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″″.     

DESCRIPTION OF THECADINIUM MUCOSUM SP. NOV. (DINOPHYCEAE), A NEW SAND‐DWELLING MARINE DINOFLAGELLATE,AND AN EMENDED DESCRIPTION OF THECADINIUM INCLINATUM BALECH1

A new thecate, phototrophic, marine, sand‐dwelling dinoflagellate, Thecadinium mucosum Hoppenrath et Taylor sp. nov., is described from a culture isolated from Boundary Bay, British Columbia, Canada. It was illustrated with LM as well as SEM and TEM, and its position in the phylogenetic tree of dinoflagellates was investigated using molecular methods. Cells are asymmetrical, oval, laterally flattened, and strongly pigmented, with the plate formula P 3′ 1a 6′′ 7/8c 5 s 6′′′ 2′′′′. Thecal plates are smooth with scattered pores, and there is a distinctive anterior intercalary plate that could be involved in mucus secretion. Thecadinium inclinatum Balech (=Sabulodinium inclinatum (Balech) Saunders et Dodge), a thecate, marine, sand‐dwelling species that has been previously confused with what we now call T. mucosum, was also examined and illustrated through LM and SEM. New information on T. inclinatum is provided, including its plate formula P 3′ 6′′ 7c ?s 5′′′ 1p 1′′′′; we consider T. inclinatum to be related to most other Thecadinium species and not to Sabulodinium. Molecular phylogenetic analyses based on the small subunit ribosomal gene of T. mucosum, T. kofoidii (the type species of the genus), and T. dragescoi weakly support earlier suspicions based on morphology that T. dragescoi is not a member of Thecadinium. Tabulational patterns of the species suggest a relationship to the genus Amphidiniopsis.     

CRYPTOPERIDINIOPSIS BRODYI GEN. ET SP. NOV. (DINOPHYCEAE), A SMALL LIGHTLY ARMORED DINOFLAGELLATE IN THE PFIESTERIACEAE1

A new genus and species of heterotrophic dinoflagellate, Cryptoperidiniopsis brodyi gen. et sp. nov., are described. This new species commonly occurs in estuaries from Florida to Maryland, and is often associated with Pfiesteria piscicida Steidinger et Burkholder, Pseudopfiesteria shumwayae (Glasgow et Burkholder) Litaker et al., and Karlodinium veneficum (Ballantine) J. Larsen, as well as other small (<20 μm) heterotrophic and mixotrophic dinoflagellates. C. brodyi gen. et sp. nov. feeds myzocytotically on pigmented microalgae and other microorganisms. The genus and species have the enhanced Kofoidian plate formula of Po, cp, X, 5′, 0a, 6″, 6c, PC, 5+s, 5″′, 0p, and 2″″ and are assigned to the order Peridiniales and the family Pfiesteriaceae. Because the Pfiesteriaceae comprise small species and are difficult to differentiate by light microscopy, C. brodyi gen. et sp. nov. can be easily misidentified.     

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.     

First records of the benthic,bloom-forming,non-toxic dinoflagellate <Emphasis Type="Italic">Thecadinium yashimaense</Emphasis> (Dinophyceae) in Europe: with special emphasis on the invasion in the North Sea

Thecadinium yashimaense was recorded for the first time in France, Great Britain, The Netherlands, and Germany. The invasion and establishment of the species in the German Bight was documented reliably and is presented here. The geographic expansion of the species from the North Pacific to the North Atlantic Ocean is discussed. This bloom-forming, marine, sand-dwelling dinoflagellate was shown to be non-toxic. Also Thecadinium kofoidii, the type species of the genus, was analyzed for potential toxin production and turned out to be non-toxic as well.     

