ULTRASTRUCTURE OF THE DINOFLAGELLATE PERIDINIUM CINCTUM F. OVOPLANUM. II. LIGHT AND ELECTRON MICROSCOPIC OBSERVATIONS ON FERTILIZATION

Fertilization in Peridinium cinctum f. ovoplamtm has been investigated at both the light and electron microscopic levels. Gamete formation occurs when vegetative cells are placed into nitrogen deficient media. The majority of gametes observed possess thin thecal plates; however, some are naked. Gametes have few chloroplasts as compared to vegetative cells, numerous membrane bounded storage bodies, many starch grains, and chromosomes which appear slightly unwound. Gamete fusion is observed to peak 7–10 days after inoculation into nitrogen deficient media. Fusion occurs in an area of the sulcus devoid of reticulate thecal plates at or adjacent to the flagellar pores. A fertilization tube is formed and proceeds to widen along the sulcus. Karyogamy occurs within the fertilization tube before plasmogamy is completed. The resulting planozygote is a two walled structure containing two longitudinal flagella. It enlarges over a 2-week period giving rise to the hypnozygote.     

OBSERVATIONS ON THE SYMBIOSIS OF PERIDINIUM BALTICUM AND ITS INTRACELLULAR ALGA. I. ULTRASTRUCTURE1,2

The ultrastructure of Peridinium balticum indicates that an eudosymbiont is present within the dinoflagellate. The structure and probable function of the organelles of both protists arc described and discussed. The origin of photosynthetic dinoflagellates from heterotrophic forms by means of a chrysophyte-like endosymbiont is postulated.     

ULTRASTRUCTURE AND LSU rDNA–BASED REVISION OF PERIDINIUM GROUP PALATINUM (DINOPHYCEAE) WITH THE DESCRIPTION OF PALATINUS GEN. NOV.1

The name Peridinium palatinum Lauterborn currently designates a freshwater peridinioid with 13 epithecal and six cingular plates, and no apical pore complex. Freshwater dinoflagellate floras classify it in Peridinium group palatinum together with P. pseudolaeve M. Lefèvre. General ultrastructure, flagellar apparatus, and pusular components of P. palatinum were examined by serial section TEM and compared to P. cinctum (O. F. Müll.) Ehrenb. and Peridiniopsis borgei Lemmerm., respectively, types of Peridinium and Peridiniopsis. Partial LSU rDNA sequences from P. palatinum, P. pseudolaeve and several peridinioids, woloszynskioids, gymnodinioids, and other dinoflagellates were used for a phylogenetic analysis. General morphology and tabulation of taxa in group palatinum were characterized by SEM. Differences in plate numbers, affecting both the epitheca and the cingulum, combine with differences in plate ornamentation and a suite of internal cell features to suggest a generic‐level distinction between Peridinium group palatinum and typical Peridinium. The branching pattern of the phylogenetic tree is compatible with this conclusion, although with low support from bootstrap values and posterior probabilities, as are sequence divergences estimated between species in group palatinum, and typical Peridinium and Peridiniopsis. Palatinus nov. gen. is proposed with the new combinations Palatinus apiculatus nov. comb. (type species; syn. Peridinium palatinum), P. apiculatus var. laevis nov. comb., and P. pseudolaevis nov. comb. Distinctive characters for Palatinus include a smooth or slightly granulate, but not areolate, plate surface, a large central pyrenoid penetrated by cytoplasmic channels and radiating into chloroplast lobes, and the presence of a peduncle‐homologous microtubular strand. Palatinus cells exit the theca through the antapical‐postcingular area.     

COMPARATIVE ULTRASTRUCTURE OF VEGETATIVE AND SEXUAL THECAE OF PERIDINIUM LIMBATUM AND PERIDINIUM CINCTUM (DINOPHYCEAE)

Peridinium limbatum (Stokes) Lemmerman reproduces sexually in nitrogen deficient medium. Sexual reproduction is homothallic and similar to that reported for other Peridinium species. Thecate planozygotes of P. limbatum and P. cinctum enlarge greatly. Suture bands connecting thecal plates enlarge unequally in P. cinctum producing a “warty” zygote and equally in P. limbatum maintaining the regular but enlarged appearance of the cell. Zygotes can be recognized by greatly enlarged striated suture bands.     

