@article {1859, title = {A new species of Polycelis (Platyhelminthes, Tricladida, Planariidae) from China}, journal = {Hungarian Natural History Museum, Budapest Acta Zoologica Academiae Scientiarum Hungaricae}, volume = {63}, year = {2017}, pages = {263{\textendash}276}, url = {http://actazool.nhmus.hu/63/3/ActaZH_2017_Vol_63_3_263.pdf}, author = {Zi-Mei Dong and Guang-Wen Chen and He-Cai Zhang and De-Zeng Liu} } @article {1802, title = {Population genetics and dispersal of the flatworm, Polycelis coronata: a test of the habitat stability hypothesis}, journal = {Journal of Freshwater EcologyJournal of Freshwater Ecology}, volume = {32}, year = {2017}, pages = {179-192}, abstract = {

ABSTRACTThe habitat stability hypothesis states that species in spring-like habitats have little reason to disperse compared to species in temporary habitats. Planarians commonly inhabit springs around the world and they have long been considered poor dispersers. Recently, however, genetic analyses have shown contradictory results on the dispersal of planarians. Asexual planarians that can establish a new population by colonization of a single individual showed little genetic differentiation between sites separated by hundreds of kilometers, whereas species inhabiting springs showed deep differentiation between sites separated by hundreds of meters. The latter results are consistent with the habitat stability hypothesis. We used the cytochrome oxidase subunit I gene from 468 individuals of Polycelis coronata, an asexual species, collected from 50 sites, nested in 26 tributaries, in 4 catchments of the Wasatch Mountains of Utah, USA, to explore the dispersal capabilities of P. coronata. The longest distance between sites was 66\ km. Despite this small spatial extent, we found that 77\% of the 130 haplotypes were collected from a single site and 89\% from a single catchment. FST values between local populations in the same tributary (0.221, 0.266, 0.389) were similar to the average FST values in different catchments for other headwater taxa. Also, variation among individuals accounted for the majority of genetic structuring with little differentiation beyond the scale of a single site. Dispersal is very slow in this species which is consistent with the habitat stability hypothesis. However, we suggest that other explanations also warrant consideration. We also identified two potential cryptic species suggesting a high degree of hidden variation at the level of species in this genus.ABSTRACTThe habitat stability hypothesis states that species in spring-like habitats have little reason to disperse compared to species in temporary habitats. Planarians commonly inhabit springs around the world and they have long been considered poor dispersers. Recently, however, genetic analyses have shown contradictory results on the dispersal of planarians. Asexual planarians that can establish a new population by colonization of a single individual showed little genetic differentiation between sites separated by hundreds of kilometers, whereas species inhabiting springs showed deep differentiation between sites separated by hundreds of meters. The latter results are consistent with the habitat stability hypothesis. We used the cytochrome oxidase subunit I gene from 468 individuals of Polycelis coronata, an asexual species, collected from 50 sites, nested in 26 tributaries, in 4 catchments of the Wasatch Mountains of Utah, USA, to explore the dispersal capabilities of P. coronata. The longest distance between sites was 66\ km. Despite this small spatial extent, we found that 77\% of the 130 haplotypes were collected from a single site and 89\% from a single catchment. FST values between local populations in the same tributary (0.221, 0.266, 0.389) were similar to the average FST values in different catchments for other headwater taxa. Also, variation among individuals accounted for the majority of genetic structuring with little differentiation beyond the scale of a single site. Dispersal is very slow in this species which is consistent with the habitat stability hypothesis. However, we suggest that other explanations also warrant consideration. We also identified two potential cryptic species suggesting a high degree of hidden variation at the level of species in this genus.

}, isbn = {0270-5060}, url = {http://dx.doi.org/10.1080/02705060.2016.1253624}, author = {Rader, Russell B. and Unmack, Peter J. and Moore, Jeffrey N.} } @article {1730, title = {Sulphated glycosaminoglycans support an assortment of planarian rhabdite structures}, journal = {Biol Open}, year = {2017}, month = {2017 Mar 16}, abstract = {

Planaria are soft-bodied, bilateral flatworms of the phylum Playhelminthes. They are covered in cilia and use ciliary-gliding to traverse the substratum while hunting. Their body surface is covered in a layer of viscous slime primarily derived from specialised secretory granules known as rhabdites. The slime must somehow stay associated with the surface of the animal in aqueous environments whilst also lubricating the interface of the animal and the surfaces over which the animal moves. The slime prevents damage to the animal\&$\#$39;s soft body and also contributes to adhesion to the substratum. In order to gain insight into how it might achieve these diverse functions, we performed electron microscopic examination of the slime\&$\#$39;s structure. Analysis of two freshwater flatworms from the UK Schmidtea polychroa (Schmidt, 1861) and Polycelis tenuis (Ijima, 1884) revealed a high level of organisation of the slime layer and a variety of ejected slime structures. We show that these structures are rich in sulphated glycosaminoglycans (sGAGs). Most of these (269 of 285 examined) appear to be topologically-closed spheroids that we name ball-GAGs Another class appears to burst to release flower- and star-like clusters which adhere to motile cilia. We also observe fibrous nets that are associated with entrapped bacteria. Examination of the structure of rhabdites ejected onto a porous surface suggests a mechanism by which their structure allows them to both bind to the porous surface and provide a smooth layer over which the animal could glide. Such sGAG-based structures might provide models for the design of artificial biomimetic replacements for tears, saliva, bio-compatible lubricants or drug-delivery vehicles.

}, doi = {10.1242/bio.024554}, author = {Hayes, Matthew J} }