Peculiarities of the Pontogammarus robustoides (Amphipoda, Gammaridae) Adaptive Reactions to the Water Temperature Increasing in the Model Ecosystem – Microcosm

The crustaceans’ family Gammaridae populations’ adaptive reactions with a water temperature increasing to the critical values were studied in the model ecosystem – the microcosm. The experiment included investigation of such indexes as population dimensional composition, precopulatory activity, number of oviparous females, embryogenesis duration, and energy metabolism at the different phases of thermocycle. Obtained data revealed optimal and critical for gammarid’s viability temperature conditions of environment. It is assumed that under conditions of climate change, when water temperature sharp fluctuations take place, in the Kyiv reservoir (Dnipro River, Ukraine) coastal shallow water crustacean’s family Gammaridae components of the invertebrates associations the structural and functional changes are expected. Temperature increasing to the critical values will promote the animals migration processes intensification; incapable of this animals will perish. Gammarids with ability to migrate in direction of areas with more favorable for their viability conditions will have a significant advantage.

Near-shore distribution of alien Ponto-Caspian amphipods in a European dam reservoir in relation to substratum type and occurrence of macroinvertebrate taxa

Knowledge of habitat requirements and interspecific interactions of invasive species helps predict their impact and spread. We determined the relationships within the invasive freshwater Ponto-Caspian amphipod assemblage, and their associations with macroinvertebrates in the near-shore zone of a central European lowland dam reservoir. We sampled five habitat types: bare sand at the water line, bare sand (0.2 m depth), bare sand (0.5 m depth), macrophyte-overgrown sand (1 m depth), stones (0.3 m depth) on four dates (October 2015–October 2016). Pontogammarus robustoides occurred in all habitats, Dikerogammarus villosus and Echinogammarus ischnus were limited to the stony bottom. Amphipod densities were positively associated with one another except Dikerogammarus juveniles, negatively correlated with adults. The occurrence of D. villosus, juvenile Dikerogammarus and E. ischnus was positively related to the presence of the shelter-forming bivalve Dreissena polymorpha. Pontogammarus robustoides was positively associated with sphaeriid clams and gastropods (shelters), as well as oligochaetes and chironomids (potential prey items). Dikerogammarus villosus and E. ischnus were positively related to chironomids and oligochaetes, respectively. Coexistence of various alien amphipods in the studied area, indicated by prevailing positive relationships in their assemblage, may be enabled by the abundance of shelters and rich food sources allowing habitat partitioning.

Mass appearance of the Ponto-Caspian invader Pontogammarus robustoides in the River Tisza catchment: bypass in the southern invasion corridor?

The river Danube is the backbone of the ‘southern invasion corridor’, one of the most important passages for the spread of Ponto-Caspian invaders in Europe. However, not all of these species used the passive or active upstream movement in the main channel to reach the upper sections and tributaries, some found detours. Mass occurrences of the Ponto-Caspian peracarid, Pontogammarus robustoides (Sars, 1894) were recorded at 17 sites along the entire Hungarian section of the River Maros, for the first time in the River Tisza catchment and also in Hungary. Those populations are found ca. 707 km upstream from the closest known and confirmed locality in the lower Danube section. We confirmed their identity by DNA barcoding and showed that all individuals fit in with the lower Danube population, thus identifying the source of this introduction. The most likely vector allowing the jump dispersal of the species is fish stocking in the Romanian section of the River Maros, which − combined with downstream drift to the Serbian Danube section and the relatively busy ship traffic between Belgrade and Vienna − might provide the opportunity to bypass the dispersal barrier represented by the unregulated Middle Danube and open the way towards Western Europe.

Changes in the distribution of amphipods in the Daugava River, Latvia

Scientific information on amphipods and other peracaridan crustaceans in Latvian inland waters is insufficient. Therefore investigations of these animals are indispensable, especially because of the ongoing biological invasions of Ponto-Caspian amphipods causing changes in macroinvertebrate assemblages. Our recent investigation revealed that the alien amphipod Gammarus varsoviensis dominates amphipods in the upper courses of the Daugava River, whereas the other alien amphipod Pontogammarus robustoides prevails in the lower reaches of the river. Both these Ponto-Caspian amphipods were found co-occurring with the indigenous Gammarus pulex in the middle course of the Daugava River upstream from the Pļaviņas Reservoir. We predict that in the future the indigenous G. pulex will be fully exterminated by alien amphipods in the Latvian part of the Daugava River.