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Item Batrachophagy of the Eastern Grass Snake, Natrix natrix (Linnaeus, 1758), in Bulgaria: published data and new records(Plovdiv University "Paisii Hilendarski", 2026-05-12) Mitrevichin, Emanil; Sakelarieva, Lidia; Peshev, Hristo; Gorzdanov, Atanas; Pulev, AlexanderThe food spectrum of Natrix natrix in Bulgaria remains understudied, despite the few works on this topic. We summarize all data reported in the literature on the batrachophagy of the species in the country and provide 17 new observations. The results indicated that N. natrix has a wide food spectrum and may feed on at least 11 amphibian species. Pelophylax ridibundus was the most preferred prey. Rana dalmatina and Bufo bufo were also important components of the diet. In some areas, Salamandra salamandra may be more frequent prey for N. natrix than previously thought. However, most of the amphibian species, including Triturus ivanbureschi, Bombina variegata, Pelobates balcanicus, and Rana temporaria, were consumed less frequently. These findings can have important implications for the conservation of the species. Yet, further research on the feeding ecology of N. natrix in Bulgaria is needed to better understand its ecological requirements and to support effective conservation planning.Item Surprising finding of the species Dolocerus reichii Mulsant, 1862 (Cerambycidae: Cerambycinae) in urban parks in Sofia, Bulgaria(Plovdiv University "Paisii Hilendarski", 2026-06-09) Gradinarov, DenisLonghorn beetle species Dolocerus reichii Mulsant, 1862 is reported for the first time with exact localities from Bulgaria. Numerous adult beetles were collected and observed on flowers of Spiraea x vanhouttei (Briot) Zab. and Crataegus monogyna Jacq. in two of the parks of the city of Sofia – Zdrave Park and Borisova Gradina Park.Item Abundance, biomass and seasonal dynamics of Cyclopoida (Crustacea, Copepoda) in Vaya Lake (Burgas Lake), Bulgaria(Plovdiv University "Paisii Hilendarski", 2026-06-03) Nenova, ElenaA quantitative analysis of Copepoda abundance and biomass in Vaya Lake (Burgas Lake, Bulgaria) was conducted at 11 sampling stations during 2003–2007, with samples collected seasonally (autumn, winter, spring and summer). The cumulative abundance recorded during the study period was 26.48 × 106 ind./m3, corresponding to a mean abundance of 6.62 × 106 ind./m3. Copepodites dominated the community (14.89 × 106 ind./m3), followed by Nauplii (9.96 × 106 ind./m3). Among adult copepods, Cyclops vicinus Uljanin, 1875 ranked third in abundance (1.36 × 106 ind./m3), whereas Thermocyclops oithonoides (G.O. Sars, 1863) showed the lowest abundance (271,500 ind./m3). The cumulative biomass recorded during the study period was 258.97 g/m3, with the highest seasonal value observed in spring 2006. Biomass was dominated by Cyclops vicinus (175.05 g/m3), followed by Copepodites (74.32 g/m3), Nauplii (4.98 g/m3) and Thermocyclops oithonoides (4.62 g/m3). Cluster analysis based on the Bray–Curtis similarity index revealed more than 85% similarity among most sampling stations with respect to abundance. Station 12 was clearly separated from all other stations because of its exceptionally high biomass, dominated by C. vicinus and Copepodites, whereas stations 3, 4, 8, 1, 11, 2 and 6 showed approximately 87% similarity. Seasonal dynamics were characterized by contrasting patterns in juvenile and adult development: Nauplii and Copepodites reached maximum abundance during winter, whereas biomass peaked in spring due to the development of the dominant species C. vicinus.Item Prey type influences predator–prey size relationship in Natrix natrix (Linnaeus, 1758) (Reptilia: Colubridae)(Plovdiv University "Paisii Hilendarski", 2026-05-28) Mollov, IvelinIn the current study the relationship between predator body length and prey body length in the Grass Snake (Natrix natrix) is examined, based on data from 39 individuals collected in the city of Plovdiv, Bulgaria. Prey items were classified into two categories - “fish” and “frog”. A significant positive relationship between snake length and prey length was registered, indicating size-mediated prey selection. The scaling relationship was stronger in snakes consuming frogs than in those consuming fish. Relative prey size differed significantly between prey types, with fish representing proportionally larger prey.Item The system of plates in the basal part of the wing veins in Diptera (Insecta)(Plovdiv University "Paisii Hilendarski", 2026-02-05) Hubenov, ZdravkoThe sclerites (plates) from which the wing veins begin in the various families of Diptera are scrutinized. A general plan of the sclerites and their localization between the axillary area and the vein system are presented. Some morphological differences in 6 families are considered.Item Some new records of terrestrial snails from coastal continental Tanzania(Plovdiv University "Paisii Hilendarski", 2026-04-21) Georgiev, DilianThis paper presents new records of nine terrestrial gastropod species collected from the coastal area of Bagamoyo, Tanzania, in early 2026. The findings include the first record of the introduced snail Gastrocopta servilis (Gould, 1843) for Tanzania, marking only its second known occurrence on the African continent. Additionally, the presence of Streptostele acicula (Morelet, 1877) is confirmed for the East African coast, and Opeas delicatum