New records of Peyssonnelia armorica and Peyssonnelia harveyana (Rhodophyta, Gigartinales) from Japan

Two species of the crustose red algal genus Peyssonnelia (Gigartinales, Peyssonneliaceae) are reported from Japanese waters for the first time. These species share the following combination of vegetative and reproductive features: thalli with appressed margins, perithallial filaments arising from the whole upper surface of each hypothallial cell (the Peyssonnelia rubra‐type anatomy), unicellular rhizoids, hypobasal calcification and spermatangia that are produced in double chains (the Peyssonnelia harveyana‐type spermatangial filament). However, they differ obviously from each other in the hypothallus orientation as seen from below, the perithallus structure in relation to the consistency of the crust, the origin of gonimoblasts and the elevation of the nemathecia. Peyssonnelia armorica is characterized by: (i) hypothallial filaments comprising a polyflabellate layer; (ii) easily separable perithallial filaments in a gelatinous matrix; (iii) gonimoblasts originating exclusively from the auxiliary cell; and (iv) semi‐immersed (slightly elevated) nemathecia. Peyssonnelia harveyana is characterized by: (i) hypothallial filaments arranged in parallel rows; (ii) closely packed perithallial filaments in a firm matrix; (iii) gonimoblsts originating from both the auxiliary cell and the connecting filament; and (iv) conspicuously elevated nemathecia.     

Characterization of the crustose red alga Peyssonnelia japonica (Rhodophyta,Gigartinales) and its taxonomic relationship with Peyssonnelia boudouresquei based on morphological and molecular data

The vegetative and reproductive morphology of the crustose red alga Peyssonnelia japonica (Segawa) Yoneshigue was re‐examined based on the holotype specimen and recent collections from various localities in Japan, including the type locality, and Hawaii. This species is characterized by the following features: thallus with appressed margins, perithallial filaments arising from the entire upper surface of each hypothallial cell (the Peyssonnelia rubra‐type), easily separable perithallial filaments in a gelatinous matrix, hypothallial filaments arranged in parallel rows, unicellular rhizoids, hypobasal calcification, gonimoblasts derived mainly from connecting filaments, and spermatangia produced in a series of whorls comprised of one to four paired spermatangia surrounding each central cell (the Peyssonnelia dubyi‐type). In addition to these features, the dimensions of the vegetative and reproductive structures of Peyssonnelia boudouresquei Yoneshigue described from Brazil were consistent with those of P. japonica. Molecular phylogenetic analyses using partial 26S rDNA, rbcL, and cox2‐3 spacer DNA sequences also supported the monophyly of P. japonica (from 16 localities in Japan and one locality in Hawaii) and P. boudouresquei (from two localities in Brazil). Therefore, P. boudouresquei may be a taxonomic synonym of P. japonica. However, considering the relatively high sequence divergences between the two taxa (2.1–2.5% in partial 26S rDNA, 5.9–6.7% in rbcL, and 5.8–6.7% in cox2‐3 spacer), and the relatively limited geographic sampling ranges, we reserve the taxonomic conclusion until further morphological and genetic data of the specimens from other geographic areas connecting Japan and Brazil become available.     

Verosphacela silvae sp. nov. (Onslowiaceae, Phaeophyceae) from the Mediterranean Sea

We describe Verosphacela silvae sp. nov., from the Mediterranean Sea. It consists of horizontal filaments living on the lower face of the red alga Peyssonnelia rubra (Greville) J. Agardh, from which erect filaments up to 1.5 mm high rise and grow upright after passing through the thallus of the supporting species. There are both horizontal and erect filaments growing by apical cells. In the subapical cells, 1–2 longitudinal divisions occur (more frequently in the erect filaments) but no secondary transverse divisions occur. Erect filaments bear lateral propagules on a stalk of one to three (rarely more) cells. Propagules, with neither apical cells nor arms, consist of seven cells. Zoidangia are borne at the apex of erect laterals. The new species differs from V. ebrachia Henry mainly in habit, propagules and zoidangia. In addition, distinct from V. ebrachia, filaments of V. silvae never penetrate between the cuticle and the cell wall of the supporting alga. Moreover, propagules of V. silvae consist of seven cells, whereas those of V. ebrachia consist of 9–13 cells, and zoidangia are terminal on laterals in V. silvae, whereas in V. ebrachia they are sessile on both axes and laterals.     

