Mantis shrimp are famous for their love of throwing punches, delivering a blow so powerful it can kill their prey in a single strike using appendages reinforced with impact-resistant nanoparticles. However, to make it to the top, a boxer must find their feet through some awkward early-life stages – and the mantis shrimp is no different. Incredibly, while these capable crustaceans can’t pull punches straight out of the egg, new research published in the Journal of Experimental Biology has found that they get going impressively early. After undergoing a few transformations, mantis shrimp larvae are ready to get smashing at just nine days old.
Studying larval fish and crustacean forms is no easy task, especially species who put on spectacular light displays for blackwater divers but return to the lab like pale, ghostly blobs. Species who prefer to make the water’s surface their nursery (water slicks are basically larvae creches) might be easier to collect, but sifting through for just the one species you’re after is like searching for a needle in a wet haystack. "It can be incredibly challenging to sift through a bucket teeming with larval crabs, shrimp, fish and worms to find the mantis shrimp," said study author Jacob Harrison from Duke University, USA, in a statement.
Species-specific larvae secured, the researchers' next obstacle was establishing a technique for getting one 4-millimeter (0.16-inch) Gonodactylaceus falcatus larvae in a position where it could be filmed. Eventually, a setup employing some improvised kit (a toothpick, some glue, and a custom-designed rig) was able to orientate the larvae so that the team could begin collecting data. A welcome prospect for the researchers, who said it took almost a year to settle on the functional design.
Looking at their results, the team was able to ascertain that the boxing shrimp were throwing punches nine days after hatching. Pretty impressive, no? Well, there’s more. The mechanics of the little’uns punches weren’t all that dissimilar to that of the adults (though, of course, on a smaller scale) and the see-through appearance of these tiny fighters delivered some significant insights. The team was able to observe tiny muscles in the larvae’s body contracting during the snap, something that’s never been observed in the adults owing to their opaque exoskeletons. As it turns out, the larvae’s glassy body isn’t just good for science.
“Mantis shrimp larvae live a pelagic lifestyle,” said Harrison in an email to IFLScience. “They float around in the open ocean, sometimes for weeks at a time until they are ready to settle out and become juvenile mantis shrimp. So, their transparent flat body shape allows them to float through the water mostly unseen!"
Add to all that the fact that these tiny critters’ limbs were reaching speeds 5 to 10 times faster than the larval snacks they’re hunting (and matching the acceleration of their parents), and you’ll probably agree these nine-day-old shrimps are quite the skilled assassins. While a fascinating insight into the early life stages of these talented crustaceans, Harrison and colleagues aren’t done with the magical mantis claw just yet.
“There is a lot we don’t know about how these mechanisms operate and how they are tuned, the transparent mechanism in larvae allowed us to address these questions without needing to do anything invasive with the animal,” Harrison said. “I’m interested in how spring actuated mechanisms, like the mantis shrimps, develop and change over the life history of the animal.”