THREE NEW BENTHIC SPECIES OF PROROCENTRUM (DINOPHYCEAE) FROM CARRIE BOW CAY,BELIZE: P. SABULOSUM SP. NOV., P. SCULPTILE SP. NOV., AND P. ARENARIUM SP. NOV.1

Three new benthic, sand-dwelling dinqflagellate species, Prorocentrum sabulosum, Prorocentrum scuptile, and Prorocentrum arenarium, from coral rubble are described from scanning electron micrographs. Species were identified based on shape, size, surface micromorphology, ornamentation of thecal plates, and architecture of the periflagellar area and intercalary band. Cells of P. sabulosum are oval with a cell size of 48–50 μm long and 41–48 μm wide. The areolae are round to oval and numerous (332–450 per valve) and range from 1 to 1.6 μm in size. The periflagellar area of P. sabulosum bears a wide V-shaped depression with a flat ridge and lacks ornamentation; it accommodates six pores: one large flagellar pore, an adjacent smaller auxiliary pore, and four pores of unknown function. The flagellar and auxiliary pores are surrounded by a narrow apical collar. The intercalary band of P. sabulosum is smooth. Prorocentrum sculptile cells are broadly oval, 32–37 nm long, and 30–32 μm wide in valve view with a deep-sculptured apical area. The valves are smooth and are marked with shallow depressions (856–975 per valve). Some of these depressions have a small round opening (0.13 μm in diameter). The periflagellar area is V-shaped with a deeply indented depression; it accommodates the two flagella and a thin angled apical plate. The intercalary band is smooth. Prorocentrum arenarium cells are nearly round in valve view 30–32 μm in diameter. Thecal surface is smooth with scattered kidney-shaped valve poroids (65–73 per valve) and marginal poroids (50–57 per valve). Length and width of poroids are 0.62 μm and 0.36 μm, respectively. The periflagellar area is an unornamented, broad triangle into which a large flagellar pore and a smaller auxiliary pore are fitted. Both flagella, longitudinal and transverse, protrude from the flagellar pore. The intercalary band is smooth. The presence of a peduncle-like structure (2–3 μm long) in P. arenarium was observed situated in the flagellar pore.     

THREE NEW BENTHIC SPECIES OF PROROCENTRUM (DINOPHYCEAE) FROM BELIZE: P. NORRISIANUM SP. NOV., P. TROPICALIS SP. NOV., and P. RETICULATUM SP. NOV.1

Three new benthic, photosynthetic dinoflagellate species, Prorocentrum norrisianum, Prorocentrum tropicalis, and Prorocentrum reticulatum, from floating detritus and coral rubble of Central America are described from scanning electron micrographs. Species were identified based on shape, size, surface micromorphology, thecal plate ornamentation, and architecture of the periflagellar area and intercalary band. Cells of P. norrisianum are ovate with a cell size of 20–25 μm long and 13–16 μm wide. The theca is delicate, its surface smooth, pores species specific with 95 to 105 pores per valve. Pores are round with a diameter of about 0.1 μm. The periflagellar area is V-shaped, located on the right valve in a shallow depression. It has no ornamentation. The flagellar and auxiliary pores are unequal in size. The intercalary band is smooth. Prorocentrum tropicalis cells are ovoid, 50–55 μm long and 40–45 μm wide in valve view with maximum width behind the middle region, narrow at the anterior end. The periflagellar area, situated in the right valve, is a V-shaped wide triangle with a deeply indented depression; the left valve exhibits a flat ridge. The periflagellar area is unornamented, and the flagellar and auxiliary pores are unequal in size. The valve surface is rugose with evenly distributed valve poroids. Each poroid appears to have a small dome in the center. The intercalary band is rimlike around the cell margin, granulated, and horizontally striated. Prorocentrum reticulatum cells are oblong in valve view; cells are 55–60 μm long and 40–45 μm wide. Thecal surface is reticulated; it is composed of a labyrinth of ridges with alternating depressions that vary in size and shape. Each depression has a narrow, oblong-kidney-shaped opening about 0.6 μm long. The periflagellar area is a deep, V-shaped triangle. The right valve of P. reticulatum is excavated, and contains a large flagellar pore and a smaller auxiliary pore surrounded by a narrow apical collar. The left valve margin exhibits a curved flat ridge. The intercalary band is smooth.     

