Half-a-billion-year-old microscopic treasures-the Cambrian 'Orsten' fossils of Sweden

The creatures that gaze back at us through the binocular microscope are so uniquely well-preserved and life-like that had we not known better we would have thought that they were modern. Instead they are half-a-billion-year-old arthropods extracted from Cambrian rocks of Sweden. The microscopic fossils, colloquially known as the 'Orsten' fossils, are now world-famous and basking in the light of the research catwalk since their discovery in the 1970s. These fossils have provided significant insight into the long lost Cambrian biotas and early animal evolution

Mouthpart Morphology of Three Sympatric Native and Nonnative Gammaridean Species: Gammarus pulex, G. fossarum, and Echinogammarus berilloni (Crustacea: Amphipoda)

In the last 20 years several nonnative amphipod species have immigrated inland waters of Germany and adjacent central European countries. Some of them have been very successful and could establish stabile populations. In some places, they have even replaced native or earlier established species. The gammarid Echinogammarus berilloni originates from the Atlantic region of France and the north-western part of Spain and coexists in some central European waters with the native Gammarus pulex and G. fossarum. Here, we describe and compare the mouthparts and other structures involved in food acquisition of these three sympatric gammaridean species. Our hypothesis was that differences in the mode of feeding of the three species could be the reason for their coexistence and that these differences would be expressed in differences in mouthpart morphology. The results of our SEM study demonstrate that there are indeed interspecific differences in details of the morphology of the feeding structures. This is especially true for the setation of antennae, maxillulae, gnathopods, and third uropods, which can be interpreted as adaptations to special modes of feeding. Generally, all three species are omnivorous, but specializations in details point to the possibility to use some food resources in a special effective way

Uropods of Eumalacostraca (Crustacea s.l.: Malacostraca) and their phylogenetic significance

The uropods are the specialised sixth pair of pleopods of eumalacostracan Crustacea. Their quite variable morphology is suggestive of a good potential as a phylogenetic signal. Because uropods have hitherto been neglected in analyses of malacostracan phylogeny, we examined them in 11 representative species of Eumalacostraca and the sixth pleopods of a phyllocarid malacostracan for outgroup comparison. Uropods have apparently evolved in the stem species of Eumalacostraca, possibly being leaf-shaped in the ground-pattern state but already with stabilising carinae along their surface and marginal setae enlarging the effective surface of the rami. Functionally, uropods aid in locomotion and, within the taxon Caridoida, also add to the special tail-flip mechanism. From an original leaf-shaped design in adaptation to different functions and lifestyles uropods may have become rod-shaped, as in Bathynellacea, Cumacea and Amphipoda, but independently so in the first taxon, while this shape might have developed in a common stem species of the latter two, inter alia. Among the taxa that have retained the leaf shape, mysidacean uropods possess a basipod that is drawn out medio-proximally into an outgrowth; Lophogastrida have a triangular median keel there. The uropods of both Euphausiacea and Decapoda also have a laterodistal prolongation, while those of Decapoda are special in bearing a longitudinal median keel on their basipod. All these differences appear to be exclusive to the respective higher taxa, demonstrating the value of uropods, and pleonal structures in general, for phylogenetic considerations