REASSESSMENT OF THE LITTLE‐KNOWN CRUSTOSE RED ALGAL GENUS POLYSTRATA (GIGARTINALES), BASED ON MORPHOLOGY AND SSU rDNA SEQUENCES1

The taxonomic distinctiveness of the crustose red algal genus Polystrata Heydrich (Peyssonneliaceae) is confirmed on the basis of morphological and molecular data. The vegetative and reproductive morphology of the type species Polystrata dura Heydrich is newly described. Polystrata thalli are thick multi‐layered crusts, each crust of which is composed of a mesothallus, a superior perithallus, and an inferior perithallus. P. dura is characterized by a poorly developed inferior perithallus consisting of single‐celled perithallial filaments and each layer of multi‐layered crusts being closely adherent to the parental layer. This Polystrata species is identical to Peyssonnelia species, the type genus of the Peyssonneliaceae in the morphology of sexual reproductive organs: a carpogonial branch and an auxiliary cell branch are formed laterally on respective nemathecial filaments; the gonimoblasts are developed from connecting filaments and auxiliary cells; the spermatangia are produced in male and female nemathecia; and the spermatangial filament produces a series of one to four paired spermatangia that form a whorl surrounding each central cell (the Peyssonnelia dubyi‐type development). Polystrata fosliei (Weber‐van Bosse) Denizot is clearly distinguished from P. dura by an inferior perithallus as well‐developed as the superior perithallus, and each layer of multi‐layered crusts being loosely adherent to the parental layer. In our small subunit rDNA trees of the Peyssonneliaceae, these Polystrata species formed a clade with low to medium supports, although the phylogenetic position of Polystrata was unresolved in this family. Therefore, the thallus structure of Polystrata may be regarded as an important taxonomic character at the genus rank.     

Taxonomic features of the red alga Meristotheca coacta (Solieriaceae, Gigartinales)

Vegetative and reproductive structures of the little‐known red alga, Meristotheca coacta Okamura (Solieriaceae, Gigartinales) were described on the basis of specimens collected from three localities in southern Japan, including an island close to the lectotype locality. Meristotheca coacta was shown to be a strongly supported monophyletic clade in our rbcL analyses. The taxonomic features of this species were reassessed. This species is characterized as follows: (i) the thalli consist of relatively thick (300–1400 μm from the uppermost to basal regions), elastic and rose‐red blades; (ii) the blades are irregularly lobed and branched into variously shaped segments with undulate and crispate margins; (iii) tetrasporangial initials are laterally attached to their parental cells and the lateral pit‐connections remain in mature tetrasporangia; (iv) gametophytes are dioecious; (v) carpogonial branches are three‐celled (occasionally two‐ or four‐celled); (vi) a darkly staining auxiliary cell complex is present and recognizable prior to diploidization; and (vii) cystocarps are produced along (or near) the margins of the blades and on the marginal proliferations and lack spinous outgrowths.     

Observations on Purpureofilum apyrenoidigerum gen. et sp. nov. from Australia and Bangiopsis subsimplex from India (Stylonematales, Bangiophyceae, Rhodophyta)

Purpureofilum apyrenoidigerum gen et sp. nov. was obtained from a mangrove habitat in New South Wales, Australia. It had unbranched uniseriate to multiseriate filaments less than 1 mm tall, with a unicellular base. Each cell had a single multilobed parietal chloroplast without a pyrenoid. During reproduction vegetative cells were discharged directly as monospores that remained motile for several hours after release. Spores with long tails moved more slowly (0.053–0.195 μm sχ) than spores without tails (0.43–1.76 μm s′¹). Phylo‐genetic analysis of sequences of the small subunit of the nuclear‐encoded rRNA and plastid‐encoded ribu‐lose bisphosphate carboxylase/oxygenase genes revealed that Purpureofilum is a member of the Stylonematales and is most closely related to the filamentous genus Bangiopsis. Bangiopsis differs from Purpureofilum by having longer (to 5 mm) multiseriate filaments, cells containing a stellate chloroplast, a conspicuous central pyrenoid, and monospores often formed in packets. Monospores of Bangiopsis were also motile. Transmission electron microscopy investigation of Purpureofilum and Bangiopsis revealed that the Golgi complexes are associated only with rough endo‐plasmic reticulum and that the plastid contains a peripheral thylakoid; this combination of features being the same as in all other multicellular members of the Stylonematales. The low molecular weight carbohydrates of Purpureofilum and Bangiopsis were digenea‐side and sorbitol, which were present in most other Stylonematales.     