MORPHOLOGIC DETAILS OF SIX BENTHIC SPECIES OF PROROCENTRUM (PYRROPHYTA) FROM A MANGROVE ISLAND,TWIN CAYS,BELIZE, INCLUDING TWO NEW SPECIES1

Two new dinoflagellate species, Prorocentrum hoffmannianum and Prorocentrum ruetzlerianum, and four known species, Prorocentrum emarginatum Fukuyo 1981, Prorocentrum mesicanum Tafall 1942, Prorocentrum concavum Fukuyo 1981, and Prorocentrum lima (Ehr.) Dodge 1975, from floating detritus and sediments in a subtropical mangrove island, Twin Cays, Belize, Central America are described from scanning electron micrographs. Differences in the following characters of surface micromorphology separated the species: ornamentation of thecal plates (shape, size, and number of valve pores and areolae) and the architecture of the periflagellar area and intercalary band.     

PHYLOGENETIC ANALYSIS OF NINE SPECIES OF PROROCENTRUM (DINOPHYCEAE) INFERRED FROM 18S RIBOSOMAL DNA SEQUENCES, MORPHOLOGICAL COMPARISONS, AND DESCRIPTION OF PROROCENTRUM PANAMENSIS, SP. NOV.

Sequences of 18S rRNA genes were obtained from eight species of Prorocentrum Ehrenberg: P. minimum (Pavillard) Schiller, P. mexicanum Osorio Tafall, P. emarginatum Fukuyo, P. lima (Ehrenberg) Dodge, P. arenarium Faust, P. maculosum Faust, P. concavum Fukuyo, and P. panamensis, sp. nov. Prorocentrum panamensis is a new species of tropical dinoflagellate isolated from a benthic coral reef on the Pacific coast of Panama and described here using scanning electron microscopy. Cells are heart shaped, 46–52 μm long and 43–46 μm wide. The valve surfaces are areolate except in the central area. Pores of 0.15 μm in diameter are scattered in areolae, mainly around the periphery of the cell. The right valve has a specific ovoid depression with numerous appressed pores; we named this structure the sieve-like depression. The periflagellar area is nearly ovoid, located in a shallow depression, and almost equally set into both valves. It is unornamented (no apical expansion) but has numerous depressions in platelets. The flagellar and auxiliary pores are different in size and shape. The intercalary band is transversally striated. Phylogenetic relationships of gonyaulacoid, peridinioid, gymnodinioid, and prorocentroid dinoflagellates were inferred from complete 18S rDNA sequences. Two distinct phylogenetic analyses are presented for armored and unarmored Dinophyceae in an attempt to make the phylogenetic relationships between these different kinds of organisms clearer. The Prorocentrales appear to have a common origin, although two groups of Prorocentrum spp. are apparent. The first group includes benthic, symmetrical species (P. lima, P. arenarium, P. maculosum, and P. concavum). The second group contains planktonic and bentho-planktonic species (P. micans Ehrenberg, P. minimum, P. mexicanum, and P. panamensis sp. nov.). Genetic distances between species within these two groups were high; however, the divergence between the two groups seems to have occurred late in dinoflagellate evolution. In addition, the bentho-planktonic P. emarginatum appeared distantly related to both groups; however,its 18S rDNA sequence shares specific nucleotide substitutions with the two groups, suggesting an older origin of this species compared to the others. A morphological interpretation of this phylogenetic analysis is made on the basis of the specific structure of the periflagellar area. Finally, genetic data and morphological observations support the hypothesis that the genus Prorocentrum is rather heterogeneous; several species could be considered to constitute distinct genera.     

MORPHOLOGY AND MOLECULAR PHYLOGENY OF A NEW MARINE SAND‐DWELLING PROROCENTRUM SPECIES,P. TSAWWASSENENSE (DINOPHYCEAE,PROROCENTRALES), FROM BRITISH COLUMBIA,CANADA1

