2004 Volume 69 Issue 2 Pages 197-201
Flagellar movement and mating behavior of the biflagellate gametes of the marine green alga, Ulva arasakii was studied using high-speed video microscopy to clarify the rapid fertilization process of marine green algae. Discharged male and female gametes always swing their flagella backward during forward swimming. The beat pattern is flagellar beat with undulatory waves produced at the flagellar base being propagated toward the tip. One beat cycle takes 15 ms in both male and female gametes. When the male gamete encountered the female gamete, initial contact between the two gametes took place at one flagellar tip and at the anterior end of the cell body. Although attachment and detachment of flagellar tips occurred during the fertilization process, the male gamete kept in contact with the female gamete. Then male and female gametes adhered respectively at the anterior side of the cell body and at the flagellar tips. Nevertheless, they continued to move their flagella with a flagellar beat and oscillated their cell bodies. Finally, the gamete pair lay side by side with their longitudinal axes nearly parallel to one another within 30–100 ms after initial contact of the two gametes.
