Autecology of Limnomysis benedeni Czerniavsky, 1882 (Crustacea: Mysida) in Lake Constance, Southwestern Germany

AbstractThe Ponto-Caspian mysid Limnomysis benedeni was first recorded in Lake Constance in summer 2006, and a stable population developed at the site of discovery. Although this mysid is common in the Rhine and Danube rivers, little is known about its ecology and impact in systems of invasion. We investigated the autecology of L. benedeni in habitat-choice and food experiments. In the habitat-choice experiments, highly structured habitats, i.e., stones covered with zebra mussels (Dreissena polymorpha), macrophytes, and especially stonewort, were strongly preferred. In food experiments, L. benedeni fed mostly on food sources with a small particle size, e.g., biofilm on leaf litter, biodeposited material of zebra mussels, epilithon, and phytoplankton. We also compared the L. benedeni population data from Lake Constance with that from rivers. In Lake Constance, female L. benedeni were nearly 30% larger and carried more than three times more eggs in spring (9.4±0.6mm and 28.4±5.7 eggs) than in summer (6.7±0.8mm and 8.7±2.9 eggs). The mysids present in spring might be the generation that over-wintered; in summer, this generation was probably replaced by a new generation of smaller individuals. The large brood size and the detritivorous feeding strategy might allow L. benedeni to colonize Lake Constance rapidly

Katamysis warpachowskyi Sars, 1877 (Crustacea, Mysida) invaded Lake Constance

The mysid Katamysis warpachowskyi Sars, 1877 originated in the Ponto-Caspian region and the associated river systems. The first evidence of its transgression of the limits of the watersheds of its natural Ponto-Caspian origin was found when three individuals were recorded in October 2009 in eastern Lake Constance (Austria). In March 2010, K. warpachowskyi comprised 10% of the mysid assemblage and was mainly found in rocky habitats. On both sampling dates, breeding females were present. Before this invasion, Limnomysis benedeni Czerniavsky, 1882, was the only mysid in Lake Constance and is also distributed in the Rhine river system. Since the two mysids coexist in Lake Constance, K. warpachowskyi will likely become established in the lake and further expand into the main part of the Rhine. K. warpachowskyi is known as a benthic organism and feeds on detritus and small algae; therefore, the impact on the lake ecosystem should be weaker than that of pelagic mysids

Niche differentiation between sympatric alien aquatic crustaceans : An isotopic evidence

Among the mechanisms that allow competing species to coexist are resource partitioning and dietary segregation. The current study uses multiple stable isotopes, carbon ( 13C), nitrogen ( 15N) and sulphur ( 34S), to test the hypothesis that dietary segregation in cohabiting invasive mysids (Limnomysis benedeni and Katamysis warpachowskyi) and gammarids (Dikerogammarus villosus and Gammarus roeselii) will be reflected by differences in isotope values. Furthermore, IsoError mixing models were used to estimate the relative contributions of periphyton and seston to the invaders’ diets. Whole tissue 13C, 15N and 34S analysis in L. benedeni and K. warpachowskyi imply that these sympatric, non-native mysids maintain differentiated feeding niches or resource partitioning by feeding on distinct components of the available food resources (predominantly seston by L. benedeni and periphyton by K. warpachowskyi). By contrast, the gammarids D. villosus (‘killer shrimp’) and G. roeselii exhibited no significant difference in 13C and 15N, indicating a considerable overlap between the dietary sources of these sympatric invaders. Feeding niche differentiation, irrespective of season or the nature of habitat invaded (lake or river), might facilitate the coexistence of invasive mysids in their ‘new’ environment by minimizing direct resource competition. The mutual interaction by the invasive gammarids, coupled with voracious behavior, could assist their success at co-invasion with serious implications for local biodiversity including the potential extinction of native species