I continue to read Ed Yong’s book “An Immense World”.
He writes about the emerald jewel wasp. This wasp—a beautiful creature about an inch long with a metallic green body and orange thighs—is a parasite that raises its young on cockroaches. When the female Ampulex compressa finds a cockroach (which is twice her size), she stings it twice: first in the middle of the body to temporarily paralyze its legs, and a second time in the brain. The second sting targets two specific groups of neurons and delivers a venom that deprives the cockroach of the desire to move on its own, turning it into an obedient zombie. In such a state, the wasp can lead the cockroach to its lair by the antennae, much like a person leads a dog. There, she lays an egg on it, providing her future larva with a compliant source of fresh meat.
This act of mind control depends on the second “sting,” which the wasp must deliver precisely to the right spot in the brain. There’s almost no brain there, and what is there is hidden somewhere among a tangle of muscles and internal organs. How does she manage?
Fortunately for the wasp, its stinger is not only a drill, venom injector, and egg-laying tube, but also a sensory organ. Its tip is covered with small bumps and indentations, sensitive to both smell and touch. With their help, she can detect the cockroach’s brain. When Gal and Libersat removed a cockroach’s brain before offering it to the wasp, she tried to find the organ, but in vain. If the brain was replaced with something of the same consistency, then the wasp found the brain, but then got confused. Thus, it can distinguish the brain from everything else with its “nose.”
Another interesting story is about the red knots, shorebirds. There are many such birds on the ocean, they probe the sand along the shore with their beaks in search of buried treasures—worms, mollusks, and crustaceans. Under the microscope, the tips of their beaks are pitted like corncobs from which all the kernels have been eaten. These pits are filled with mechanoreceptors, similar to those on our skin, particularly on our palms and fingers, and allow the birds to detect buried prey by touch.
But how does a shorebird know where to insert its beak first? Underground prey is not visible from the surface, so one might assume that the birds simply dig randomly and hope for the best.
However, in 1995, Dutch scientist Theunis Piersma showed that the birds find mollusks eight times more often than one would expect if they were searching randomly. They must have some technique. To figure it out, Piersma trained birds to inspect buckets filled with sand for buried objects and report if they found anything by approaching a specially equipped feeder. This simple experiment showed that the birds could detect mollusks buried even deeper than they can reach with their beaks. During the process, it turned out they were able to sense stones, so they clearly did not rely on smells, sounds, tastes, vibrations, heat, or electric fields.
Piersma suggested that these birds use a special form of touch that works at a distance. When a red knot’s beak plunges into wet sand, it “pushes” fine jets of water between the grains, creating a wave of pressure that radiates outward from that spot. If there is any solid object in the path (like a mollusk or a stone), the water has to flow around it, distorting the pressure pattern. The pits at the beak tip of the knot are tuned to sense these distortions. Moreover, the bird “collects” data from its radar from different points, allowing it to make fewer attempts than if it acted by unscientific probing.
It’s clear that this is a hypothesis, but one backed by experiments making it quite plausible. Because nothing else can explain the observations.
Ed also writes something interesting about the touch sensation in star-nosed moles. These are eyeless animals with a large red star on their nose. This star-shaped growth is the most sensitive tactile system known to contemporary science. Biologists have counted more than 100,000 nerve fibers in it: this is five times more than in a human hand, which is also considered to have very high sensitivity. And these 100,000 are packed into their organ, smaller than a fingertip. The sensory receptors are known as “Eimer’s organs,” named after the scientist who first observed them. They help the mole detect seismic vibrations from the environment.
Thanks to the vast number of sensory receptors, the star-nosed mole is able to find an object, determine whether it’s edible or not, and then eat it (if it’s an insect or worm) in less than 120-150 ms. That’s about the time it takes for us to blink. In this time, by merely touching what can be a worm, they understand it’s edible, and manage to “chew” it before we finish blinking. As a result, the star-nosed mole can touch and check up to 13 different small objects per second. Data exchange occurs fantastically quickly: the brain makes a decision in 8 milliseconds, which is the theoretical speed limit of neurons.
The sense of smell is also unusual. It is usually believed that mammals cannot smell underwater. Well, this creature can. To do this, moles use a unique technology. Chasing prey in swampy areas, they blow bubbles into the water, then inhale them back through their nostrils. Meanwhile, the direction of their movement correlates with the movement of the prey.
Hi, I'm Rauf Aliev. 