@article {1766, title = {Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex.}, journal = {Chromosoma}, volume = {123}, year = {2014}, month = {2014 Jun}, pages = {265-72}, abstract = {

Although polyploids are common among plants and some animals, polyploidization often causes reproductive failure. Triploids, in particular, are characterized by the problems of chromosomal pairing and segregation during meiosis, which may cause aneuploid gametes and results in sterility. Thus, they are generally considered to reproduce only asexually. In the case of the Platyhelminthes Dugesia ryukyuensis, populations with triploid karyotypes are normally found in nature as both fissiparous and oviparous triploids. Fissiparous triploids can also be experimentally sexualized if they are fed sexual planarians, developing both gonads and other reproductive organs. Fully sexualized worms begin reproducing by copulation rather than fission. In this study, we examined the genotypes of the offspring obtained by breeding sexualized triploids and found that the offspring inherited genes from both parents, i.e., they reproduced truly bisexually. Furthermore, meiotic chromosome behavior in triploid sexualized planarians differed significantly between male and female germ lines, in that female germ line cells remained triploid until prophase I, whereas male germ line cells appeared to become diploid before entry into meiosis. Oocytes at the late diplotene stage contained not only paired bivalents but also unpaired univalents that were suggested to produce diploid eggs if they remained in subsequent processes. Triploid planarians may therefore form euploid gametes by different meiotic systems in female and male germ lines and thus are be able to reproduce sexually in contrast to many other triploid organisms.

}, keywords = {Animals, Chromosomes, Female, Germ Cells, Male, Meiosis, planarians, reproduction, Triploidy}, issn = {1432-0886}, doi = {10.1007/s00412-013-0449-2}, author = {Chinone, Ayako and Nodono, Hanae and Matsumoto, Midori} } @article {1719, title = {Resistance of two planarian species to UV-irradiation}, journal = {Folia Biol (Krakow)}, volume = {54}, year = {2006}, month = {2006}, pages = {103-8}, abstract = {

The aim of this work was to determine the effects of 20, 25 and 30 minute UV-irradiation periods lambda = 253.5 nm to two planarian species Dugesia tigrina (Gir.) and Polycelis felina (Daly.). In vivo, UV light effects have been reported to affect intracellular receptors and disrupt simple behaviour. The effects of UV-rays on mortality and behavior as well as morphological, cytological and histological changes in the two planarian species were assessed, and the course and the dynamics of regenerative processes were compared between them. Experimental populations of Dugesia tigrina and Polycelis felina species were maintained in laboratory conditions at room temperature. Mortality, behavioral and morphological changes were monitored daily by means of a light stereomicroscope. For cytological and histopathological analysis, planarians were fixed in Bouine fixative on the first, second, third, fifth and seventh day after exposure to UV-irradiation, respectively. They were embedded in paraffin, cut on a microtome, stained with toluidin blue and embedded in Canada-balsam. UV-rays caused mortality, behavioral, morphological, cytological and histological changes in each planarian species. In regeneration of damaged body parts reticular cells and neoblasts played the main role. Neoblasts as totipotent cells extremely increased in number in the area of damaged tissue, immediately after UV-exposure. Dugesia tigrina was more sensitive to UV-rays than Polycelis felina due to possession of less pigmented cells. The course of regeneration in both species was similar. Most individuals of both species regenerated in 5 to 12 days after UV-irradiation.

}, keywords = {Animals, planarians, Ultraviolet Rays}, issn = {0015-5497}, author = {Kalafati{\'c}, Mirjana and Kovacevi{\'c}, Goran and Franjevi{\'c}, Damjan} } @article {1710, title = {On the distribution of neoblasts of Dugesia lugubris (Turbellaria, Tricladida) before and during regeneration}, journal = {C R Hebd Seances Acad Sci}, volume = {250}, year = {1960}, month = {1960 Mar 28}, pages = {2465-7}, keywords = {Animals, Annelida, Asteraceae, planarians, Platyhelminths, regeneration, Turbellaria}, issn = {0001-4036}, author = {LENDER, T and GABRIEL, A} }