Ultrastructure and Differentiation of Hydrodictyon Reticulatum IV. Conjugation of Gametes and the Development of Zygospores and Azygospores

Abstract

In H. reticulatum, gametes differed from other zooids principally in that some of them bore an electron·dense apical cap between their flagella. Conjugation did not take place until the walls of the coenobia, in which the gametes developed, ruptured; and often did not occur even among the liberated gametes. Only in zooids collected from cultures in which conjugation was evident were these apical caps extended as fertilization tubules. Fertilization took place by the fusion of the tip of this tubule on one gamete with the membrane between the flagella of another which apparently lacked a fertilization tubule. Subsequent lateral fusion of the united zooids produced quadriflagellate zygotes which were active for only a short time before flagellar retrac· tion and cell wall deposition. Karyogamy usually preceded wall secretion. Gametes failing to conjugate often laid down a wall to form azygotes.

DIVERSITY AND PHYLOGENETIC PLACEMENT OF BRACTEACOCCUS TEREG (CHLOROPHYCEAE, CHLOROPHYTA) BASED ON 18S RIBOSOMAL RNA GENE SEQUENCE DATA1

“…Bracteacoccus also lacks flagellar structures typical of the Hydrodictyaceae/Neochloridaceae, such as the ribbed structure and basal bodies with interconnected cores (Marchant and Pickett-Heaps 1972, Wilcox and Floyd 1988, Watanabe and Floyd 1989. Reclassifjmg Bructeucoccus to one of the families currently in the Sphaeropleales is at present difficult, because while the 18s data unequivocally support a relationship of Bracteacoccus to the Sphaeropleales the Bracteacoccus clade is not closely grouped with any of the currently included representatives of these families.…”

Inheritance pattern of chloroplast DNA is correlated with gamete types based on sex‐specific arrangement of the cell fusion site in Caulerpa (Ulvophyceae, Chlorophyta)

“…1968; Cavalier‐Smith 1975; Goodenough & Weiss 1975; Ch. moewusii Gerloff,Triemer & Brown 1975; Hydrodictyon reticulatum (L) Lagerh., Marchant and Pickett‐Heaps (1972). In Ch.…”

Aspects ultrastructuraux de la fécondation chez l'Acrosiphonia spinescens(Kütz.) Kjellm. (Acrosiphoniales, Chlorophyta)

“…diverses espèces planogames de Chlamydomonas (Wiese, 1965 ;Brown et coll., 1968;Friedmann et coll., 1968;Cavalier-Smith, 1975;Triemer et coll., 1975;Goouenough et Wei~s. 1978;Goodenough, 1977, pour revue), l'lJ1va mutabilis (Braten, 1971, 11J73), 1 'Ulva lac tuca (Melkonian, 1980), l'Hydrodictyon reticulatum (Marchant et Pickett-Heaps, 1972), l'Acetabularia mediterranea (Crawley, 1972), l'Oedogonium cardiacum (Hoffman, 1973, 197 4) …”