Off to a shaky start for locust nymphs.
The uniform motion swarming desert locusts is a highly coordinated activity. Their proclivity to coordinate starts as early as hatching, when locust nymphs emerge simultaneously from their eggs.
Various cues enable animals to synchronize their hatching. Embryos of crocodilians and some birds vocalize to coordinate hatching, snake-induced vibrations in the red-eyed tree frog induce joint hatching, and giant water bug males spray water over the egg mass when it’s time to emerge.
Desert locust mother aggregate to deposit their eggs into pods simultaneously. Though temperature and light cues are believed to control when the locust eggs hatch, when Yudai Nishide and Seiji Tanaka from the National Agriculture and Food Research Organization in Japan transported egg pods to the laboratory where those cues were absent, they found that hatching was still synchronized within a pod, but not among different pods.
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It was clear that these locust embryos were using some other cue, aside from temperature or light, to coordinating hatching within a pod. To figure out what that cue might be, the researchers took eggs from the same pod and placed them either in contact with each other or separated by a divider that still allowed them to transmit odor and sound, but not vibrations.
Neither sound nor odor cues appeared to be required for the eggs to hatch in synchrony. It was only when the eggs were placed in direct contact with each other that they would reliably hatch at once.
Thus, it was likely that the embryos were sensing vibrations, which helped them to coordinate their hatching. To be sure, the researchers isolated eggs and vibrated each one in a vortexer — a laboratory device often used to mix small vials of liquid. Most eggs hatched within 3 hours of being shaken, indicating that they were hatching in response to the vibrations.
Insects frequently communicate through vibrations. For desert locusts, the tiny tremors produced by a single nymph wriggling free from its shell could set off a chain reaction, reverberating through the entire pod and leading an army of nymphs to emerge at once from the ground.
The authors write in the journal Behavioral Ecology and Sociobiology that hatching in sync “helps hatchlings to form aggregations and to reduce the risk of predation and cannibalism.”
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