MORPHOLOGY AND REPRODUCTION OF THE RED ALGA ACROCHAETIUM PECTINATUM IN CULTURE12

The life history of the marine red alga Acrochaetium pectinatum (Kylin) Hamel was studied in unialgal culture using supplemented natural seawater media. The tetrasporophytes are larger than the gametophytes, have a compact filamentous basal system, and produce monosporangia and tetrasporangia. Mono-spores give rise to tetrasporophytes. Tetraspores develop into small gametophytes with unicellular bases. The gametophytes are heterothallic when small (usually less than 500 μ) but as some females become larger (2-3 mm) they produce spermatangia as well as carpogonia. Gametophytes may bear mono-sporangia in addition to carpogonia or spermatangia. These monospores give rise to gametophytes. Fertilization of the carpogonia has not been observed. The tetrasporophytes produce only monosporangia in day-lengths of 12-16 hr, but both tetrasporangia and monosporangia are formed in daylengths of 6–10 hr. Tetrasporangial production is reduced at 15 C compared with 10 C. Light intensity in the range of 5-200 ft-c (cool white fluorescent lighting) has no apparent influence on induction of tetrasporangia. Induction of tetrasporangia is not a photoperiodic response because their development is not inhibited by a brief light break in the middle of the dark period in short daylengths. Plastid morphology, origin, and frequency of sporangia and vegetative branching are variable during the ontogeny, and consequently are somewhat unreliable as taxonomic criteria. Differences in basal systems between gametophytes and tetrasporophytes also indicate that this feature, which is used to distinguish major subgeneric groupings in Acrochaetium, may not be as useful as previously thought.     

Studies on Metamastophora (Corallinaceae,Rhodophyta). I. M. flabellata (Sonder) Setchell: Morphology and anatomy

A morphological-anatomical study of Australian populations of Metamastophora flabellata (Sonder) Setchell, the type species of Metamastophora (Corallinaceae, Rhodophyta), has revealed that the primarily erect or ascending non-geniculate thallus possesses a dorsi-ventral organization of tissues. All conceptacles are uniporate and arise dorsally. Two distinct vegetative meristems occur: an apical primary meristem from which hypothallial cells are produced basipetally and a sub-epithallial secondary meristem which generates perithallial cells basipetally and secondary epithallial cells acropetally. Primary epithallial cells arise from divisions of subapical hypothallial cells. In younger parts, tissues are produced only dorsal to the hypothallium; in veins and stipes, tissue production occurs both dorsal and ventral to the hypothallium. Mature tetrasporic conceptacles contain peripheral tetrasporangia with zonately divided contents and a central sterile columella. Gametic conceptacles produce fertile tissue across the entire conceptacle chamber floor. After fertilization, the zygotic nucleus or a derivative is transferred (presumably) to an auxiliary cell through cells of the carpogonial branch; no tubular transfer siphon develops. Mature fusion cells are composed of the amalgamated supporting cells of carpogonial branches and are initiated from a single supporting cell which functions as an auxiliary cell. Unbranched 3–4 celled gonimoblast filaments arise from the fusion cell, do not become connected to other cells, and produce terminal carposporangia. Results from this study have led to a redefinition of hypothallium and perithallium in relation to meristems rather than substrate. In addition, carposporophyte ontogeny in the Corallinaceae is considered in terms of the presumed mode of transfer of the zygotic nucleus to the fusion cell, the extent of fusion cell development, and gonimoblast filament production in relation to auxiliary cells and fusion cells.     

Role of Cell Hydrophobicity on Colony Formation in Microcystis (Cyanobacteria)

Colony formation is highly import ant for the competitive advantage of the cyanobacterium Microcystis over other phytoplankton species. The laboratory‐grown colonial Microcystis strains isolated from Lake Taihu (China) maintained colonial forms under the low light condition (10 μE m^–2 s^–1). The cell surface hydrophobicities of the Microcystis colonies were measured by cyanobacterial adherence to xylene in comparison with unicellular Microcystis strains. The cells of the tested colonial strains were all hydrophobic, while the cells of the tested unicellular strains were all hydrophilic. Incubation under the higher light condition (75 μE m^–2 s^–1) leaded to the significant decrease in the cell hydrophobicities of the colonial Microcystis and the transition from colonial forms to unicellular forms. These findings indicated that the cell hydrophobicity of Microcystis may play a role in cell‐cell adherence and colony formation. Phosphate‐limitation, nitrate‐limitation and pH did not affect cell hydrophobicities of colonial Microcystis. Treatment with proteolytic enzymes had no effect on the cell hydrophobicity, indicating that cell surface proteins did not contribute to high cell hydrophobicity. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

