Click image to see a larger view of Ulva's life history
All Ulva species are isomorphic, meaning that they alternate between gametophytic and sporophytic life stages with similar morphologies. The gametophytes are haploid and the sporophytes are diploid. The gametophytes produce biflagellate haploid gametes through mitosis, and the sporophytes produce quadriflagellate haploid zoospores through meiosis. Ulva are slightly anisogamous, in that both gametes are motile and the female is a little bit larger.
Vegetative cells Reproductive cells
activities occur near the margins of Ulva fronds, with the fertile
portions turning slightly brown. Both
gametogenesis and sporogenesis are accompanied by a sharp reduction in photosynthetic
capacity. The motile reproductive cells all contain the ability
The motile reproductive cells all contain the ability to photosynthesize.
©Anna Kirby 2001