In recent years, scientists have been paying increasing attention to the so-called micro-syascomal – miniature species, whose sizes are much smaller than the majority of representatives of this class. Among these fascinating creatures are wasps, beetles, and ants. One of the most notable examples is MEGAPHRAGMA MYMARIPENNE OSA, measuring only 200 micrometers (1/125 inch), which ranks third in the list of the smallest inhabitants of the microworld.
The sizes of these creatures are comparable to some unicellular organisms. The brain of M. Mymaripenne contains only 4600 neurons – the absolute minimum among all the species studied. For comparison, the brain of a honey bee contains about a million nerve cells. As the brain size decreases, specific changes occur: neurons become smaller and denser, while the number of synaptic connections between them increases.
The reduction in the size of nerve cells in micro-syascomal species is of particular interest to researchers. While the bodies of neurons in the human brain reach approximately 20 micrometers in diameter, and their nuclei 5-10 micrometers, these species have the smallest recorded diameter of neuron bodies at 2-3 micrometers. This limit is likely related to restrictions imposed by the size of the nucleus. Scientists believe that smaller neurons offer an evolutionary advantage: they require less energy both at rest and when transmitting signals, while being able to be arranged more compactly.
The parasitic wasp Trichogramma Evanescens presents another remarkable example of miniaturization: its entire brain is only slightly larger than a single motor neuron of a person. The brain size of these tiny creatures ranges from 160-330 micrometers, while the largest motor neurons in humans, Betz cells, reach 50-100 micrometers.
The beetle Scydosella musawasens, recognized as the smallest free-living organism in its class, measures only 325 micrometers. Its brain contains approximately 9500 cells with an average diameter of about 1.25 micrometers, yet it maintains a complex organization of the nervous system despite its extremely small size.
Researchers have discovered an astonishing feature in some species – the absence of nuclei in neurons. The M. Mymaripenne wasps lack nuclear nerve cells in the brain, with their bodies being nearly half the size of neurons with nuclei. Russian scientists have recently identified a second type of parasitic wasp, Megaphrag