IN-SITU MORPHOLOGY AND OCCURRENCE OF EUCARYOTIC PHOTOTROPHS OF BACTERIAL SIZE IN THE PICOPLANKTON OF ESTUARINE AND OCEANIC WATERS1

Concentrates of the picoplankton (0.2–2.0 μm) sized fraction from the euphotic zone of estuarine and oceanic waters were examined by transmission electron microscopy. In addition to the numerous phototrophic procaryotes (chroococcoid cyanobacteria) previously reported, small phototrophic eucaryotes were observed in 20 of 25 samples examined. Micromonas pusilla (Butcher) Manton and Parks, a 1 × 1.5 μm flagellate, was abundant in estuarine samples in summer. Similar sized cells of non-flagellated chlorophytes, either Nannochloris Naumann or Chlorella Beijerinck, were observed sporadically in many samples. The most ubiquitous microalga was a scaled, non-flagellated prasinophyte that occurred at 9 of 15 different locations on 15 of 20 sampling dates in water samples from Iceland to the Caribbean Sea, This tiny alga (0.5 to 1.0 μm in diam.) is probably the smallest known photo-trophic eucaryote and has not heretofore been described. Enrichment cultures using conventional techniques on several cruises yielded only the Chlorella-type of green alga, as well as numerous isolates of unicellular chroococcoid cyanobacteria.     

Dasya enomotoi sp. nov. (Dasyaceae,Ceramiales), a new large Dasya from Japan

A new red alga, Dasya enomotoi, is described from Japan. This species is characterized by having a large thallus consisting of an elongated axis and many, radially arranged, polysiphonous branches both of which are heavily corticated and densely covered with numerous, soft monosiphonous filaments. It is distinguished from several similar species by the combination of the following: (i) indistinct pericentral cells in transverse sections except near the apices, (ii) the presence of enlarged, inner cortical cells, (iii) radially arranged adventitious monosiphonous filaments, (iv) three‐celled carpogonial branches, (v) six (sometimes five) tetrasporangia in each fertile segment of the stichidia, and (vi) three tetrasporangial cover cells that are not elongated longitudinally and usually not divided transversely. This species may have been identified as D. villosa Harvey by previous investigators in Japan.     

New record of Sporochnus dotyi (Sporochnales,Phaeophyceae) from Kii Peninsula,Japan

The subtidal brown algal species Sporochnus dotyi Brostoff (Sporochnales, Phaeophyceae), which has been regarded as a Hawaiian endemic, is reported from Kushimoto, Kii Peninsula, Pacific coast of central Honshu, Japan, for the first time outside Hawai'i. The species grew on subtidal rocks ca. 5–20 m deep attached by a small conical holdfast. The erect thalli were 5–30 cm high, terete, robust and alternately branched in 1–2 orders. When mature, pedicellate receptacles developed on the branches, and formed elliptical sori 1 mm long with a pedicel 3–5 mm long. The apical parts of the thalli and the receptacles were terminated with a tuft of simple assimilatory filaments of up to 4 mm long and showed prominent green to yellow underwater iridescence. Reproductive filaments (paraphyses) were densely packed, simple, up to 200 μm long and bore 4–6 mostly unilateral unilocular zoidangia 20–22 μm long and 5–6 m in diameter. In the genetic analyses, the Sporochnus alga from Kushimoto had partial rbcL sequence identical to S. dotyi from Hawai'i. The cox3 phylogeny revealed that this alga formed a fully supported clade with S. dotyi. Therefore, we identified the alga from Kushimoto as S. dotyi. This finding of S. dotyi from Japan, together with the recent reports of the mesophotic macroalgae Ryuguphycus kuaweuweu (=Umbraulva kuaweuweu), Ulva iliohaha and Newhousia imbricata from various localities in the Pacific Ocean including Japan, suggest closer biogeographical connections of subtidal/mesophotic macroalgae in the Pacific than previously recognized.     

Two species of Dasya (Ceramiales, Rhodophyta) from Bonin Islands, southern Japan, with the description of Dasya boninensis sp. nov.

