Reproduction in the Red Algae (DVD)
Reproduction in the red algae is unique. No flagellated stages are ever
formed, and it is generally assumed that the various reproductive
spores are inert. This video demonstrates that spores in many species
are actively motile, either by gliding or amoeboid activity. This
limited power of movement may turn out to be of considerable
significance in survival strategies (e.g. dispersion, optimization of a
germination site) .
Sexual reproduction is also unique. The video briefly reviews the three-phase life cycle of red algae and then illustrates how sexual reproduction occurs. After release, male spermatia are passively carried to receptive female hairs, the trichogynes. Once attached, spermatia undergo a cycle of nuclear division (mitosis) without cell division. Then the wall between spermatium and trichogyne erodes away to form a fertilization pore. A little later, the two nuclei move through the pore into the trichogyne. We demonstrate that the behavior of the two nuclei is quite different. One (not always the first to emerge) moves toward the female cell for fertilization; the other moves toward the tip of the trichogyne where it appears to play no further role in reproduction. Thus, the two nuclei are subtly differentiated so as to interact with the motile systems of the trichogyne in different fashion.