A new marine benthic, sand‐dwelling Prorocentrum species from the temperate region of the Pacific coast of British Columbia, Canada, is described using LM and EM and molecular phylogenetic analyses. The cells have a broad oval shape, 40.0–55.0 μm long and 30.0–47.5 μm wide, and a wide U‐shaped periflagellar area on the right thecal plate. The left thecal plate consists of a straighter apical outline in the form of a raised ridge. Five to six delicate apical spines in the center of the periflagellar area are present. The nucleus is located in the posterior region of the cell, and a conspicuous pusule is located in the anterior region of the cell. The cells have golden‐brown chloroplasts with a compound, intrachloroplast pyrenoid that lacks a starch sheath. The thecal plates are smooth with round pores of two different sizes. The larger pores are arranged in a specific pattern of radial rows that are evenly spaced around the plate periphery and of irregular rows (or double rows) that form an incomplete “V” at the apical end of the plates. Large pores are absent in the center of the left and right thecal plates. The intercalary band is striated transversely and also has faint horizontal striations. Trichocysts and two types of mucocysts are present. The molecular phylogenetic position of Prorocentrum tsawwassenense sp. nov. was inferred using SSU rDNA sequences. This new species branched with high support in a Prorocentrum clade containing both benthic and planktonic species.     

MORPHOLOGY AND MOLECULAR PHYLOGENY OF PROROCENTRUM CONSUTUM SP. NOV. (DINOPHYCEAE), A NEW BENTHIC DINOFLAGELLATE FROM SOUTH BRITTANY (NORTHWESTERN FRANCE)1

A new marine benthic Prorocentrum species from sandy habitats of South Brittany (northwestern France), P. consutum sp. nov., is described using LM and SEM and molecular phylogenetic analyses. Cells have a subcircular to broadly ovoid shape and are plainly flattened. They are 57–61 μm long and 52–55 μm wide. A central pyrenoid is present, and the kidney‐shaped nucleus is positioned in the posterior region. In right valve view, the periflagellar area is deeply excavated, and the left valve forms a prominent apical ridge. The periflagellar area consists of nine platelets, and a small narrow collar is present around the flagellar pore. The ornamentation of this new species is very peculiar and is characterized by a ring of round areolae located at the periphery of the valves, each areola containing three or four pores. Apart from this ring of areolae, the cell surface is smooth and with scattered pores. Pores are not present in the center of the right or left valve. The intercalary band is generally narrow and faintly striated horizontally. The molecular phylogenetic position of P. consutum sp. nov. was inferred using SSU and LSU rDNA. In both analyses, this species branched with high support in the clade comprising species with a symmetric shape and appeared to be a sister group to that formed by P. lima and other tropical benthic species, such as P. arenarium, P. belizeanum, P. hoffmannianum, and P. maculosum.     

PROROCENTRUM BIMACULATUM SP. NOV. (DINOPHYCEAE,PROROCENTRALES), A NEW BENTHIC DINOFLAGELLATE SPECIES FROM KUWAIT (ARABIAN GULF)1

A new benthic dinoflagellate species, Prorocentrum bimaculatum sp. nov., is studied from Kuwait’s marine sediments, based on detailed morphological and molecular data. Cells are large, oblong oval in shape. They are 49.9–55.3 μm long and 38.4–43.2 μm wide. The ornamentation of this new species is peculiar, and characterized by smooth valves with large pores (0.32–0.50 μm) scattered on their surface, except in two circular patches of ～15 μm in diameter, devoid of ornamentation and located on both sides of the valve centers. The periflagellar area is widely triangular, located in a moderate excavation of the right valve, and comprises nine platelets. The intercalary band of P. bimaculatum is smooth. The molecular phylogenetic position of this new taxon was inferred from SSU and LSU rDNA genes. In both phylogenetic analyses, P. bimaculatum branched with high support with Prorocentrum consutum and formed a clade sister to the one including P. lima and related species such as P. arenarium, P. belizeanum, P. hoffmannianum, and P. maculosum. From the phylogenetic study, since most species related to P. bimaculatum are known for their toxic effects and production of okadaic acid, this new species can be considered as a potential toxin producer, but this has to be analyzed.     

MICROMORPHOLOGY OF A SMALL DINOFLAGELLATE PROROCENTRUM MARIAE-LEBOURIAE (PARKE & BALLATINE) COMB. NOV.1,2,3

The surface structures of the bivalvate dinoflagellate Prorocentrum mariae-lebouriae are described in detail. It has an almost spheroidal shape in face-view, a compressed saucer-shape in side view, with a distinct striated band at the edge of the cell. Its surface is covered with small spines in a regular pattern, with 450 nm distance between pairs. The spines are 100–120 nm wide and 200–300 nm long. There are 600–700 spines on each valve. At the anterior cell end, one of the values has a V-shaped depression which contains a specialized structure accommodating the 2 flagellar pores. The flagellar pores are-enclosed by 8 small, thick plates held together and to the values by sutures. The flagellar pore area consists of 2 distinct structures: an apical collar possessing a curved forked plate and a larger structure composed of an unbranched, plate. There are 2 flagellar canals located between the flagellar pore plates. Beneath each flagellar canal lies a row of 11 microtubules. A row of microtubules forming a microtubular cylinder is situated adjacent to the oblong flagellar canal near a simple pusule. The microtubular cylinder encircles electron dense bodies. The bases of the longitudinal and transverse flagella appear to lie at an angle to each other. The above features are illustrated with transmission and scanning electron micrographs.     

