Nature: Chinese scientists unravel the mystery of bat echolocation in unexpected places

2022-06-17 0 By

Mammals thrive in diversity, and bats, as we know them, are unique among them.They are the only mammals that can fly on their own, and they are surprisingly diverse — there are at least 1,440 species of bats, one in every five mammal species.Another important evolutionary feature of bats for us is their echolocation system.Echolocation is a very specific behavioral function that requires specialized vocal structures and highly sensitive auditory perception to allow them to “hear” their surroundings, find food or avoid obstacles even in the dark.Bats are often equated with echolocation, but the truth is that not all bat species have this ability.The function of echolocation in bats also varies between species.Bats belong to the order pterodactyl, which science once divided into two groups based on how they live — the sighted, vegetarian-oriented suborder Macropterodactyl, and the micropterodactyl, which uses echolocation to hunt flying insects.This traditional classification is straightforward, but with the development of modern phylogeny, the bat species have been reclassified into two groups, namely, the dipterophora and the dipterophora, based on the new study of molecular sequence and genotype evolution.While these new studies provide a more accurate way to classify bats, scientists have also noted that the emergence of echolocation features in bats is more complex than previously thought.The echolocation of large brown bats belonging to the suborder Heliopteria and part of the suborder Heliopteria have the ability of echolocation, suggesting that there are two possible evolutionary processes of bat echolocation.”Or two species of bat could have independently evolved different echolocation systems,” said Luo, of the University of Chicago.Or maybe echolocation was already present in its common ancestor, but was subsequently lost in distantly related pteropodidae members of the suborder Pteropodidae.”For a long time, however, these hypotheses were supported only by evidence of DNA sequence and phylogenetic deduction, but not by evidence of neuroanatomy and auditory function in the ear region.”If either hypothesis is correct, there should be differences in the neuroanatomy of the cochlea, the inner ear that receives the echo.”Professor Luo zhexi said.In a new study published in Nature, Luo led a team from the University of Chicago in collaboration with scientists from the American Museum of Natural History and the Field Museum of Natural History to identify key neuroanatomical differences in the cochlea, the inner ear of the two bat species.This study suggests that it is structural differences in the inner ear that have evolved neuroanatomical features that give bats of the pterodactyls different echolocation behavioral functions.The clue that led the team to focus on the cochlea of the inner ear was the difference in the echolocation patterns of the two bat species: echolocation in the hyacinth suborder relies more on constant frequency sounds, while echolocation in the hyacinth suborder uses more complex and variable frequency modulation.Since the inner ear is the starting point for receiving these echoes, its structure was the team’s first concern.Cochlear spiral ganglion is the key structure of hearing.Professor Luo says the structural difference they are looking for is the cochlear ganglion, which has not received much attention: “It has never been suspected that there are anatomical differences between the helical ganglion of the hynopterus and the hynopterus suborder.Neuroanatomical studies of bats in the 1970s and 1980s focused on auditory hair cells and the density of peripheral nerves around ganglia.However, earlier studies did not pay much attention to the morphology of the ganglia, neurons and axons of the auditory cranial nerve, and surrounding bone.”Starting in 2016, the team spent four years using CT scans to study the inner ear structures of 39 bat species, covering 19 of 21 bat families.Anatomical patterns of Rosenthal tube wall and spiral auricular ganglion in bat inner earCT scans of April Neander show that the inner ear of the suborder Pterogiformis has a structure similar to that of other mammals, with a protective bone wall (called the Rosenthal wall) outside the spiral ganglion. The wall is densely filled with tiny openings for nerve fibers to pass through and connect to the auditory cranial nerve.However, the helical ganglion is open and there is no surrounding tube wall structure.No longer limited by the number and size of micropores in the bone wall, the inner ears of these bats can evolve to produce larger ganglia, which can contain more neurons, higher innervation density, and denser and more varied bundles of nerve fibers.The discovery in the structure of the inner ear may also explain the differences in species diversity between the suborders Anochiropteris and Anochiropteris.There are five times as many species in the dipterophanes suborder than in the dipterophanes suborder, and they forage for prey in more diverse ways and ranges.The team speculates that larger ganglia and more neurons helped them form specialized inner ear structures and more varied FREQUent-modulated echolocation, thus enriching the evolutionary prosperity and diversification of these bats.Arguably, it is these different echolocation methods that have contributed to bats’ great evolutionary success.”The echolocation behavior of bats is like the animals’ language,” luo said.’The two types of bats seem to speak different dialects.But in different ways, they all lead to the same goal.The parasophanes have developed a very specific ganglion anatomy, so they have a more sophisticated hearing for their own dialects.”References:[1] R. Benjamin Sulser et al., Evolution of inner ear neuroanatomy of bats and implications for echolocation. Nature (2022). https://doi.org/10.1038/s41586-021-04335-z [2] Bats use company’s inner ear structures to help navigate the world through sound. Retrieved Jan. 26, 2022 from https://www.eurekalert.org/news-releases/940788[3] Microscopic inner ear structures reveal why major groups ofBats echolocate differently. The Retrieved, Jan. 26, 2022 from https://www.eurekalert.org/news-releases/940785? disclaimer:Content from the network, copyright belongs to the original author.This article is for informational purposes only and does not necessarily reflect the views expressed herein.If there are copyright issues, please contact us to delete.For more exciting content, follow us on the pursuit of new knowledge