Flagellar beating pattern of male gametes during the fertilization process of the marine green macroalga Bryopsis maxima (Ulvophyceae, Chlorophyta)

• Published in: Phycological research Vol. 69; no. 3; pp. 200 - 214
• Main Author: Miyamura, Shinichi
• Format: Journal Article
• Language: English
• Published: Kyoto, Japan John Wiley & Sons Australia, Ltd 01.07.2021; Wiley Subscription Services, Inc
• Subjects: Attraction; Biological fertilization; Bryopsis; Bryopsis maxima; Ca2; Calcium; Calcium chloride; Calcium ions; Calcium signalling; Cell body; Chemical analysis; Ethylene glycol; Females; Fertilization; Flagella; flagellar movement; gamete; Gametes; high‐speed video microscopy; Males; Mating behavior; Mating types; Microscopy; Reproductive behaviour; Seawater; Seaweeds; Swimming; Tips; Water analysis; Wave propagation
• ISSN: 1322-0829; 1440-1835
• DOI: 10.1111/pre.12451

SUMMARY I studied the flagellar movements and mating behavior of biflagellate gametes produced by the green marine macroalga Bryopsis maxima using high‐speed video microscopy. This procedure allowed me to visualize the very rapid fertilization process in a marine ulvophycean. Discharged male and female gametes always swung their flagella backwards during forward swimming. They swam with a flagellar beat type pattern in which undulatory waves produced at the flagellar bases propagated towards the tips. Each beat cycle lasted 15–20 ms. Male gametes were immediately attracted to the vicinity of female gametes when the two mating types were mixed. As each male gamete swam past a female, it reversed direction towards the female by changing the beat pattern of one of its two flagella. The attraction of male gametes to the female ones was inhibited in calcium‐free seawater in both the presence and absence of 10 mM ethylene glycol‐bis(β‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid, a calcium chelator, but attraction recovered in the presence of 10 mM CaCl2, suggesting that Ca2+ is necessary for the attraction response. The initial contact between the two gametes occurred when one of the male flagellar tips encountered a female flagellum. The male gamete kept in contact with the female gamete (i) at the flagellar tips, and then (ii) by anterior cell body contact. Flagella continued to beat and cell bodies oscillated as gametes maintained contact. In the final step, the gametes fused.