Subterranean Mammals Research Articles

Evolutionary shifts in the thermal biology of a subterranean mammal: the effect of habitat aridity.

Subterranean mammals representing a single subspecies occurring along an aridity gradient provide an appropriate model for investigating adaptive variation in thermal physiology with varying levels of precipitation and air temperature (Tair). This study examined the thermal physiological adaptations of common mole-rats (Cryptomys hottentotus hottentotus) across five populations along an aridity gradient, challenging the expectation that increased aridity would lead to reduced metabolic rate (MR), lower body temperatures (Tb), and broader thermoneutral zones (TNZ). No significant, consistent differences in MR, Tb, or thermal conductance were observed between populations, suggesting uniform thermoregulatory mechanisms across habitats. Instead, behavioral strategies such as huddling and torpor may play a more prominent role than physiological adaptations in managing temperature regulation and water balance. The study also observed osmoregulatory differences, with populations employing distinct behavioral cooling strategies in response to water availability. These results underscore the need for further research into the responses of subterranean species to climate change, particularly in understanding how increasing global temperatures and aridification might influence species distribution if they lack the physiological capacity to adapt to future climatic conditions.

The geomorphic work of the European mole (Talpa europaea): Long‐term monitoring of molehills using structure‐from‐motion photogrammetry

AbstractMoles—small insectivorous mammals of the family Talpidae—are widespread across the Northern Hemisphere. These subterranean mammals are easily detected through the mounds, or molehills, they construct as surface bioproducts of tunnel systems excavated underground. The dense aggregation of these bioconstructions in a range of environments (e.g., floodplains, woodland, coastal dunes and upland regions) indicates that moles may play an important role in sediment systems. However, compared with other fossorial mammals (e.g., gophers and rabbits), the impact of moles as direct and indirect biogeomorphic agents is poorly understood. Furthermore, little is known about how molehills develop and degrade over time or how long they persist as landscape features. By examining molehills created by the European mole (Talpa europaea) over 4 months on a floodplain in Oxfordshire, UK, we provide a quantitative assessment of how these landforms evolve over time and space. Through the creation of high‐resolution digital elevation models (DEMs) using structure‐from‐motion (SfM) photogrammetry, we derive a variety of metrics describing molehill morphology and produce a detailed record of how molehills change at weekly time intervals. In addition, measurements of molehill volume are used to estimate the excavation rate of moles over a month. Findings show that (i) molehills are dynamic landforms that change in size and shape in response to phases of construction, collapse, erosion and rebuilding; (ii) rates of degradation are influenced by soil characteristics and seasonal weather conditions; (iii) molehills can persist as landscape features for several months; and (iv) moles are capable of moving a substantial volume of sediment in highly active areas (3.89 m3 ha−1 month−1). Future work is now needed to determine the geomorphic impact of T. europaea over larger spatial scales (e.g., river catchments) and longer timescales (e.g., years–decades) to determine its importance in relation to other bioturbators and within the wider sediment system.

Ultradian rhythms of activity in a wild subterranean rodent.

Many animals adapt their activity patterns to the best environmental conditions using daily rhythms. African mole-rats are among the mammals that have become models for studying how these rhythms can be entrained by light or temperature in experimental laboratory studies. However, it is unclear whether they exhibit similar circadian rhythms in their natural lightless, subterranean environment. In this study, we used biologging to investigate the activity rhythms of wild, highveld mole-rats. We show that their activity cycle exhibited an ultradian rhythm with a length between 4 and 8 h. On an individual level, mole-rats displayed about five activity bouts per day, occurring at various times during the day and night. On a population level, activity peaked in the afternoon, coinciding with the peak in ambient temperature. Our research suggests that wild subterranean mammals, which experience reduced environmental variation, are unlikely to show clear circadian rhythmicity in activity patterns. Instead, activity periods are distributed over several bouts throughout the day and night, and activity coincides with the peak in daily temperature. We propose that ultradian rhythms in activity may be more common than previously thought and discuss how physiological processes may generate differences in periodicity between laboratory and wild populations.

