LIFE HISTORY AND SYSTEMATIC POSITION OF PSEUDOCHORDA GRACILIS SP. NOV. (LAMINARIALES, PHAEOPHYCEAE)¹

Abstract

Pseudochorda gracilis sp. Nov. (Pseudochordacease, Laminariales) is described from the Japan Sea coast of Hokkaido/ the species is subtidal, epilithic and annual, appearing in spring and maturing in winter. Erect thalli grow solitary or in tufts on a small discoid holdfast. They are simple, cord‐shaped and hollow, with inner hyphal filaments, cylindrical medullary cells and paraphyses consisting of 3–6 cells. Hair tufts are observed only in young thalli. Unilocular sporangia are sessile and narrowly ovate. In culture, P. gracilis shows a heteromorphic life history with oogamy, characteristic of the order Laminariales. Gametophytes are dioecious and dimorphic. Gametophytes mature under lower temperature conditions (usually below 10°C), and sporophytes mature under low temperature and short‐day conditions (5°C, SD). The seasonal growth pattern of the species results from the photoperiod‐temperature conditions controlling saprophyte maturation.

MORPHOLOGY, LIFE HISTORY, AND MOLECULAR PHYLOGENY OF CHORDA RIGIDA, SP. NOV. (LAMINARIALES, PHAEOPHYCEAE) FROM THE SEA OF JAPAN AND THE GENETIC DIVERSITY OF CHORDA FILUM

“…However, in our observations, C. filum (data not shown) and C. rigida had a longer posterior flagellum and lacked an eyespot. This latter sperm morphology basically agrees with Halosiphon tomentosus (Maier 1984), Pseudochordaceae (Kawai and Kurogi 1985, Kawai and Nabata 1990), Phyllariaceae (Henry 1987), and advanced Laminariales (Henry and Cole 1982). Therefore, all known members of the order Laminariales are considered to lack eyespots in sperm and have a longer posterior flagellum.…”

“…Six families are included in the order at present: Alariaceae, Chordaceae, Laminariaceae, Lessoniaceae, Phyllariaceae, and Pseudochordaceae (Setchell and Gardner 1925, Tilden 1935, Kawai and Kurogi 1985, Henry and South 1987). Although phylogenetic relationships relative to other phaeophycean orders are unclear (Clayton 1984, Müller et al 1985, Kawai 1992, Tan and Druehl 1996, Boo et al 1999), within the Laminariales the families with terete sporophytes (Chordaceae and Pseudochordaceae) have been considered to be primitive based on the following characteristics (Kawai and Kurogi 1985, Henry and South 1987, Kawai and Nabata 1990): 1) relatively simple organization of sporophytes without differentiation between blade and stipe and lack of a meristematic rhizoidal holdfast, 2) annual nature of sporophytes and lack of distinct intercalary meristem (except for Chorda filum ), 3) lack of mucilage organs (e.g., mucilage gland cells or mucilage ducts) and mucilage caps on paraphyses, 4) presence of eyespots in zoospores, 5) occurrence of monoecious ( Chorda tomentosa Lyngbye = Halosiphon tomentosus [Lyngbye] Jaasund) or monomorphic dioecious ( Pseudochorda nagaii [Tokida] Inagaki) gametophytes, and 6) lack of inner hyphae ( C. tomentosa, Pseudochorda spp. ).…”

The biogeography of kelps (Laminariales, Phaeophyceae): a global analysis with new insights from recent advances in molecular phylogenetics

“…The 'ancestral' members of the Laminariales are currently considered to consist of three families, the Chordaceae (four species of Chorda, Sasaki and Kawai 2007), the Pseudochordaceae (two species of Pseudochorda: Kawai and Kurogi 1985;Kawai and Nabata 1990) and the Akkesiphycaceae (one species of Akkesiphycus: . Species of Chorda and Pseudochorda have cylindrical, chord-like sporophytes, and Chorda has monoecious gametophytes and zoospores with eyespots, all considered primitive traits in this group (Maier 1984;Lüning and Tom Dieck 1990;.…”

MORPHOLOGY AND MOLECULAR PHYLOGENY OF AUREOPHYCUS ALEUTICUS GEN. ET SP. NOV. (LAMINARIALES, PHAEOPHYCEAE) FROM THE ALEUTIAN ISLANDS1

“…The order Laminariales is thought to have originated on the northwestern coast of the Pacific Ocean and then to have expanded and diverged eastward along the Bering Sea and Aleutian Islands to the northeast Pacific and northward through the Arctic Ocean to the Atlantic Ocean. This scenario is based on a number of lines of evidence: (i) the basal-most taxa of the order, namely, Akkesiphycaceae and Pseudochordaceae, are distributed only in the northwest Pacific around the Okhotsk Sea (Kawai and Kurogi 1985, Kawai 1986, Kawai and Nabata 1990; and (ii) the Chordaceae, the sister group of the advanced (foliose) Laminariales (i.e., Alariaceae ⁄ Laminariaceae ⁄ Lessoniaceae), has higher species and genetic diversities in the northwest Pacific (Lü ning and Tom Dieck 1990, Kawai et al 2001, Sasaki and. On the other hand, the nearly equal species and generic diversity of the advanced Laminariales on the two sides of the North Pacific (Lane et al 2006) indicate that both regions have been involved in its diversification, as previously argued by Estes and Steinberg (1988) and Stam et al (1988).…”