Testudodinium gen. nov. (Dinophyceae), a new genus of sand‐dwelling dinoflagellates formerly classified in the genus Amphidinium

A new genus of sand‐dwelling photosynthetic dinoflagellate, Testudodinium Horiguchi, Tamura, Katsumata et A. Yamaguchi is proposed based on Testudodinium testudo (Herdman) Horiguchi, Tamura, Katsumata, et A. Yamaguchi comb. nov. (Basionym: Amphidinium testudo Herdman) and a new species in this new genus, Testudodinium maedaense Katsumata et Horiguchi sp. nov. is described. Amphidinium corrugatum is also transferred to this genus, making a new combination T. corrugatum (Larsen et Patterson) Horiguchi, Tamura et A. Yamaguchi. These three species are similar to the members of the genus Amphidinium in having an extremely small episome and a dorsoventrally flattened cell body. They are, however, distinguished from the genus Amphidinium seusu stricto by the possession of a distinct longitudinal furrow in the middle of ventral side of the episome. Phylogenetic trees based on small subunit (SSU) rDNA revealed that all three of these Testudodinium species formed a robust clade and, although statistical support is not high, the tree suggests Testudodinium clade is not closely related to Amphidinium seusu stricto clade. The morphological differences together with molecular data support the establishment of a new genus for A. testudo and its related species.     

Fine-scale diversity and specificity in the most prevalent lineage of symbiotic dinoflagellates (Symbiodinium, Dinophyceae) of the Caribbean

The success of coral reefs is due to obligate mutualistic symbioses involving invertebrates and photosynthetic dinoflagellate symbionts belonging to the genus Symbiodinium. In the Caribbean, the vast majority of octocorals and other invertebrate hosts associate with Symbiodinium clade B, and more selectively, with a single lineage of this clade, Symbiodinium B1/B184. Although B1/B184 represents the most prevalent Symbiodinium in the Caribbean, there is little evidence supporting fine-scale diversity and host-alga specificity within this lineage. We explored simultaneously the questions of diversity and specificity in Symbiodinium B1/B184 by sequencing the flanking regions of two polymorphic microsatellites from a series of Symbiodinium clade B cultures along with Symbiodinium B1/B184 populations of the octocorals Pseudopterogorgia elisabethae, P. bipinnata and Gorgonia ventalina. Seven unique sequence variants were identified based on concatenation of the two loci. Phylogenetic analyses of these variants, which we refer to as phylotypes, recognized five as belonging to B1/B184, thus providing the first evidence of distinct taxa within this Symbiodinium lineage. Furthermore, sympatric P. elisabethae and P. bipinnata at San Salvador in the Bahamas were found to harbour distinct Symbiodinium B1/B184 phylotypes, demonstrating unequivocally the existence of fine-scale specificity between Caribbean octocorals and these algae. Taken together, this study exemplifies the complex nature of Symbiodinium biodiversity and specificity.     

Studies on woloszynskioid dinoflagellates VI: description of Tovellia aveirensis sp. nov. (Dinophyceae), a new species of Tovelliaceae with spiny cysts

A new species of Tovellia, T. aveirensis, is described on the basis of light (LM) and scanning electron microscopy (SEM) of motile cells and resting cysts, complemented with transmission electron microscopy (TEM) of flagellate cells and phylogenetic analysis of partial sequences of the large subunit ribosomal rRNA gene. Both vegetative cells and several stages of a life cycle involving sexual reproduction and the production of resting cysts were examined in cultures established from a tank in the University of Aveiro campus. Vegetative cells were round and little compressed dorsoventrally; planozygotes were longer and had a proportionally larger epicone. Chloroplast lobes were shown by TEM to radiate from a central, branched pyrenoid, although this was difficult to ascertain in LM. The amphiesma of flagellate cells had mainly 5 or 6-sided vesicles with thin plates, arranged in 5–7 latitudinal series on the epicone, 3–5 on the hypocone. The cingulum had 2 rows of plates, the posterior row extending into the hypocone and crossed by a series of small projecting knobs along the lower edge of the cingulum. A line of narrow amphiesmal plates extended over the cell apex, from near the cingulum on the ventral side to the middle of the dorsal side of the epicone. Eight or 9 narrow amphiesmal plates lined each side of this apical line of plates (ALP). Resting cysts differed from any described before in having numerous long, tapering spines with branched tips distributed over most of the surface. Most mature cysts showed an equatorial constriction. Neither cysts nor motile cells were seen to accumulate red cytoplasmic bodies in any stage of the cultures. The phylogenetic analysis placed, with high statistical support, the new species within the genus Tovellia; it formed a clade, with moderate support, with T. sanguinea, a species notable for its reddening cells.     

