Pro-ecological and conservation activities are not always beneficial to nature: a case study of two lowland streams in Central Europe.

Since 1990 and in particular, after the implementation of the Water Frame Directive, many positive effects of pro-ecological projects are evident; unfortunately, examples of adverse effects have also been observed. This study aims to indicate how some ill-considered actions, called "pro-ecological", may lead to habitat degradation and the disappearance of valuable hydrobiont species. Two watercourses, representing the lowland gravel stream and sandy stream type, were selected for the study. Literature indicated that in the past, these watercourses were characterized by an excellent ecological status and the presence of valuable rheophilic fauna and flora. Environmental parameters were recorded, macroinvertebrates and ichthyofauna were sampled and analyzed, and finally, indexes were calculated. The results were compared with literature data. In the course of studies conducted in 2011-2015, drastic habitat deterioration and extensive changes in the species structure of ichthyofauna and aquatic invertebrates were observed. Changes in the Smolnica stream have been caused by the three retention basins constructed in 2000, along the lower and middle course; while in Kiszewko, however, the factor for habitat deterioration was connected with the excessive expansion of the Eurasian beaver (Castor fiber), which created a beaver pond 20 m in width, with impoundment elevations of up to 2 m.

Lake-stream transition zones support hotspots of freshwater ecosystem services: Evidence from a 35-year study on unionid mussels.

Securing adequate supply of high-quality water is of increasing global importance and relies in large part on ecosystem services provided by freshwater biota. Unionid mussels are important keystone species and habitat engineers that shape freshwater ecosystems through water filtration, nutrient cycling and provision of habitats; their rapid global declines result in dramatic losses of ecosystem functions. Maintenance and enhancement of the services they provide depend on the identification of their crucial habitats. Following theoretical assumptions, this study analyses the importance of lake-stream transition zones for unionid mussels, based on data collected in 1984 and 2019 from an undisturbed stream flowing through five consecutive lakes. Mussel distribution matched the distribution of host fish and was strongly influenced by lakes: densities were highest near lake outlets, reaching 290 ind. m-2 (14.7 kg m-2) in 2019, and declined with downstream distance following a negative power function. This pattern was spatially consistent and sustained over time. All six unionid species native to north-central Europe were present, but common species (Anodonta anatina, Unio pictorum, U. tumidus) contributed about 80% of individuals and were responsible for most of the ecosystem services provided by unionid mussels. Estimated 1.9 × 106 mussel individuals inhabiting 3.2 km of stream length filtered a water volume equivalent to the total stream discharge approximately 2.5 times daily. Aggregations of spent shells, up to 17 kg m-2, accumulated downstream of lakes, forming extensive shell and mussel beds, providing habitats and contributing shell hash that improved stream-bed conditions. Globally invasive Dreissena polymorpha was present at low densities and did not spread or increase in abundance, indicating a long-term biotic resistance of the natural native community. Our study underscores the importance of undisturbed lake outlets, longitudinal connectivity of riverine ecosystems, and of common mussel species in maintaining freshwater ecosystem functionality and provision of vital services.

Selected Quality Attributes of Freshwater Mussel Powder as a Promising Ingredient for Pet Food.

The aim of this study was to describe the quality attributes of a freeze-dried preparation obtained from freshwater mussel Sinanodonta woodiana (SW) soft tissue in respect to its potential as a novel pet food ingredient. After ecotoxicological testing of the raw material with MARA (Microbial Assay for Risk Assessment), the basic physico-chemical properties of the powder, such as approximate composition, bulk density, color parameters, water activity, electrophoretic analysis (SDS-PAGE), solubility, gelling and emulsifying capacity, were analyzed. The powder with a water activity of 0.43 offers a toxically safe preparation that contains over 34% protein/100 g of dry matter (DM). The SDS-PAGE profile showed twelve protein bands with a molecular weight (MW) ranging from >250 to 10 kDa. Taurine content has been estimated at an essential amount above 150 mg/100 g of DM. The powder possessed desirable emulsifying properties with 230 mL per 1 g and demonstrated the ability to form a firmer gel with a strength of 152.9 g at a temperature above 80 °C with at least 10% protein content. The L*, a*, and b* values characterizing powder color were found to be 69.49, 16.33, and 3.86, respectively. The SW mussel powder seems to be a promising ingredient that can be added with other binding or gelling agents in order to improve both the taste and acceptance of the final pet food products.

Morphology of the inferior pharyngeal bones of white bream (Blicca bjoerkna) in River Warta.

The inferior pharyngeal bones are a characteristic feature of the Cyprinidae. Morphology of inferior pharyngeal bones is important in the diagnosis of carnivorous food, or determining the diet of fishes. Due to the lack of literature data, the aim of the study was to examine the morphology of the inferior pharyngeal bone in detail. 102 Blicca bjoerkna specimens caught in the River Warta (Poland) were analysed. 204 inferior pharyngeal bones were collected. The parameters of the inferior pharyngeal bones correlated with the measured head features and the total fish length. The arches of inferior pharyngeal bones did not have directional asymmetry for the two main parameters (height and width of inferior pharyngeal bone). However, there was a left-sided directional asymmetry of the ventral part of inferior pharyngeal bone. In the case of the B. bjoerkna from River Warta, large differences in terms of individual parameters of inferior pharyngeal bones were observed. Fluctuation asymmetry was low. Shape of inferior pharyngeal bones was very round. In total, 12 teeth formulas were described. The 35.29% of the fish had formula different than described in the literature 2.5-5.2 and more teeth in the right arches. Following identification, measurements of the structures enable estimation of the lengths and weights of prey to be determined from biometric relationships. Analysis of body morphological features in combination with pharyngeal bone morphology could show a hybrid in the Warta river's population.

Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo (Phalacrocoracidae, Aves).

The tongue of the cormorant Phalacrocorax carbo is a small, immobile structure with a length of 1.4 cm, situated in the middle part of the elongated lower bill. The uniquely shaped tongue resembles a mushroom, with a short base and an elongated dorsal part with sharpened anterior and posterior tips. A median crest can be observed on the surface of the tongue. Examination by light and scanning electron microscopy revealed that the whole tongue is formed by a dense connective tissue with many bundles of elastic fibers. The lingual mucosa is covered by a multilayered keratinized epithelium. The thickest, horny layer of the lingual epithelium was observed on the surface of the median crest and on the posterior tip of the tongue. Lingual glands are absent in cormorants. The framework of the tongue is composed of a hyoid cartilage incorporated into the base. The localization and structure of the tongue in the cormorant show that it is a rudimentary organ and that the lingual body, usually well-developed in birds, is conserved.