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Background and Aims Through careful field examination of the growth habit of the gametophytes and sporophytes of Hymenasplenium volubile across an ontogenetic series, we aim to understand better the evolution of epiphytism in this poorly understood group of ferns Methods We made field observations of H. volubile sporophytes and gametophytes, and brought specimens back to the lab for microscopic analysis. In the field, sporophytes at each ontogenetic stage were photographed to document the species’ growth habit. We used an existing phylogeny to optimize growth form of New World Hymenasplenium. Key Results Young sporophytes were at first fully epiphytic and produced one or two long feeding roots that extend to the soil where they branch profusely. The feeding roots remain in contact with the soil throughout the life of the plant. Thus, H. volubile is a hemiepiphyte. While immature, gametophytes are appressed to the tree trunk, but, as their gametangia mature, their lower margin lifts upward, imparting a shelf-like appearance to the thallus. The thallus attaches to the substrate by branched rhizoids produced along the margin of the thallus in contact with the substrate. Conclusions Hemiepiphytes are a key link in the evolution of epiphytic ferns and may act as a bridge between the forest floor and the canopy. Our finding is the first report of hemiepiphytism in Aspleniaceae, a large lineage with many epiphytic and terrestrial taxa. This work serves as an important model to understand the evolution of epiphytism in this group specifically and in ferns in general. The majority of our understanding of fern gametophyte biology is derived from laboratory studies. Our efforts represent a fundamental contribution to understanding fern gametophyte ecology in a field setting.

The paper reports a process of sexual reproduction in the Black Sea diatom Climaconeis scalaris (Brebisson) E.J. Cox, 1982, initiated in laboratory conditions. A crossing system of this species allows both homo- and heterothallic reproduction. The fertilization is allogamous. Diploid mother gametangial cells secreted mucilage, forming a mucilage track, while actively gliding relative to each other. Each gametangium in a pair produced two elongated, cylindrical round-ended haploid gametes, which were largely morphologically and behaviorally isogamous. The division of the protoplast of the gametangial cell occurred in the transapical plane without the rearrangement of gametes. Growing auxospores were located parallel to the parent frustules. The research produced data on changes in the cell size, number of chloroplasts, and the position of cardinal points in the life cycle of the examined species.

In the Baltic area, the long-lived dioicous wetland moss Drepanocladus turgescens (T.Jensen) Broth. produces sporophytes rarely and at irregular intervals. Based on surveys of sporophyte occurrences at 13 sites in two regions in northern Gotland (Sweden) during three to five years, we ask: (1) Is sporophyte formation associated with precipitation and a precipitation index that considers the dry periods during July-August of the preceding year, when gametangia are formed and fertilization occurs? (2) Does the estimated spore output suffice for the species’ long-term persistence of the (Northern) European population species? In one of the study regions, where D. turgescens occurs in depressions, sporophyte formation was associated with the two precipitation parameters. In the other study region, with relatively higher precipitation and exposed occurrences on a slightly sloping bedrock with very little accumulated soil, no such association existed. We suggest that this lack of weather effects results from that the exposed rock habitat requires longer continuously wet periods than the depression habitat to allow for gametangia initiation and development, and fertilisation. Average spore production for six spore capsules, from three Gotland localities was 181,000. Based on the sporophyte counts during the survey years, we estimated the total reproductive output as 411.5 million spores in 2013, and 42.5 million in 2015, in the two respective study regions. Taken together with data on haplotype patterns and considering observations on recent colonisations, we argue that such a relatively low and episodic regional spore production is sufficient to maintain global populations of long-lived species, even if these occur in specialized and geographically restricted habitats.

Ferns have conspicuous sporophytes as the dominant phase in their life cycle, however, the gametophytes are completely separated from the sporophytes and supply their own nutrition, unlike in bryophytes and seed plants. Among the gametophytes, some maintain their populations in the gametophyte phase without progressing to sporophyte production and are known as independent gametophytes. Independent gametophytes of Antrophyum obovatum Baker were recently reported in one population on Jeju Island, Korea. In the present study, we surveyed more places to find new independent gametophyte populations of A. obovatum using the rbcL gene sequence-based DNA barcoding technique. We identified two new sites inhabited by independent gametophytes. Archegonia and juvenile sporophytes were independently observed in each location under slightly different environmental conditions. Consequently, in the case of this species, functional sporophyte production is likely suppressed by prezygotic and postzygotic sterility, depending on microenvironmental factors.