Pyramidodinium spinulosum sp. nov. (Dinophyceae), a sand‐dwelling non‐motile dinoflagellate from the seafloor (36 m deep) off Mageshima Island,Kagoshima, Japan

A new species of benthic marine dinoflagellate, Pyramidodinium spinulosum Horiguchi, Moriya, Pinto & Terada is described from the deep (36 m) seafloor off Mageshima Island, Kagoshima Prefecture, Japan in the subtropical region of the northwest Pacific. The life cycle of the dinoflagellate consists of a dominant, attached, dome‐shaped, vegetative form and short‐lasting, motile cell. Asexual reproduction takes place by the formation of two motile cells within each non‐motile cell. The released motile cells swim only for a short period and transform directly into the dome‐shaped vegetative form. The duration of the cell cycle varies and can be extremely long, ranging 5–38 days under culture conditions. The non‐motile cell is enclosed by a cell wall and its surface is covered with many (80 – 130) spines of various length. The dinoflagellate is photosynthetic and contains many (more than 50) discoidal chloroplasts. Phylogenetic analysis reveals that the dinoflagellate is closely related to the type species of the genus Pyramidodinium, P. atrofuscum which also possesses a dominant, attached, non‐motile form. However, P. spinulosum can be clearly distinguished from P. atrofuscum by the cell shape (dome‐shaped vs. pyramid‐shaped) and surface ornamentation (spines vs. wart‐like processes) of the non‐motile form. Based on these morphological differences together with molecular evidence, it was concluded that this organism from a deep water sand sample should be described as a second species of the genus Pyramidodinium, P. spinulosum.     

Gymnoxanthella radiolariae gen. et sp. nov. (Dinophyceae), a dinoflagellate symbiont from solitary polycystine radiolarians

The symbiotic dinoflagellate Gymnoxanthella radiolariae T. Yuasa et T. Horiguchi gen. et sp. nov. isolated from polycystine radiolarians is described herein based on light, scanning and transmission electron microscopy as well as molecular phylogenetic analyses of SSU and LSU rDNA sequences. Motile cells of G. radiolariae were obtained in culture, and appeared to be unarmored. The cells were 9.1–11.4 μm long and 5.7–9.4 μm wide, and oval to elongate oval in the ventral view. They possessed an counterclockwise horseshoe‐shaped apical groove, a nuclear envelope with vesicular chambers, cingulum displacement with one cingulum width, and the nuclear fibrous connective; all of these are characteristics of Gymnodinium sensu stricto (Gymnodinium s.s.). Molecular phylogenetic analyses also indicated that G. radiolariae belongs to the clade of Gymnodinium s.s. However, in our molecular phylogenetic trees, G. radiolariae was distantly related to Gymnodinium fuscum, the type species of Gymnodinium. Based on the consistent morphological, genetic, and ecological divergence of our species with the other genera and species of Gymnodinium s.s., we considered it justified to erect a new, separate genus and species G. radiolariae gen. et sp. nov. As for the peridinioid symbiont of radiolarians, Brandtodinium has been erected as a new genus instead of Zooxanthella, but the name Zooxanthella is still valid. Brandtodinium is a junior synonym of Zooxanthella. Our results suggest that at least two dinoflagellate symbiont species, peridinioid Zooxanthella nutricula and gymnodinioid G. radiolariae, exist in radiolarians, and that they may have been mixed and reported as “Z. nutricula” since the 19th century.     

