Auditory Low Frequency Adaptation Of Myospalax Cansus

Subterranean rodents show a series of changes in sense organs to adapt theunderground environment, for example, olfaction highly evolved, be sensitive to touch,and bones structure of forelimbs obviously changed in order to dig holes efficiently.In order to find the evidence of Myospalax cansus' adaptation to low frequencysound waves, three groups experiments about the hearing ability of Myospalax cansushave finished, which are histological research, sanning electron mieoscope research aboutMyospalax cansus' cochlea, and the measure of auditory brainstem response aboutMyospalax cansus.The results show that the cochlea structures between Myospalax cansus and othermammals are similar, it also have a typical screwy structure, and it have three point fivecircles aggregately. The helix ganglions are clear, which include big deeply dyed cellsand small shallowly dyed cells, from the bottom to the top of the cochlea, the number ofthe helix ganglions gradually increases.Tissue treated with scanning electron microscopy, in Myospalax cansus' cochlea,the inner hair cells are arranged in a line, and there are about thirty stereocilia on the topof inner hair cells, they are arranged in linear. Outer hair cells are arranged in three rows,there are about four rows stereocilia on every outer hair cell, and there are about thirtystereocilia every row, about one hundred and twenty stereocilia every bundle, they arearranged like a "C" do not present typical "W" shape. These stereocilia arranged orderly,and the length of the stereocilia heightened from inside to outer side of the stereociliabundle gradually. The space between outer hair cells is small, and outer hair cells indifferent rows arranged inlaid.During auditory brainstem response process, the result of click stimulate show thatthe lowest auditory threshold of female Myospalax cansus only reach 35±5dB SPL, andthe male 40±5dB SPL, under the same condition, the lowest auditory threshold ofMicrotus oeconomus can reach 21±0.67dB SPL. Results of single frequencies stimulateshow that the best sound waves for Myospalax cansus are around 12 kHz, the lowest auditory threshold of female Myospalax cansus reach 37±0.5dB SPL, and the male40±0.0dB SPL, the best sound waves for Microtus oeconomus are around 24kHz, thelowest auditory threshold of Microtus oeconomus reach 19±0.17 dB SPL.Waves below 1 kHz or higher than 16 kHz, the auditory threshold of Myospalaxcansus overrun 60dB SPL, which show that the auditory sensitive waves of Myospalaxcansus focus on medial and low frequencies.