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Partial nucleotide sequences from the 5′ terminus of the nuclear large-subunit (LSU) ribosomal DNA gene (domains C1, C2, D1, and D2) have been determined for ten fucalean species representing eight genera to assess their interfamilial and intergeneric relationships: Ascophyllum nodosum (Linnaeus) Le Jolis, Fucus vesiculosus Linnaeus, Pelvetia canaliculata (Linnaeus) Decaisne et Thuret, Himanthalia elongata (Linnaeus) S.F. Gray, Bifurcaria bifitrcata Ross, Cystoseira humilis Kutzing, C. nodicaulis (Withering) M. Roberts, C. tamariscifolia (Hudson) Papenfuss, Halidrys siliquosa (Linnaeus) Lyngbye, and Sargassum muticum (Yendo) Fensholt. Sequences of five other species were used as an outgroup: three from Laminariales [Chorda filum (Linnaeus) Stackhouse, Macrocystis pyrifera (Linnaeus) C. Agardh, and Saccorhiza polyschides (Lightfoot) Batters], one from Sphacelariales [Cladostephus spongiosus (Hudson) C. Agardh,] and one from Cutleriales [Cutleria multifida (Smith) Greville as both its gametophytic ...

The sex ratio (ratio of male to female gametophytes in field populations) of Cutleria cylindrica Okamura (Cutleriales, Phaeophyceae) in the Tsugaru Strait, Japan varies in different localities. Fem...

The spermatozoids of Zonaria angustata (Kutzing) Papenfuss (Phaeophyta) are biflagellate, and not uniflagellate as reported in other species of the Dictyotales. The anterior flagellum is 20–27 μm long and, in addition to mastigonemes and a terminal acronema, has a row of 23–33 spines distributed along its length. The posterior flagellum is very short, 1–1.5 μm long. Gametangial walls are not contiguous and sterile cortical cells occur between oogonia. The outer tier of the antheridia consists of sterile cells containing numerous physodes. It is argued that these characteristics of Z. angustata indicate that the order Dictyotales is more closely related to other brown algae than was previously thought, and the possibility of a phylogenetic relationship between the orders Dictyotales and Cutleriales is discussed.

The sperm attractant of Zonaria angustata has been isolated from egg secretions and identified as (+)-(3S,4S)-3[(Z)-1-butenyl]-4-vinylcyclopentene (multifidene). Multifidene has not been reported previously in the Dictyotales but it is known to occur in the egg secretions of Cutleria multifida (Cutleriales) and Chorda tomentosa (Laminariales).