Molecular phylogeny of the spiny-surfaced species of the dinoflagellate Prorocentrum with the description of P. thermophilum sp. nov. and P. criophilum sp. nov. (Prorocentrales,Dinophyceae)

Spiny-surfaced species of Prorocentrum form harmful algal blooms, and its taxonomic identity is obscure due to the size and shape variability. Molecular phylogenies reveal two major clades: one for P. cordatum with sequences mainly retrieved as P. minimum, and the other for P. shikokuense with sequences also retrieved as P. dentatum and P. donghaiense. Several closely related clades still need to be characterized. Here, we provide nuclear SSU and LSU rRNA genes, and nuclear ITS region (ITS1-5.8S gene-ITS2) sequences of the strain CCMP3122 isolated from Florida (initially named P. donghaiense) and strains Prorocentrum sp. RCC6871–2 from the Ross Sea, Antarctica. We describe Prorocentrum thermophilum sp. nov. based on the strain CCMP3122, a species also distributed in the open waters of the Gulf of Mexico, New Zealand, and the Arabian Gulf; and Prorocentrum criophilum sp. nov. based on the strain RCC6872, which is distributed in the Antarctic Ocean and Arctic Sea. Prorocentrum thermophilum is roundish (~14 μm long, ~12 μm wide), with an inconspicuous anterior spine-like prolongation under light microscopy, valves with tiny, short knobs (5–7 per μm²), and several (<7) large trichocyst pores (~0.3 μm) in the right valve, as well as smaller pores (~0.15 μm). Prorocentrum criophilum is round in valve view (~11 μm long, 10 μm wide) and asymmetrically roundish in lateral view, the periflagellar area was not discernible under light microscopy, valves with very tiny, short knobs (6–10 per μm²), and at least 12 large pores in the right valve. Other potentially undescribed species of spiny-surfaced Prorocentrum are discussed.     

Genetics and Morphology Characterize the Dinoflagellate Symbiodinium voratum,n. sp., (Dinophyceae) as the Sole Representative of Symbiodinium Clade E

Dinoflagellates in the genus Symbiodinium are ubiquitous in shallow marine habitats where they commonly exist in symbiosis with cnidarians. Attempts to culture them often retrieve isolates that may not be symbiotic, but instead exist as free‐living species. In particular, cultures of Symbiodinium clade E obtained from temperate environments were recently shown to feed phagotrophically on bacteria and microalgae. Genetic, behavioral, and morphological evidence indicate that strains of clade E obtained from the northwestern, southwestern, and northeastern temperate Pacific Ocean as well as the Mediterranean Sea constitute a single species: Symbiodinium voratum n. sp. Chloroplast ribosomal 23S and mitochondrial cytochrome b nucleotide sequences were the same for all isolates. The D1/D2 domains of nuclear ribosomal DNA were identical among Western Pacific strains, but single nucleotide substitutions differentiated isolates from California (USA) and Spain. Phylogenetic analyses demonstrated that S. voratum is well‐separated evolutionarily from other Symbiodinium spp. The motile, or mastigote, cells from different cultures were morphologically similar when observed using light, scanning, and transmission electron microscopy; and the first complete Kofoidian plate formula for a Symbiodinium sp. was characterized. As the largest of known Symbiodinium spp., the average coccoid cell diameters measured among cultured isolates ranged between 12.2 (± 0.2 SE) and 13.3 (± 0.2 SE) μm. Unique among species in the genus, a high proportion (approximately 10–20%) of cells remain motile in culture during the dark cycle. Although S. voratum occurs on surfaces of various substrates and is potentially common in the plankton of coastal areas, it may be incapable of forming stable mutualistic symbioses.     

A revision of the Dip lop salts group of dinoflagellates (Dinophyceae) based on material from the British Isles

SEM has made possible a detailed re-examination of the thecal plates of marine dinoflagellates belonging to the Diplopsalis group which have been collected in an extensive survey of the seas around the British Isles. Six genera are recognized: Diplopsalis, Diplopsalopsis, Dissodium, Oblea, Zygabikodinium and die new genus and species Boreadinium pisiformis Dodge 8c Hermes. The confused taxonomic history of the group is discussed, the valid species are listed and a key for the identification of the genera is given.     