Hypoxia-induced downregulation of RNA m6A protein machinery in the naked mole-rat heart

Naked mole-rats, Heterocephalus glaber, are champion hypoxia-tolerant rodents that live under low oxygen conditions in their subterranean burrows. Detrimental effects of low oxygen can be mitigated through metabolic rate depression (MRD), metabolic reorganization, and global downregulation of nonessential cellular processes. Recent research has progressively implicated epigenetic modifications – rapid, reversible changes to gene expression that do not alter the DNA sequence itself – as major players in implementing and maintaining MRD. N6-adenosine (m6A) methylation is the most prevalent mammalian RNA modification and is responsible for pre-mRNA processing and mRNA export from the nucleus. Hence, m6A -mediated conformational changes alter the cellular fate of transcripts. The present study investigated the role of m6A RNA methylation responses to 24 h of hypoxia exposure in H. glaber cardiac tissue. Total protein levels of m6A writers/readers/erasers, m6A demethylase activity, and total m6A quantification were measured under normoxic vs. hypoxic conditions in H. glaber heart. While there was no change in either demethylase activity or total m6A content, many proteins of the m6A pathway were downregulated during hypoxia. Overall, m6A may not be a signature hypoxia-responsive characteristic in H. glaber heart, but downregulation of the protein machinery involved in m6A cycling points to an alternate biological involvement. Further research will explore other forms of RNA modifications and other epigenetic mechanisms to determine the controls on hypoxia endurance in this subterranean mammal.

Functional and morphological divergence in the forelimb musculoskeletal system of scratch-digging subterranean mammals (Rodentia: Bathyergidae).

Whether the forelimb-digging apparatus of tooth-digging subterranean mammals has similar levels of specialization as compared to scratch-diggers is still unknown. We assessed the scapular morphology and forelimb musculature of all four solitary African mole rats (Bathyergidae): two scratch-diggers, Bathyergus suillus and Bathyergus janetta, and two chisel-tooth diggers, Heliophobius argenteocinereus and Georychus capensis. Remarkable differences were detected: Bathyergus have more robust neck, shoulder, and forearm muscles as compared to the other genera. Some muscles in Bathyergus were also fused and often showing wider attachment areas to bones, which correlate well with its more robust and larger scapula, and its wider and medially oriented olecranon. This suggests that shoulder, elbow, and wrist work in synergy in Bathyergus for generating greater out-forces and that the scapula and proximal ulna play fundamental roles as pivots to maximize and accommodate specialized muscles for better (i) glenohumeral and scapular stabilization, (ii) powerful shoulder flexion, (iii) extension of the elbow and (iv) flexion of the manus and digits. Moreover, although all bathyergids showed a similar set of muscles, Heliophobius lacked the m. tensor fasciae antebrachii (aiding with elbow extension and humeral retraction), and Heliophobius and Georychus lacked the m. articularis humeri (aiding with humeral adduction), indicating deeper morphogenetic differences among digging groups and suggesting a relatively less specialized scratch-digging ability. Nevertheless, Heliophobius and Bathyergus shared some similar adaptations allowing scratch-digging. Our results provide new information about the morphological divergence within this family associated with the specialization to distinct functions and digging behaviors, thus contributing to understand the mosaic of adaptations emerging in phylogenetically and ecologically closer subterranean taxa. This and previous anatomical studies on the Bathyergidae will provide researchers with a substantial basis on the form and function of the musculoskeletal system for future kinematic investigations of digging behavior, as well as to define potential indicators of scratch-digging ability.

Effect of foraging tunnels created by small subterranean mammals on soil microbial biomass carbon and organic carbon storage in alpine grasslands