espanolSe estudio la fase gametofitica de las especies Amblovenatum immersum y Christella subpubescens (Thelypteridaceae) incluyendo la germinacion, el desarrollo morfologico, caracteristicas vegetativas y estrategias reproductivas. El modelo de germinacion para ambas especies se ajusta al tipo Vittaria, mientras que el modelo de desarrollo del gametofito corresponde con el tipo Drynaria. Los gametofitos adultos eran cordados, con multitud de pelos unicelulares y secretores tanto por el margen, como por ambas caras del protalo. Ademas, en C. subpubescens se detectaron otro tipo de pelos aciculares, unicamente en el margen. Los gametangios presentaban el aspecto tipico de los helechos leptosporangiados. En A. immersum todos los gametofitos se desarrollaron como femeninos. En C. subpubescens los gametofitos primeramente son femeninos, con el paso del tiempo se vuelven bisexuales. Se detecto actividad de anteridiogeno en ambas especies, ya que despues del desarrollo de los gametofitos femeninos aparecieron en los alrededores protalos masculinos en fases muy tempranas de desarrollo (con ausencia de meristemo), pero sexualmente maduros. EnglishThe gametophytic generation of Amblovenatum immersum and Christella subpubescens (Thelypteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and reproduction strategies, was studied. For both species, the spore germination was of the Vittaria type and the developmental pattern was of the Drynaria type. Adult gametophytes were cordate and hairy, with unicellular and secretory hairs located in the margins and both the ventral and dorsal surfaces of the prothalli. C. subpubescens has another type of acicular hairs only in the margin of the prothallus. Gametangia were of the normal type described for leptosporangiate ferns. In A. immersum all the gametophytes were female. In C. subpubescens the gametophytes produced at first instance female gametangia and then became bisexual with time. Antheridiogen activity was observed in both species, suggested by the presence of small young ameristic gametophytes with antheridia surrounding well-developed female ones.

The sexual reproduction and life history of the marine pennate diatom Entomoneis cf. paludosa have been described for the first time. The sexual process has been found to involve two gametangia, each producing two gametes. This species is characterized by morphological and behavioral isogamy. Its mating system includes the heterothallic mode of reproduction, with no cases of homothallic reproduction recorded. The type of sexual process is categorized as IC in Geitler’s system. © 2021, Pleiades Publishing, Ltd.

Within-clutch gamete size variability in Monostroma angicava. In many organisms, it is unclear how the size variation in gametes is generated in each clutch (i.e., total gametes produced by a gametophyte for a single spawning) or how gamete size is adjusted. Within-clutch variation in gamete size has been explained as a result of either physiological/developmental constraints or bet hedging during gametogenesis. These two explanations have been assumed to be mutually exclusive, and related observations are conflicting. The slightly anisogamous dioecious green alga Monostroma angicava employs a simple mechanism to produce gametes of each sex: each vegetative cell becomes a single gametangium cell, which synchronously divides to form equally sized gametes. The number of such cell divisions has several variations, which might vary gamete size. We measured the volume of gametangia in each clutch, counted the number of cell divisions in each gametangium and estimated the size of the gametes. We found that larger gametangia divided more times than smaller gametangia in both sexes, although male gametangia were smaller than female gametangia when they underwent the same number of cell divisions. Therefore, the variation in the number of cell divisions during gametogenesis serves to adjust gamete size in each sex rather than to vary it. Within-clutch gamete size variability originates in within-clutch variation in gametangium size: any factors that increase the variation in the size of gametangia can increase the within-clutch variation in gamete size.

Matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) was employed to discriminate between cell differentiation processes in macroalgae. One of the key developmental processes in the algal life cycle is the production of germ cells (gametes and zoids). The gametogenesis of the marine green macroalga Ulva mutabilis (Chlorophyta) was monitored by metabolomic snapshots of the surface, when blade cells differentiate synchronously into gametangia and giving rise to gametes. To establish MSI for macroalgae, dimethylsulfoniopropionate (DMSP), a known algal osmolyte, was determined. MSI of the surface of U. mutabilis followed by chemometric data analysis revealed dynamic metabolomic changes during cell differentiation. DMSP and a total of 55 specific molecular biomarkers, which could be assigned to important stages of the gametogenesis, were detected. Our research contributes to the understanding of molecular mechanisms underlying macroalgal cell differentiation. Graphical abstract Molecular changes during cell differentiation of the marine macroalga Ulva were visualized by matrix assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI).