Ankistrodinium armigerum sp. nov. (Dinophyceae), a new species of heterotrophic marine sand‐dwelling dinoflagellate from Japan and Australia

A new heterotrophic sand‐dwelling dinoflagellate, Ankistrodinium armigerum K. Watanabe, Miyoshi, Kubo, Murray et Horiguchi sp. nov., is described from Ishikari Beach, Hokkaido, Japan and Port Botany, NSW, Australia. The dinoflagellate is laterally compressed, possessing a short triangular epicone and a large sac‐like hypocone. It possesses a right‐handed cingulum and a deeply‐incised sulcus. The sulcus descends towards the posterior of the cell where it becomes much deeper and wider, resulting in a bilobed ventral side to the hypocone, with a greater excavation of the left lobe than the right. In addition, the right lobe of the hypocone is shorter than the left lobe, which allows a partial view of the left sulcal wall when the cell is viewed from its right side. The sulcus ascends in the epicone to form an apical groove. The apical groove is linear but terminates in an ellipsoid fashion and its extremity approaches, but does not form a closed loop with the apical end of the linear portion. The dinoflagellate possesses two distinct size classes of trichocysts. The large trichocysts are located in the posterior part of the cell, while small trichocysts are distributed throughout the cell. The dinoflagellate shares morphological characteristics with the heterotrophic sand‐dwelling dinoflagellate, Ankistrodinium semilunatum, the type species of the genus. These include a laterally compressed cell, a right‐handed cingulum, a deeply‐incised sulcus and the same basic structure to the apical groove. Molecular phylogenetic analyses based on small and large subunits of rDNA showed that in both trees, A. semilunatum and A. armigerum formed a robust clade, suggesting that these two species are closely related. Because no organism with the characteristics of this species exists and because this species is closely related to A. semilunatum, we concluded that this species should be described as a second species of the genus Ankistrodinium.     

Studies on woloszynskioid dinoflagellates V. Ultrastructure of Biecheleriopsis gen. nov., with description of Biecheleriopsis adriatica sp. nov.

An isolate of the very small marine dinoflagellate Biecheleriopsis adriatica gen. et sp. nov. (12–15 µm long) has been examined by light, scanning and transmission electron microscopy, combined with partial sequencing of nuclear-encoded large subunit rRNA. Biecheleriopsis is a genus of thin-walled dinoflagellates, related to Biecheleria and the taxonomic group of Polarella , Protodinium and Symbiodinium , the latter comprising mainly symbionts of marine invertebrates. The mixotrophic Biecheleriopsis adriatica is characterized by: (i) a special type of apical furrow apparatus; (ii) an eyespot of Type E sensu Moestrup and Daugbjerg; (iii) an unusual type of pyrenoid; and (iv) a spiny resting cyst. Thin sections showed the presence a fibrous connection between the flagellar apparatus and a finger-like extension of the nucleus ('rhizoplast'). It forms a physical connection between the flagella and the nucleus. This unusual structure has previously been considered to characterize the 'true' gymnodinioids, represented by Gymnodinium sensu Daugbjerg et al. and related forms. However, the apical furrow apparatus and the nuclear envelope of Biecheleriopsis are woloszynskioid rather than gymnodinioid. The related genus Biecheleria lacks a rhizoplast, and it also lacks a 51-base pair fragment of domain D2 of the large subunit rRNA, which is present in other woloszynskioids. A physical connection between the flagellar apparatus and the nucleus mediated by a fibrous structure is known in other groups of protists, for example, the 'rhizoplast' of many heterokont flagellates, some green algal flagellates, etc. The phylogenetic significance of a rhizoplast in two groups of dinoflagellates that are only distantly related is presently difficult to assess.     

A new potentially toxic Azadinium species (Dinophyceae) from the Mediterranean Sea,A. dexteroporum sp. nov.

A new photosynthetic planktonic marine dinoflagellate, Azadinium dexteroporum sp. nov., is described from the Gulf of Naples (South Tyrrhenian Sea, Mediterranean Sea). The plate formula of the species, Po, cp, X, 4′, 3a, 6″, 6C, 5?S, 6? and 2″″, is typical for this recently described genus. Azadinium dexteroporum is the smallest rep‐resentative of the genus (8.5 μm average length, 6.2 μm average width) and shares the presence of a small antapical spine with the type species A. spinosum and with A. polongum. However, it differs from all other Azadinium species for the markedly asymmetrical Po plate and the position of the ventral pore, which is located at the right posterior end of the Po plate. Another peculiarity of A. dexteroporum is the pronounced concavity of the second intercalary plate (2a), which appears collapsed with respect to the other plates. Phylogenetic analyses based on the large subunit 28S rDNA (D1/D2) and the internal transcribed spacer (ITS rDNA) support the attribution of A. dexteroporum to the genus Azadinium and its separation from the other known species. LC/MS‐TOF analysis shows that Azadinium dex‐teroporum produces azaspiracids in low amounts. Some of them have the same molecular weight as known compounds such as azaspiracid‐3 and ‐7 and Compound 3 from Amphidoma languida, as well as similar fragmentation patterns in some cases. This is the first finding of a species producing azapiracids in the Mediterranean Sea.     

