SUMMARY The brown algal order Asterocladales, which contains the single genus Asterocladon and is the sister order of the Ectocarpales, has stellate chloroplasts. We investigated newly established isolates of Asterocladon from southern/subtropical Japan to reveal their taxonomic positions based on morphological and molecular analyses using rbc L and psa A genes. An isolate of Asteronema breviarticulatum , which was so far classified in the Scytothamnales, was revealed to belong to Asterocladon , and thus Asterocladon breviarticulatum comb. nov. is proposed. Two other isolates of Asterocladon are described here as new species, Asterocladon iriomotense sp. nov. and Asterocladon discoideum sp. nov. Asterocladon iriomotense was characterized by small filamentous thalli having oligostichous parts, phaeophycean hairs, and globular masses on which plurilocular sporangia are formed. Asterocladon discoideum was characterized by small discoid thalli with phaeophycean hairs and globular or semiglobular masses, cells of which were differentiated into plurilocular sporangia.

SUMMARY Although asexual populations and species have been frequently reported in seaweeds, their nature (e.g. origins and distribution patterns relative to closely related sexual counterparts) remains largely unknown. This is likely because determining the species identity, sex, and phase of individual organisms is often troublesome, making it difficult to comprehensively survey reproductive modes across many populations within a single species. In this study, we demonstrated that reduced‐representation sequencing (RRS), a method of sequencing a fraction of the genome using high‐throughput DNA sequencing platforms, is a simple and effective tool to investigate the reproductive modes of populations. To uncover the evolutionary trajectory of asexuals in S. promiscuus , which is known to include both sexual and asexual populations, we performed an RRS approach, MIG‐seq. By applying MIG‐seq to 122 individuals from 20 localities, mainly across Japan, we were able to: (i) estimate genetic diversity and phylogenetic relationships of populations; (ii) detect possible cryptic species ( spro1 and spro2 ); (iii) develop a pair of polymerase chain reaction‐based sex markers to identify the sex and ploidy of individuals; and (iv) discover polyploid populations in spro1 and female‐dominant populations in spro2 , both of which appear to be maintained asexually. By subsequently conducting crossing experiments and phylogenetic analysis using the mitochondrial gene cox1 and nuclear gene cetn‐int2 , we confirmed that spro1 and spro2 are reproductively isolated. We also uncovered that polyploid populations have emerged multiple times in spro1 , and one of these populations originated from hybridization between S. promiscuus and S. shibazakiorum , while the other populations originated from intraspecies crossing within S. promiscuus . It is surprising that multiple pathways to asexuality were found within such a narrow phylogenetic scope.

Summary Iron is essential for the growth and metabolism of marine algae. It also participates in the biosynthesis pathway of saxitoxins in dinoflagellates. High iron concentration may enhance the biosynthesis of saxitoxin in Alexandrium species. To better understand the effect of iron on the growth and metabolism of Alexandrium species, the dominant red tide species in Korea, A. catenella , was cultivated at four different iron concentrations (1, 10, 100, and 1000 nM). The growth data show that, within the range from 1 to 100 nM, growth was positively correlated with the iron concentration. High iron concentration (1000 nM) inhibited the growth of A. catenella. The data from the photosynthesis analysis showed that iron enhanced the maximum relative electron transport rate when the concentration was not higher than 100 nM. A similar result was also found in chlorophyll a content. At the same time, the expressions of several genes related to photosynthesis and saxitoxin synthesis were analyzed at three iron concentrations (1, 10 and 100 nM). The results show that psbE , a gene encoding iron‐binding protein in photosystem II, was significantly upregulated at the iron concentration of 100 nM. Our results increase the knowledge of the effects of iron on the growth, photosynthesis, and gene expression of A. catenella .