Extensive foraging tunnel disturbances created by small subterranean mammals have important impacts on soil physical properties and nutrients in grasslands. This study took plateau zokor (Eospalax baileyi) as an example mammal to investigate the impacts of foraging tunnel disturbances by small subterranean mammals on soil microbial biomass carbon (SMBC) and soil organic carbon (SOC) storage. A paired design was used to locate 90 tunnel quadrats and 90 non-tunnel quadrats in alpine grasslands across three sites. This study showed that SMBC, SOC concentrations and SOC storage in tunnel quadrats were 47.4 %, 26.8 % and 22.0 % lower than those in non-tunnel quadrats, respectively. This study also showed that soil microbial biomass nitrogen was a major factor affecting SOC storage in non-tunnel quadrats, while it was not a major factor in tunnel quadrats. Soil pH and soil ammonium nitrogen were not major factors in non-tunnel quadrats, while they were the major factors influencing SOC storage in tunnel quadrats. In contrast to non-tunnel quadrats, foraging tunnel disturbances led to a new pathway in which soil pH positively affected SOC storage in tunnel quadrats. The findings of this study demonstrated that foraging tunnel disturbances had negative impacts on soil fertility due to lower SMBC concentrations and might cause soil carbon loss in alpine grasslands because of lower SOC storage. Given the effect of foraging tunnels on soil carbon cycling and climate regulation in the Qinghai-Tibet Plateau's alpine grasslands, it is crucial to take them into account when assessing grassland carbon storage and formulating strategies for effective grassland management and conservation.

The role of ambient temperature and light as cues in the control of circadian rhythms of Damaraland mole-rat

ABSTRACT Light is considered the primary entrainer for mammalian biological rhythms, including locomotor activity (LA). However, mammals experience different environmental and light conditions, which include those predominantly devoid of light stimuli, such as those experienced in subterranean environments. In this study, we investigated what environmental cue (light or ambient temperature (Ta)) is the strongest modulator of circadian rhythms, by using LA as a proxy, in mammals that experience a lifestyle devoid of light stimuli. To address this question, this study exposed a subterranean African mole-rat species, the Damaraland mole-rat (Fukomys damarensis), to six light and Ta cycles in different combinations. Contrary to previous literature, when provided with a reliable light cue, Damaraland mole rats exhibited nocturnal, diurnal, or arrhythmic LA patterns under constant Ta. While under constant darkness and a 24-hour Ta cycle mimicking the burrow environment, all mole-rats were most active during the coolest 12-hour period. This finding suggests that in a subterranean environment, which receives no reliable photic cue, the limited heat dissipation and energy constraints during digging activity experienced by Damaraland mole-rats make Ta a reliable and consistent “time-keeping” variable. More so, when providing a reliable light cue (12 light: 12 dark) to Damaraland mole-rats under a 24-hour Ta cycle, this study presents the first evidence that cycles of Ta affect the LA rhythm of a subterranean mammal more strongly than cycles of light and darkness. Once again, Damaraland mole-rats were more active during the coolest 12-hour period regardless of whether this fell during the light or dark phase. However, conclusive differentiation of entrainment to Ta from that of masking was not achieved in this study, and as such, we have recommended future research avenues to do so.

The double skin of the pink fairy armadillo, the peculiar integumentary system of Chlamyphorus truncatus Cingulata (Mammalia, Xenarthra)

AbstractChlamyphorus truncatus is the smallest known armadillo, weighing about 100 grams and measuring less than 15 cm from head to tail. It is endemic to central Argentina and the species is named after its unique carapace. This armadillo has almost completely subterranean habits and, unlike all other subterranean mammals, C. truncatus has a carapace composed of osteoderms and cornified scales. Furthermore, the skin and carapace show unique characteristics compared even with other armadillos. Owing to the reduced development of its eyes, it is important to analyse the skin morphology of this species, as well as specialized sensory organs like vibrissae. The aim of this contribution is to describe the histomorphology of the integumentary system of C. truncatus. For this, histological sections of the skin with and without osteoderms were made, and routine histological and immunohistochemical techniques were performed. Furthermore, microCTs were performed on osteoderms to describe their micromorphology. Our results show that the integumentary system presents unique characteristics compared to other armadillos, such as the peculiar skin under the dorsal shield and the flexibility of almost all of its carapace. Furthermore, the modification of the arrangement of hairs in the first pelvic buckler osteoderms may suggest biomechanical adaptations, such as an improvement in the displacement through the tunnels of sandy soils. The skin without osteoderms presents convergent characteristics with that of other subterranean mammals. Furthermore, the vibrissae conserve the structure of the armadillos (the cavernous sinuses extend throughout the follicle‐sinus complex) with a thinning and shortening of the hairs, which are probably linked to passive monitoring of the surrounding environment. Evidently, the adaptations of subterranean mammals to their environment imply structural and functional changes, which are both regressive and progressive in nature.

