Systematics and phylogeny of Swedish freshwater Gastrotricha
Tobias Kånneby
Gastrotrichs (Phylum Gastrotricha) are small aquatic invertebrate animals. The phylum is divided into the two orders Macrodasyida and Chaetonotida. To date around 750 species are known from both freshwater and marine environments. The phylum is considered cosmopolitan. The Swedish fauna consists of 44 marine species, most found on the west coast, and 20 freshwater species.
Enviroment
In marine environments most gastrotrichs live interstitially and can easily be collected by taking wet sand back to the laboratory. In freshwater environments most species are found on plants (epiphytic) or on the sediment surface (epibenthic). Freshwater gastrotrichs are collected by means of plankton net. The small size of the animals (0.06-4 mm) makes them hard to find and a dissecting microscope is usually needed. For proper species identification special microscopes (DIC-microscopes) are needed.Characteristics of the group
The name Gastrotricha refers to the cilia, used for locomotion, covering the ventral side. The group is also characterized by bearing adhesive tubes. Many genera (e. g. Chaetonotus, Aspidiophorus, Heterolepidoderma etc.) have cuticular structures like spined or keeled scales. At a first glance the animals are very similar to rotifers or ciliates.The aim of the project
This PhD-project aims to study the Swedish gastrotrich fauna and will mainly deal with freshwater species. Moreover inter and intra relationships of the group will be studied. Molecular studies include genes such as 18S, 28S and COI. Barcoding in gastrotrichs may be one of the outcomes of this project, helping biologists to identify these small animals.
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