Journal of Phycology最新文献

A major challenge faced by kelp aquaculture operations is the control of contaminants, including by marine ciliates. Biokos® is a commercially available treatment for ciliate parasites in fish, in which the active ingredient is a viscosin-like lipopeptide surfactant. This study aimed to determine whether Biokos® is effective at controlling ciliate contamination in Saccharina latissima cultures without impacting gametophytes. Two experiments were conducted. Biokos® was first added to a live ciliate culture, and mortality was compared to a control. Subsequently, Biokos® was added to a culture of S. latissima gametophytes. The growth, density, and reproduction of gametophytes were compared to a control. Biokos® was highly effective at destroying ciliates within 24 h of treatment. We observed no impact on the vegetative growth of gametophytes. However, Biokos® did reduce gametophyte densities and may have had an impact on adherence. Biokos® also induced higher egg and sporophyte production in female gametophytes, potentially as a response to changes in pH associated with the treatment. There is potential for Biokos® to be effective at controlling ciliate contamination in gametophyte cultures, and at this stage, we would recommend treatment at manufacturer-recommended doses, along with appropriate buffering to maintain the pH of the culture. Further research is recommended on the identity of ciliate species contaminating gametophyte cultures and the response of different kelp species to Biokos®. Additionally, we would recommend that Biokos® now be tested in a commercial hatchery setting to identify impacts on S. latissima throughout the cultivation process and to determine optimal dosing procedures.

Three strains of fine filamentous cyanobacteria were isolated from freshwater lakes in Hubei province, China. A polyphasic analysis based on morphology, ecology, 16S rRNA gene phylogenies, and 16S-23S internal transcribed spacer (ITS) rRNA region secondary structures was undertaken. Based on the 16S rRNA gene phylogeny, three strains (JYH02, JYH03, and ZYHGY02) are likely new species of Nodosilinea, sharing <98.7% similarity to other species. Furthermore, the ITS rRNA region secondary structures from all three strains were distinct and unique compared with other Nodosilinea species. These results support the establishment of two new species: Nodosilinea jinyiensis sp. nov. and Nodosilinea qiaokuensis sp. nov.

For the freshwater red algal order Batrachospermales, the number of plastid genomes available is relatively small compared to the number of genera. Fully assembled plastid genomes can provide insights into plastid evolution and crucial data for phylogenetic reconstruction. In the present study, 18 plastid genomes were generated for a total of 40 plastid genomes from 38 species representing 18 of the 23 genera. The greatly expanded dataset allowed for comparison of the plastid genome structural characteristics with the other orders in the Nemaliophycidae and inference of the phylogenetic relationships of the genera within the order. Results showed the plastid genomes had either one or two RNA operons, and this variation could be intrageneric. All plastid genomes had the chlB gene with an intron like all Nemaliophycidae but lacked the apcF gene present in all Nemaliophycidae. The loss of the pbsA gene was variable in the Batrachospermales and the Nemaliophycidae. Phylogenetic analysis using a 126-gene concatenated dataset produced a fully supported Batrachospermales. In addition, generally high support for the relationships among the genera resulted in the most robust phylogeny to date. Nevertheless, the phylogeny also highlighted that potentially more data will be needed to resolve the relationship among sections of Nothocladus and other related genera. Overall, the Batrachospermalean genera were split into two well-supported lineages, which had been noted in other studies using plastid and mitochondrial genomes. However, we lack a combination of characters to distinguish these two lineages, as the morphological characters to describe taxa are shared between them.