Investigation of Clock Gene Variations in Nannospalax Cytotypes

Blind mole rats (Nannospalax) are subterranean mammals noted for their longevity and cancerresistance. It is known that these animals' vestigial eyes, particularly the Harder gland around the eyes, maygenerate considerable amounts of melatonin. Furthermore, the melatonin production mechanism in thecircadian rhythm cycle of blind mole rats is regarded to be different from that of other living beings. Themelatonin and Clock genes are hypothesized to be linked to the formation, development, and spread ofcancer, but the researchers still cannot explain their extraordinary cancer resistance.In this study, we hypothesized that the melatonin production mechanism in the circadian rhythm cycle ofblind mole rats, which have been shown in the literature to be cancer-resistant, may differ from that of otherliving species due to the difference in their amino acid variations. Differences in the DNA of the Clockgenes (Cry1 and Per1) involved in melatonin biosynthesis in blind mole rats were studied compared toother model species (Spalax galili, Mus musculus, Heterocephalus glaber, Rattus norvegicus, and Homosapiens). As a result, while no variations were found in the Cry1 gene; only p.G7R variation was found inthe Per1 gene. The SNAP2 software had demonstrated that the human analogs of this variation harmfuleffects. It was suggested that more or full exon sites, more samples and genes should be studied to observemore variants in Nannospalax species. Thereby, the cancer resistance of blind mole rats may be explainedbetter by these variations and the functions of protein domains where these variants are located in.

Livestock and subterranean mammals have contrasting impacts on soil infiltration of grasslands

The role of the increasing rodent population in grassland degradation on the Qinghai–Tibet Plateau (QTP) is the subject of continuing debate. We conducted a five-year grazing experiment to investigate the responses of soil permeability to livestock grazing and subterranean plateau zokor (Myospalax baileyi) burrowing activity in grasslands. In addition, using a meta-analysis approach, we generalized the effects of livestock grazing on soil permeability in global grasslands. The objective was to test the hypothesis that underground soil disturbance by burrowing mammals helps to improve the permeability of soil that has been compacted by trampling from grazing livestock. In the grazing experiment, soil saturated hydraulic conductivity (Ksat) in the upper 10 cm layer under livestock grazing (47.9 mm h−1) was less than one half of that under no grazing (116.8 mm h−1) in zokor-excluded plots. The Ksat value on zokor mounds (>two years old) (313.6 mm h−1) was eight times greater than that of inter-mound areas (38.5 mm h−1) in livestock-grazed plots. These contrasting effects on soil permeability of livestock grazing and subterranean zokor disturbance were ascribed to their opposite effects on soil macroporosity. Meta-analysis indicated that livestock grazing significantly decreased soil Ksat or steady infiltration rate in global grasslands by decreasing soil macroporosity, across grazing intensities, strategies, durations and climatic features, compared with no grazing. As such, the decreased soil permeability in grazed compared with non-grazed grasslands was a global generality. This research provided new insight into the ecohydrological function of subterranean mammals in pastures. The potential beneficial effects to soil permeability should be among the consideration for the management of subterranean mammals in grazed grasslands.

Oxidative status of Ctenomys flamarioni (Rodentia: Ctenomyidae) in natural areas with different levels of anthropic activity in southern Brazil

Rampant urbanization in coastal environments turns areas close to the seafront into a highly impacted ecosystem, possibly affecting the health and well-being of resident animal species. The tuco-tuco Ctenomys flamarioni is an endemic and endangered subterranean mammal from southern Brazil, and the anthropic influence was considered one of the main threats to the species. In this context, the present study aimed to investigate the patterns of oxidative status of the species in natural areas with different levels of anthropogenic disturbance. We evaluated two populations of C. flamarioni, one located in an area with intense anthropogenic impact due to urbanization and tourist activity, and the other in a non-impacted area. Oxidative injury parameters (lipid peroxidation and carbonylated protein levels), and the activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glucose 6-phosphate dehydrogenase, glutathione S-transferase and carboxylesterase were measured. Individuals inhabiting the impacted area had lower G6PDH activity and higher levels of carbonylated proteins. This combination of higher level of oxidative damage and lower antioxidant activity is an indication that the oxidative status of animals in the impacted population is possibly being affected as a consequence of anthropogenic activities in this environment. The values of the parameters obtained in the current study can be used as a reference of the oxidative state of C. flamarioni in future studies with tuco-tucos.

