyn Wilke
‘Sea fireflies’ set off fireworks
In 2017, two evolutionary biologists snorkeling off Panama’s coast made a dazzling discovery.
Night was falling over the shallow waters of Bocas del Toro, and James Morin, an emeritus professor at Cornell University, flicked on his underwater flashlight to catch a glimpse of the seabed.
Seemingly in answer, hundreds of tiny blue lights sparked to life, rippling out in waves.
“We were both kind of swearing into our snorkels in amazement,” said Todd Oakley, a professor at the University of California, Santa Barbara. In a paper published in Proceedings of the Royal Society B, the scientists detailed the courtship rituals of a new species of “sea firefly” — a tiny crustacean that stages a spectacular underwater display by sneezing up glowing mucus.
But these aren’t simple flashes. Like the synchronous group displays of lightning bugs on land, the sea fireflies’ light show is a carefully choreographed dance in harmony with the rhythms of the night sky. “It’s a fireworks display underwater — the best Fourth of July you’ve ever seen,” said Nicholai Hensley, a postdoctoral fellow at Cornell who led the new study.
The creatures behind the eerie Panamanian light show are called ostracods. Hensley compares the itty-bitty crustaceans to sesame seeds with eyeballs. Under a microscope, you can make out an ostracod’s shrimplike body encased in a see-through shell.
An organ called the upper lip makes many ostracods bioluminescent. The upper lip stores two chemicals that when combined, create a bright blue burst. “It’s literally like a handlebar mustache of glowing light right above their mouth,” Hensley said.
Ostracods use their luminous snot for many purposes, like performing courtship displays or forcing predators to spit them back up (apparently the mucus tastes really bad). But Morin said the light display of the sea fireflies was “on steroids” the night he and Oakley observed them. The team studied this mysterious population of sea fireflies and convinced it to give encores of the light show in captivity. Now, the researchers believe they’ve pieced together the individual steps of the courtship dance.
The romance begins at nautical twilight — an in-between time when the sun has set, the moon has yet to rise. Each male motors up from the grass beds and then descends in a corkscrewing plunge, sneezing up between four and eight globs of light as it goes. The result is stunning, like a string of Christmas lights or a strand of glowing pearls.
— Elizabeth Anne Brown
Termites don capes for science
The researchers started by collecting plain-looking termites from the wild. Then they pasted pieces of paper to their backs that more or less looked like capes — either solid black, solid white or striped in black and white.
This was not the latest effort to introduce tiny heroes to the Marvel Cinematic Universe. It was an attempt to learn something about how jumping spiders, some of nature’s most widespread and canny predators, perceive their prey.
In nature, most prey avoid being detected by predators by blending into their surroundings. But some species strive to stand out. Monarch butterflies, yellow jacket wasps and ruby-red velvet ants, for example, use bright or contrasting coloration to warn predators of their toxicity. Scientists are still trying to decipher which predators perceive such displays. Little is known about how jumping spiders process these color patterns.
To determine how two species of jumping spiders react to vibrant warning signals, a team led by Lisa Taylor, a behavioral ecologist at the University of Florida outfitted termites in capes fit for scientific cosplay and put them in a petri dish with the arachnids.
Their findings, published in the journal Royal Society Open Science, reveal that while the spiders quickly spotted termites in striped capes, they rarely attacked the striped termites, providing an explanation for why myriad other species use striking stripes to scare off predators.
Most research on how predators perceive colorful displays has revolved around carnivorous birds. But a majority of species with such patterns are small insects. This means that they most likely evolved their visual defenses in response to arthropod predators, like arachnids.
The new findings suggest that many jumping spiders may inherently be able to pinpoint striped patterns.
— Jack Tamisiea