On the Reproduction of Some Pacific Coast Species of Ulva

Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae

“…Similarly, the release of gametes was periodic in Enteromorpha, whereas the release of zoospores was not (Pringle, 1986). In Ulva, periodic release of both gametes and zoospores was observed (Smith, 1947), but gametes were released over a shorter period than zoospores.…”

“…However, the reproductive thalli of multicellular algae generally release gametes in response to a different cue from the one that confers an overall seasonality to the life history. For example, gametes may be released on a lunar or semilunar cycle (Williams, 1905;Tahara, 1909;Hollenberg, 1936;Smith, 1947;Subrahmanyan, 1957;Bfinning & Mfiller, 1961;Mfiller, 1962;Christie & Evans, 1962;Chihara, 1968;Ohno, 1972;Fletcher, 1980;Norton, 1981;Phillips et al, 1990a, b;May & Clayton, 1991;Phillips & Clayton, 1991;Brawley, 1992). In many such cases, the release appears to be related to tidal height (e.g.…”

“…Gamete release also commonly occurs following a change in irradiance (light after a dark-induction period or vice versa, Hollenberg, 1935;Jaffe, 1954;Smith, 1947;Page & Kingsbury, 1968;Burr & West, 1970;Kumke, 1973;La Claire & West, 1979;L/.ining, 1981;Clayton, 1984;Miiller, Clayton & Germann, 1985;Phillips et al, 1990a, b;Brawley, 1991). In most of the cases in which algae are known to release gametes in response to changes in light, release occurs at daybreak (or artificial day in culture on a light/dark cycle), often explosively (e.g.…”

“…However, Smith (1947) observed gamete release from the green alga Ulva lobata (Kiitzing) Setchell & Gardner on morning high tides, and Brawley (1992) found that Fucus ceranoides L. liberated gametes almost exclusively on daytime high tides. In contrast, May & Clayton (1991) reported that gametes were shed from the monoecious fucoid Sargassum vestitum (R. Brown ex Turner) C. Agardh during both night and daytime high tides, or on either the morning or evening high tide; this variation occurred within the population at one field site among different tidal pools, and it suggests genetic variability in the characters determining gamete release within the population.…”

“…Gametes that show phototaxis, whether positive (e.g. Ulva: Smith, 1947) or negative (e.g. Fucus, Pelvetia), might be presumed to be released more often during day than night in nature.…”