Diatoms are known for their extraordinary species richness, cornerstone roles in aquatic ecosystems, and immense contributions to the global cycling of carbon, oxygen, and silica. For nearly 2 centuries, taxonomic classifications of diatoms have been based on interpretations of their feature-rich, silica cell walls. These classifications, in turn, have been used to make broad inferences about diatom ecology and evolution, but decades of molecular phylogenetic research have shown that historical and contemporary classification systems do not reflect evolutionary history, severely limiting their utility and insights. We took advantage of recent advances in our understanding of the diatom phylogeny to develop the first entirely natural classification of diatoms, in which only monophyletic groups have been recognized and named. The classification is comprehensive, dividing 431 genera among 68 families, 44 orders, and 10 classes. Among these, seven classes, 13 orders, three families, and one genus are proposed as new. Although the new classification includes many areas of overlap with previous systems, one principal departure is the increased number of classes, which reflects that "centric" and "araphid" diatoms are comprised of multiple lineages recognized here as distinct classes. By providing a more accurate representation of phylogenetic relationships, the proposed classification facilitates clearer communication about all aspects of diatom biology.

The green alga Pleodorina japonica is an interesting volvocine species that harbors abundant rickettsial endosymbionts ("MIDORIKO") within its cytoplasm. However, the diversity and transmission of these endosymbionts within the species remain unclear. In this study, we examined the presence or absence of "MIDORIKO" and the genetic diversity in 21 culture strains of the host P. japonica population from various localities in Japan. Genomic polymerase chain reactions using "MIDORIKO"-specific primers and 4',6-diamidino-2-phenylindole-staining demonstrated that only five of the 21 strains harbored "MIDORIKO." The 16S ribosomal DNA sequences of "MIDORIKO" from these five strains (1148 bp) were identical to each other and distinct from the sequences of the rickettsial endosymbionts harbored by other algal species and protists, suggesting that "MIDORIKO" from P. japonica is specific to P. japonica. The phylogenetic results for the 21 host strains, which were resolved based on three nuclear genes encoding oxygen-evolving enhancer protein 1, F1F0 ATP synthase subunit beta and actin disagreed significantly. None of the three gene phylogenies supported the close relationship of the five "MIDORIKO"-harboring strains. A recombination test using the three concatenated genes provided strong evidence of recombination. Therefore, gene flow by sexual reproduction has likely occurred in the natural habitats of P. japonica. The transmission of "MIDORIKO" among different P. japonica genotypes could also be considered to occur via sexual reproduction, although it is likely infrequent via that method given the sporadic nature of "MIDORIKO" within the P. japonica population. Although P. japonica exhibits homothallic sexual reproduction, the present genetic data demonstrate that it is undoubtedly a biological species.

Seaweed-associated microbiota distribution is influenced by factors such as symbiosis, season, life cycle, environmental conditions, and geographic location. This study investigated how microbial communities vary across different parts of benthic Sargassum thalli from nine locations spanning three regions over 600 km apart along Brazil's coast, with sites in each region within 20 km of each other. Using 16S rDNA gene sequencing of the V4 region, we identified 16,802 amplicon sequence variants (ASVs), with 1169 shared across thallus structures and 1100 shared across regions. Our analysis showed that microbial communities varied both along the thallus and between regions, though communities were similar within regions less than 20 km apart. Among thallus structures, the holdfast had the most distinct microbiota, differing from the phylloid and receptacle. This pattern was consistent across Brazil's coastline and has also been observed in studies from Singapore and Portugal. The holdfast microbiota was marked by an unidentified Alphaproteobacteria, along with sulfur-cycling families Desulfocapsaceae and Desulfosarcinaceae. Phylloids and receptacles were mainly associated with photosynthetic cyanobacteria. We also identified shared taxonomic biomarkers across Sargassum species from Asia, Europe, and South America. These results suggest that the microbiota are more influenced by the thallus structure than by geographic location. These consistent patterns across Sargassum species from different continents-Asia, Europe, and South America-support the hypothesis of microbiota specialization within morphological niches.

Here, we have presented draft genome sequences from the type strain of Almyronema epifaneia MCC 5313 as well as Thainema salinarum MCC 5402, two filamentous cyanobacteria obtained from the Sundarbans, the largest intertidal mangrove forest in the world. AntiSMASH analysis revealed that the two genomes contained distinct biosynthetic gene clusters (BGCs), which may help in supporting their adaptation to the fluctuating intertidal environment. These BGCs encode the production of secondary metabolites such as terpenes, hapalosin, anachelin, bovienimide A, and scytocyclamide. The whole-genome shotgun projects for Almyronema epifaneia MCC 5313 and Thainema salinarum MCC 5402 have been deposited in GenBank under accession numbers GCA_042788235.1 and GCA_052168235.1, respectively.

