@article {4774, title = {A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size.}, journal = {Journal of Zoological Systematics and Evolutionary Research}, volume = {58}, year = {2020}, pages = {41{\textendash}65}, abstract = {

The free-living flatworm Macrostomum lignano is used as a model in a range of research fields\—including ageing, bioadhesion, stem cells, and sexual selection\—leading to the recent establishment of genome assemblies and transgenics. However, the Macrostomum community has run into a roadblock following the discovery of an unusual genome organization in M. lignano, which could impair the development of essential resources and tools. Briefly, M. lignano has undergone a whole-genome duplication, followed by rediploidisation into a 2n=8 karyotype (distinct from the canonical 2n=6 karyotype in the genus). Although this karyotype appears visually diploid, it is in fact a hidden tetraploid (with rarer 2n=9 and 2n=10 individuals being pentaploid and hexaploid, respectively). Here we report on a phylogenetically-informed search for close relatives of M. lignano, aimed at uncovering alternative Macrostomum models with the canonical karyotype and a simple genome organization. We taxonomically describe three new species: the first, Macrostomum janickei n. sp., is the closest known relative of M. lignano, and shares its derived genome organization; the second, Macrostomum mirumnovem n. sp., has an even more unusual genome organization, with a highly variable karyotype based on a 2n=9 base pattern; and the third, Macrostomum cliftonensis n. sp., does not only show the canonical 2n=6 karyotype, but also performs well under standard laboratory culture conditions and fulfils many other requirements. M. cliftonensis is a viable candidate for replacing M. lignano as the primary Macrostomum model, being outcrossing and having an estimated haploid genome size of only 231 Mbp.

}, doi = {10.1111/jzs.12344}, author = {Sch{\"a}rer, Lukas and Brand, Jeremias N. and Singh, Pragya and Zadesenets, Kira S. and Stelzer, Claus-Peter and Viktorin, Gudrun} } @article {pdf, title = {A new model organism among the lower Bilateria and the use of digital microscopy in taxonomy of meiobenthic Platyhelminthes: Macrostomum lignano, n. sp. (Rhabditophora, Macrostomorpha)}, journal = {Journal of Zoological Systematics and Evolutionary Research}, volume = {43}, number = {2}, year = {2005}, note = {Describes: Macrostomum lignano n. sp.}, pages = {114{\textendash}126}, type = {article}, abstract = {Macrostomum lignano n. sp. is a member of the Macrostomorpha, the basal-most subtaxon of the Platyhelminthes, Rhabditophora. This new species can be easily cultured in the laboratory and has been already the subject of several developmental/evolutionary studies. The small size, with only about 25 000 cells constituting the major bilaterian organ systems, makes this simultaneous hermaphrodite a possible candidate for a new model organism that is phylogenetically more basal than any of the model organisms currently used in such studies within the Bilateria. M. lignano belongs to the largest genus of the Macrostomorpha. Over 100 marine, fresh water and brackish water species are contained in the genus Macrostomum, some of them with worldwide distribution pattern. Within it, M. lignano is a member of the M. tuba-species group, which we have summarized here. In the species description, we have used a novel approach to document such small soft-bodied meiobenthic organisms: we provide extensive digital micrographical documentation, which are deposited as a CD together with the type material.}, keywords = {Macrostomum}, author = {Ladurner, P. and Sch{\"a}rer, Lukas and Salvenmoser, W. and Rieger, Reinhard M} }