THE CALCAREOUS RESTING CYST OF PENTAPHARSODINIUM TYRRHENICUM COMB. NOV. (DINOPHYCEAE)1

While investigating dinoflagellate cyst assemblages in surface sediments of the Gulfs of Naples and Salerno (Mediterranean Sea), we found a new calcareous resting cyst. This cyst has a round to oval body surrounded by a thick mineral layer, which gives it the shape of a Napoleon hat, with a flat, oval face bearing the archeopyle and a convex keel on the opposite side. The cyst shape is variable in both natural samples and clonal cultures. The organic membrane underlying the calcareous covering is resistant to acetolysis, thus demonstrating the presence of sporopolleninlike material. The cyst germinated into a motile stage having the same morphological features and thecal plate pattern as Peridinium tyrrhenicum Balech. We believe the validity of the genus Pentapharsodinium Indelicato & Loeblich should be accepted. Based on the comparative examination of the species we collected and of a similar species, Pentapharsodinium trachodium Indelicato & Loeblich, we propose Pentapharsodinium tyrrhenicum as a new combination for Peridinium tyrrhenicum. The genus Pentapharsodinium also includes P. dalei Indelicato & Loeblich (= Peridinium faeroense Dale), which produces spiny, organic-walled cysts. The presence of species forming calcareous cysts and species producing noncalcareous cysts in the same genus raises questions about maintaining the family Calciodinellaceae. This family should only include calcareous cyst-forming peridinioids, in order to maintain a unified system of classification of fossil and recent dinoflagellates.     

FRESHWATER DINOFLAGELLATES OF BELIZE,C.A.

Freshwater dinoflagellates have not previously been reported from Belize, although there has been extensive work with marine dinoflagellates and some work with other freshwater groups. Freshwater dinoflagellates are more frequently observed in standing water and none have been observed in the several streams and rivers sampled since 1990. The goal in 1998 was to examine water samples from small ponds within hours of collection to improve the chance of observing swimming dinoflagellates. A plankton net was used and whole water samples also were collected. A small brown water pond on a peninsula and 30m from the Caribbean yielded a bloom of Thompsodinium intermedium. Dinoflagellates, including Peridinium centenniale, Katodinium sp., and Peridinium sp. in the Umbonatum Group, were observed within “Crocodile pond” and “Lily pond” on the mainland.     

PERIDINIUM PENARDII (LEMM.) LEMM. FO. CALIFORNICUM,FORMA NOVA1

A new forma of Peridinium penardii (Lemm.) Lemm. (Dinophyceae) is described from Clear Lake, California, based upon the morphology of a theca. The forma californicum Javorn. is believed to be a connecting link between P. penardii and P. berolinense Lemm. A nomenclatural survey of the species, as well as a key to its formae, are given.     

The genus Glochidinium gen. nov., with two species: G. penardiforme comb. nov. and G. platygaster sp. nov. (Peridiniaceae)

Glochidiniumgen. nov., a ncw genus of Peridiniaceae based on Peridinium penardiforme Lindemann, is herewith erected. Its plate formula is: Po+X+4′+6′′+3C+4S+5′′′+2′′′′ Main diagnostic characters of this new genus are the presence of only 3 cingular plates (it lacks the transitionalone), the third cingular contacting the anterior sulcal plate, and an unusual sulcus holding a small triangular posterior sulcal plate. The thecal morphology and structure of two freshwater planktic species of the genus are described on the basis of LM and SEM observations. G. penardiforme comb. nov. is an infrequent species, albeit widely distributed world-wide. It has been recorded under the names of Peridinium, Glenodinium and Peridiniopsis. Peculiar features in the tabulation of the furrows and of the surface sculpture show that the species does not fit any of the known genera, for which reason the new genus Glochidinium is established. G. platygaster sp. nov., the second species included in the genus, differs from the former by its elongated body, the regular pentagonal shape of its large first apical plate, an equally large sulcal anterior plate, and well developed sculpture, chiefly on the antapical plates. Glochidinium penardiforme and G. platygaster were found in some reservoirs from central and northern Argentina. G. penardiforme was also found in several Argentine rivers and ponds.     

