Taxonomy and phylogenetic relationship of zokors

Seismic Signaling for Detection of Empty Tunnels in the Plateau Zokor, Eospalax baileyi

There are considerable challenges involved in studying the behavior of subterranean rodents owing to the underground nature of their ecotope. Seismic communication plays a crucial role in the behavior of subterranean rodents, particularly solitary ones. The plateau zokor (Eospalax baileyi), a solitary subterranean rodent species endemic to the Qinghai−Tibet Plateau, will usually occupy empty neighboring tunnels in order to extend their territory. Little is known, however, about the process of territorial occupation or the function of animal communication when occupation is taking place. Based on previous studies of subterranean rodent communication, we hypothesized that plateau zokors use seismic signals to detect neighboring tunnels and then occupy them when it was found their neighbors were absent. To test this, we placed artificial tunnels close to active original zokor tunnels to simulate the availability of an empty neighboring tunnel, and then the seismic signals when a zokor chose to occupy the empty artificial tunnel were recorded. The results showed that the frequency of zokors occupying artificial empty tunnels within 48 h was 7/8, In all of these instances, the zokors generated seismic signals before and after occupation of the empty artificial tunnel. The number of seismic signals generated by the zokors increased significantly (p = 0.024) when they detected and occupied the artificial tunnels, compared to those generated in their original tunnels without the presence of an artificial tunnel alongside. Inside the original tunnels, the inter-pulse time interval of the seismic signals was significantly higher (p < 0.001), the peak frequency of these signals was significantly higher (p < 0.01), and the energy of the signals was significantly lower (p = 0.006), compared with those when an artificial tunnel was positioned next to the original. The results of this study suggest that plateau zokors first generate seismic signals to detect empty neighboring tunnels and that they are empty. In the absence of neighbor plateau zokors, they occupy the empty tunnels to extend their own territory.

The Complex and Well-Developed Morphological and Histological Structures of the Gastrointestinal Tract of the Plateau Zokor Improve Its Digestive Adaptability to High-Fiber Foods

The morphological and histological traits of the gastrointestinal tract (GIT) enable the animal to perform some specific functions that enhance the species’ adaptability to environments. The plateau zokor (Eospalax baileyi) is a subterranean rodent that mainly forages on plant roots in the Qinghai-Tibet Plateau, but little is known about the mechanism by which the plateau zokor digests roots that have high fiber contents. In this study, we used comparative anatomy methods to compare the morphological and histological traits of the GIT of both the plateau zokor and the plateau pika (Ochotona curzoniae), a small, fossorial lagomorph that forages aboveground plant parts, in order to clarify the traits of the plateau zokor’s GIT and to understand its adaptations to high-fiber foods. The results showed that the foods which plateau zokors eat have a higher fiber content than those which the plateau pikas eat. The plateau zokor has a double-chambered and hemi-glandular stomach (the tubular glands are only in the gastric corpus II, and the gastric fundus is keratinized), whereas the plateau pika has a simple, wholly glandular stomach. The gross morphological indicators (organ index and relative length) of the GIT were significantly lower in the plateau zokor than they were in the plateau pika (p < 0.001). However, the thickness of the gastric corpus II mucosal layer and the gastric fundus muscle layer are significantly higher in the plateau zokor than they are in the plateau pika (p < 0.001), and the thickness of each layer of intestinal tissue is higher in the plateau zokor than it is in the plateau pika. Additionally, the small intestinal villi also are higher and wider in the plateau zokor than they are in the plateau pika. Our results suggest that instead of adapting to digest the high-fiber diet by expanding the size of the GIT, the plateau zokor has evolved a complex stomach and a well-developed gastrointestinal histological structure, and that these specialized GIT structures are consistent with an optimal energy-economy evolutionary adaptation strategy.

The associations between intestinal bacteria of Eospalax cansus and soil bacteria of its habitat

Background

Intestinal bacteria of mammal can be influenced by many factors, environmental bacteria is an important factor. However, there are few studies on the interactions between environmental bacteria and intestinal bacteria in wild mammals. To explore the associations between the intestinal bacteriome and the related environmental bacteriome, the intestinal bacterial communities of Eospalax cansus at three different sites and the bacterial communities of the surrounding soil (outside and inside the cave) at each site were investigated by 16S rRNA sequencing.

