Niche segregation between two closely similar gammarids (Peracarida, Amphipoda) — native vs. naturalized non-native species

Closely similar species may occupy similar niches, but usually divergence can be found in one or more traits when they inhabit the same habitat. In this study, we examined how two co-occurring gammarids — the nativeGammarus fossarumand the naturalizedG. roeselii — are distributed among microhabitats, depending on their sympatric or allopatric distribution. We hypothesized that the larger body-sized species (G. roeselii), exploiting their advantages in competition, restrict smaller species to microhabitats with smaller particle sizes. Four headwaters were sampled in the Mecsek Mountains (SW Hungary) in May, July and October 2009, and 37 local scale environmental variables at each site were measured. AlthoughG. fossarumis smaller in size, significantly more individuals were collected from the more favourable lithal and biotic microhabitats, whereas a strong negative association was observed between the two species.Gammarus roeseliioccurred at sites characterized by degraded riparian vegetation, which indicates stronger anthropogenic impacts, but still has a disadvantage in competition in mountainous streams under anthropogenic influence.</jats:p

Microhabitat preference and biotic interactions among freshwater gammarids

The order of amphipods (Amphipoda), like most of the macroscopic crustaceans is belonging to the Malacostraca class. Despite most of the amphipods are can be found in marine environments, they inhabit a broad spectrum of freshwater habitats as well. Epibenthic groups are much more diverse and are usually bounded to the littoral vegetation in lakes and rivers or, to the sediment of small streams and springs (Väinölä et al., 2008). To reveal their ecological role as accurately as possible is urgent, because of their enormous number of individuals and biomass, they clearly stand out from the rest of the aquatic macroinvertebrates. As amphipods are occupying central position in freshwater food webs, they have a significant ecological role in the communities of flowing water systems. However, we have only limited information about their behavior and ecological needs.Niche segregation depends on multiple influencing factors, including available resources, habitat variability and structure, and consequently the temporal and spatial patterns of species (abundances and densities of competitors and mutualists) (Chesson, 2000; Chase & Leibold, 2003). Accordingly, the habitat choice of freshwater gammaridscan be influenced by a complex sequence of interacting biotic andabiotic factors (Dahl & Greenberg, 1996). The factors that may affect the distribution and number of Gammarusspecies can be grouped as follows: (1) environmental variables that determine the habitat choice of species regardless of other species (Savage, 1996), (2) differences in life cycle characteristics and fecundity (Pöckl, 1993) (3) biotic interactions such as predation and competition (Dick et al., 1994; Dick, 1996; MacNeil et al., 1999)

Oxidative Stress in Assisted Reproductive Techniques, with a Focus on an Underestimated Risk Factor

Based on current findings, the presence of oxidative stress has a significant impact on the quality of gametes and embryos when performing assisted reproductive techniques (ART). Unfortunately, in vitro manipulation of these cells exposes them to a higher level of reactive oxygen species (ROS). The primary goal of this review is to provide a comprehensive overview of the development of oxidative stress in female and male reproductive systems, as well as in the case of the pre-implantation embryo and its environment. This review also focuses on the origins of ROS and the mechanisms of oxidative stress-induced damage during ART procedures. A well-known but underestimated hazard, light exposure-related photo-oxidation, is particularly concerning. The effect of oxidative stress on ART outcomes, as well as the various strategies for preventing it, are also discussed. We emphasize the role and significance of antioxidants and light protection including forms, functions, and mechanisms in the development of gametes and embryos in vivo and in vitro