Two species of Dasya in the Dasyaceae (Ceramiales, Rhodophyta) are reported from Bonin Islands, southern Japan. Dasya murrayana Abbott et Millar, new to Japan, is characterized by the following set of features: the tufted habit (up to 30 erect axes developing from a basal disc), small‐sized (6–10 mm high and 350–500 μm in diameter in the middle region), thinly but completely corticated axes, rigid and incurved pseudolaterals forming corymbose heads at the apices of axes and branches, the absence of adventitious monosiphonous filaments, a large number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral and slender spermatangial branches (35–45 μm in diameter). Dasya boninensis Masuda, Kurihara et Kogame, sp. nov. is characterized by short but thick (10–30 mm high and 600–1000 μm in diameter at the middle portion), heavily corticated axes, indistinct pericentral cells except for the upper portion in transverse sections, soft, straight pseudolaterals and adventitious monosiphonous filaments densely covering the axis and branches, a small number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral, thick spermatangial branches (65–90 μm in diameter), and short‐necked cystocarps. A dichotomous key to the taxa found in Japanese waters is given.     

LIFE HISTORIES IN THE PHYLLOPHORACEAE (RHODOPHYTA: GIGARTINALES) FROM THE PACIFIC COAST OF NORTH AMERICA. I. GYMNOGONGRUS LINEARIS AND G. LEPTOPHYLLUS1

Carpospores of Gymnogongrus linearis (C. Ag.) J. Ag. collected from Sonoma Co., California were cultured and gave rise to crustose plants. Tetrasporogenesis could not be induced. However, tetraspores from field-collected crustose tetrasporophytes found near G. linearis from San Mateo Co., California were cultured. These field crusts superficially resemble Petrocelis middendorffii (Ruprecht) Kjellman, but differ in size, color, number of tetrasporangia per filament, and distal dichotomous branching of the perithallial filaments. Tetraspores gave rise to upright plants identical to G. linearis. Gymnogongrus leptophyllus J. Ag. collected from California and Baja California, Mexico were found as narrow and wide forms. Narrow form isolates recycled directly without producing a crustose tetrasporophyte. These are interpreted as apogamous. Carpospores of the wide form grew into crusts resembling Petrocelis (=Erythrodermis) haematis Hollenberg. Tetrasporogenesis was induced in culture by abrasion or dehydration. Tetraspores from field-collected crusts and laboratory cultured tetrasporophytes grew into plants identical to G. leptophyllus, completing a sexual life history with an alternation of heteromorphic generations.     

Mutations of Anacystis nidulans that affect cell division

Summary Following nitrosoguanidine treatment of the blue-green alga Anacystis nidulans strain 6311, mutants which grow predominantly as short or long filaments are commonly produced. Cytological study shows that the filaments are multinucleate, coenocytic structures. Such mutations are therefore best interpreted as ones that impair cell division in a normally unicellular organism.     

BATRACHOSPERMUM HETEROCORTICUM SP. NOV. AND POLYSIPHONIA SUBTILISSIMA (RHODOPHYTA) FROM FLORIDA SPRING-FED STREAMS1

Polysiphonia subtilissima Mont. Is reported for the first time from a freshwater environment. The presence of four pericentral cells, subdichotomous branching, apical trichoblasts and rhizoids arising from pericentral cells combined with a lack of cortication and reproductive cells is consistent with marine populations of this species. The range of filament length is 1.4–4.7 cm. Branch diameters are 38–76 μm and pericentral cell lengths are 58–125 μm. Batrachospermum heterocorticum sp. nov. is distinguished primarily by a developmental change in cortical filaments from typical cylindrical cells (5.0–7.9 μm diam in initial stages to enlarged, elliptical cells (12.9–24.1 μm diam) in mature axes. Another unique feature of this species is carpogonia with cylindrical, pedicellate trichogynes on stringht carpogonial branches in mid to outer portions of lateral whorls. Other characteristics of B. heterocorticum include the following: olive-green color, 2–6 cm length, dichotomous to trichotomous fascicles in 4–7 tiers, 385–647 μm whorl diameters, 109–198 μm carpospore diameters and relatively small “chantransia” filaments.     

Metapeyssonnelia tangerina (Peyssonneliaceae,Rhodophyta), a new species associated with coral reef habitats in Puerto Rico,Caribbean Sea

A new Metapeyssonnelia species that comprises up to 7% bottom cover at shallow‐water reef habitats in southwest Puerto Rico is described herein. It forms conspicuous orange encrustations on hard substrata and does not grow on living coral as does its two Caribbean congeners. The new species possesses conspicuous, to 30 cm in extent, tightly adherent crusts up to 950 μm thick, only hypobasal calcification, hypothallial cells arranged in broad flabellules and superficial (raised) tetrasporangial and carposporangial nemathecia. Tetrasporangia are pedicellate, borne laterally from cup‐like cells that are derived from basal paraphysal cells. Tetrasporangia measure up to 120 μm long and individual carposporangia to 80 μm long. The new species differs from other Metapeyssonnelia species developmentally in that perithallial cells at mid thallus height will divide laterally to form a new hypothallium. Small subunit gene sequences relate the new species to the two Metapeyssonnelia species that are previously known from Puerto Rico.     