Results

The composition and structure between zokor intestinal bacteria and related soil bacteria were distinct, and the soil of zokor habitat harbored significantly higher diversity than that of zokor intestinal bacteria. We have found that host factors may be more important than environmental factors in shaping intestinal bacteriome. In addition, it was found that the relative abundances of shared OTUs between zokors and related soil were significantly negatively related. These shared OTUs were present in the soil at relatively low abundance. However, these shared OTUs between zokors and soil were affiliated with diverse bacterial taxa, and they were related to the degradation of complex carbohydrates.

Conclusions

These results suggested that the zokor gut may mainly select for low-abundance but diverse soil bacteria, which may be a host- specific choice for zokor to meet the needs of its phytophagous dietary.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03223-6.

Functional differentiation related to decomposing complex carbohydrates of intestinal microbes between two wild zokor species based on 16SrRNA sequences

BACKGROUND

The intestinal microbes in mammals play a key role in host metabolism and adaptation. As a subterranean rodent, zokor digs tunnels for foraging and mating. These digging activities of zokors increase the energy expenditure relative to their aboveground counterparts. However, relatively little is known regarding intestinal microbes of zokor and how they make full use of limited food resources underground for high energy requirements.

RESULTS

Eospalax cansus and Eospalax rothschildi had distinct intestinal microbes. Although the composition of intestinal microbes is similar in two species, the proportion of bacterium are distinctly different between them. At phylum level, 11 phyla were shared between two species. Firmicutes and Bacteroidota were two dominant microbes in both of two species, while Eospalax cansus have a significantly high proportion of Firmicutes/Bacteroidota than that of Eospalax rothschildi. At genus level, norank_f_Muribaculaceae were dominant microbes in both of two zokor species. The relative abundance of 12 genera were significantly different between two species. Some bacterium including unclassified_f__Lachnospiraceae, Lachnospiraceae_NK4A136_group, Ruminococcus and Eubacterium_siraeum_group associated with cellulose degradation were significantly enriched in Eospalax cansus. Although alpha diversity was with no significant differences between Eospalax cansus and Eospalax rothschildi, the intestinal microbes between them are significant distinct in PCoA analysis. We have found that trapping location affected the alpha diversity values, while sex and body measurements had no effect on alpha diversity values. PICRUSt metagenome predictions revealed significant enrichment of microbial genes involved in carbohydrate metabolism in Eospalax cansus rather than Eospalax rothschildi.

CONCLUSIONS

Our results demonstrate that Eospalax cansus harbor a stronger ability of fermentation for dietary plants than Eospalax rothschildi. The stronger ability of fermentation and degradation of cellulose of intestinal microbes of Eospalax cansus may be a long-time adaptation to limited food resources underground.

Morphology, ultrastructure, genomics, and phylogeny of Euplotes vanleeuwenhoeki sp. nov. and its ultra-reduced endosymbiont "Candidatus Pinguicoccus supinus" sp. nov

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics and, more recently, on evolutionary relationships. With the birth of novel genomics/bioinformatics techniques and the increasing interest in microbiome studies, a further advance of taxonomic discipline appears not only possible but highly desirable. The present work proposes a new approach to modern taxonomy, consisting in the inclusion of novel descriptors in the organism characterization: (1) the presence of associated microorganisms (e.g.: symbionts, microbiome), (2) the mitochondrial genome of the host, (3) the symbiont genome. This approach aims to provide a deeper comprehension of the evolutionary/ecological dimensions of organisms since their very first description. Particularly interesting, are those complexes formed by the host plus associated microorganisms, that in the present study we refer to as "holobionts". We illustrate this approach through the description of the ciliate Euplotes vanleeuwenhoeki sp. nov. and its bacterial endosymbiont "Candidatus Pinguicoccus supinus" gen. nov., sp. nov. The endosymbiont possesses an extremely reduced genome (~ 163 kbp); intriguingly, this suggests a high integration between host and symbiont.