Does the morphology of the ear of theChinese bamboo rat (Rhizomys sinensis) show “Subterranean” characteristics?

Abstract

In spite of the growing interest in rodents with subterranean activity in general and the spalacids (Spalacidae) in particular, little is known about the biology of most members of this clade, such as the Chinese bamboo rat (Rhizomys sinensis). Here, we analyzed the ear morphology of R. sinensis with respect to hearing specialization for subterranean or aboveground modes of communication. It is well-known that ecology and style of life of a particular species can be reflected in morphology of its ear, its hearing and vocalization, so we expect that such information could provide us insight into its style of life and its sensory environment. The ratio between the eardrum and stapedial footplate areas, which influences the efficiency of middle ear sound transmission, suggests low hearing sensitivity, as is typical for subterranean species. The cochlea had 3.25 coils and resembled species with good low frequency hearing typical for subterranean mammals. The length of the basilar membrane was 18.9 ± 0.8 mm and its width slowly increased towards the cochlear apex from 60 to 85 μm. The mean density of outer hair cells was 344 ± 22 and of inner hair cells 114 ± 7.3 per 1 mm length of the organ of Corti, and increased apically. These values (except for relatively low hair cell density) usually characterize ears specialized for low frequency hearing. There was no evidence for an acoustic fovea. Apart of low hair cell density which is common in aboveground animals, this species has also relatively large auricles, suggesting the importance of sound localization during surface activity. The ear of the Chinese bamboo rat thus contains features typical for both aboveground and subterranean mammals and suggests that this spalacid has fossorial habits combined with regular aboveground activity.

Morphological and morphometrical aspects of the auditory ossicles in goat (Capra hircus)

“…Given the surgical importance of this ossicle in humans (Saha, Srimani, Mazumdar, & Mazumdar, 2017), size and morphology of this piece is important. The overall shape in C. hircus resembles the one described for the Chinese bamboo rat (Pleštilová et al, 2016), degu and paca, hamster (Mohammadpour, 2010),…”

“…Given the surgical importance of this ossicle in humans (Saha, Srimani, Mazumdar, & Mazumdar, 2017), size and morphology of this piece is important. The overall shape in C. hircus resembles the one described for the Chinese bamboo rat (Pleštilová et al., 2016), degu and paca, hamster (Mohammadpour, 2010), wolf (Gürbüz et al., 2019) or guinea pig (Albuquerque, Rossato, De Oliveira, & Hyppolito, 2009). Slightly different from these previous species, the overall shape of the stapes is almost rectangular in ruminants or almost rounded in rat (Albuquerque et al., 2009; Gürbüz et al., 2019).…”

“…Thanks to its important integrative function, present‐day research for middle ear structure was reported for several species such as the chinese bamboo rat (Pleštilová, Hrouzková, Burda, & Šumbera, 2016), toad (Womack, Stynoski, Voyles, Coloma, & Hoke, 2018), rabbit (Guan et al., 2019), pig (Pracy, White, Mustafa, Smith, & Perry, 1998), miniature pigs (HaiJin et al., 2013), humans, (Arechvo et al., 2013; Isaacson, 2014; Luers & Hüttenbrink, 2016; Sawada, Nara, Fukui, Dodo, & Hirata, 2014; Stieger, Djeric, Kompis, Remonda, & Häusler, 2006; Whyte et al., 2001) other primates, moles (Mason, 2006), dog (Berghes, Parvu, Cucoanes, & Cuca, 2010; Ortug & Türkmenoğlu, 2005), Indian mangoose (Kamali, Gholami, Ahrari‐Khafi, Rasouli, & Shayegh, 2015), horse, cat, cow, rat, mouse (Amin & Tucker, 2006; Blanke, Aupperle, Seeger, Kubick, & Schusser, 2015; Botti, Secci, Ragionieri, Dessole, & Acone, 2006; Mohammadpour, 2010) or other extinct rodents (Lange, Stalleicken, & Burda, 2004), hamster, gerbil, New Zeeland rabbit (Kurtul, Cevik, Bozkurt, & Dursun, 2003), ostrich (Beșoluk et al., 2019; Keenan, Mears, & Skedros, 2017), degu (Argyle & Mason, 2008), weasel or chinchilla (Bergin, Vlajkovic, Bird, & Thorne, 2013; Carrasco, Maass, Dentone, Miranda, & Kukuljan, 2008; Charuta et al., 2011; Hoffstetter et al., 2011; Maier, Tröscher, & Ruf, 2018; Maravilla et al., 2011; Martonos et al., 2019; Rodrigues, Shinohara, Andreo, Buchaim, & Ahmed, 2012; Wang & Gan, 2016).…”

Into the dark: patterns of middle ear adaptations in subterranean eulipotyphlan mammals

“…Talpa europaea and Mogera robusta , both highly subterranean, are reported to respond to frequencies from 0.01 to 22 kHz and to be most sensitive around 3 kHz [ 13 ]. Further studies on actual hearing capabilities are needed, but our findings that subterranean talpids are equipped with an enlarged incus and stapes footplate are overall consistent with previous studies on other subterranean rodents, marsupials and golden moles [ 12 , 14 , 16 , 18 , 20 ] and what has been found previously in several talpid species [ 15 , 16 ].…”

3D atlas and comparative osteology of the middle ear ossicles among Eulipotyphla (Mammalia, Placentalia).

“…Improvements of non-visual sensory organs are critical to live in the darkness where available light is limited. Previous studies have identified that subterranean mammals tend to exhibit larger tympanic membrane, larger stapes footplate, loose connection between malleus and tympanic bone, and reduced middle ear muscles (Fleischer, 1978;Burda, 1979Burda, , 2006Burda et al, 1990Burda et al, , 1992Mason, 2001Mason, , 2003Mason, , 2006Pleštilová et al, 2016;Wannaprasert, 2016). Their morphology is argued to be related to hearing low-frequency sounds and reduced impedance performance (Burda et al, 1990(Burda et al, , 1992.…”