Plurilocular of zoidangia (left) formed on the surface of a mature Petalonia fascia (KU‐1293) cultured thallus, and swarmers (right) released from the zoidangia and settled on the substrate. In this issue Hiyama and Yoshikawa report swarmer release in P. fascia. The photographs were taken by T. Hiyama and S. Yoshikawa. image

SUMMARYA small marine dinoflagellate was isolated from fish‐kill bloom in Manila Bay, Luzon Island, Philippines, and described as a new Scrippsiella species based on the cellular morphology, thecal arrangement and molecular phylogeny inferred from internal transcribed spacer and large subunit rDNA sequences. Cells were ellipsoid, appearing teardrop‐shaped with a prominent apical horn, and the conical episome was slightly larger than the hyposome. Its plate tabulation Po, X, 4′, 3a, 7′′, 6c, 5s, 5′′′, 2′′′′ shown by scanning electron microscopy was consistent with Scrippsiella, and a thecal variation was often found in the anterior sulcal plate. The apical pore plate and canal plate were surrounded by an upright collar of apical plates 2′–4′, and the elongated canal plate was distinctive, being more than half‐length of narrow 1′ plate. The nucleus was laterally elongated and located at the center. The cysts formed in culture were spherical, small (10.1 μm in diameter), and covered by a transparent and smooth wall without calcareous crystals. In the phylogenetic trees, it was accommodated in the clade of Scrippsiella sensu lato, but its close relative was not revealed. Because the species could be differentiated from other Scrippsiella species, in the shape of cell, apical pore complex and nucleus, as well as the formation of non‐calcareous cyst, it is proposed as a novel species Scrippsiella luzonensis sp. nov. An occurrence of another species Scrippsiella masanensis, forming non‐calcareous cysts, was also reported from the Philippines.

SUMMARYExploration of Australian fucoids for aquaculture has been limited, despite their high diversity and endemism. Sargassum fusiforme (hijiki in Japanese) is a highly‐valued seaweed worldwide for human consumption, but concerns about high arsenic concentrations limit importation into countries with strict safe‐food regulations. We investigated the temporal and small‐scale spatial variation in distribution, abundance, thallus length, reproduction and biofouling of two Australian fucoids, Cystophora torulosa and Caulocystis uvifera, as candidates for aquaculture production and alternatives to hijiki. Temporal variation was assessed quarterly over a 12‐month period at a single site for each species, while small‐scale spatial variation was assessed at a single site for each species, comparing high‐shore and low‐shore for intertidal C. torulosa, and distance from the shore for subtidal C. uvifera. For C. torulosa, no significant variation in distribution, abundance or reproduction was observed; however, thallus lengths peaked in June (winter). Moreover, biofouling was minimal overall. Significant temporal variation was observed for C. uvifera with peaks in thallus lengths and reproduction in November (spring), and biofouling in February (summer). The temporal and spatial consistency in reproduction and minimal biofouling may render cultivation of C. torulosa more practical for successful commercialization than C. uvifera. Further investigation of these two Australian hijiki analogues is warranted to inform aquaculture investment.

Two species of the ultrasmall green algal genus Mychonastes, M. gigas sp. nov. (light) and M. kasaiae sp. nov. (right) originating from Lake Nakatsuna (Nagano Pref., Japan) and Lake Kasumigaura (Ibaraki Pref., Japan), respectively. The photographs were obtained by light microscopy with India ink preparation. In this issue, Nozaki and colleagues report four new species of Mychonastes from Japanese freshwater environments, based on molecular analyses and morphological characteristics. The photographs were taken by H. Nozaki. image

SUMMARYFucose‐rich sulfated polysaccharides such as fucoidans are primarily found in brown algae. These compounds possess interesting pharmacological perspectives for antiviral and antioxidant drug development. The brown alga Myriogloea major (Chordariaceae, Ectocarpales) is an endemic brown alga from Argentine Patagonia similar to other members of the Chordariaceae family used as a commercial source of fucoidans. In the present study, M. major was extracted with diluted hydrochloric acid (pH 2) solution in a protocol usually utilized for obtaining fucoidans. The dry weight from two extracts at different extraction stages (E1 and E2) represented 42% of the extracted dried biomass. Chemical analysis showed that the extracts contained between 15% (E2) and 20% (E1) of sulfate esters and approximately 80% of fucose constituents on their polysaccharides. The total phenolic content was lower than 1% (gallic acid equivalents). We analyzed the antioxidant activity of these extracts against the anti‐herpes simplex virus (HSV)‐1, HSV‐2 and bovine coronavirus. The antioxidant activity was lower than 50% at a concentration of 1 mg mL−1 in both extracts. Our findings demonstrate that, in the presence of these extracts, the viral adsorption and internalization were reduced by up to 75%. By applying its antiviral action to block the viral infection, the progeny virus released from host cells was significantly restricted, without affecting cell‐to‐cell spread of virus or virus viability.