Mantis shrimp fisticuffs start soon after hatching

and cleaner than other sources.”

Wells can also be nurseries for cottonwood seedlings that require moist, open areas to grow. The seedlings struggle to break through vegetation-stuffed riverbanks and rely on floods for their first sips of water. But at one site, researchers found seedlings thriving in equid holes. Many seedlings survived the summer, growing as tall as 2 meters. In areas where dams reduce flooding, equid wells could fulfill an important ecosystem service for these iconic trees, the team says.

It’s too early to conclude that feral donkeys and horses are good for ecosystems, says Jeffrey Beck, a restoration ecologist at the University of Wyoming in Laramie. “The benefits [the equids] demonstrate in this study might be limited to this area.”

Still, the team hopes the study can chip away at the notion that introduced species are wholly bad. In some areas, feral equids “are being killed by the hundreds of thousands in the name of purifying nature,” says study coauthor and ecologist Arian Wallach of the University of Technology Sydney. These animals are part of nature too, she says, and eradication efforts might ripple through an ecosystem in unforeseen ways. s

“Erin’s work is fabulous,” says Karen Neely, a marine biologist at Nova Southeastern University in Fort Lauderdale, Fla. Neely and colleagues saw similar results in their two-year experiment at the Florida Keys National Marine Sanctuary. Her team used the same antibiotic and epoxy treatments on more than 2,300 lesions on upward of 1,600 coral colonies representing eight species.

Those antibiotic treatments were more than 95 percent effective across all species, Neely says. And treating new lesions that popped up after the initial treatment appeared to stop corals from becoming reinfected over time. The research is undergoing peer-review in Frontiers in Marine Science.

“Putting these corals in this treatment program saves them,” Neely says. “We don’t get happy endings very often, so that’s a nice one.” s

LIFE & EVOLUTION Baby mantis shrimp put up their dukes

Larvae start practicing powerful punches at just 9 days old

BY CHARLES Q. CHOI

The fastest punches in the animal kingdom probably belong to mantis shrimp — and the carnivorous crustaceans begin unleashing these attacks a little more than a week after hatching, when they have just started to hunt prey, a new study suggests.

For the first time, researchers have peered through the transparent exoskeletons of young mantis shrimp to see the inner mechanisms of their powerful weapons in motion, researchers report in the April Journal of Experimental Biology. The findings are letting scientists in on hidden details of how these speedy armaments work, something previously only imagined from surgical dissections and CT scans.

Mantis shrimp are equipped with special pairs of arms that can explode with bulletlike accelerations to strike at speeds of up to roughly 110 kilometers per hour. These weapons act like crossbows. As a latch holds each arm in place, muscles within the arm contract, storing energy within the arm’s hinge. When the crustaceans release these latches, all this energy discharges at once (SN: 8/31/19, p. 10).

But researchers didn’t know at what age mantis shrimp begin launching spring-loaded attacks. Computer simulations predicted that the armaments might be capable of greater accelerations the smaller they got, suggesting young mantis shrimp could have faster weapons than adults, says marine biologist Jacob Harrison of Duke University.

To solve this mystery, Harrison and colleagues collected the larvae of Philippine mantis shrimp (Gonodactylaceus falcatus) off boat docks in Oahu, Hawaii. The team glued the larvae, each about the size of a grain of rice, onto toothpicks and used a high-speed camera to record their punches. The researchers also captured a clutch of G. falcatus eggs and raised the hatchlings for 28 days to see how the weaponry developed over time.

Larvae began striking rapidly as soon as nine days after hatching, about when they started feeding on live prey. Punches flew at speeds of about 1.4 kilometers per hour. Given the larvae’s tiny arms — only about one-hundredth the length of an adult’s — that’s roughly proportional to the speed of an adult shrimp’s punch, Harrison says. More importantly, it’s up to 10 times the swimming speeds of crustaceans and fish roughly as big as the larvae, and more than 150 times those of brine shrimp that the team fed the larvae.

“Mantis shrimp larvae are capable of moving incredibly quickly for something so small,” Harrison says. But the larvae did not punch faster than the adults, the team found. That finding suggests there may be some constraints on these weapons at microscopic sizes.

Alternatively, larvae may simply not require weapons faster than those of adults, says Kate Feller, an invertebrate neuroecologist at Union College in Schenectady, N.Y. Larvae might “just need a crossbow that works and don’t need it to be this crazy superpowerful thing,” Feller says. “The fact these larvae are transparent is a great opportunity to answer questions like how the latch works,” she adds. “That’s very exciting.” s

At 11 days old, this mantis shrimp larva has already developed an appendage (folded below the eye) capable of ultrafast punches previously seen only in adults.