Morphology and Phylogeny of Prorocentrum texanum sp. nov. (Dinophyceae): A New Toxic Dinoflagellate from the Gulf of Mexico Coastal Waters Exhibiting Two Distinct Morphologies

A new planktonic species of Prorocentrum is described from the Gulf of Mexico. First observed with the Imaging FlowCytobot, Prorocentrum texanum sp. nov. was characterized using LM, SEM, and TEM along with sequencing of the SSU, LSU, and ITS ribosomal regions and the mitochondrial cob and cox1 regions. P. texanum sp. nov. is a round to oval bivalvate dinoflagellate, with a prominent anterior, serrated solid flange on periflagellar a platelet and an opposing short, flat flange on the h platelet. The periflagellar area consists of 10 platelets. Both left and right valves have shallow round depressions and two‐sized valve pores. The anterior ejectosome pore pattern differs between the left and right valve in relation to the periflagellar area and margins. Ten to eleven rows of tangential ejectosome pores are present on each valve. P. texanum sp. nov. has two varieties which exhibit distinct morphotypes, one round to oval (var. texanum) and the other pointed (var. cuspidatum). P. texanum var. cuspidatum is morphologically similar to P. micans in surface markings, but is smaller, and has a serrated periflagellar flange, and is genetically distinct from P. micans. Cytologically, P. texanum has two parietal chlo‐roplasts, each with a compound, interlamellar pyrenoid, trichocysts, fibrous vesicles that resemble mucocysts, pusules, V‐ to U‐shaped posterior nucleus, golgi, and tubular mitochondria. No genetic difference was found between the two varieties in the five genes examined. Phylogenetic analysis of the SSU, LSU, and ITS ribosomal regions place P. texanum sp. nov. as a sister group to P. micans. One isolate of P. texanum var. texanum produces okadaic acid.     

A FURTHER SEM STUDY OF MARINE BENTHIC DINOFLAGELLATES FROM A MANGROVE ISLAND,TWIN CAYS,BELIZE, INCLUDING PLAGIODINIUM BELIZEANUM GEN. ET SP. NOV.1

This study indicates that bilaterally flattened, armored, benthic dinoflagellates are more diverse in morphology than previously known. A new species, Plagiodinium belizeanum Faust et Balech gen. et. sp. nov., is described in floating detritus from Twin Cays, Belize, mangrove habitats. Plagiodinium belizeanum cells are small, with dimensions of 26.5–30.5 μm in length, 20–24.5 μm in width, and 6.5–8.5 μm in depth. Cells are oblong and bilaterally compressed with a posteriorly located, spherical nucleus, many chloroplasts, and spherical starch granules. The epitheca descends ventrally, is cap-shaped, and is composed of five plates and a very small platelet provisionally named P₀ situated in the center. The epitheca is narrowly oval in apical view with a pointed truncated ventral side and a rounded dorsal side. The cingulum is composed of five plates. The hypotheca is constructed of five posteriorly elongated postcingular plates and one antapical plate. The sulcus is very short and narrow, comprised of five very small plates. The thecal plate arrangement of P. belizeanum is P₀, 5′, O″, 5C, 5″′, 1″″, 5S. No lists are present. Thecal plates have a smooth surface with small and irregularly scattered pores. The intercalary band is smooth on outer cell surface and broadly striated on its inner surface. We conclude that P. belizeanum represents a new, benthic, peridinioid, armored genus, Plagiodinium gen. nov. The taxonomic position of P. belizeanum sp. nov. is compared to related sand-dwelling and bilaterally flattened benthic dinoflagellates.     