77 Cryptic speciation of Peridinium Limbatum

Cosmopolitanism vs. endemism of microbial diversity in water has been debated for a long time. Finlay (2002) argued that reported similarities in microbial biodiversity in different lakes and oceans support cosmopolitanism of microorganisms. Lee and Patterson (1998) suggested that many endemism studies are flawed due to underrepresentation of taxa. On the other hand, Theriot and Stoermer (1984) showed that Stephanodiscus niagrarae, the centric diatom once thought to be a cosmopolitan species, actually consists of four slightly different species. Mating tests of Paramecium aurelia revealed 14 sibling species, which are morphologically almost identical (Sonneborn, 1957). Here, I present evidence for the cryptic speciation of Peridinium limbatum from two water bodies (Crystal Lake and Crystal Bog) that are near each other but chemically distinct. We observed that the two Peridinium limbatum had different responses to the same growth medium. Previous works at the Microbial Observatory program showed that their seasonal population dynamics were also different; while a summer bloom of Crystal Bog Peridinium limbatum was correlated with a dramatic decrease in phytoplankton diversity, and an extreme drop in bacterial diversity, a bloom of Crystal Lake Peridinium limbatum was not. To see the genetic variations in this study, I sequenced internal transcribed spacer region 1 and 2 from the two Peridinium limbatum. The sequence variations were 8.53% in ITS1 and 8.06% in ITS2, which were much larger than within variations. In another ongoing study that I expect to complete before the meeting, I've been testing their possible allelopathic differences on Cryptomonas.     

Orientation of the photosynthetic flagellate,Peridinium gatunense,in hypergravity

The photosynthetic freshwater flagellate,Peridinium gatunense, uses both positive phototaxis and negative gravitaxis to move upwards in the water column. At higher fluence rates approaching those at the surface of their habitat, the cells tend to become unoriented and thus stop their upward movement. Orientation and motility ofPeridinium gatunense has been studied in the slow rotating centrifuge microscope (NIZEMI), which allows observation of swimming behavior during centrifugation acceleration between 1g and 5g. The movement vectors were analyzed by real time image analysis capable of tracking many cells simultaneously. At 1g the orientation was not very precise, but the degree of orientation increased significantly at higher acceleration forces up to about 3g. Most cells were capable of swimming even against an acceleration vector of 3.8g; at higher acceleration forces the cells were not able to cope with the centrifugal force. The linear velocity of cells swimming against 1g was about 20% lower than that of cells moving in other directions. The velocity decreased even more in cells swimming against higher acceleration forces.     

A SURVEY OF AUXOTROPHY IN FIVE FRESHWATER DINOFLAGELLATES (PYRRHOPHYTA)1

Peridiniopsis polonicum (Wolosz.) Bourrelly requires vitamin B₁₂, and Peridinium limbatum (Stokes) Lemm. requires thiamin for growth. Unlike marine Peridinium species, Peridinium willei Huit.-Kaas, P. volzii Lemm., and P. inconspicuum Lemm. do not display auxotrophy. Peridinium volzii is strongly inhibited by concentrations of biotin above 1 μg L^?1.     

UTEX 1336: PERIDINIUM CINCTUM OR PERIDINIUM VOLZII (DINOPHYCEAE)?1

Plate pattern variation in UTEX clone 1336 and published photographs using this clone indicate the presence of two taxa: Peridinium cinctum and Peridinium volzii. All subclones established from UTEX 1336 contain the same two cell types. The identification of UTEX 1336 and its future use by researchers are discussed.     

