The age and growth of weatherfish (Misgurnus fossilis), an endangered and protected freshwater fish with a poorly known life history, was studied in two watercourses (the River Ner and the Nowy Rów canal, Poland). The weight, length and sagittal otoliths of 166 specimens collected in April 2015 were measured for weight-length relationships, ageing and back-calculation of length at age. At both sites sex ratio did not differ from 1:1. Weatherfish otoliths were small, elliptic (1.85 mm longer axes of the largest otolith) and the annuli were clearly visible. Female lifespan was six years but the oldest males were four and five years. In both sites populations were dominated by 2+ (the River Ner) and 3+ (the Nowy Rów canal) specimens. In general, weatherfish grows isometrically (b = 3) and the intercept of the weight-length relationship differ between study sites but not between sexes. Its total length (TL) was predicted by an interaction between sex and age, as well as capture site and age. Back-calculated estimates of TL fitted a von Bertalanffy growth function, though Taylor's criterion showed that the asymptotic length were overestimated. Multiple comparisons of the von Bertalanffy growth function parameter revealed difference between sexes and sites.

The usurpation of house martin nests by house sparrows has previously been reported. However, our study demonstrates how neighbouring house martins cooperatively defended against nest-usurping attempts by house sparrows. House martins collectively helped a conspecific pair build their nest at a much faster pace than would be possible for the breeding pair alone, within several hours as compared to a couple of days, in order to overcome the continued attempts of house sparrows to usurp the partially built nest. In our study, between the two breeding seasons of 2018 and 2019, the number of breeding house martins at the study site decreased by almost 63% while in contrast the number of house sparrow breeding pairs increased almost sixfold. The number of usurped nests by house sparrows was comparatively higher in 2019 as compared to 2018.

The general status of lampreys (family Petromyzontidae) in Bosnia and Herzegovina was reviewed to determine the species composition and geographical distribution of this group in the region. This paper reviews the available literature to provide a critical analysis of the current status of lamprey species. According to the available data, their status can be considered as indeterminate, largely due to limited published records. While eight species are recorded as present in the region (Eudontomyzon danfordi, E. mariae, E. vladykovi, Lampetra fluviatilis, L. planeri, L. soljani, Lethenteron zanandreai, Petromyzon marinus), only three species (E. vladykovi, L. soljani, P. marinus) are confirmed to occur. Their distribution is recorded in waters of both the Danube and the Adriatic Sea catchments. Given the deficiencies in our understanding of the taxonomic status of some populations and knowledge of the geographical distribution of lampreys inhabiting both catchments, research focused on improving understanding of the phylogenetic, morphological and phenotypic traits of lampreys in Bosnia and Herzegovina is warranted to resolve these uncertainties. Problems related to threats and conservation, and future perspectives for protective management strategies are discussed. This paper provides the context for future biodiversity conservation and management with regard to lamprey species in Bosnia and Herzegovina.

Rhodeus cyanorostris sp. nov. and R. nigrodorsalis sp. nov. are described from two tributaries of the River Yangtze, in Sichuan and Jiangxi Provinces, China, respectively. Both species have a small number of branched dorsal-fin rays (both with a mode of 8) and anal-fin rays (mode of 7-8 and 8, respectively), which makes them easily distinguished from all congeners. Rhodeus cyanorostris sp. nov. differs from R. nigrodorsalis sp. nov. in having more predorsal scales (14-16 vs. 12-13), fewer pectoral-fin rays (10-11 vs. 12), a shorter major axis of the eggs (2.5-2.8 mm vs. mostly 3.3-3.5 mm), absence of two rows of light spots on the dorsal-fin rays (vs. presence), and absence of a black blotch on the dorsal fin in adult males (vs. presence). The breeding season in winter of the two new species is unique among the Acheilognathinae.

Understanding the diets of predators, prey selection and their impact on prey populations is pivotal to investigations on the ecology of predator and prey species. In this study, we observed a hand-reared European otter (Lutra lutra) foraging in the wild, in order to identify the type of prey captured by the predator. The study was carried out between March and June 2001 in a diverse range of natural otter habitats in Białowieża Forest (NE Poland). We found that tadpoles represented an important part of the otter's diet in June, when their frequency of occurrence and biomass reached 38% and 11%, respectively. During spring, tadpoles were less common than other types of prey, such as adult amphibians, fish, or aquatic Coleoptera. Otter diet varied among months and there were differences in the main prey type captured among water body types. Our results highlight the need to develop methods that enable the identification of tadpoles and other cryptic seasonal food items in riparian predator diets.