SPECIES BOUNDARIES IN THE TOXIC DINOFLAGELLATE PROROCENTRUM LIMA (DINOPHYCEAE,PROROCENTRALES), BASED ON MORPHOLOGICAL AND PHYLOGENETIC CHARACTERS1

Wild and cultured specimens of Prorocentrum lima (Ehrenb.) F. Stein from 26 widely different areas in 13 countries were examined in order to determine consistent characters for delimiting species boundaries in this taxon. The morphological characters valve shape, valve size, valve ornamentation, number and shape of valve pores, number and shape of marginal pores, and periflagellar platelets were observed using LM and SEM, and two molecular genetic regions were sequenced. We identified stable morphological characters that were consistent among wild specimens and all cultures, which were valve shape, valve ornamentation, and number and arrangement of periflagellar platelets. All cultures of P. lima identified by these characters formed a monophyletic group in phylogenetic analyses based on the two genes, which, however, included the species Prorocentrum arenarium. P. arenarium was determined to be within the range of morphological variation of P. lima, and therefore we synonymize the two taxa. Within this monophyletic group, P. lima was divided into several subclades in the all phylogenetic analyses. There were no morphological characters specifically related to any one subclade. The subclades appeared to correlate broadly to sample collection regions, suggesting that geographically separated populations may have become genetically distinct within this epi‐benthic species. We have emended species boundaries in P. lima.     

MORPHOLOGY AND MOLECULAR ANALYSES OF THREE TOXIC SPECIES OF GAMBIERDISCUS (DINOPHYCEAE): G. PACIFICUS, SP. NOV., G. AUSTRALES, SP. NOV., AND G. POLYNESIENSIS, SP. NOV.

Three new dinoflagellate species, Gambierdiscus polynesiensis, sp. nov., Gambierdiscus australes, sp. nov., and Gambierdiscus pacificus, sp. nov., are described from scanning electron micrographs. The morphology of the three new Gambierdiscus species is compared with the type species Gambierdiscus toxicus Adachi et Fukuyo 1979, and two other species: Gambierdiscus belizeanus Faust 1995 and Gambierdiscus yasumotoi Holmes 1998. The plate formula is: Po, 3′, 7", 6C, 8S, 5‴, 1p, 2". Culture extracts of these three new species displayed both ciguatoxin- and maitotoxin-like toxicities. The following morphological characteristics differentiated each species. 1) Cells of G. polynesiensis are 68–85 μm long and 64–75 μm wide, and the cell’s surface is smooth. They are identified by a large triangular apical pore plate (Po), a narrow fish-hook opening surrounded by 38 round pores, and a large, broad posterior intercalary plate (1p) wedged between narrow postcingular plates 2‴ and 4‴. Plate 1p occupies 60% of the width of the hypotheca. 2) Cells of G. australes also have a smooth surface and are 76–93 μm long and 65–85 μm wide in dorsoventral depth. They are identified by the broad ellipsoid apical pore plate (Po) surrounded by 31 round pores and a long and narrow 1p plate wedged between postcingular plates 2‴ and 4‴. Plate 1p occupies 30% of the width of the hypotheca. 3) Cells of G. pacificus are 67–77 μm long and 60–76 μm wide in dorsoventral depth, and its surface is smooth. They are identified by the four-sided apical pore plate (Po) surrounded by 30 round pores. A short narrow 1p plate is wedged between the wide postcingular plates 2‴ and 4‴. Plate 1p occupies 20% of the width of the hypotheca. These three newly described species were also characterized by isozyme electrophoresis and DNA sequencing of the D8–D10 region of their large subunit (LSU) rRNA genes. The consistency between species designations based on SEM microscopy and classification inferred from biochemical and genetic heterogeneities was examined among seven isolates of Gambierdiscus. Their classification into four morphospecies was not consistent with groupings inferred from isozyme patterns. Three molecular types could be distinguished based on the comparison of their LSU rDNA sequences. Although G. toxicus TUR was found to be more closely related to G. pacificus, sp. nov. than to other G. toxicus strains, the molecular classification was able to discriminate G. polynesiensis, sp. nov. and G. australes, sp. nov. from G. toxicus. These results suggest the usefulness of the D8–D10 portion of the Gambierdiscus LSU rDNA as a valuable taxonomic marker.     