ULTRASTRUCTURE OF THE CORALLINACEAE (RHODOPHYTA) II. VEGETATIVE CELLS OF LITHOTHRIX ASPERGILLUM1

The ultrastructure of the calcareous red coralline alga Lithothrix aspergillum Gray and the development of the various tissue types has been studied. The sub-apical meristematic tissue alternately produces genicular or intergenicular cells. The genicular cells rapidly elongate and their cell walls thicken and become denser as more fibrillar wall material is laid down within the cell wall. These cells contain little cytoplasm and few organelles. The inter genicular cells which elongate only slightly during development have a small vacuole and many free starch grains in the cytoplasm. The peripheral cells in each inter genicular layer remain meristematic and form a cortical cell layer over the genicular cells. These cortical cells and the apical meristematic cells are covered by small epidermal cells which have extensive cell wall ingrowths between the chloroplasts. The inter genicular cells are calcified. Although the CaCO₃ is laid down within the cell walls, there is always a thin layer of CaCO₃-free organic cell wall material between the plasmalemma and the CaCO₃ impregnated wall. Only the distal tips of the genicular cells are calcified. In old genicular tissues of Lithothrix, secondary deposits of CaCO₃ of unknown crystallography are also found in the spaces between the cell walls. Thus there appear to be at least two mechanisms of calcification in this alga.     

THE EFFECTS OF TEMPERATURE,IRRADIANCE, AND NITROGEN ON THE ENCYSTMENT AND GROWTH OF THE FRESHWATER DINOFLAGELLATES PERIDINIUM CINCTUM AND P. WILLEI IN CULTURE (DINOPHYCEAE)1

Effects of temperature, irradiance, and nitrogen availability on the encystment and growth of the freshwater dinoflagellates Peridinium cinctum Ehrenberg and Peridinium willei Huitfeld-Kaas were studied in culture. Lack of nitrogen was the main trigger of encystment in both species. Irradiance had a secondary effect on the percentage of the population of each species that encysted. Temperature did not significantly affect encystment in either species. In both species, only a small percentage of the population underwent encystment. Low light had an inhibitory effect on the growth of P. willei growing in nitrogen-sufficient medium.     

PERIDINIUM GREGARIUM,A NEW SPECIES OF DINOFLAGELLATE1,2

A dinoflagellate has been found in tidepools on the coast of the Palos Verdes Peninsula in southern California. It is described as a new species, Peridinium gregarium. In the tidepool habitat, great numbers of the organism form cloud-like masses held together by a mucous matrix. The gregarious cloud formation seems to be shared by only one other species of dinoflagellate, Peridinium sociale (Henneguy ex Labbé) Biecheler, 1935.     

Transferring the freshwater dinoflagellate Peridinium wisconsinense (Dinophyceae) to the family Thoracosphaeraceae,with the description of Fusiperidinium gen. nov.

Distinctive spindle‐shaped thecae first described by Samuel Eddy in 1930 and assigned to the genus Peridinium Ehrenberg are commonly reported from freshwater environments in eastern North America. We demonstrate that thecae incubated from cysts of Peridinium wisconsinense Eddy have six cingular plates and a protuberant apical pore complex characteristic of the family Thoracosphaeraceae Schiller 1930 emend. Tangen in Tangen et al . 1982. Small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer (ITS) sequences confirm the close genetic similarity with Chimonodinium lomnickii (Wo?oszyńska) Craveiro, Calado, Daugbjerg, Gert Hansen & Moestrup and with species recently reassigned to the genus Apocalathium Craveiro, Daugbjerg, Moestrup & Calado that was inferred from previously published LSU rDNA analysis of cysts of P. wisconsinense . Despite sharing identical tabulation with the thoracosphaeracean genera Chimonodinium Craveiro, Calado, Daugbjerg, Gert Hansen & Moestrup and Apocalathium , substantial morphological differences in the morphology of both the thecate and cyst stages of P. wisconsinense led us to reassign this species to the genus Fusiperidinium gen. nov. The phylogenetic position of Fusiperidinium wisconsinense comb. nov., inferred from concatenated data of SSU and LSU sequences, suggests that it evolved from the brackish Scrippsiella lineage, independently of the transition that produced the family Peridiniaceae. Cysts described as Geiselodinium tyonekensis Engelhardt from nonmarine strata from Alaska are apparently identical to the resistant cysts produced by F. wisconsinense . The palynologically‐constrained late Middle Miocene age for the Tyonek Formation provides a minimum age of 11.6 Ma for the evolution of this lineage, coinciding with a rapid glacioeustatic decline in sea level. Our findings also call into question the inclusion of the family Thoracosphaeraceae within the order Peridiniales Haeckel.     

