Bulgaria is one of the smaller European countries, but it keeps great biological richness and diversity. It is generally believed that many thermophilic and drought-loving Mediterranean animals live in the southern regions of the country and on the Black Sea coast. This study is a part of a project researching faunal complexes along three large river valleys and the Black Sea coast, where a Mediterranean influence can be detected and which serve as main roads for the entry of thermophilic biota. The aim of this zoocenosis monitoring is to detect any changes in the composition of Bulgarian fauna. The first indication so far is the registration of Microlestes maurus cordatulus (Reitter, 1901) (Coleoptera: Carabidae). In April 2023, one male specimen of this subspecies was collected in an MSS trap, situated less than 20 km from the southernmost point of the Bulgarian coast: N of Ahtopol, N 42°06'33'', E 27°55'02'', 9 m a.s.l. Microlestes maurus Sturm, 1827 is a small (2.2 to 2.8 mm) black ground beetle with short, truncate elytra and bulging eyes with short temples. Its main identification characteristics are its genitals, as its penis is sclerotized and has a distinct apex with a hook-shaped denticle. In Bulgaria, this species is widespread in the plains and foothills. It is distributed in Europe (except in the north), Caucasus and Anterior Asia. According to the last edition of the Catalogue of the Palaearctic Coleoptera, the subspecies M. m. cordatulus is known only in Greece, Iran, Lebanon and Syria. The two subspecies of M. maurus clearly differ by the shape of their aedeagus, with that of M. m. cordatulus having a more elongated apex with a significantly less salient hook than that in the Bulgarian specimen. This new location suggests that M. m. cordatulus most certainly occurs on the Turkish Black Sea coast, too.

The slugs of the genus Deroceras (Mollusca, Gastropoda, Agriolimacidae) include more than one hundred species. One of them, D. laeve, has a worldwide distribution, a fact that could be related to its biology and life history. This slug has an economic and sanitary importance, as it is an intermediate host of parasitic nematodes, causes crop losses, and can also affect the native fauna. In this study, we carried out a phylogenetic and phylogeographic study of D. laeve based on the cytochrome oxidase subunit I marker (COI), considering specimens collected in Buenos Aires (Argentina) and sequences deposited on online platforms. This information was integrated with anatomical dissections of the radulae, maxillae, and genitalia. As a result, we re-identified other species of Deroceras, found that D. laeve consists of a species complex of at least six operational taxonomic units (OTUs), and showed statistically that COI can be regarded as a good marker delimiting species within the D. laeve complex. In addition, possible distribution pathways of the most diversified OTU are discussed, and previous anatomical studies and radular formulas are compared with those found in the present study. In order to contribute to the knowledge of the D. laeve complex, we encourage further studies integrating molecular, anatomical and ecological results.

Trophic ecology is essential for understanding ecosystems and species interactions. Phylogenetically close groups can coexist in the same habitat and feed on similar items, resulting in niche overlap, which can compromise individual survival. In the Amazon, variations in river levels due to floods and droughts directly affect access to food resources for fish fauna. The objective of this study was to assess the influence of river discharge on the composition and dietary niche overlap of sympatric species Geophagus argyrostictus and G. altifrons in the Volta Grande of the Xingu River (Pará – Brazil). Monthly collections were conducted over a twelve-month period, and the specimens' diets were analyzed in a laboratory, with food items identified and weighed. The data were subjected to the Food Importance Index (IAi%) and Pianka's Overlap Index. The diet of G. argyrostictus consisted mainly of sediment (90.6%) and terrestrial plants (6.3%); G. altifrons fed on sediment (60.7%), terrestrial plants (31.4%), and aquatic insects (6.5%). We observed variations in diet composition between dry and wet seasons (PERMANOVA; p = 0.008) and between flood and recession periods (p = 0.037) for G. argyrostictus, as well as variations between flood and dry seasons (p = 0.004), flood and recession periods (p = 0.001), and recession and dry seasons (p = 0.001) for G. altifrons. Regarding niche overlap, Pianka's index values ranged from 0.39 during floods to 0.99 during dry seasons, with a significant effect of river discharge on niche overlap (GLM; t = -2.234, p = 0.049), which was higher during low-water periods compared to high-water periods. Our findings highlight the influence of river discharge on the diet composition of both species, which was more diverse during high-water periods. Also, we observed a greater dietary niche overlap during low-water periods, likely due to limited access to varied food resources, potentially resulting in interspecific competition.

Brazil is one of the two South American countries to have records ofthe four genera of freshwater cnidarians, being pioneers in the study of these organisms. Nevertheless, these studies were discontinued, resulting in a significant lack of information about these organisms. Hydra is the best known of these genera, and from the first report in Brazil to the present, it has four records with somewhat detailed morphological descriptions. Three of these records describe species endemic to Brazil: Hydra iheringi, Hydra salmacidis, and Hydra intermedia. However, these findings are outdated and very isolated, and they require immediate taxonomic corroboration. To achieve this objective, a sampling plan was implemented between April and June 2023 in seven freshwater bodies in São Paulo State, which also included a sample from Mafra, Santa Catarina State.