Biecheleria tirezensis sp. nov. (Dinophyceae,Suessiales), a new halotolerant dinoflagellate species isolated from the athalassohaline Tirez natural pond in Spain

A new euryhaline and eurythermal dinoflagellate species, Biecheleria tirezensis sp. nov., is described based on samples taken from an extreme environment, the athalassohaline and particularly sulphate-rich Tirez natural pond (Spain). This species is able to survive in salinities from almost fresh water up to 56 and over a 5–25°C temperature range. Thus, the ecological characteristics of this isolate differentiate it from other species of the same genus. Its morphology, as examined by light, scanning and transmission electron microscopy, shows that the cells are almost spherical, with several series of amphiesmal vesicles. It also has a single elongate amphiesmal vesicle (EAV) observed by SEM and the eyespot has a type E structure, typical of Biecheleria. Spherical and smooth cysts were observed in old cultures. The pigment composition is typical of a peridinin-containing dinoflagellate. Phylogeny inferred from nuclear rDNA SSU, ITS and LSU sequences showed the isolate belongs to the genus Biecheleria, closest to B. cincta and B. brevisulcata. Modelling and analysis of the secondary structure of its ITS2 region, and that of other species of the same genus and some representatives of the most closely related genera, indicated that the isolate represents a new species clearly separated from but related to B. cincta. The criterion of the presence of Compensatory Base Changes (CBCs) in the secondary structure of the ITS2 region as an indicator of species differentiation confirmed this, supporting the establishment of the Tirez pond isolate as a new species of Biecheleria.     

Amphidoma languida sp. nov. (Dinophyceae) reveals a close relationship between Amphidoma and Azadinium

Toxic algae such as Alexandrium and Azadinium have an important ecological impact and have originated several times independently within the dinophytes. Their closest relatives, however, are mostly unknown at present. A new dinophyte species, Amphidoma languida sp. nov., was isolated from Bantry Bay (Ireland) during a period of elevated azaspiracid toxicity in mussels. The new species was described in detail, and its phylogenetic position was analysed, by using a combination of light and electron microscopy, chemical detection methods, and sequence comparison of concatenated ribosomal RNA sequence data. Morphological similarities, such as cingular and hypothecal plates, the number and arrangement of sulcal plates, and the characteristic apical pore complex with a small X-plate centrally invading the first apical plate, indicated a close relationship between Amphidoma and Azadinium. However, no known azaspiracid analogues were detected in A. languida by liquid chromatography coupled with tandem mass-spectrometry. In a molecular phylogeny, the Amphidomataceae including Amphidoma and Azadinium were an independent lineage among other monophyletic major groups of the dinophytes such as the Suessiales, Prorocentrales, Gonyaulacales, and Peridiniales. Thus, the taxonomic affiliation of Azadinium is clarified, and our data may prove helpful in the development of specific and reliable molecular detection methods of toxic Azadinium.     

A review of the genus Dysalotus (Percomorphacea: Chiasmodontidae), with the description of Dysalotus pouliulii sp. nov.

A new species of Dysalotus (family Chiasmodontidae) known only from off the Hawaiian archipelago is described here as Dysalotus pouliulii sp. nov. It differs from all other species of Dysalotus in having a greater number of teeth on the premaxilla (151–198 v. 60–138) and dentary (136–199 v. 76–132) and in a shorter upper jaw [51·9–54·9% of head length (L_H) v. 62·4–74·4% L_H] and lower jaw (64·8–67·4% in L_H v. 75·3–88·1% in L_H). A key for the species of Dysalotus and an updated distribution map are provided. http://zoobank.org/urn:lsid:zoobank.org:pub:E9B5F1DC‐52E0‐4F53‐9109‐2A8E252AE8CE .