OBSERVATION OF SAND-DWELLING TOXIC DINOFLAGELLATES (DINOPHYCEAE) FROM WIDELY DIFFERING SITES, INCLUDING TWO NEW SPECIES

Dinoflagellate associations, including toxic and potentially toxic benthic species, were examined in sand from South Water Cay and Carrie Bow Cay, Belize. The inshore sand habitat in localized areas of warm shallow lagoonal waters supported blooms of toxic assemblages of dinoflagellates. In the sand, the dominant microalgae were dinoflagellates; cyanobacteria were a minor component and diatoms were absent. Ciliates and nematodes were present. Assemblages of microorganisms in colored sand were examined for 4 consecutive days after which a storm washed away the patch. The sand-dwelling dinoflagellate assemblage included 16 species where densities ranged from as low as 1.3% to 15% of total cell densities. The dominant species was Scrippsiella subsalsa, having 1.8 × 10⁵ to 2.6 × 10⁵ cells g^-1 sand. Toxic dinoflagellates identified in the sand were Gambierdiscus toxicus, Ostreopsis lenticularis, Prorocentrum lima, Prorocentrum mexicanum, and Amphidinium carteri. The potentially toxic Ostreopsis labens, Gambierdiscus belizeanussp. nov., and Coolia tropicalis sp. nov. were also identified. Toxic and potentially toxic species represented 36% to 60% of total microalgal cell assemblage. The morphology of a new sand-dwelling species, Gambierdiscus belizeanus sp. nov., was examined with the scanning electron microscope. The plate formula was P_o, 3′, 7″, 6c, s?, 5?, 1p, and 2″″.Dimensions of G. belizeanus cells were 53–67 pm long, 54–63 μm wide, and 92–98 μm in dorsoventral depth. Cells were deeply areolated, ellipsoid in apical view, and compressed anteroposteriorly. The cells of G. belizeanus were identified by the cell's long, narrow, pentagonal, posterior intercalary plate (1p) wedged between the wide postcingular plates 2″’and 4″; 1p occupied 20% of the width of the hypotheca. The plate formula for Coolia tropicalis sp. nov. was P_o, 3′, 7″, 7c, 8s?, 5″″, and 2″″, Cell size ranges were 23–40 μm long, 25–39 μm wide, and 35–65 μm in dorsoventral diameter. Cells were spherical, smooth, and covered with scattered round pores. The epitheca was smaller than the hypotheca. Precingular plates 1″ and 7″ were small and narrow, and the first apical plate 1″ and precingular plate 6″ were the largest plates on the epitheca. The apical pore was straight and 7 μm long, and was situated in the apical plate complex. Cells of C. tropicalis were distinguished from C. monotis by the wedge-shaped plate 1′, a four-sided 3’plate, and a short apical pore.     

MORPHOLOGY AND TAXONOMY OF PROROCENTRUM MEXICANUM AND REINSTATEMENT OF PROROCENTRUM RHATHYMUM (DINOPHYCEAE)1

Dinoflagellates collected during red tide events in Bahia Mazatlan, Mexico during the early spring of 1999 and 2000 appeared under LM to belong to Prorocentrum mexicanum Osorio‐Tafall. Observations with SEM of those populations showed marked differences in shape and microornamentation from the related species, Prorocentrum rhathymum Loeblich III, Sherley and Schmidt. In P. mexicanum, the presence and dimensions of poroids, the uneven distribution of trichocyst pores not located in depressions, and the general architecture of the periflagellar region are more closely related to Prorocentrum caribbaeum Faust. Also, P. mexicanum has a three‐horned (sometimes two‐horned) spine and is deeper in the anterior than the posterior region, whereas P. rhathymum has a simple small spine and its sagittal view is oval. Furthermore, the number and distribution of trichocyst pores in the periflagellar area is different between the two species, being located on both valves in P. mexicanum and only on the right valve in P. rhathymum. To date, true P. mexicanum has been described only from plankton sampling, whereas P. rhathymum was frequently mentioned associated with floating detritus (macroalgae) but also forming red tides. Altogether, the evidence presented demonstrates that P. mexicanum (planktonic) and P. rhathymum (epibenthic) are distinct species and are not synonyms, as is often accepted.     