Bryophytes are unique among land plants in that the gametophyte generation is photosynthetically dominant, with the sporophyte permanently attached to and partially parasitic upon the gametophyte. It is therefore convenient to consider the process of sexual reproduction as beginning with the development of gametangia upon the gametophyte and proceeding through gametangial maturation, fertilization, sporophyte development, and sporogenesis to the release of spores. There have been two main phases in studies of seasonal patterns of reproductive development. In early investigations a number of authors reported dates of fertilization and spore release in a wide range of European and North American mosses. The environmental factors controlling the different phases of development are likely to vary between species. However, common features sometimes may be detected among groups of species occupying particular habitats or showing similar patterns of geographical distribution. Reproductive phenology in several widely ranging species has been compared in temperate, boreal forest, and polar localities.

Antecedentes y Objetivos: A pesar de la importancia ecológica de las especies del Orden Bryopsidales en los ecosistemas tropicales marinos, se conoce poco sobre los aspectos reproductivos de las especies que se desarrollan en el Caribe mexicano. El estudio de las estructuras de reproducción aporta elementos útiles al entendimiento del ciclo de vida, taxonomía y filogenia. El objetivo de este trabajo es describir e ilustrar las estructuras reproductoras de Avrainvillea digitata, A. nigricans f. floridana y Halimeda incrassata.Métodos: Fueron recolectados talos fértiles de cuatro localidades en la Reserva de la Biosfera de Sian Ka´an, Quintana Roo, México. Se realizaron descripciones de su morfología y anatomía, así como de la estructura y tamaño de sus estructuras reproductivas.Resultados clave: En Avrainvillea digitata los esporangios son claviformes mientras que en A. nigricans f. floridana son elipsoidales. En ambas especies de Avrainviella las estructuras se desarrollan como proyecciones del ápice de los sifones de la porción apical del talo. En Halimeda incrassata el gametóforo surge del utrículo terciario y sostiene de ocho a 10 gametangios piriformes.Conclusiones: Este trabajo representa la primera descripción morfológica de las estructuras de reproducción de Avrainvillea digitata, A. nigricans f. floridana y Halimeda incrassata del Caribe mexicano.

Most plant pathologists know certain algae can be used as gelling agents in culture media. Pathologists practicing in tropical or subtropical environments also know that some algae damage plants. The five genera in the order Trentepohliales (Chlorophyta) are unique and fascinating. Among other characteristics, they are subaerial, bright orange to red in color, and one genus, Cephaleuros, is a plant pathogen while another, Stomatochroon, is a space parasite. Cephaleuros causes algal spot and includes 17 accepted species. Of these, 13 develop between the cuticle and the epidermis of their hosts and four grow intercellularly. The latter are especially damaging, causing chlorosis and branch dieback. Zoospores and gametes germinate on plant surfaces during the rainy season and probably penetrate through breaks in the host cuticle. Their filamentous growth forms thalli that produce sporangiophores and spherical gametangia the following year. Several species of Cephaleuros have a broad host range and though their damage is usually superficial, it can be economically important on certain crops. Plant stress is the greatest predisposing factor to this algal disease. Management includes providing plants with sufficient moisture and nutrients, modifying cultural and harvesting practices, and planting resistant cultivars when available.

The reproductive adaptations of land plants have played a key role in their terrestrial colonization and radiation. This encompasses mechanisms used for the production, dispersal and union of gametes to support sexual reproduction. The production of small motile male gametes and larger immotile female gametes (oogamy) in specialized multicellular gametangia evolved in the charophyte algae, the closest extant relatives of land plants. Reliance on water and motile male gametes for sexual reproduction was retained by bryophytes and basal vascular plants, but was overcome in seed plants by the dispersal of pollen and the guided delivery of non-motile sperm to the female gametes. Here we discuss the evolutionary history of male gametogenesis in streptophytes (green plants) and the underlying developmental biology, including recent advances in bryophyte and angiosperm models. We conclude with a perspective on research trends that promise to deliver a deeper understanding of the evolutionary and developmental mechanisms of male gametogenesis in plants.