Light and scanning microscopy of two benthic species of Amphidiniopsis (Dinophyceae), Amphidiniopsis hexagona sp. nov. and Amphidiniopsis swedmarkii from Japan

Two species of the genus Amphidiniopsis, a marine armoured, sand‐dwelling dinoflagellate, Amphidiniopsis hexagona Yoshimatsu, Toriumi et Dodge sp. nov. and Amphidiniopsis swedmarkii (Balech) Dodge were collected from Japanese sandy beaches, and their morphologic features were observed by light microscopy and scanning electron microscopy. Amphidiniopsis hexagona was hexagonal in ventral view and measured 44–59 urn in length and 40–53 urn in width. The plate formula is P_o, 4′, 2a, 7″, 3c, 4s (+ 2 accessory), 5″″, 2″″. This plate arrangement of A. hexagona is essentially the same as those of Amphidiniopsis hirusta and A. swedmarkii, but this new species can be readily distinguished from the latter two species by the following characters: (i) the cell shape; (ii) the presence of an antapical spine; and (iii) the surface ornamentation of thecal plates.     

Heterocapsa psammophila sp. nov. (Peridiniales, Dinophyceae), a new sand-dwelling marine dinoflagellate

A new armored dinoflagellate species, Heterocapsa psammophila Tamura, Iwataki et Horiguchi sp. nov. is described from Kenmin‐no‐hama beach, Hiroshima, Japan using light and electron microscopy. This dinoflagellate possesses the typical thecal plate arrangement of the genus Heterocapsa, Po, cp, 5′, 3a, 7′′, 6c, 5s, 5′′′, 2′′′′; and the 3‐D body scales of Heterocapsa on the plasma membrane. The cell shape is ovoidal. The spherical nucleus and the pyrenoid are situated in the hypotheca and the epitheca, respectively. The ultrastructure of H. psammophila is typical of dinoflagellates and the pyrenoid is invaginated by cytoplasmic tubules. H. psammophila is distinguished from all other hitherto‐described Heterocapsa species by the cell shape, the relative position of the nucleus and pyrenoid and the structure of the body scale. The habitat and behavior of this new species in culture suggest that the organism is truly a sand‐dwelling species.     

LESSARDIA ELONGATA GEN. ET SP. NOV. (DINOFLAGELLATA,PERIDINIALES, PODOLAMPACEAE) AND THE TAXONOMIC POSITION OF THE GENUS ROSCOFFIA1

We investigate an organism that closely resembles the nonphotosynthetic dinoflagellate “Gymnodinium elongatum” Hope 1954 using EM and molecular methods. Cells are 20–35 μm long, 10 μm wide, biconical, transparent, and have a faint broad girdle. Thecal plates are thin but present (plate formula Po Pi CP 3′ 1–2A 5″ 3C 6S 4? 3″″). With the exception of one feature, the presence of three antapical plates, the amphiesmal arrangement of this species is consistent with that of the order Peridiniales, family Podolampaceae; it is not at all consistent with the characteristics of the genus Gymnodinium. On the basis of these ultrastructural findings, we establish a new genus, Lessardia, and a new species, Lessardia elongata Saldarriaga et Taylor. Molecular phylogenetic analyses were performed using the small subunit rRNA genes of L. elongata as well as Roscoffia capitata, a member of a genus of uncertain systematic position that has been postulated to be related to the Podolampaceae. These analyses place Lessardia and Roscoffia as sister lineages within the so‐called GPP complex. Thecal plate arrangements led us to expand the family Podolampaceae to include the genus Lessardia and, in combination with new molecular results, to propose a close relationship between the Podolampaceae and Roscoffia. Within this lineage, Lessardia and Roscoffia appear to have retained a number of ancestral characters: Roscoffia still has a well‐developed cingulum, a feature absent in all members of the Podolampaceae, and Lessardia has more than one antapical plate, a character reminiscent of some members of the family Protoperidiniaceae.     

Scrippsiella hexapraecingula sp. nov. (Dinophyceae), a tida pool dinoflagellate from the Northwest Pacific

Specimens of dinoflagellate collected in tide pools along the Pacific coast of central and southern Japan are described as a new species,Scrippsiella hexapraecingula Horiguchi et Chihara, of the Peridiniaceae (Class Dinophyceae). The plate formula is pp, x, 4′, 3a, 6″, 6c, 5‴, 2″" and, 5s, the same as that of other species ofScrippsiella, except in lacking one precingular plate. The genus must be emended, therefore, as having either six or seven precingular plates. This dinoflagellate migrates diurnally. In the morning motile cells are released from non-motile cells attached to the substrate and in the evening the motile cells swim down to settle on the bottom of the tide pool. Attached non-motile cells form either motile mono- or bispores. Sexual reproduction was not observed.     