Sibling competition leading to physiological stress and elevated allostatic load is driven by asymmetrical development and limited resources. To investigate these predictions, we studied broods of the lesser kestrel Falco naumanni, from a nest-box population in Armenio, Central Greece. For each nestling reared in nest-boxes, we noted the age (in days) since hatching, measured the wing chord length and body mass. We also clipped the central right rectrix for ptilochronology for subsequent analysis in the laboratory. We measured 206 nestlings from 61 broods (range 2-5 nestlings). In the case of nestlings < 18 days old (n = 198, 96.1% of all) we also measured the length of feathers. As a measure of body condition, we used the residuals of the linear regression for the relationship between wing chord length and body mass, while the growth bar width of feathers was used as a second, independent index of body size and allostatic load. A GLMM and information-theory criterion showed that both measures of body condition decreased incrementally from the first sibling to the most subordinate in the brood. Body condition of subordinate siblings was influenced by the number of siblings in the nest; i.e. the larger the brood size the greater the discrepancy in body condition between siblings. At the same time, we did not find any influence of sex on either measure of fitness. Thus, our results indirectly support the hypothesis that sibling competition may cause physiological developmental stress which is reflected in decreased body condition and increased allostatic load for younger nestlings.

Parasites commonly manipulate host behaviour to increase transmission success between hosts. While most behavioural changes comprise slight alterations to host activity patterns and habitat use, some represent impressive alterations to routine behaviour which, while having direct positive effects on parasite transmission, compromise host survival. Here, we report conspicuous risky behaviour in an African annual killifish, Nothobranchius furzeri, infected by metacercariae of a strigeid trematode, Apatemon sp., residing in their cranial cavity. We demonstrate a striking contrast in the spatial and temporal behavioural responses of fish from populations naturally infected with Apatemon sp. and fish from two control populations with either a similar baseline parasite fauna but lacking Apatemon, or an overall low-level of infection. During routine activity, fish from Apatemon-infected populations positioned themselves just below the water surface, while other fish spent most of their time near the bottom. During a simulated avian attack, killifish from Apatemon-infected populations jumped above the water surface, moved in an uncoordinated manner, and rotated in the upper water layer, while fish from the control populations rapidly escaped into deeper water and ceased moving. The same self-exposing behaviour (jumping out of the water and lying on floating lily pads for extended periods) was also observed under natural conditions. Such behaviour greatly facilitates location of Apatemon-infected host fish by avian definitive hosts, especially in turbid pools. Moreover, the nothobranchiid killifish host's own life history, i.e. an extremely short lifespan limited to several months, may represent an important driver in the evolution of behavioural manipulation.

The research was aimed at examining 230 skulls and mandibles (113 males and 117 females) of the red fox (Vulpes vulpes) in the territory of the Republic of Lithuania. The object of the study was macroscopic evaluation of dental and periodontal pathologies, including changes in the structure of the skull and mandible. The most common teeth pathology was indicated to be hypodontia 13.27% in males and 5.98% in females (excluding M³ molar tooth). The hypodontia of the M³ was found to be common in males 6.19% and 7.69% in females. The findings of the research reveal that pathologies such as hyperdontia, dental fractures, enamel hypoplasia, abrasion, periodontitis stage 3 and stage 4 were less common: 1-4% in both males and females. In four skulls and mandibles of females a complex of severe pathologies of teeth and periodontium were found. There were no similar cases observed in males. This was the only significant difference between males and females. Other pathologies, including fractures of the skull or mandible, atypical form of foramen magnum, and changes in bone structure were rare overall, though slightly more common in males but not significantly.

Hosts have evolved a multiplicity of defensive responses against avian brood parasites. One of them is mobbing behaviour which often includes direct contact attacks. These aggressive strikes may not only distract the parasites but may also be fatal to them, as documented by cases of dead brood parasite females found near host nests. Here, we present the first video-recording of a great reed warbler (Acrocephalus arundinaceus) host whose vigorous nest defence appears to directly lead to the death of a female common cuckoo (Cuculus canorus). We suggest that the chance of parasite death probably rises with the presence of unfavourable factors, such as water below the nest. Our observation supports previous suggestions that hosts may pose a lethal danger to their parasites.