Hydra specimens were found to be adhered to different species of floating and submerged vegetation. All polyps were morphologically described in detail, their cnidocysts and sexual structures were measured and typed, and the cytochrome oxidase I (COI) marker was extracted, amplified, and purified using a protocol that was applied for subsequent sequencing. Morphological and molecular analyzes indicated the presence of two species: the cosmopolitan Hydra vulgaris and the green species Hydra sinensis, first described in China. This is the first time that both species have been described in Brazil, based on more exhaustive identification methodologies.

These results are the first of this type obtained for Brazil, and they reveal that Hydra is a frequent and abundant genus in the freshwater fauna from this study region. Continuing these analyses in other states would provide valuable data for the phylogeny of the group, as well as the possibility of discovering new species. Considering that the presence or absence of these organisms reflects the conservation status of the ecosystem, and that they are also bioindicators of hydrographic conditions, our studies are a valuable tool for the sustainable management of continental aquatic ecosystems.

Ciliates are fundamental and diverse components of freshwater ecosystems. Despite their ecological importance, freshwater ciliates are understudied in Argentina, where research has primarily focused on taxonomic studies. Our investigation was conducted in Iberá (Corrientes, Argentina), one of the most significant subtropical wetlands, characterized by its vast extension and unique biodiversity. Between March 2022 and 2024, we sampled plankton from three Iberá portals: Carambola, Iberá, and San Antonio. Fixed samples were taken for quantitative analysis and live samples for qualitative analysis, along with physicochemical data. We assessed the composition of ciliates in terms of richness, analyzed β diversity to compare ciliate compositions across different portals, and estimated multiple β-diversity. A total of 69 ciliate taxa new to Iberá were identified, distributed across ten groups, with Oligohymenophorea, Spirotrichea, and Litostomatea being particularly diverse classes in the studied region. San Antonio exhibited the highest species richness (55), followed by Iberá (27) and Concepción (14). This demonstrates notable variability in species richness between different sites, suggesting habitat heterogeneity. The β diversity was high (βSOR=65%), indicating that each portal has a unique and distinct species composition from the others. This indicates a high degree of differentiation among ciliate communities in the different Iberá portals. Multiple β diversity analysis revealed that the main contributor to β diversity was species turnover (βSIM >50%). The high beta diversity and the predominance of species turnover highlight the importance of conserving multiple sites within the Iberá region to preserve the total diversity of planktonic communities, such as ciliates. Each portal contributes a unique species composition, significantly contributing to regional biodiversity, thereby emphasizing the uniqueness of planktonic ciliate communities in the Iberá region.

Zygentoma is a small ancient order of primitive hexapods with over 500 described species, distributed worldwide. The original data about Bulgarian Zygentoma is scarce and refers to only four species: Atelura montana (Nicoletiidae), Coletina bulgarica (Nicoletiidae) (described from Bulgaria and known only from its first description), Ctenolepisma lineatum (Lepismatidae), and Neoasterolepisma balcanicum (Lepismatidae). In this paper, the fauna of Zygentoma from Bulgaria is reviewed and extended by new distributional data with the addition of four more species: Ctenolepisma calvum, C. ciliatum, C. longicaudatum, and Lepisma saccharinum. The newly established species are from the Lepismatidae family and are synanthropic, showing increased spreading trends in recent years, except the Ctenolepisma ciliatum, which is not synanthropic but in Bulgaria has been found only in the vicinity of human dwellings. The collected specimens were preserved in 70-80% ethanol and deposited in the collection of the Institute of Biodiversity and Ecosystem Research at the Bulgarian Academy of Sciences (IBER). This study is a part of the Project “Monitoring the effects of global climate changes through qualitative and quantitative analysis of model animal groups in selected corridors of thermophilic fauna penetration in Bulgaria” (funded by the National Science Fund of Bulgaria under Grant contract number KP-06-N61/6 – 14.12.2022).

The Iberá Natural Reserve (Corrientes, Argentina) shows off a significant diversity of macrophytes, which, along with the chemical composition of its waters, profoundly influence the diversity of zooplankton communities. Testate amoebae play a crucial role in aquatic ecosystems. In Argentina, research on these organisms has been scarce thus far, requiring exhaustive studies on this group in the Iberá aquatic environments. For this study, sampling was conducted in June 2023 at Portal Carambola, where representative sites were selected, differentiating between vegetated and non-vegetated environments. Qualitative and quantitative samples were obtained, and in situ physico-chemical variables were measured. Testate amoebae were observed in vivo using an optical microscope, and specific literature was followed for taxonomic classification. Richness (S), β-diversity, and multiple β-diversity were analysed to compare the communities in the two environments and to determine the factors influencing them. Preliminary results demonstrated that testate amoebae communities in vegetated areas exhibited greater taxonomic richness (22 taxa) compared to communities in non-vegetated areas (8 taxa), with 6 taxa shared between the two. The β-diversity analysis, based on the Sörensen index (55%), suggests that the species composition of testate amoebae in both communities tends to differ between the two types of environments analyzed. The component most contributing to the observed differences is the βSNE (=30%). These results suggest that macrophytes provide resources and favorable environmental conditions that benefit a greater diversity of testate amoebae. Most of the exclusive taxa are found in vegetated areas, highlighting the specialization of some species in these resource-rich environments. The density and presence of macrophytes are key determinants for the diversity of testate amoebae communities. The reduction in macrophytes is associated with a decrease in taxonomic richness, underscoring their crucial role in these ecosystems.

