Symbiotic interactions between pelagic hosts and microalgae have received little attention, although they are widespread in the photic layer of the world ocean, where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders S pumellaria, C ollodaria and N assellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate S crippsiella nutricula , a species originally described by K arl B randt in the late nineteenth century as Z ooxanthella nutricula . The free‐living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free‐living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine‐symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free‐living stage does not match that of S crippsiella or related genera, and LSU and SSU r DNA ‐based molecular phylogenies place these symbionts in a distinct clade within the P eridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name B randtodinium gen. nov. and the recombination of S . nutricula as B . nutricula comb. nov.
Abstract True branching is a facultative characteristic only known from two cyanobacteria in the Aphanizomenonaceae, Umezakia natans and Dolichospermum brachiatum . In both cases, its expression has been associated with environmental stress, and its practical use as a diacritical feature has been previously evaluated. In this study, we undertook further evaluation of the phylogeny of Umezakia natans and its relationship to Chrysosporum ovalisporum as a previous study suggested the two were potentially congeneric. We used combined morphological, phylogenetic, and phylogenomic approaches to determine their relatedness using new strains available from a broad geographic range. Phylogenetic analysis based on 16S rRNA gene sequences showed that Australian C. ovalisporum and Japanese U. natans strains clustered together with accessions of C. ovalisporum originating from Australia, Israel, and Spain, with high p‐distance similarity values (99.5%–99.9%). Additionally, differences between the two species in the 16S–23S ITS region was low (0%–2.5%). The average nucleotide identity of the U. natans and C. ovalisporum strains was also high (ANI of > 99.5 and AF > 0.9) and supported a genus‐level separation from Chrysosporum bergii (83 ANI between clusters). Furthermore, in culture, strains of both species grown in vitamin‐free media showed facultative true branching, a feature not previously known in C. ovalisporum . Collectively, the results support unification of C. ovalisporum and U. natans according to the principle of priority as Umezakia ovalisporum .
Abstract Nitzschia taikiensis sp. nov. is a brackish diatom species found in the Toberi River marsh, eastern Hokkaido, Japan. This species has characteristics similar to Nitzschia subamphioxoides Hustedt, which was originally described by Hustedt in 1959. In the present study, we conducted a comparative morphological analysis of N. taikiensis and N. subamphioxoides . The obtained results showed that they are different species. Sampling sites of N. taikiensis were located in salt marsh environments with very low salinity (1-5‰), acidic pH (5.2-5.9) and high mud content (95.0-97.5%). Identification of this species was relatively easy based on LM and SEM image analysis of its frustule features, such as the external form and stria density. This species has not been previously reported in Japan, which could be attributed to the reduction or loss of Japanese freshwater and salt marsh environments in the coastal areas, resulting from urban and industrial development.
"Re-typification of Fragilaria subconstricta and F. tenuistriata, and a correction for Tuji & Williams (2008, Diat. Res. 23: 503-510)." Diatom Research, 34(4), pp. 271–272
Three new combinations of Japanese planktonic cyanobacteria species, Sphaerospermopsis oumiana, Dolichospermum minisporum and D. ucrainicum are proposed.
SUMMARY Fragilaria rumpens (Kütz.) G. W. F. Carlson is assumed to be a cosmopolitan species, and is often reported from ponds and lakes. Nevertheless, this species is similar to both Fragilaria capucina Desm. and Fragilaria vaucheriae (Kütz.) J. B. Petersen and, as a consequence, the taxonomy of all three species has been confusing. In an attempt to solve the taxonomic problems within this group, we have examined the type material of Synedra rumpens and discuss the differences between it and some of those species said to be similar.
The morphology and the 16S rDNA sequences of Shaerospermopsis oumiana (M.Watan.) Tuji et Niiyama from Japan and S. torques-reginae (Komarek) Werner et al. from South America are compared and their phylogenetic relationship are discussed. The results show that S. oumiana and S. torques-reginae are distinct species.