ALEXANDRIUM SATOANUM SP. NOV. (DINOPHYCEAE) FROM MATOYA BAY,CENTRAL JAPAN1

The gonyaulacoid dinofiagellate Alexandrium satoanum Yuki et Fukuyo sp. nov. is described from Matoya Bay, Pacific coast of central Japan. The species is distinctive in its conical epitheca with almost straight sides and dorsal concavity of the hypotheca. The plate formula is Po, pc, 4′, 6″, 6c, 10s, 5″″, and 2″″, including two accessory plates inside the sulcus. The apical pore plate is triangular and possesses an anterior attachment pore at the right margin. The first apical plate does not make contact with the apical pore plate and lacks a ventral pore. A posterior attachment pore lies at the center of the posterior sulcal plate. In Matoya Bay, vegetative cells occur as solitary cells or sometimes in pairs during late spring and early summer in low concentrations. In connection with this study, the following new combination is proposed: Alexandrium pseudogonyaulax (Biecheler) Horiguchi ex Yuki et Fukuyo comb. nov.     

Amphidiniella sedentaria gen. et sp. nov. (Dinophyceae), a new sand-dwelling dinoflagellate from Japan

A new sand-dwelling dinoflagellate is described from Sesoko Beach, Okinawa Island, subtropical Japan and its micromorphology is studied by means of light and electron microscopy. The cell consists of a small epitheca and a large hypothecs superficially resembling members of the unarmored genus Amphidinium. The cell is dorso-ventrally flattened and possesses a single chloroplast with a large conspicuous pyrenoid. Transmission electron microscopy revealed that the dinoflagellate possesses typical dinoflagellate cellular organization. Scanning electron microscopy demonstrated that the organism is thecate and the thecal plate arrangement is Po, 4′, 1a, 7″, 5c, 4s, 6″′, 2″″. Most of the characteristics suggest gonyaulacalean affinity of the new species. These are the presence of ventral pore, lack of canal plate, direct contact between the sulcal anterior plate and the flagellar pore, possession of six postcingular plates and asymmetrical arrangement of the antapical plates. Affinity to existing families of the order Gonyaulacales has not been determined. Based on the unique cell shape, thecal plate arrangement and the presence of ventral pore, a new genus, Amphidiniella, is established for this organism and the species is named A. sedentaria Horiguchi gen. et sp. nov.     

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.     

A NEW SPECIES OF ENSICULIFERA,E. IMARIENSE (DINOPHYCEAE), PRODUCING ORGANIC-WALLED CYSTS1

We describe a new organic-walled resting cyst from surface sediments of Imari Bay in western Japan. The cysts are spherical, 23–29 pm in diameter, and their surface is covered with spinous to membranous ornaments that are 5–7 μm long and 1.5–2.2 μm wide. The ornaments vary from slender and bifurcate to membranous and multifurcate distal extremities. No archeopyle was observed. The cyst shape is variable in both natural samples and clonal cultures. Vegetative cells are small and ovoid, 17–25 μm long and 14–21 μm wide, and are yellow-brown in color. The epitheca is conical with a conspicuous apical horn, and the hypotheca is hemispherical. The cingular transitional plate has a needle-like spine at its anterior right corner. The plate formula is Po, X, 4″3a, 7″, 5c, 5s 5″and 2″. Although vegetative cells of the present species correspond to Ensiculifera, it is distinct from other species in producing no calcareous cysts. No species of Ensiculifera has been reported to produce cysts composed of only an organic wall. The present species is provisionally placed in the genus Ensiculifera as E. imariense sp. nov.     