We provide first-time estimates of the standard metabolic rates (SMR) of Australoheros facetus , a freshwater cichlid fish that lives in streams and lakes in South America. Individuals of A. facetus were sourced from the Naposta Grande river, located in southern Buenos Aires province, Argentina, during spring (September–November in the southern hemisphere) of 2023. The individuals of A. facetus were captured using traps, baited and set close to submerged vegetation on the margins of the river at shallow depths. The traps were left undisturbed for up to 45 minutes. Traps were then pulled up by hand, and the individuals were collected and transferred to aerated transportation tanks. The fish were allowed to recover in these acclimation tanks from the stress originated from the capture and transport for 1 month. Experiments were conducted following the guidelines established by the EU Directive 2010/63/EU and the Argentinean Law n° 14346 on “The protection of animals”, as well as recommendations of the institutional committee for the use and care of laboratory animals (CICUAL). We quantified SMR and aerobic scope and daily activity patterns, finding this fish to be active during the day and sluggish during the night. Its metabolic rate is within the ranges expected for cichlids (SMR: 104.48 mg O2 kg–1h–1) and increases slightly during the daylight hours (126.25 mg O2 kg–1h–1). Having information on the metabolic rates and aerobic scope of this species provides another piece to the puzzle of the biology of A. facetus , complementing the research on oxidative stress and social behavior that has already been published and future research efforts. Furthermore, it constitutes progress towards the development of predictive models on the effects of increasing water temperatures in a global warming scenario.

The apoid fauna of Bulgaria is considered one of the richest in Europe. However, despite the numerous sampling efforts over the last century, it remains insufficiently studied and a clear overview of its diversity and the ecology of species present is lacking. This lack of understanding is further exacerbated by the changing climate, which continually alters the northern and southern limits of species distributions, especially in the warm southern parts of the country. In this study, the megachilid and colletid fauna of a dry sub-Mediterranean steppe habitat were surveyed using standardized transect walks, whereby all bees belonging to the two families were collected, and their floral visits were recorded. Flower abundance was noted during each survey, and pollen was taken from the identified species for a reference collection. A total of 76 plant and 31 bee species were observed, with 45 individual plant–pollinator associations being identified at a species level. The most visited plants were the flowers of Centaurea salonitana Vis. (six species), Eryngium campestre L. (four species), Ajuga chia Schreb. (four species), Ornithogalum montanum Cirillo (three species), Onobrychis arenaria (Kit.) DC. (three species) and Knautia arvensis (L.) Coult. (three species). Two species, Hoplitis pici (Friese, 1899) and Megachile semicircularis van der Zanden, 1996, are reported as new for Bulgaria, and twenty-two species are new for the locality. Considering the relative popularity and available historical data from the study location, the Besapari Hills, these results reconfirm the apoid fauna of the country as severely understudied, furthermore accentuating the need for a comprehensive pollinator monitoring in Southern Europe.

Information on how parasitoids of herbivorous insects use herbivore-induced volatile organic compounds (VOCs) to find potential hosts on saplings in forests with varying tree composition is scarce. Therefore, we performed an experiment where we placed pairs of oak saplings (Quercus robur or Q. petraea) in neighborhoods dominated by oak, beech, or pine trees in a forest in Poland. We treated one sapling in each pair with the phytohormone methyl jasmonate, which triggers induced responses in plants. We measured the VOC emissions of thirty-six saplings and placed Malaise traps with five of the pairs. We counted the parasitoids in the ten Malaise samples and identified them using DNA metabarcoding. The two oak species differed in both the proportions of VOCs and the specific VOCs that were elevated following the application of methyl jasmonate. The parasitoid community appeared hyper diverse: Our study included 1,129 individuals belonging to 344 species, and most species could not be linked to a named species using DNA metabarcoding. We did not detect any overall effects of treatment on parasitoid abundance or community composition. However, some parasitoid species appeared to be attracted to elevated emissions of specific induced VOCs. Parasitoid communities differed significantly between areas and showed marginally significant differences between neighborhoods. Overall, our results suggest that parasitoids in the understory are affected by tree composition, although the effects of VOC emissions were limited. Nevertheless, our study demonstrates how VOC-mediated insect–plant interactions can be effectively investigated under field conditions.