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SUMMARY Molecular phylogenetic analyses of representative Cutleria species using mitochondrial cox3, chloroplast psaA, psbA and rbcL gene sequences showed that C. cylindrica Okamura was not included in the clade composed of other Cutleria species including the generitype C. multifida (Turner) Greville and the related taxon Zanardinia typus (Nardo) P.C. Silva. Instead, C. cylindrica was sister to the clade composed of the two genera excluding C. cylindrica. Cutleria spp. have heteromophic life histories and their gametophytes are rather diverse in gross morphology, from compressed or cylindrical-branched to fan-shaped, whereas the sporophytes are rather similar. In contrast, the monotypic species Z. typus has an isomorphic life history and resembles fan-shaped Cutleria in morphology. Morphological comparisons of these taxa revealed that C. cylindrica is morphologically distinct from other Cutleria spp. and Z. typus in having cylindrical gametophytes with multiseriate trichothallic filaments instead of uniseriate filaments (hairs) characteristic of Cutleriales (or Cutleriaceae, Tilopteridales), and in lacking rhizoidal filaments in the crustose sporophytes. Therefore, based on the molecular and morphological data, the establishment of a new genus Mutimo to accommodate C. cylindrica, and the new combination of M. cylindricus, is proposed.

Cutleria cylindrica Okamura was described from Japan in 1902 and has been reported only from northwestern Asia until its relatively recent discovery in California, USA, and Baja California, Mexico. To clarify the genetic relationships within and among the disjunct populations, we carried out a molecular phylogenetic study, as well as the examination of sex ratio and the life-history patterns, of populations in Japan, Korea, and California. Based on the DNA sequences of mitochondrial genes cox2, cox3, the open reading frame (ORF) region, and the spacer between cox3 and ORF, a total of 23 haplotypes were detected in the 85 individuals from 20 localities in Japan, Korea, and California. All localities in Japan and Korea included multiple haplotypes, but only a single haplotype was found in California. There was a positive relationship between distance and genetic divergence in Japan and Korea. The single haplotype found in California was the same as one occurring in Japan (Aomori Pref. and Fukuoka Pref.) and Korea (Daedaepo, Pusan). Both male and female gametophytes were distributed in most northeastern Asian populations. Only female gametophytes, developing parthenogenetically from female gametes, were found in California and Aomori Pref., Japan. On the basis of these results, we conclude that the disjunct population of C. cylindrica in California originated from a relatively recent introduction from Japan and shares its origin with the parthenogenetic population in the Tsugaru Strait.

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).

A range extension of Cutleria hancockii Dawson to the southern portion of the Gulf of California is presented based on collections in Concepcion Bay, La Paz Bay and Muertos Bay between March, 1996 and May, 2000. Mature gametangial and sporangial plants were collected in several localities in the low intertidial zone and in subtidial areas. The present records represent a range extension of 500 km for the species with the new southern limit in Punta Perico in Los Muertos Bay. The plants mostly were observed in low intertidial-shallow subtidial areas associated with Sargassum forest, but also were observed at depths of 30 ft. Based on analysis of the basic morphological and anatomial features of the plants, significant differences within geographic position and depth distribution were noted. Our data suggest that the temperature may be the determining factor in the distribution of this species.