Turbellarian taxonomic database

Record # 22844
Author
Title
Journal
Schärer L, Brand JN, Singh P, Zadesenets KS, Stelzer C-P, Viktorin G (2019)
A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size
Journal of Zoological Systematics and Evolutionary Research, Vol 58(1): 41-65
[doi: 10.1111/jzs.12344
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Abstract / Notes

The free-living flatworm Macrostomum lignano is used as a model in a range of research fields—including
aging, bioadhesion, stem cells, and sexual selection—culminating in the 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 now impair the development of additional resources and
tools. Briefly, M. lignano has undergone a whole?genome duplication, followed by rediploidization 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 fulfills
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.

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