Karyological analysis on Macrobiotus pseudohufelandi (Tardigrada, Macrobiotidae) and a new finding of a tetraploid population

Three populations of Macrobiotus pseudohufelandi (Eutardigrada, Macrobiotidae) were studied with karyological techniques not previously utilized for tardigrades. These observations provided detailed information on the karyology of these animals, particularly single chromosome morphology. A diploid amphimictic cytotype and a triploid thelytokous parthenogenetic cytotype were confirmed. In addition, a new tetraploid thelytokous parthenogenetic cytotype was found. Tetraploidy, as defined by chromosome number, was confirmed by DNA-Feulgen content evaluations. Indeed, the minimum DNA content in the tetraploid population is about four fold that in sperm from the diploid population.