The structure of splanchnocranium bones has been studied in four endemic benthivorous charrs (the genus Salvelinus) from Lake Kronotskoe (Kamchatka). It has been found that, according to the whole set of characters of the splanchnocranium structure, the most expressed differences are observed between specialized forms, nosed and largemouth charrs, inhabiting different biotopes of the lake. Differences between small-mouth and white charrs are less pronounced, and the species are characterized by generalized features of the structure of jaws. It can be suggested that, in addition to diverse feeding preferences within a feeding niche, an extremely high diversity of charrs in Lake Kronotskoe is due to a complex geomorphological structure of the water system. Thus, the "species flock" comprising a complex set of diverse benthivorous morphotypes has been formed and exists in Lake Kronotskoe. Charrs from Lake Kronotskoe are a representative example of sympatric speciation by way of formation of new forms differing from each other in morphological, ecological, and trophic features.

The heavy metal contents in the scales of bream (Abramis brama) from the Mozhaisk Reservoir collected in the second half of the 1980s were compared to the current values. The concentrations of three out of the seven elements studied in the bream scales have changed severalfold during the past quarter century: that of strontium has decreased, and those of barium and lead have increased. Short-term variations of heavy metal contents have proved to be smaller than the observed long-term differences. There is grounds to believe that these long-term differences adequately reflect the changes that have occurred in the water body.

The article presents a literature review that analyzes the impact of climate change and environmental pollution on the nosoareals of major natural focal diseases in the territories of the Russian Federation. The literature was searched using Scopus, Web of Science, MedLine, CyberLeninka, and RSCI databases. Those natural focal diseases transmitted by mosquitoes, ticks, and rodents depend most on the climate. Climate warming contributes both to an increase in the number of arthropods carrying pathogens of these diseases and their feeders, and to the expansion of the habitats of these animals. In addition, conditions for the adaptation of non-endemic vectors of natural focal diseases introduced into Russia are improving. Climate change causes different trend in biological risks in different regions. Another significant factor affecting nosoareals is anthropogenic pollution and accumulation of heavy metal ions in soil, surface, and groundwater. In recent decades, under the influence of environmental pollution with heavy metals, primarily cadmium, ixodes mites with exoskeleton abnormalities have appeared, differing both in the degree of accumulation of heavy metals in their bodies and in their susceptibility to pathogenic microorganisms. The analysis of the results of scientific research aimed at studying the influence of environmental factors on the spread of major natural focal diseases in different territories of the Russian Federation allows concluding that climate warming will lead to the expansion of the corresponding nozoareals to the north and NorthEast. At the same time, a significant reduction in the area of such areas is not expected. Increased cadmium contamination of soils is a factor contributing to an increase in the potential risk of human infection in the corresponding nosoareals, as well as an increase in the proportion of the urban population infected with tick-borne diseases.Contribution: Saltykova M.M. — the concept and design of the study, writing the text; Zhernov Yu.V. — concept and design of research, editing; Saltykova E.A. — collecting material, writing text; Yudin S.M. — research concept. All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.Conflict of interest. The authors declare no conflict of interest.Funding. The work was carried out within the framework of the state assignment with the code “Risk indicator 25-27”, registration number EGISU 125032604484-5.Received: July 4, 2025 / Revised: August 13, 2025 / Accepted: September 19, 2025 / Published: October 20, 2025

Paederus dermatitis is an acute irritant contact dermatitis caused by inadvertent contact with rove beetles of the genus Paederus (Coleoptera: Staphylinidae). The condition may be difficult to recognize in individuals and healthcare professionals from non‑endemic regions because the characteristic skin lesions can mimic other inflammatory, infectious, or vesiculobullous dermatoses. The causative toxin, pederin, is associated predominantly with female beetles and is produced by endosymbiotic bacteria of the genus Pseudomonas. We present a series of cases of Paederus dermatitis observed in Russian physicians working in Nicaragua. Several hours after presumed contact with Paederus beetles, the patients developed burning and mild pruritus followed by erythematous macules and streak‑like lesions. Over the following days, grouped vesicles and non‑tense bullae developed, with subsequent erosions, crusting, and post‑inflammatory hyperpigmentation and hypopigmentation. The diagnoses were established clinically on the basis of the characteristic morphology, exposure history, and epidemiological setting. Conservative treatment resulted in gradual resolution of the inflammatory lesions within approximately 2–3 weeks, with residual post‑inflammatory hyperpigmentation. This case series highlights the diagnostic value of recognizing the characteristic linear and bizarrely configured lesions of Paederus dermatitis, particularly in healthcare professionals working in endemic regions.