Life cycle and systematics of boring bryozoans

Bryozoans are filter-feeding animals that form colonies living normally attached to substrates with over 6.000 recent species descibred. The project aims to study and analyse a group of almost unknown group of bryozoans, the ones that bore into mineralized substrates, hence called boring or endolithic bryozoans. Such forms are known from the Palaeozoic, but remain little investigated. Current forms most likely evolved independently from a non-boring ancestor. Virtually nothing is known on reproduction, larval forms, settlement or metamorphosis in these forms. Likewise, species diversity is little known and molecular sequence data is entirely missing. Preliminary observations have shown that boring bryozoans are incredibly abundant and very easy to sample in numerous localities around the world. The aim thus aims to gain first insight into the life cycle of boring bryozoans, add to the sparse morphological data available and generate first molecular sequence data for phylogenetic inferences.

The project analysed a group of little-known bryozoans, moss animals, that have evolved specific adaptations to drill into hard substrates such as mineralized shells, mostly of molluscs in recent days - hence the name boring bryozoans. Aim of this project was to assess the diversity in terms of species and distribution, analyse the morphology in detail and find suitable characters applicable for systematic purposes and obtain more information about their unknown life cycle. The project was very successful in studying the morphology of all recent genera of borings bryozoans and contribute new characters for systematic assessment of the different species. Also, first sequence data were obtained for all genera as well, which were completely missing before this project. This baseline of sequence data will be important for future biodiversity assays and aid in future determination of species. Based on our integral approach, several new species, one new genus in a newly erected family have been described in this species. Not surprising, we also found evidence for cryptic species in several localities. Long term observations at marine stations allowed for studying their life cycle for prolonged period. This was possible for two local genera at the respective marine stations, the genus Immergentia in Roscoff, France and the genus Penetrantia in Guam in the Pacific Ocean. First growth data for boring bryozoans was thus recorded for 1-2 months observation time and revealed rather slow growth in these organisms. Additional food supplement to colonies kept in aquaria proved to be advantageous for growth and survival of the animals. Based on these first observations future studies will be able to tackle the issue how potential ocean acidification effects can influence bioerosion caused by bryozoans. Since many of the boring bryozoans are known only from traces, including the fossil representatives, a collaboration was established to determine rules and guidelines for assessing ichno- (traces) vs. biotaxa (biological taxa, not only traces). This involved detailed study also of most types of boring bryozoans to provide a viable assessment of the various species. In addition, we promote a clear separation of true biotaxa, described from soft-body morphological features, vs. ichnotaxa where only trace character, which are easily subject to erosion, are applied.