Chromosome number and ploidy-level in a Dutch population ofCrenobia alpina Dana (Planaria)

A Dutch population ofCrenobia alpina was found to have a chromosome number of 2n=42. One pair of large chromosomes is acrocentric and probably shows a secondary constriction; one small pair is acrocentric as well. All other chromosomes are metacentric or sub-metacentric; it has not been possible to discriminate with certainty between them. According to the hypothesis ofDahm (1958) populations with, 2n=42 are autohexaploid, the basic genome consisting of seven chromosomes. On basis of the karyotype it was concluded that the Dutch population described here, is not autohexaploid but functionally diploid, perhaps allohexaploid.