Taylor, 1877 is reported from a new locality outside of Amani.Item New locality of Rana graeca Boulenger, 1891 and a previously undescribed threat for the species from Western Rhodopes, Bulgaria(Plovdiv University "Paisii Hilendarski", 2026-04-21) Mollov, Ivelin; Chetalbashev, TeodorA new locality for Rana graeca is reported from the Western Rhodopes Mountains. Although the location of the observation falls within the already known range of the species, a newly recorded threat for this and other anuran species is described. In addition habitat characteristics and coordinates are provided.Item Contribution to the study of the free-living freshwater nematodes from Vodas River, Edessa, Greece(Plovdiv University Press "Paisii Hilendarski", 2026-03-15) Stoichev, StefanHydrobiological studies of Vodas River in Edessa, Greece were performed in 2022. The present study provides the first information on free-living freshwater nematodes from Voda River in Edessa, Greece. In our study, we identified 7 species of freshwater free-living nematodes belonging to 6 genera. This is the first detailed study on free-living freshwater nematodes from the Vodas River in Edessa, Greece. The 3 species (marked by +) and 2 genera (marked by *) are new to the hydrofauna of Greece.Item A contribution to the knowledge of the sexual size dimorphism of the narrow-clawed crayfish (Pontastacus leptodactylus Eschscholtz, 1823) from Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2026-03-16) Mollov, IvelinThis study examines the sexual size dimorphism in 20 adult Pontastacus leptodactylus from “Kardzhali” Dam Lake, Bulgaria, via 15 morphometric traits. MannWhitney U-tests reveal significant differences in 19 parameters: males exhibit larger carapaces and chelae (e.g., chela length SDI 42.5%), while females have wider abdomens and telsons, aligning with previous studies. The results contribute to the data on phenotypic plasticity and conservation needs, considering the scarce regional data. The present study could provide additional information for future studies and management plans.Item Contribution to the Tachinids (Diptera: Tachinidae) of Vietnam(Plovdiv University Press "Paisii Hilendarski", 2026-02-05) Hubenov, ZdravkoThe tachinid fauna of Vietnam has not been studied. Totally, 37 species of the family Tachinidae beloning to 32 genera and 4 subfamilies have been recorded. Their distribution is analysed and an areographical characteristic of the species is presented. Five species are endemics. The tachinids belong to 25 zoogeographical categories. The species (27 species - 73.0%) distributed in the Oriental and Palaearctic Regions are predominant. The most widely distributed are 7 species (18.9%), represented in 3 zoogeographical areas.Item Species of the family Lumbricidae (Oligochaeta) found in uranium mining areas in Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2026-01-08) Tsekova, Ralitsa; Sakelarieva, LidiaThis paper presents the list of earthworms found in five affected by the uranium mining activities areas in Bulgaria. For the whole period of study (2011-2016) ten species belonging to six genera of family Lumbricidae were recorded. The genera Aporrectodea and Lumbricus were represented by 3 species each, and the other four by one species only. Half of all registered earthworms were endogeic. Three species (Aporrectodea rosea, Eisenia fetida and Octolasion lacteum) were found in all sampling sites.Item Studies on free-living freshwater nematodes from Skadar Lake Montenegro(Plovdiv University Press "Paisii Hilendarski", 2026-01-12) Stoychev, StefanHydrobiological studies of Skadar Lake, Montenegro were performed in 2014. The present study provides the first information on free-living freshwater nematodes from Skadar Lake, Montenegro. In our study, we identified 15 species of freshwater free-living nematodes belonging to 11 genera. This is the first detailed study on free-living freshwater nematodes from the Skadar Lake, Montenegro. The identified 15 species and 11 genera are new to the hydrofauna of Montenegro.Item Evaluation of Gill Histopathological Biomarkers in Neogobius sp. for Monitoring Freshwater Quality: A Case Study of the Veleka River, Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2025-12-18) Stoyanova, Stela; Yancheva, Vesela; Georgieva, ElenkaWe studied the changes in the histological structure of the gills of Neogobius sp. collected from the Veleka River in Bulgaria. The results showed mainly proliferative changes in the gill structure associated with proliferation of stratified epithelium in the filament and secondary lamellae. To our knowledge, this is the first histopathological study of a fish species from the river. The observed histopathological lesions could serve as useful biomarkers for monitoring water quality and, consequently, the health of species. We emphasize the importance of such research programs that monitor the fish health in rivers, considering the dynamics of various environmental factors and pollution.Item Histopathological Alterations in Vimba sp. Gills as Biomarkers of Freshwater Quality in the Veleka River, Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2025-12-18) Stoyanova, Stela; Yancheva, Vesela; Georgieva, ElenkaIn the present research, we evaluated the alterations in the histological structure of Vimba sp. gills as a biomarker of freshwater quality. Fish were collected from the Veleka River. Based on