Environmental and climatic drivers of phenotypic evolution and distribution changes in a widely distributed subfamily of subterranean mammals

How environmental factors shape species morphology and distributions is a key issue in ecology, especially in similar environments. Species of Myospalacinae exhibit widespread distribution spanning the eastern Eurasian steppe and the extreme adaptation to the subterranean environment, providing an excellent opportunity for investigating species responses to environmental changes. At the national scale, we here use geometric morphometric and distributional data to assess the environmental and climatic drivers of morphological evolution and distribution of Myospalacinae species in China. Based on phylogenetic relationships of Myospalacinae species constructed using genomic data in China, we integrate geometric morphometrics and ecological niche models to reveal the interspecific variation of skull morphology, trace the ancestral state, and assess factors influencing interspecific variation. Our approach further allows us to project future distributions of Myospalacinae species throughout China. We found that the interspecific morphology variations were mainly concentrated in the temporal ridge, premaxillary-frontal suture, premaxillary-maxillary suture, and molars, and the skull morphology of the two current species in Myospalacinae followed the ancestral state; temperature and precipitation were important environmental variables influencing skull morphology. Elevation, temperature annual range, and precipitation of warmest quarter were identified as dominant factors affecting the distribution of Myospalacinae species in China, and their suitable habitat area will decrease in the future. Collectively, environmental and climate changes have an effect on skull phenotypes of subterranean mammals, highlighting the contribution of phenotypic differentiation in similar environments in the formation of species phenotypes. Climate change will further shrink their habitats under future climate assumptions in the short-term. Our findings provide new insights into effects of environmental and climate change on the morphological evolution and distribution of species as well as a reference for biodiversity conservation and species management.

Naked Mole-Rats Demonstrate Profound Tolerance to Low Oxygen, High Carbon Dioxide, and Chemical Pain.

Naked mole-rats (Heterocephalus glaber) are very unusual among subterranean mammals in that they live in large colonies and are extremely social, spending large amounts of time gathered together in underground nests more than a meter below the surface. Many respiring individuals resting in deep, poorly ventilated nests deplete the oxygen supply and increase the concentration of carbon dioxide. Consistent with living in that atmosphere, naked mole-rats tolerate levels of low oxygen and high carbon dioxide that are deadly to most surface-dwelling mammals. Naked mole-rats appear to have evolved a number of remarkable adaptations to be able to thrive in this harsh atmosphere. In order to successfully survive low oxygen atmospheres, they conserve energy utilization by reducing the physiological activity of all organs, manifest by reduced heart rate and brain activity. Amazingly, they resort to the anaerobic metabolism of fructose rather than glucose as a fuel to generate energy when challenged by anoxia. Similarly, high carbon dioxide atmospheres normally cause tissue acidosis, while naked mole-rats have a genetic mutation preventing both acid-induced pain and pulmonary edema. Together, these putative adaptations and the tolerances they provide make the naked mole-rat an important model for studying a host of biomedical challenges.

Social Isolation Does Not Alter Exploratory Behaviour, Spatial Learning and Memory in Captive Damaraland Mole-Rats (Fukomys damarensis).

