Function-related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

Two plants improve stress response of a subterranean herbivore by downregulating amphetamine addiction pathways

Introduction

Captivity serves as the primary method for enhancing animal survival and productivity. However, the stress induced by confinement can hinder animal growth and reproduction. The administration of drugs to captive animals can effectively regulate their stress response and can also be used inartificial breeding, reproduction, and experimental animalization of wild species. The plateau zokor (Eospalax baileyi), a subterranean herbivore, experiences significant stress during the captive process owing to its unique habitat.

Methods

In our study, we utilized Radix astragali (RA) and Acanthopanax senticosus (AS) extracts to intervene in the stress response of plateau zokors.

Results

Our findings demonstrated that RA and AS treatment considerably improved food intake and reduced weight loss, stress-related behavior, and stress hormone levels in plateau zokors. Furthermore, the excitatory pathway of amphetamine addition in the hypothalamus was suppressed by RA and AS treatment, acting through the Grin and Prkc gene families. Notably, after RA treatment, the extracellular matrix-receptor interaction pathway, enriched by the Col1a1/3a1/1a2/6a1 gene, was significantly upregulated, potentially enhancing the immune function of captive plateau zokors.

Discussion

In conclusion, our research demonstrates that RA and AS treatment can effectively alleviate the stress response of plateau zokors in captive environments. The downregulation of the excitation pathway and upregulation of the immune pathway offer valuable insights into the response and potential mechanisms of plant-based drugs in mitigating animal stress.

Estimating body mass of wild pigs (Sus scrofa) using body morphometrics

Wild pigs (Sus scrofa) are invading many areas globally and impacting biodiversity and economies in their non-native range. Thus, wild pigs are often targeted for eradication efforts. Age- and sex-specific body measurements are important for informing these eradication efforts because they reflect body condition, resource availability, and fecundity, which are common indicators of population trajectory. However, body mass is often difficult to collect, especially on large individuals that require specialized equipment or multiple people to weigh. Measurements that can be rapidly taken by a single land or wildlife manager on any size wild pig without aid from specialized equipment would be beneficial if they accurately infer wild pig body mass. Our goals were to assess whether morphometric measurements could accurately predict wild pig body mass, and to provide tools to directly input these measures and estimate wild pig body mass. Using linear models, we quantified the relationship between body mass and morphometric measurements (i.e., body length, chest girth, ear length, eye to snout length, hindfoot length, shoulder length, and tail length) from a subset (n = 102) of wild pigs culled at the Mississippi Alluvial Valley, Mississippi, USA. We evaluated separate models for each individual morphometric measurement. We then used the model coefficients to develop equations to predict wild pig body mass. We validated these equations predicting body mass of 1592 individuals collected across eight areas in Australia, Guam, and the USA for cross-validation. Each developed equation remained accurate when cross-validated across regions. Body length, chest girth, and shoulder length were the morphometrics that best predicted wild pig body mass. Our analyses indicated it is possible to use the presented equations to infer wild pig body mass from simple metrics.

Increased availability of preferred food and decreased foraging costs from degraded grasslands lead to rodent pests in the Qinghai-Tibet Plateau

The increased population density of rodent species during ongoing grassland degradation further deteriorates its conditions. Understanding the effects of grassland degradation on rodent feeding habits is of great value for optimizing grassland management strategies. In this study, lightly degraded (LD), moderately degraded (MD), severely degraded (SD), and reseeded grassland (RG) were selected and their plant resources and soil physical properties were investigated. In addition, the study used ITS2 barcode combined with the Illumina MiSeq sequencing method to analyze the food composition and proportion of plateau zokors in different grassland conditions. The results showed that, with grassland degradation, plant biomass decreased, but the relative proportion of forbs increased (LD: 32.05 ± 3.89%; MD: 28.97 ± 2.78%; SD: 49.16 ± 4.67% and RG: 10.93 ± 1.53%). Forbs were the main food of the plateau zokor, accounting for more than 90% of their diet, and the animal had a clear preference for Potentilla species; the soil compaction of feeding habits showed a decreasing trend in the 10–25 cm soil layer, suggesting a decreased foraging cost. Nutritional analysis showed that the stomach content of crude protein in zokors feeding on MD grassland was significantly higher than that of animals feeding on the other grassland types. Structural equation modeling showed that soil physical properties and the relative biomass of forbs had significant (P < 0.05) and extremely significant (P < 0.001) impacts on the population density of plateau zokors, with direct impact contribution rates of 0.20 and 0.63. As the severity of grassland degradation increased, although the aboveground and underground biomass of the plants decreased, the proportion of food preferred by the plateau zokor increased, and the corresponding changes in the feeding environment resulted in decreased foraging energy expenditure, thereby increasing the suitability of the degraded grassland for the plateau zokor. Compared with degraded grassland, the food diversity and evenness of zokors increased, the food niche width enlarged, and the proportion of weeds decreased in RG, which increased the difficulty of obtaining food. Reseeding in grassland management is therefore an effective way to control plateau zokors.