The canopy-forming feather boa kelp Egregia menziesii exhibits remarkable morphological variability across its geographic range. Regional morphotypes of Egregia were once considered separate species, but they were not determined to be genetically distinct; instead, their morphology was thought to reflect local physical or environmental conditions. Although morphological variation in Egregia has long been observed and was previously characterized through field surveys in the early 2000s, we revisited this topic using digital morphometrics (i.e., image analysis) of 1624 macroalgal herbarium specimens from California dating back to the 19th century. We observed that the morphology of Egregia (rachis texture, lateral blade shape, and blade or pneumatocyst density) varied along a latitudinal gradient and could be predicted by seawater temperature and wave height. We also identified some region-specific morphological changes in recent decades. Further, the monthly presence or absence of sporophylls in southern-region specimens provided preliminary evidence into the reproductive phenology of Egregia. Herbarium collections are invaluable for studying patterns in morphology because they showcase inter- and intraspecific variability and establish a baseline for comparison through time. Integrating natural historical and contemporary data will be critical for understanding and predicting future trends in the context of ocean warming.

Algal turfs are assemblages consisting of small marine green, brown, and red algae on the scale of millimeters to a few centimeters. Due to their small size, they have been less intensively studied by macroalgal taxonomists, and they also fall outside the scope of microalgal taxonomists, who tend to focus on smaller, often unicellular, taxa. They often have a rather simple structure and a tendency to converge onto similar morphologies with creeping and upright axes. Because of all of this, there is a substantial amount of undocumented algal biodiversity in turfs, as has been shown in several molecular surveys. Our aim in this paper was to explore some integrative taxonomic methods that could help accelerate the discovery and description of very small turf species. We focused on Pseudoderbesia, a genus of extremely small green algae from the family Bryopsidaceae. We used a combination of multifocal imaging of field-collected samples, microsample genomics, and culturing to document the Pseudoderbesia biodiversity from Heron Island on the Great Barrier Reef. Algorithmic species delimitation based on rbcL and tufA marker genes indicated that likely six (possibly five) species exist in Pseudoderbesia, but only two have been described. We have formally described the two species discovered at Heron Island as P. luxurians and P. epilithica. The latter was described using a multifocal image as the holotype, following an exception to the nomenclatural code for microscopic algae. We have justified this choice extensively, both based on an interpretation of the code and on the broader conceptual need to name newly discovered species, facilitating their use in science, conservation, and policy.

The benthic diatom species Achnanthidium minutissimum belongs to a species complex with a challenging taxonomy. Achnanthidium minutissimum has been reported to be a widespread and abundant species occurring in a broad range of freshwater habitats. However, differentiating and delimiting it from other Achnanthidium species is challenging due to the small size and great similarity of the different species, often with overlaps in morphological features. Therefore, reports of the occurrence of these taxa probably come with a large uncertainty due to potential misidentification. To gain a better understanding of the boundaries between species within the A. minutissimum species complex, we applied an integrative taxonomic approach and investigated the congruence between morphological, molecular, and ecophysiological variability among 13 monoclonal strains isolated from Germany, Sweden, and Spitsbergen. In addition to the characterization of valve morphology, we assessed their growth under different temperatures and salt concentrations and compared sequences of the rbcL marker gene as well as of a broad set of homologous loci sampled by genome skimming. Molecular and ecophysiological variability was mostly congruent with scanning electron microscopy-based morphological identification; the main exception was that two pairs of strains identified as A. cf. microcephalum and A. jackii could be distinguished neither in their ecophysiological profiles nor in their DNA sequences. Extending this integrated taxonomic approach to more strains will be beneficial for a better understanding of the morphological, molecular, and niche differentiation among different Achnanthidium species. The added value of the combined morphological-molecular-ecophysiological approach is an improved delineation of morphological features applicable for species differentiation and a better understanding of ecological differentiation.