Exploratory behaviour, spatial learning and memory affect the survival of animals and appear to be dependent on the specific habitat that a species occupies. Good spatial navigation and memory are particularly important for subterranean animals, as it is energetically expensive to inhabit this niche. Damaraland mole-rats are subterranean mammals that live in colonies with organised social structures. Damaraland mole-rats have been maintained in the laboratory for many years and can be housed in groups or individually. We evaluated the effect of social isolation on the exploratory behaviour and spatial memory of single-housed and colony-housed animals and also considered potential differences in animals with different social statuses. We predicted that solitary housing would increase anxiety-like behaviour and result in higher activity and more errors when solving a maze. Exploration by colony- and single-housed mole-rats was tested in an open-field test, where all individuals explored readily. Single-housed queens and non-breeding females showed increased activity and spent more time in tunnels, which can be explained by increased anxiety. In the Y-maze, improvements in solving the maze were observed in all experimental groups, except in single-housed non-breeding females. In addition, all males showed a decrease in the number of errors in the maze. Spatial learning is thus apparent but could not be conclusively proven. It was possibly underestimated, as magnetic cues that may be used by mole-rats as stimuli for navigation were removed in the experimental setup. Overall, it appears that social isolation has a limited effect on the exploratory behaviour and spatial learning of Damaraland mole-rats.

Genome coding and noncoding structure function and evolution in Spalax ehrenbergi superspecies and Hordeum spontaneum in Israel: a review (Rodentia: Spalacidae)

The structure and function of the intergenic noncoding genome (repeatome) whether “selfish” and “junk” or “biochemically functional and regulatory” is still hotly debated, despite the mounting empirical and theoretical evidence supporting the regulatory role, provided by transposable elements, and the ENCODE results. In our studies in Israel on sympatric speciation (SS) in two evolutionary speciation models of abutting divergent ecologies, microclimatic at “Evolution Canyon” and geologic-edaphic at “Evolution Plateau”, we showed genomically that SS is a common speciation model across life from bacteria to mammals. Since such contrasting and abutting ecologies, climatic, geologic, edaphic, abiotic and biotic abound globally, SS might be a common speciation model across the planet. During our SS studies we discovered an additional remarkable result supporting the regulatory role of the repeatome. We found that the noncoding genome, in both subterranean mammals and wild barley at “Evolution Plateau” present a genomic mirror image of the coding genome supporting the regulatory hypothesis of the repeatome. Moreover, the repeatome also succeeded to identify the four subterranean chromosomal climatically adaptive mole rat species in Israel. This genomic mirror imaging and repeatome function is now open to genomic exploration across life.

Adaptive strategies of aquatic mammals: Exploring the role of the HIF pathway and hypoxia tolerance.

Aquatic mammals (marine and freshwater species) share significant and similar adaptations, enabling them to tolerate hypoxia during regular breath-hold diving. Despite the established importance of HIF1A, a master regulator in the molecular mechanism of hypoxia response, and other associated genes, their role in the evolutionary adaptation of aquatic mammals is not fully understood. In this study, we investigated this topic by employing a candidate gene approach to analyze 11 critical genes involved in the HIF1A signaling pathway in aquatic mammals. Our gene analyses included evaluating positive and negative selection, relaxation or constriction of selection, and molecular convergence compared to other terrestrial mammals, including subterranean mammals. Evidence of selection suggested a significant role of negative selection, as well as relaxation of the selective regime in cetaceans for most of these genes. We found that the glutamine 68 variant in the HIF3α protein is unique to cetaceans and initial evaluations indicated a destabilizing effect on protein structure. However, further analyses are necessary to evaluate its functional impact and adaptive relevance in this taxon.

Terrestrial and Subterranean Mammals as Reservoirs of Zoonotic Diseases in the Central Part of European Russia

Russia has a number of historical foci of zoonotic anthropogenic diseases. In Central Russia, the Republic of Mordovia is one of such areas, a region being known to have foci of haemorrhagic fever with renal syndrome (HFRS) and tularemia. It therefore requires continuous monitoring. The role of small terrestrial mammals as reservoirs of zoonoses has been previously proven for the region. The aim of this work is to take an integrated approach to assess the role of terrestrial and subterranean small mammals. Subterranean mammals are often not considered important reservoirs of zoonotic pathogens that cause human morbidity. Among small mammals in the wild environment, the bank vole, the yellow-necked mouse and the house mouse play important roles as vectors of zoonoses. Among wild subterranean mammals, the greater mole rat is important as a vector of tularemia and HFRS. We analyzed homogenized internal organs of these animals (lungs, spleen, kidneys). Of all samples from the greater mole rat, 83% were positive for tularemia antigens and 17% were positive forHFRS. None of the analyzed European moles had antigens of tularemia and HFRS. No double infection with both tularemia and hantavirus was detected in the subterranean mammals. Double infection was found among terrestrial mammals in the bank vole and the forest dormouse.

