This database aims to contribute to an easy access to identification of cnidarians through DNA-barcodes and to facilitate the standardisation of methods and approaches in this extremely diverse group.

The phylum Cnidaria comprises highly divergent organisms with different life cycles, morphologies and ecology such as Medusozoa (grouping the classes Hydrozoa, Scyphozoa, Cubozoa and Staurozoa) and Anthozoa. Within such groups, classes and orders are often divergent in morphology, ecology and molecular evolution. Such diversity makes it impossible at the moment to have a single standard barcode system efficient at the same taxonomic level for all cnidarians. Moreover, due in part to the simple morphology of most cnidarians, knowledge of diversity and taxonomy are very limited, and even the fundamental concept of species is unclear for many groups. Cnidarians are found in most aquatic environments and can play a major ecological role in aquatic ecosystems. Therefore, the identification of cnidarian species is an essential element in the assessment of aquatic ecosystems, especially in marine environments. However, in many situations identification is limited to the order level or family level without examination of difficult morphological characters and the help of expert taxonomists. A DNA barcoding approach offers an interesting potential to facilitate identification of cnidarians to a higher taxonomic resolution. This initiative intends to help expert taxonomists to achieve the most standardised system and to share their knowledge with non-specialists to facilitate rapid and easy specimen identification.

DNA barcoding has been shown to offer interesting potential in several groups of cnidarians already (Moura et al. 2008, Sinniger et al. 2008, Huang et al. 2008, McFadden et al. 2011) although species-level identification remains problematic for some groups.

Given the actual state of knowledge of cnidarians, often an identification to genus or species group is already sufficient. In order to accommodate the specificities of the different cnidarian groups, this initiative will promote a hierarchical approach: a first step with the use of one or two general barcodes to allow a rapid and simple identification followed by a second step using different markers more specific to certain groups to provide a finer resolution that could not be reached in the first stage.

Reference specimens and sequences are controlled by expert taxonomists to ensure accurate identification