the obtained results, we established the highest degree of proliferative changes. These alterations concerned mainly the covering epithelium of the secondary lamellae and proliferation of the cells in the cartilage tissue (chondrocytes). Overall, the study emphasizes the importance of biomonitoring in natural ecosystems in order to assess the health of native fish and hence the quality of surface waters.Item Fifty Shades of Pollution: Microplastic Color Diversity in Mytilus galloprovnicialis (Lamarck, 1819) from the Black Sea, Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2025-12-05) Yancheva, Vesela; Valkanov, KirilMicroplastics (MPs) are emerging pollutants of global concern, infiltrating marine environments and posing potential risks to aquatic organisms. The Mediterranean mussel (Mytilus galloprovincialis), a widely distributed and economically significant bivalve, serves as a reliable bioindicator for assessing MP pollution. In this study, mussels collected from the Bulgarian Black Sea coast were analyzed to determine the presence, abundance, polymer type, shape, and color composition of accumulated MPs in whole soft tissues. MPs of various colors were detected, with transparent and blue particles being the most prevalent, followed by white, black, red, green, and yellow. The observed chromatic diversity indicates multiple pollution sources, including domestic, urban, and maritime activities. These results highlight the extensive contamination of coastal ecosystems and reinforce the value of M. galloprovincialis as a sentinel species for monitoring both the quantity and qualitative attributes - such as color - of MPs in marine environments.Item MICROPLASTIC ACCUMULATION IN TWO INVASIVE MUSSEL SPECIES FROM CHEPINTSI SAND-PIT LAKE, BULGARIA(Plovdiv University Press "Paisii Hilendarski", 2025-11-29) Terzieva, Vera; Rozdina, Desislava; Zaharieva, Zornitsa; Kozuharov, DimitarThis study aimed to assess the quantity and diversity of microplastics (MPs) accumulated in two invasive freshwater mussels: the Asian clam (Corbicula fluminea Müller, 1774) and the zebra mussel (Dreissena polymorpha Pallas, 1771). Artificial lakes near large urban areas often support multiple human activities and are exposed to considerable anthropogenic pollution. For this reason, mussel samples were collected from the Chepintsi sand-pit lake near Sofia, Bulgaria. Sampling was conducted in the spring using a hand dredge (front edge, 17.5 cm; total length, 190 cm). The analysis detected microplastic particles - mainly fibers and fragments of different colors and sizes - in almost all specimens. Fragments were the most common type, and colorless particles were the dominant color category.Item Assessing environmental stress through lysosomal membrane stability in wild and farmed mussels (Mytilus galloprovincialis Lamarck, 1819) across seasons(Plovdiv University Press "Paisii Hilendarski", 2025-10-30) Yancheva, Vesela; Stoyanova, Stela; Georgieva, Elenka; Antal, Laszlo; Uzochukwu, Ifeany Emmanuel; Nagy, Laszlo; Nyeste, Krisztian; Samogyi, DoraThis study assessed lysosomal membrane stability (LMS) in hemocytes of Mytilus galloprovincialis from wild and farmed populations, using the Neutral Red Retention Time (NRRT) assay as a biomarker of environmental stress. Mussels were sampled in summer and autumn to evaluate seasonal variability, and the results were compared with our previous winter and spring data. NRRT values showed a significant reduction in both populations across seasons, indicating compromised lysosomal integrity and exposure to environmental stressors. Notably, wild mussels consistently exhibited lower NRRT values compared to farmed individuals, suggesting a higher stress burden. The underlying causes of this difference remain to be clarified.Item Notes on the presence of Harpalus luteicornis (Duftschmid, 1812) (Coleoptera: Carabidae) in Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2025-09-30) Teofilova, TeodoraThis communication confirms the presence of the ground beetle Harpalus luteicornis (Duftschmid, 1812) (Coleoptera: Carabidae) in the Bulgarian fauna.Item New host record for the parasitoid fly Phryxe nemea (Meigen, 1824) (Diptera: Tachinidae) in Bulgaria(Plovdiv University Press "Paisii Hilendarski", 2025-09-22) Plashkova, BoryanaThis research presents new data on the host selection behaviour of the parasitoid fly Phryxe nemea (Meigen, 1824). The observation was made during sample collection in an open-field experiment conducted at the University of Forestry’s experimental station in Sofia. The experiment aimed to assess how intercropping kale (Brassica oleracea L. var. acephala) with various companion plants would impact the activity of key pests and their natural enemies. This is the first record of the host-parasitoid association between Pieris rapae (Linnaeus, 1758) and Phryxe nemea in Bulgaria.Item A case of partial albinism in the western jackdaw Coloeus monedula (Linnaeus, 1758)(Plovdiv University Press "Paisii Hilendarski", 2025-09-09) Boev, ZlatozarOn 04.11.2024, an adult Western Jackdaw was observed in the centre of the city of Razgrad. The pure white feathers are located on the upper part of the wings, the lower part of the chest, on the neck and cheeks. Three unpublished cases of complete albinos in Coloeus monedula and Garrulus glandarius from the collection of the National Museum of Natural History in Sofia are also presented.