Examining sex disparities in risk/reward trade-offs in Smith's zokors, Eospalax smithii

Risk taking is imperative for the survival and fitness of animals since they are constantly facing innumerable threats from various sources. Indeed, the ability of the individual to balance the costs and benefits of various options and adopt a wise decision is critical for the animal well-being. We modified several traditionally used anxiety tests [The modified light-dark box (mLDB), the modified open field test (mOFT) and the modified defensive withdrawal apparatus (mDWA)] by adding a palatable food reward within the anxiogenic zone which granted us to assess the sex differences in risk-taking behavior in Smith's zokors (Eospalax smithii), a typical subterranean rodent species endemic to the Qinghai-Tibetan Plateau. Concomitant with our working hypothesis, female zokors showed strong aversion and avoidance behavioral responses when tested in the mOFT and mDWA while there were no apparent sexually dimorphic behavioral changes when they were tested in the mLDB (Except for the percentage of food consumed and the latency till start feeding). Furthermore, comparison between the three behavioral paradigms revealed that both sexes showed different behavioral responses toward the different behavioral tests. Sex differences in repeatable behaviors were more profound in females than males. This might reflect different degrees of risk perception and emotionality that may differ considerably between the different models of anxiety. Our results highlighted the functional significance of a trade-off between risk and incentives in natural environment that both male and female zokors differ in the processing of risk assessment in the presence of a food reward.

A geometric morphometric analysis of geographic variation in the Cape Short-eared gerbil, Desmodillus auricularis (Rodentia: Gerbillinae)

The genus Desmodillus is monospecific, consisting of only the Cape short-eared gerbil (Desmodillus auricularis). Despite being widely distributed across southern Africa, previous studies did not find evidence of intraspecific phenotypic geographic differentiation. The objectives of this study is to use geometric morphometrics to investigate if and how the skull of D. auricularis varies spatially. It examines the covariation of skull morphology with broad spatial (latitude and longitude) and climatic variables, based on a sample of 580 specimens from southern Africa (Botswana, Namibia, and South Africa). The results did not support the differentiation of D. auricularis populations into distinct geographically isolated phenotypic groups. However, there is strong evidence for clinal variation in skull morphology; the most prominent pattern being a decrease in size from the west (closest to the South Atlantic coast) to the east (towards the continent’s interior). Shape variation was not localized in any skull region and seem to be driven mostly by size (allometry), although it also covaried significantly with latitude and longitude. Statistically significant skull shape sexual dimorphism was also detected, with males having larger crania than females. Spatial clinal variation in skull morphology was mostly associated with differences in the aridity of the habitats relative to their distance from the coast as evidenced by precipitation-related bioclimatic variables—annual precipitation (BIO12), precipitation of driest month (BIO14), and precipitation of driest quarter (BIO17)—covarying the most with skull morphology. This could be driven by either the climate influencing local resources available to populations or by the climate directly instigating phenotypic climatic adaptations.

Molecular Characterization of a New Moniliformis sp. From a Plateau Zokor (Eospalax fontanierii baileyi) in China

In the present study, a new species of the genus Moniliformis species is described taxonomically in the mitochondrial genomic context. The parasite was found in a plateau zokor captured in a high-altitude area of Xiahe County of Gansu Province, China. The mitochondrial (mt) genome length of this new species was 14,066 bp comprising 36 genes and 2 additional non-coding regions (SNR and LNR), without atp8. The molecular phylogeny inferred by the cytochrome c oxidase subunit I gene (cox1) and the18S ribosomal RNA gene (18S rDNA) sequences showed that the parasite as a sister species to other Moniliformis spp. and was named Moniliformis sp. XH-2020. The phylogeny of the concatenated amino acid sequences of the 12 protein-coding genes (PCGs) showed Moniliformis sp. XH-2020 in the same cluster as Macracanthorhynchus hirudinaceus and Oncicola luehei confirming the cox1 and 18S rDNA phylogenetic inference. In addition, the entire mt genome sequenced in this study represents the first in the order Moniliformida, providing molecular material for further study of the phylogeny of the class Archiacanthocephala. Moreover, the species of this class, use arthropods as intermediate hosts and mammals as definitive hosts and are agents of acanthocephaliasis, a zoonosis in humans. Therefore, this study not only expands the host range among potential wild animal hosts for Archiacanthocephalans which is of great ecological and evolutionary significance but also has important significance for the research of zoonotic parasitic diseases.

