Bosmina longirostris is a small-bodied, filter-feeding cladoceran. The species is widely distributed throughout the world in temperate and tropical climates, where it persists in all kinds of freshwater bodies regardless of their trophy, acidification, or salinity. Its wide distribution causes B. longirostris to be one of the most taxonomically recognizable Cladocera species all over the world, despite the fact that the species is a well-known example of a taxon with confused taxonomy. Although B. longirostris often displays high abundances in the world’s freshwaters and sporadic studies on its feeding suggest that the species can have an important role in energy transfer throughout the food web, B. longirostris is still perceived by scientists as having a minor role in the classical food web structure. This perception of B. longirostris as a food web component could be altered in the near future due to global climatic changes, including increases in temperature which may cause cyanobacterial blooms that may be more harmful to Daphnia than B. longirostris. The response of B. longirostris to environmental, competitive, and predatory conditions has been repeatedly studied to search for application of that species as indicator in ecological, neolimnological, and paleolimnological research. Regardless of its common use as test species in ecological and limnological studies, B. longirostris still lacks appropriate study by researchers because of its problematic systematics. Research directed at this species seems to be hampered by the absence of an accurate taxonomical revision of B. longirostris or group of cryptic species called B. longirostris.

Niche separation by littoral-benthic Chydoridae (Cladocera, Crustacea) in a deep lake - potential drivers of their distribution and role in littoral-pelagic coupling

The consequences of raising temperatures have been intensively studied by biologists and ecologists for the past few decades. However, current climatic changes also include many anomalous weather events, such as intra-seasonal heatwaves followed by immediate decreases in temperature. In this study, the responses of population development and life history traits to different thermal regimes were investigated. The freshwater water flea Daphnia magna (Cladocera, Crustacea) was used as a model organism. Daphnia magna populations were monitored under temperature regimes of warm (25 °C), cold (5 °C), synchronous (gradual changes between 25 °C and 5 °C) or stochastic (random changes between 25 °C and 5 °C). Population size of D. magna populations decreased with unpredictability of thermal conditions; the highest density of D. magna was found in the warm environment and the lowest density in the stochastic environment. Thermal regime had significant impact on the prevalence of asexual and sexual reproduction of D. magna. Under a synchronous regime, an accumulation of asexual reproduction was observed during cold episodes; this was followed by a phase of population disturbance, manifesting itself in high fluctuations of asexual reproduction and a pattern of sexual reproduction typical of a cold regime. Under a stochastic regime, the population disturbances were observed throughout the duration of the experiment. Daily observations of individual life history traits revealed that the development of populations under different thermal regimes resulted from the regime-specific survivability of neonates. Population development was also affected by the frequency of reproduction, which consisted of the number of broods carried per lifetime. The results indicate that not only temperature but also shifts in thermal conditions have an important influence on individual life history traits and population dynamics of D. magna. It is important to consider the effects of shifts in water temperature on demographic and individual traits simultaneously because the impact of thermal changes on population traits can be modified by individual life histories.

Ibuprofen is a nonsteroidal anti-inflammatory drug that can be found in freshwater ecosystems. Due to its current presence in aquatic ecosystems, this pharmaceutical has aroused concerns about its impact on aquatic biota. As a result, ibuprofen is the one of the most frequently studied pharmaceuticals. However, most of these studies focus on short-term observations of biomarkers and physiological endpoints. This paper presents the outcomes of whole-life-cycle observations and six-month observations of the population dynamics of Daphnia magna reared under the influence of 1 μg/L, 2 μg/L and 4 μg/L of ibuprofen. Individuals reared under the influence of ibuprofen grew slowly, matured later and lived longer. Moreover, they displayed a higher reproduction rate and carried smaller broods but delivered larger neonates. Ibuprofen in concentrations of 1 μg/L and 2 μg/L had the most significant effect on the above traits. The observed impact of ibuprofen at the individual level did not transfer to population size and dynamics. All the populations represented a typical boom and bust cycle with restricted reproduction during the periods of highest population size. This is the first study to explore the linkage between the life histories of aquatic invertebrates and the actual response of their populations to the occurrence of ibuprofen in the environment. The study emphasizes the need to apply the protocol of whole life-cycle observation in tandem with population scrutiny, since such a protocol can reveal the virtual responses of aquatic biota to the presence of chemicals in the environment.

Spatial distribution of juvenile and adult stages of limnetic Cladocera in relation to selected environmental factors