A Report of Chigger Mites on the Striped Field Mouse, Apodemus agrarius, in Southwest China

Based on the field investigations in 91 investigation sites (counties) in southwest China between 2001 and 2019, the present paper reported the chigger mites on A. agrarius mice in southwest China for the first time by using a series of statistical methods. From 715 striped field mice captured in 28 of 91 investigated sites, only 255 chiggers were collected, and they were identified as 14 species, 6 genera in 3 subfamilies under 2 families. Of 715 A. agrarius mice, only 24 of them were infested with chigger mites with low overall prevalence (PM=3.4%), overall mean abundance (MA=0.36 mites/host) and overall mean intensity (MI=10.63 mites/host). The species diversity and infestation of chiggers on A. agrarius were much lower than those previously reported on some other rodents in southwest China. On a certain species of rodent, A. agrarius mouse in southwest China seems to have a very low susceptibility to chigger infestations than in other geographical regions. Of 14 chigger species, there were 3 dominant species, Leptotrombidium sialkotense, L. rupestre and Schoengastiella novoconfuciana, which were of aggregated distribution among different individuals of A. agrarius hosts. L. sialkotense, one of 6 main vectors of scrub typhus in China, was the first dominant on A. agrarius. The species similarity of chigger mites on male and female hosts was low with CSS=0.25, and this reflects the sex-bias of different genders of A. agrarius mice in harboring different chigger species.

Cross-Context Responses to Novelty in Rural and Urban Small Mammals

The Anthropocene is the era of urbanization. The accelerating expansion of cities occurs at the expense of natural reservoirs of biodiversity and presents animals with challenges for which their evolutionary past might not have prepared them. Cognitive and behavioral adjustments to novelty could promote animals’ persistence under these altered conditions. We investigated the structure of, and covariance between, different aspects of responses to novelty in rural and urban small mammals of two non-commensal rodent species. We ran replicated experiments testing responses to three novelty types (object, food, or space) of 47 individual common voles (Microtus arvalis) and 41 individual striped field mice (Apodemus agrarius). We found partial support for the hypothesis that responses to novelty are structured, clustering (i) speed of responses, (ii) intensity of responses, and (iii) responses to food into separate dimensions. Rural and urban small mammals did not differ in most responses to novelty, suggesting that urban habitats do not reduce neophobia in these species. Further studies investigating whether comparable response patters are found throughout different stages of colonization, and along synurbanization processes of different duration, will help illuminate the dynamics of animals’ cognitive adjustments to urban life.

Histological analysis of implantation embryos in large Japanese field mouse (Apodemus speciosus) and estimation of developmental stage

The large Japanese field mice (Apodemus speciosus) are small rodent specie endemic to Japan. The genetic characteristics of A. speciosus is different chromosome numbers within one species. Furthermore, A. speciosus is used for research in radiation and genetics. In this present study, a pregnant A. speciosus was obtained, and histochemical analysis of the implanted embryos was performed and compared with developmental stages of the mouse. Although there were some differences, the structures of the implanted embryos including the primitive streak and placenta of A. speciosus were similar to that of the mouse. Our study will be important report in the construction of a developmental atlas of A. speciosus.

MORPHOSTRUCTURE OF THE FIELD MOUSE THYROID GLAND IN NORMAL STATE IN THE CONDITIONS OF FOREST-STEPPE NEAR KRASNOYARSK

The regional research of the zonal undisturbed (normal) morphology of the thyroid gland of young field mice was carried out in the conditions of forest-steppe near Krasnoyarsk. The most important indicators of the thyroid gland are identified: macroscopically, the width of each lobe is 2-2. 7 mm, the length is 1.5-2 mm, the height is 1-2 mm. The width of the isthmus is 1.5-2 mm. The color of the gland ranges from red to dark red and it clearly contrasts with the background of the larynx and thyroid cartilage. The thyroid and parathyroid glands are a single organocomplex. The specific features of the structure of the thyroid gland of field mice are the small size of the organ, a thin capsule, the presence of internal accessory parathyroid glands, a compactly organized parenchyma, and a moderately developed vascular network. The stroma of the gland is relatively poorly developed, it contains a thin network of reticular cells, a small number of macrophages. The epithelium of large follicles has a prismatic shape, although middle size follicles have cubic shaped epithelium. The height of thyrocytes is 6.83 microns, the mean area of follicles is 467.9 microns; Brown index is 9.7; follicular-colloid index is 3.72; the sclerosis index is 0.81. The field mouse, due to its ecological and morphological features, is a valuable object of bioindication for assessment of the state of background and anthropogenic landscape in the conditions of the Krasnoyarsk forest-steppe. The size of the gland (taking into account age of a mouse), the Brown index, as well as the height and shape of thyrocytes (follicular epithelium) are significant bioindication criteria to assess the changes in the case of technogenic exposure influenced by pollutants.

Frequency of Occurrence and Ingested Biomass of Different Prey of the Barn Owl Tyto alba in an Island Ecosystem

The Barn Owl Tyto alba is commonly reported as a non-selective predator of small mammals, and its diet has been thoroughly analyzed also to assess the small mammal assembly composition in many study areas. The aim of this work was to analyze the diet of the Barn Owl in the Elba island through the analysis of 161 pellets collected in September 2020. Undigested fragments were isolated and compared with reference collections. We confirmed that the Barn Owl is a typical predator of field mice (62% of relative frequency), with synanthropic murid rodents as the second category of prey. The frequency of consumption of shrews increased by 9% with respect to the previous work, suggesting that the natural environment of Elba island is still in a good health status. Moreover, fragments of two newborn hares were detected, increasing the knowledge on the local trophic spectrum of the Barn Owl. Finally, the skull of a Geoffroy’s Myotis Myotis emarginatus confirmed the presence of this species in Elba island after over 60 years from the first unconfirmed record. Repeated studies conducted in the same study site may provide useful information on prey population trends and local environmental status.