New species of freshwater Ulva, Ulva limnetica (Ulvales, Ulvophyceae) from the Ryukyu Islands, Japan

Abstract

Ulva limnetica Ichihara et Shimada, sp. nov. (Ulvales, Ulvophyceae) is described from the Ryukyu Islands, Japan, and is characterized by thalli that are: (i) branched, tubular, fragile and wrinkled; (ii) up to 80 cm in height and up to 2 cm in diameter; (iii) light to yellowish green in color; and (iv) having an asexual reproduction by means of quadriflagellate swarmers. Rhizoidal cells bear tubular extensions on the outside of the cell layer in the stipe. Ulva limnetica is distinguished from species with similar thalli by chloroplast disposition, branching pattern, number of pyrenoids per cell and gross morphology. It is also distinguished by sequences of the nuclear-encoded 18S ribosomal RNA gene, internal transcribed spacer 2 region and the plastid-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxgenase gene (rbcL). Ulva limnetica was clustered with other Ulva species in an early diverging lineage within the genus.

Ulva flexuosa(Ulvaceae, Chlorophyta) inhabiting inland aquatic ecosystems: molecular, morphological and ecological discrimination of subspecies

“…Research so far (Ichihara et al, 2009a(Ichihara et al, , 2009bMareš et al 2011;Ogawa et al 2013) has indicated that either a single Ulva flexuosa species or a complex of separate taxa that are adapted to fresh water occur in inland waters (including those of anthropogenic origin). The objectives of the present study were to: (1) characterize the environmental niches of freshwater Ulva, (2) identify the key habitat parameters that determine the occurrence of Ulva in inland aquatic ecosystems, and (3) clarify limnic Ulva taxa morphologically and genetically in comparison with marine species.…”

“…Three Ulvaceae taxa: Ulvaria obscura var. blyttii (Areschoug) Bliding (1969) (Hayden & Waaland, 2002;Hayden et al, 2003;Ichihara et al, 2009aIchihara et al, , 2009b. Sequences of reference taxa were obtained from the NCBI database, based on the available literature (Supplementary Table 3).…”

“…Ulva flexuosa Wulfen, 1803); no taxa with foliaceous thalli have been found in fresh waters. The only species of Ulva known to occur exclusively in fresh waters is Ulva limnetica Ichihara and Shimada, which has only been found on the Yonaguni and Ishigaki Islands of the Ryuku Archipelago in Japan (Ichihara et al, 2009a(Ichihara et al, , 2009b.…”

Phylogeny and Molecular Evolution of the Green Algae

“…The group is predominantly marine, but several transitions to freshwater or terrestrial habitats have occurred independently (Shimada et al, 2008;Ichihara et al, 2009;Suutari et al, 2010). The orders Ulvales and Ulotrichales have traditionally been distinguished based on life history features: the Ulvales have a life cycle involving isomorphic alternations of multicellular stages, while in the Ulotrichales the diploid, spore-producing stage is a small, thick-walled unicell that is attached to the substrate by a stalk (Codiolum stage) (O'Kelly et al, 2004b).…”

<i>Ulva partita</i> sp. nov., a Novel <i>Enteromorpha</i>-Like <i>Ulva</i> Species from Japanese Coastal Areas

“…The green algal genus Ulva, including species previously placed in the genus Enteromorpha (Hayden et al 2003), is known for its wide distribution in marine, brackish water, and freshwater environments globally (van den Hoek et al 1995, Maggs et al 2007, Shimada et al 2008, Ichihara et al 2009, Mareš et al 2011. A total of 107 species are taxonomically accepted (Guiry and Guiry 2015), of which 29 are currently recognized in Japan (Masakiyo and Shimada 2014).…”