Neue und wenig bekannte Flagellaten aus dem Hausersee (Schweiz)

Zusammenfassung Eine Anzahl seltener oder neuer Flagellaten, welche im Zentrifugenplankton des Hausersees bei Andelfingen (Kt. Zürich, Schweiz) beobachtet wurden, werden beschrieben. Peridinium penardiforme, Strombomonas urceolata, Chlamydomonas insignis und Sphaerellopsis Lefèvrei wurrden bisher im Limnoplankton nur vereinzelt oder an geographisch weit voneinander entfernten Stellen festgestellt. Neu beschrieben werden insgesamt 11 Arten: Cryptomonas globosa, Amphidinium Skujae, Gymnodinium titubans, Peridinium sphaeroideum, Petalomonas pygmaea, Petalomonas elongata, Anisonema hexagonale, Carteria Huberi, Chlamydomonas deludens, Chlamydomonas opisthostigma, Chlamydomonas crassa.

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Summary Some rare or new flagellates, found in the Hausersee (Kt. Zurich, Switzerland) are described. Peridinium penardiforme, Strombomonas urceolata, Chlamydomonas insignis and Sphaerellopsis Lefèvrei, seldom found in limnological investigations, live euplanctical in the Hausersee. The new species described are: Cryptomonas globosa, Amphidinium Skujae, Gymnodinium titubans, Peridinium sphaeroideum, Petalomonas pygmaea, Petalomonas elongata, Anisonema hexagonale, Carteria Huberi, Chlamydomonas deludens, Chlamydomonas opisthostigma, Chlamydomonas crassa.

     

THE ULTRASTRUCTURE OF LICHENS. I. A GENERAL SURVEY

The fine structure of 10 lichens was examined. A comparison was made of the storage products of the algal symbiont (Trebouxia) in situ in the desiccated and hydrated states of the lichens. All the Trebouxia phycobionts, with the exception of that in Usnea strigosa, had lipid-containing globules in the pyrenoid. The globules were present in both the hydrated and desiccated conditions. Trebouxia in the hydrated condition contained starch granules in the chloroplast as well as the lipid-containing globules in the pyrenoid. The cell wall of Trebouxia consists of an outer electron-dense layer and an inner electron-light layer. Fungal haustoria (in Lecanora rubina) rupture the outer layer of the algal cell wall and invaginate the inner layer. A thick polysaccharide fibrillar material surrounds the fungal cells. Many bacteria were observed within this material. Septa and lomasomes are described. Ellipsoidal bodies, which appear to be an integral and unique part of the lichen fungal ultrastructure, were observed associated with membrane profiles.     

NUCLEAR BASIC PROTEINS FROM THE BINUCLEATE DINOFLAGELLATE PERIDINIUM FOLIACEUM (PYRROPHYTA)1

Histories of the endosymbiont nucleus of the binucleate dinoflagellate Peridinium foliaceum Stein were prepared from isolated nuclei and analyzed by peptide mapping, ammo acid composition, and two-dimensional gel electrophoresis. Using these criteria, we identified the presence of two HI-like histories and the core histones H3, H2A, H2B, and H4. These histones are similar but not identical to those of the endosymbiont nucleus of the bi-nucleate dinoflagellate Peridinium balticum Levander.     

STUDIES OF A MARINE GRASS,THALASSIA TESTUDINUM. I. ULTRASTRUCTURE OF THE OSMOREGULATORY LEAF CELLS

Thalassia testudinum (Turtle Grass), a marine monocot which grows completely submerged, differs from intertidal and other halophytic angiosperms in that it has no specialized saltsecretory glands. Osmoregulation appears to be accomplished by the epidermal leaf cells which have highly invaginated plasmalemmas with numerous mitochondria situated in the interdigitations. The ultrastructure and proposed mode of secretion are similar to that of the salt-marsh monocot Spartina, but differ from that found in dicots. Evidence is presented to show why monocots are the only angiosperms which have adapted to a completely marine environment.