TIP CELL GROWTH AND THE FREQUENCY AND DISTRIBUTION OF CELLULOSE MICROFIBRIL-SYNTHESIZING COMPLEXES IN THE PLASMA MEMBRANE OF APICAL SHOOT CELLS OF THE RED ALGA PORPHYRA YEZOENSIS1

The supramolecular organization of the plasma membrane of apical cells in shoot filaments of the marine red alga Porphyra yezoensis Ueda (conchocelis stage) was studied in replicas of rapidly frozen and fractured cells. The protoplasmic fracture (PF) face of the plasma membrane exhibited both randomly distributed single particles (with a mean diameter of 9.2 ± 0.2 nm) and distinct linear cellulose microfibril-synthesizing terminal complexes (TCs) consisting of two or three rows of linearly arranged particles (average diameter of TC particles 9.4 plusmn; 0.3 nm). The density of the single particles of the PF face of the plasma membrane was 3000 μm^?2, whereas that of the exoplasmic fracture face was 325 μm^?2. TCs were observed only on the PF face. The highest density of TCs was at the apex of the cell (mean density 23.0 plusmn; 7.4 TCs μm^?2 within 5 μm from the tip) and decreased rapidly from the apex to the more basal regions of the cell, dropping to near zero at 20 μm. The number of particle subunits of TCs per μm² of the plasma membrane also decreased from the tip to the basal regions following the same gradient as that of the TC density. The length of TCs increased gradually from the tip (mean length 46.0 plusmn; 1.4 nm in the area at 0–5 μm from the tip) to the cell base (mean length 60.0 plusmn; 7.0 μm in the area at 15–20 μm). In the very tip region (0–4 μm from the apex), randomly distributed TCs but no microfibril imprints were observed, while in the region 4–9 μm from the tip microfibril imprints and TCs, both randomly distributed, occurred. Many TCs involved in the synthesis of cellulose microfibrils were associated with the ends of microfibril imprints. Our results indicate that TCs are involved in the biosynthesis, assembly, and orientation of cellulose microfibrils and that the frequency and distribution of TCs reflect tip growth (polar growth) in the apical shoot cell of Porphyra yezoensis. Polar distribution of linear TCs as “cellulose synthase” complexes within the plasma membrane of a tip cell was recorded for the first time in plants.     

Vesicle transport and the cytoskeleton in the unicellular red alga Glaucosphaera vacuolata

Vesicles are continually transported from the perinuclear region to the cell's exterior in the unicellular red alga Glaucosphaera vacuolata Korshikov. This phenomenon is recorded here with time‐lapse videomicroscopy. The mechanism governing this intracellular motility is unknown but the cytoskeleton is believed to be involved. Microtubules and actin filaments are located in Glaucosphaera using fluorescently conjugated antibodies and FITC‐phallicidin, respectively. Microtubules radiate in all planes from the perinuclear region to the periphery whereas actin filaments form rings around migrating vesicles. This pattern of location might indicate that both microtubules and actin filaments are involved in vesicle transport. However, this conclusion is not confirmed directly because the thick mucilaginous wall material seemed to prevent the entry of cytoskeletal inhibitors. A video clip of vesicle movement is available at http://www.cytographics.com/ .     

ULTRASTRUCTURE OF TETRASPOROGENESIS IN THE MARINE RED ALGA PTILOTA HYPNOIDES1

Both tetrasporangia and dormant apical cells of short vegetative filaments of the marine red alga Ptilota hypnoides have been examined by electron microscopy. Various cytoplasmic inclusions readily distinguish the vegetative apical cells from the reproductive apical cells which become tetrasporangial mother cells. The transformation of tetrasporangial mother cells into mature tetrasporangia involves a series of cytoplasmic changes which can be correlated with specific changes in the investing wall layers. The extracellular changes provide the basic criteria for the division of tetrasporogenesis into 3 successive stages. The ultrastructure of each stage is described and discussed in relation to the current knowledge of red algal cytology. In addition, a possible mechanism for the liberation of spores and gametes of red algae is proposed.