Effects of Sex and Breeding Status on Skull Morphology in Cooperatively Breeding Ansell’s Mole-Rats and an Appraisal of Sexual Dimorphism in the Bathyergidae

African mole-rats of the genus Fukomys (Northern common mole-rats) combine a monogamous mating system and pronounced sexual size dimorphism; a pattern highly untypical for mammals. At the same time, they live in cooperatively breeding groups composed of reproductive and non-reproductive members of both sexes. How and to which degree sex and breeding status influence morphofunctional characters in eusocial mole-rats is not well characterized but essential to come to a comprehensive understanding of their peculiar social system. Here, we explore patterns of morphological differentiation in skulls of Ansell’s mole-rats (Fukomys anselli) by means of multivariate analysis of linear skull measurements combined with a 2D shape analysis of cranium and mandible. Compared to females, males display larger skulls relative to body size and show an expansion of the facial portion of the cranium, while reproductive status did not have an effect on any of the traits studied. We also show that species of Fukomys mole-rats display a scaling of relative sexual body size dimorphism in compliance to Rensch’s rule, which is deemed indicative of intense male intrasexual competition. For the bathyergid family as a whole, results of scaling analyses were more ambiguous, but also indicative of Rensch’s rule conformity. In line with genetic field data, our results point to a greater role of male-male conflicts in Fukomys than is traditionally assumed and support the notion that reproductive status does not correlate with morphofunctional segregation in these unusual rodents.

Convergent Evolution of Himalayan Marmot with Some High-Altitude Animals through ND3 Protein

The Himalayan marmot (Marmota himalayana) mainly lives on the Qinghai-Tibet Plateau and it adopts multiple strategies to adapt to high-altitude environments. According to the principle of convergent evolution as expressed in genes and traits, the Himalayan marmot might display similar changes to other local species at the molecular level. In this study, we obtained high-quality sequences of the CYTB gene, CYTB protein, ND3 gene, and ND3 protein of representative species (n = 20) from NCBI, and divided them into the marmot group (n = 11), the plateau group (n = 8), and the Himalayan marmot (n = 1). To explore whether plateau species have convergent evolution on the microscale level, we built a phylogenetic tree, calculated genetic distance, and analyzed the conservation and space structure of Himalayan marmot ND3 protein. The marmot group and Himalayan marmots were in the same branch of the phylogenetic tree for the CYTB gene and CYTB protein, and mean genetic distance was 0.106 and 0.055, respectively, which was significantly lower than the plateau group. However, the plateau group and the Himalayan marmot were in the same branch of the phylogenetic tree, and the genetic distance was only 10% of the marmot group for the ND3 protein, except Marmota flaviventris. In addition, some sites of the ND3 amino acid sequence of Himalayan marmots were conserved from the plateau group, but not the marmot group. This could lead to different structures and functional diversifications. These findings indicate that Himalayan marmots have adapted to the plateau environment partly through convergent evolution of the ND3 protein with other plateau animals, however, this protein is not the only strategy to adapt to high altitudes, as there may have other methods to adapt to this environment.

Geometric morphometric analysis of the plateau zokor (Eospalax baileyi) revealed significant effects of environmental factors on skull variations

The plateau zokor (Eospalax baileyi) is employed as an ideal model for examining the relationships between phenotypic and ecological adaptations to the underground conditions in which the skull morphology evolves to adapt to tunnel environment. We evaluated the influence of environmental factors (altitude, temperature, and precipitation) and geographical distance on the variations in skull morphology of a native subterranean rodent plateau zokor population. Thin-plate spline showed that the trend of morphological changes along the CV1 axis was as follows: the two zygomatic arch and the two postorbital processes moved down, the two mastoid processes and the tooth row moved upward, and the tympanic bulla grew longer. The changes along the CV2 axis were as follows: the nasal bone and the tooth row became longer, the distance between the two anterior tips of zygomatic arch lengthened, the infraorbital foramen became smaller, the whole posterior part of the skull became shorter, the zygomatic bone and the two posterior tips of zygomatic arch moved down, and the foramen magnum became bigger. Thus we found significant differences in the skull shape among the seven populations studied. Along with the reduction in the altitude and increase in the mean annual temperature and mean annual precipitation, the nasal bone became shorter, the distance between the two anterior tips of the zygomatic arch became shorter, the whole posterior part of the skull lengthened, the infraorbital foramen became smaller, the two mastoid processes moved upward, and the occipital bone moved down on the dorsal surface of the skull. On the ventral surface of the skull, with an increase in the altitude, mean annual temperature, and mean annual precipitation, the tympanic bulla became shorter, the tooth row moved down, and the foramen magnum became smaller. The morphological changes in the skull were significantly positively correlated with environmental factors. Finally, there was a significant positive correlation between the Procrustes distance matrix of the skull and the geographic distance matrix, which indicates that the evolution of the plateau zokor follows the distance isolation model, but it needs to be further explored from genetic perspectives.