Amphidiniopsis uroensis sp. nov. and Amphidiniopsis pectinaria sp. nov. (Dinophyceae): Two new benthic dinoflage llates from Japan

Two new armoured, heterotrophic sand‐dwelling marine dinoflagellates, Amphidiniopsis uroensis Toriumi, Yoshimatsu et Dodge sp. nov. and Amphidiniopsis pectinaria Toriumi, Yoshimatsu et Dodge sp. nov. were collected from Japanese sandy beaches, and their morphological features observed by light microscopy and scanning electron microscopy (SEM). The cell size of A. uroensis is 28–31 μm in length and 23–28 μm in width. The plate formula is Po 3′, 3a, 6″, 3c, 4s (+1 acc.), 5″′, 2″″. The thecal surface is ornamented with small processes, pores and spines, however, the surface of plate 2a is smooth. The epitheca possesses a narrow ridge that is extended along on the suture between 1′ and 3′. Plate 1″ connects with the right sulcal (Sd) and right sulcal accessory (Sda) plates, so the cingulum is incomplete. A nucleus is situated in the central part of the cell. There are a few small spines at the antapex. There are no stigma or chloroplasts. Amphidiniopsis pectinaria cells are 33–40 urn in length and 29–35 μm in width. The plate formula is Po 4′, 3a, 7″, 3c, 4s (+1 acc.), 5″′, 2″″. Plate 1″ connects directly with Sd and Sda plates, so the cingulum is incomplete. The thecal surface is ornamented with small processes, spines and pores. The epitheca is provided with a narrow ridge that is extended along on the suture between plates 1′, 4′ and 7″. The ornamentation on the antapical plates is unique. It is arranged in 10 straight rows on the hypotheca; each row has a strong spine at its posterior end. In addition, there is a long spine at the antapex. There are no stigma or chloroplasts. A nucleus is located in the central part of the cell.     

Mixotrophy in the sand-dwelling dinoflagellate Thecadinium kofoidii

Thecadinium kofoidii is a marine sand-dwelling dinoflagellate that sometimes forms dense blooms. This species was previously thought to be an exclusively autotrophic dinoflagellate, and its mixotrophic ability has not been explored yet. By investigating its ecophysiology, its trophic mode should be revealed. We explored the mixotrophic ability of T. kofoidii by examining its protoplasm under light and transmission electron microscopes with diverse algal prey species. Furthermore, the feeding mechanism of T. kofoidii and prey species on which it feeds were investigated. In addition, the growth and ingestion rates of T. kofoidii as a function of prey concentration were determined when feeding on the benthic cryptophyte Rhodomonas salina. Thecadinium kofoidii was able to feed on R. salina and the dinoflagellate Symbiodinium voratum, which had equivalent spherical diameters (ESDs) ≤ 10.1?µm, while it did not feed on the benthic dinoflagellates Levanderina fissa, Prorocentrum concavum or Ostreopsis cf. ovata, which had ESDs ≥ 15?µm. Thecadinium kofoidii fed on the edible prey cells using the peduncle. The maximum ingestion rate of T. kofoidii on R. salina was 1.3 cells predator^?1 d^?1. However, feeding on R. salina did not significantly increase the growth rate of T. kofoidii. The low ingestion rate of T. kofoidii on R. salina may have partially resulted in the lack of significant increase in its growth rate due to mixotrophy. The present study discovered predator–prey relationships between T. kofoidii and R. salina and S. voratum, which may change our view of the energy flow and carbon cycling in marine benthic food webs.     

SOME PRYMNESIACEAE (HAPTOPHYTA,PRYMNESIOPHYCEAE) FROM THE MEDITERRANEAN SEA,WITH THE DESCRIPTION OF TWO NEW SPECIES: CHRYSOCHROMULINA LANCEOLATA SP. NOV. AND C. PSEUDOLANCEOLATA SP. NOV.1

