Morphology and reproduction of Volvox capensis (Volvocales, Chlorophyceae) from Montana, USA

Volvox capensis was recorded previously only from South Africa. Here we established culture strains of this species from a sample collected in Montana, USA. Morphological details of asexual and sexual spheroids and molecular phylogeny of these strains were studied. The present alga was identified as V. capensis on the basis of morphological characteristics of asexual spheroids and zygotes. However, differences between the Montana and South African materials were recognized in number of sperm packets in a sexual, monoecious spheroid as well as in mode of gametic union between sperm and eggs. Possible polyspermy was observed in eggs of V. capensis by 4′-6-diamidino-2-phenylidole staining. Genetic difference between these two entities was small based on sequences of internal transcribed spacer 2 region of nuclear ribosomal DNA.