Unique bone microanatomy reveals ancestry of subterranean specializations in mammals.

Acquiring a subterranean lifestyle entails a substantial shift for many aspects of terrestrial vertebrates' biology. Although this lifestyle is associated with multiple instances of convergent evolution, the relative success of some subterranean lineages largely remains unexplained. Here, we focus on the mammalian transitions to life underground, quantifying bone microanatomy through high-resolution X-ray tomography. The true moles stand out in this dataset. Examination of this family's bone histology reveals that the highly fossorial moles acquired a unique phenotype involving large amounts of compacted coarse cancellous bone. This phenotype exceeds the adaptive optimum seemingly shared by several other subterranean mammals and can be traced back to some of the first known members of the family. This remarkable microanatomy was acquired early in the history of the group and evolved faster than the gross morphology innovations of true moles' forelimb. This echoes the pattern described for other lifestyle transitions, such as the acquisition of bone mass specializations in secondarily aquatic tetrapods. Highly plastic traits-such as those pertaining to bone structure-are hence involved in the early stages of different types of lifestyle transitions.

Parallel evolution of semicircular canal form and sensitivity in subterranean mammals.

The vertebrate vestibular system is crucial for balance and navigation, and the evolution of its form and function in relation to species' lifestyle and mode of locomotion has been the focus of considerable recent study. Most research, however, has concentrated on aboveground mammals, with much less published on subterranean fauna. Here, we explored variation in anatomy and sensitivity of the semicircular canals among 91 mammal species, including both subterranean and non-subterranean representatives. Quantitative phylogenetically informed analyses showed significant widening of the canals relative to radius of curvature in subterranean species. A relative canal width above 0.166 indicates with 95% certainty that a species is subterranean. Fluid-structure interaction modelling predicted that canal widening leads to a substantial increase in canal sensitivity; a reasonably good estimation of the absolute sensitivity is possible based on the absolute internal canal width alone. In addition, phylogenetic comparative modelling and functional landscape exploration revealed repeated independent evolution of increased relative canal width and anterior canal sensitivity associated with the transition to a subterranean lifestyle, providing evidence of parallel adaptation. Our results suggest that living in dark, subterranean tunnels requires good balance and/or navigation skills which may be facilitated by more sensitive semicircular canals.

A comparative SEM study of the guard hair architecture in subterranean moles (Talpidae, Soricomorpha), golden moles (Chrysochloridae, Afrosoricidae), and silvery mole-rats (Bathyergidae, Rodentia)

The architecture (external and internal structure) of guard hairs was studied using SEM and comparative morphological approach in representatives of three orders of subterranean mammals: Eurasian moles Talpa altaica and Mogera robusta; American moles Scapanus townsendii and Urotrichus talpoides (Talpidae, Soricomorpha); African golden moles (Chrysochloridae, Afrosoricidae) Amblysomus hottentotus, Calcochloris obtusirostris, Carpitalpa arendsi, Chrysochloris asiatica, Chrysospalax villosus, Cryptochloris wintoni, and Eremitalpa granti; and an African rodent, the subterranean mole-rat Heliophobius argenteocinereus (Bathyergidae, Rodentia). We have shown that representatives of phylogenetically distant taxa of high rank (at the order level) have examples of convergent evolution of pelage in the adaptation to a digging tunneling life-style. At the same time, comparison of the entire set of parameters of the studied structures reveals species-specific features of the hair structure, which possibly reflect certain differences in living conditions, including various substrate types. Hairs from different parts of the body exhibit no topographic differences in structure, which is explained by a relative homogeneity of moles’ habitat. Cuticular ornamentation may prove useful in species identification of these mammals.