Five species belonging to the family Prymnesiaceae (one Prymnesium and four Chrysochromulina) have been identified in cultures obtained from water collected in the Bay of Banyuls‐sur‐Mer (Mediterranean Sea, France) using LM, SEM, and TEM. Two are described as new species, Chrysochromulina lanceolata sp. nov. and C. pseudolanceolata sp. nov. Both species are large and lanceolate with an acute posterior and two anterior arms. They are easily detectable with LM but difficult to distinguish to species level with live cells, without experience. EM reveals two completely different scale patterns in the two species. Cells of C. lanceolata are 21–38 μm long, 7–12 μm wide, and 3–7 μm thick. They possess two subequal flagella (30–51 and 29–44 μm), and the haptonema is shorter than the flagella (23–37 μm). The cell body is covered by plate and spine scales. Cells of C. pseudolanceolata sp. nov. are slightly smaller (15–18 × 6–8 μm) with more rounded extremities, two subequal flagella (19–26 and 17–24 μm), and the haptonema is longer than the flagella (about 35 μm). Three types of plate scales are observed in this species. Other findings are C. alifera Parke et Manton and C. throndsenii Eikrem (a new record for the Mediterranean Sea). Prymnesium faveolatum Fresnel, a new toxic species recently described, is illustrated with both LM and SEM.     

Taxonomy, phylogeny, biogeography, and ecology of Sabulodinium undulatum (Dinophyceae), including an emended description of the species

Samples of Sabulodinium undulatum Saunders et Dodge, the type species of the monospecific genus, were collected and characterized from Germany, Russia, Japan and Canada. This species has a laterally flattened, oval cell with a truncated apex and a dorsally pointing small episome. The dorsal margin of the hyposome has an undulating shape. A dorsal spine and/or antapical spine are sometimes present. The specimens of this heterotrophic species are 27.5–42.5 μm long and 18.5–36.0 μm wide, and have a theca with the plate arrangement apical pore complex (APC) 5′ 1a 6″ 5c 4s 6′′′ 1′′′′. The shape of the dorsal theca is variable. The species distribution seems to be restricted to northern temperate regions. Sabulodinium undulatum occurred in all sandy eulittoral areas throughout the year and was also present in sandy sublittoral and supralittoral (beach) samples. The species can tolerate a broad range of temperatures and salinities. Sabulodinium occurred from −2.0 to +24.3°C and 4–35 salinity. It is likely that the observed variability in morphology and habitat reflect several varieties. We propose to establish three varieties within the species, namely S. undulatum var. undulatum, S. undulatum var. glabromarginatum, and S. undulatum var. monospinum. The systematic position of Sabulodinium is discussed in the context of comparative morphological and molecular phylogenetic data.     

A new species of Tardigrada (Eutardigrada: Milnesiidae): Milnesium krzysztofi from Costa Rica (Central America)

Abstract

A new eutardigrade species Milnesium krzysztofi sp. nov. is described from Costa Rica. M. krzysztofi sp. nov. differs from the most similar Milnesium katarzynae Kaczmarek et al., 2004 mainly by the presence of spurs on internal claws I–III and on external claw IV.     

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.     

FURTHER SEM STUDY OF MARINE DINOFLAGELLATES: THE GENUS OSTREOPSIS (DINOPHYCEAE)1

This paper presents a comprehensive examination of the taxonomy of the genus Ostreopsis Schmidt. The morphology of six species of marine dinoflagellates, Ostreopsis siamensis Schmidt 1902. Ostreopsis lenticularis Fukuyo 1981, Ostreopsis ovata Fukuyo 1981, Ostreopsis heptagona Norris, Bomber, et Balech 1985, Ostreopsis mascarenensis Quod 1994, and Ostreopsis labens Faust et Morton 1995 from three geographical regions (Japan, Southwest Indian Ocean, and the Caribbean) and three marine habitats (sand, water column, and macroalgal surfaces) are described from scanning electron micrographs. Differences in the following morphological characteristics differentiated the species: cell shape and size, and ornamentation of the epitheca, cingulum, and hypotheca. The thecal plate formula of the six Ostreopsis species is P_o, 3′, 7″, 6C, 6S?, V_p, R_p, 5′″, 1p, 2″″, with differences in thecal plate size and shape. The cingulum in ventral view has two prominent structures: a ventral plate (V_p) with a ventral pore (V_o) and a ridged plate (R_p) that distinguishes Ostreopsis species from any other dinoflagellate taxa. This paper also includes ecological and toxicity information regarding the six Ostreopsis species.