MORPHOLOGY AND ECOLOGY OF THE MARINE DINOFLAGELLATE OSTREOPSIS LABENS SP. NOV. (DINOPHYCEAE)1

A new species, Ostreopsis labens Faust et Morton sp. nov., is described from three marine habitats: lagoonal water and lagoonal sand from the barrier reef of Belize, and associated with macroalgae from coral reef habitats of Oshigaki and Iriomote Islands, Japan. Dimensions of Ostreopsis labens cells are 60–86 μm long, 70–80 μm wide, and 81–110 μm in dorsoventral depth. Cells are broadly ovoid, anterioposteriorly compressed bearing a spherical nucleus and many chloroplasts. The epitheca is convex and composed of three apical plates, seven precingular plates, and an apical pore plate. The cingulum is composed of six plates. The hypotheca is constructed of five postcingular plates, one posterior intercalary, and two antapical plates. The sulcus is small, recessed, and hidden and exhibits a ventral pore and a ridged, curved plate. The thecal arrangement of O. labens is P_o, 3′, 7″ 6C, 6S(?), V_p, R_p, 5″, 1p, 2″. Only one sulcal list is present. The thecal plates have a smooth surface with distinct round pores. The intercalary band between the thecal plates is smooth. A row of marginal pores line the lipped cingulum. Ostreopsis species are anteroposteriorly flattened, photosynthetic, benthic dinoflagellates that are more diverse in ecology than previously known. Ostreopsis labens is capable of living in three marine habitats: in the water column, in sand, and on macroalgal surfaces. It was most numerous in sand and less in lagoonal waters, and only a few cells were associated with macroalgae. Light and scanning electron microscopy studies revealed engulfed cells within O. labens, which indicates mixotrophic/phagotrophic behavior. A ventral opening situated in the cingulum of O. labens exhibits size variability; it may serve as an opening for engulfiing food particles because it varies in size. We propose that ingestion of prey by O. labens occurs through the ventral opening, the proposed feeding apparatus of this species, which is similar to the function of the peduncle-like structure of mixotrophic dinoflagellates. The behavior of O. labens appears similar to that previously described for Dinophysis species.     

Morphology and taxonomy of five marine sand-dwelling Thecadinium species (Dinophyceae) from Japan, including four new species: Thecadinium arenarium sp. nov., Thecadinium ovatum sp. nov., Thecadinium striatum sp. nov. and Thecadinium yashimaense sp. nov.

Thecadinium inclinatum Balech and four new marine sand‐dwelling species of the dinoflagellate genus Thecadinium are described from the sandy beaches along the coast of Shikoku, Japan. Thecadinium inclinatum is thecate, bilaterally flattened, elliptical in shape, non‐photosynthetic, and measures 55–75 μ in length and 43–59 μ in depth. The epi‐ and hypotheca theca are semielliptical and the thecal surface is smooth with small pores. The plate formula is Po (pore plate), 3′, 7″,?c,?s, 5″′1″′.Thecadinium ovatum sp. nov. is thecate, non‐photosynthetic, bilaterally flattened and almost oval in lateral view. The cell measures 40–50 μm in length and 33–40 μm in depth. The hypotheca has two or three strong antapical spines. The plate formula is 3′, 6″,6c, 5s?, 5″′, 1″′. Thecadinium striatum sp. nov. is thecate, non‐photosynthetic, bilaterally flattened and somewhat elliptical in lateral view. The cell is 33–41 μm long and 23–30 μm deep. Several striae are present on the hypotheca. The plate formula is 3′, 6″, 6c, 5s?, 5″′, 1″″. Thecadinium yashimaense sp. nov. is bilaterally flattened, photosynthetic and elliptical in ventral view. The cell is 44–65 μm long and 23–36 μm wide. The thecal surface is smooth with small pores. he cingulum forms a steep left–handed spiral. The plate formula is Po, 3′, la, 6″, 5c, 4s, 5″′, 1″′. Thecadinium arenarium sp. nov. is somewhat wedge‐shaped in ventral view, photosynthetic with brownish chloroplasts and almost rounded in cross section. The cingulum forms a steep left‐handed spiral. The cell measures 35–41 μm in length and 25–30 μm in width. The thecal surface is weakly reticulated with small pores. The hypotheca is conical. The plate formula is Po, 3′, la, 6″, 5c, 4s, 5″′, 1″″.     

Morphology and toxicology of Prorocentrum arabianum sp. nov., (dinophyceae) a toxic planktonic dinoflagellate from the Gulf of Oman, Arabian Sea

A new species of planktonic dinoflagellate, Prorocentrum arabianum isolated from the Gulf of Oman, is described using both scanning electron microscopy (SEM) and light microscopy. This clonal isolate has the following morphological characteristics: (1) cell shape is asymmetric; (2) thecal surface is rugose, covered with small poroids; (3) periflagellar area is unornamented, and (4) intercalary band is horizontally striated. Analysis of P. arabianum confirms the production of one cytotoxic compound and one ichthyotoxic compound. P. arabianum is the second known toxic planktonic Prorocentroid dinoflagellate.