Summary In angiosperms, the phase transition from vegetative to reproductive growth involves the de-repression of the squamosa promoter-binding-protein-like (SPL) class of transcription factors, which is negatively regulated by the specific microRNAs (miRNAs/miRs) miR156/529 [ 1 ]. Non-vascular land plants also undergo growth-phase transition to the reproductive state, but knowledge regarding the controlling mechanisms is limited. Here, we investigate the reproductive transition in the liverwort Marchantia polymorpha, focusing on the roles of miR529c [ 2 , 3 , 4 ] and MpSPL2. First, we established mir529c-null mutants using CRISPR/Cas9. Even in the absence of far-red light-supplemented long-day condition, which is usually needed to induce reproductive development [ 5 , 6 ], the mutant thalli developed sexual reproductive organs (gametangia) and produced gametes. Transgenic plants expressing a miR529-resistant MpSPL2 transgene also showed a similar phenotype of reproductive transition in the absence of inductive far-red light signals. In these mutants and transgenic plants, the MpSPL2 mRNA abundance was elevated. Mpspl2ko mutant plants showed successful gamete development and fertilization, which suggests that MpSPL2 is involved in, but not essential for, sexual reproduction in M. polymorpha. Furthermore, analysis of Mpspl2ko mutant and its complemented lines suggests that MpSPL2 may have a role in promotion of reproductive transition. These findings support the notion that the transition to reproductive development in liverworts is controlled by a system similar to that in angiosperms, and the miR156/529-SPL module has common significance in the control of the vegetative-to-reproductive transition during development in many land plants, including liverworts.

Spirogyra is a zygnematalean green algal genus that is ubiquitous in a broad range of freshwater habitats throughout the world. Samples collected throughout Korea from October 2004 to July 2015 were examined using light microscopy. Morphological characteristics (e.g., size of vegetative cells, number of chloroplasts in each cell, type of end walls of adjacent cells, details of conjugation, shape of female gametangia, dimensions and shape of zygospores, color and ornamentation of median spore walls) were used as diagnostic characteristics for species identification. In this study, five species of Spirogyra (i.e., S. emilianensis Bonhomme, S. jaoensis Randhawa, S. pascheriana Czurda, S. weberi var. farlowii (Transeau) Petlovany, and S. weberi var. grevilleana (Hassall) Kirchner) were described as newly recorded in Korea.

Some charophyte species reproduce sexually by oospores and vegetatively by bul- bils, and the proportion of branch whorls that contain reproductive organs can be used as quanti- tative measures of the degree of sexual reproduction. We examined inter-specific differences in the proportion of bulbils (PB) by total weight and the proportion of branch whorls containing gametangia (PG) or oospores (PO), as well as morphological and physiological differences among 3 charophyte species (Chara vulgaris Linnaeus, Chara braunii Gmelin, and Nitella gracilens Morioka) responding to variation in water depth (0.5, 1, 1.5, 2, and 3 m) in an outdoor experiment. A 2-way ANOVA contrasting species and water depth revealed that shoot elongation and the chlorophyll a to carotenoid (chl a/caro) ratio were primarily affected by water depth. However, variation among species contributed more than water depth to the differences in weight, sexual reproduction (PG and PO), and the chl a/chl b ratio. Additionally, variation among species con- tributed almost equally to the differences in PB that occurred among different water depths. Both Chara species extended their shoots and increased their PB in response to increasing water depth (from 0.5 to 1.5 m). However, deeper water (2 and 3 m) led to elongated shoots as well as decreased PB, PG, and PO. For N. gracilens, elongated shoots with increased water depth (from 0.5 to 3 m) occurred at the expense of both vegetative (decreased PB) and sexual reproduction (reduced PG and PO).

A fossil of the aerophytic green algal genus Phycopeltis (Trentepohliaes, Ulvophyceae) dated to 35 Ma, is reported from the Pikopiko Fossil Forest, Southland, New Zealand. Previous reports of fossilized Phycopeltis have been subsequently synonymized with fungi by other authors; however, our specimen is not vulnerable to their criticisms. Inflated cells present in two approximately concentric rings are interpreted as gametangia, with irregular structures resembling the gametangial pores of modern material; sporophytic material is absent. The fossil resembles the modern disc-forming species P. novae-zelandiae, P. expansa, and P. arundinacea. The limited material available prevents the assignation of a specific epithet, but the habit and dimensions of the fossil clearly fall within those of modern representatives of the genus. Its single cell thickness throughout, absence of distinct melanization, and larger size demonstrate that it is not a fungal shield. The specimen constitutes arguably the most convincing fossil belonging to Trentepohliales, and the first unambiguously for the genus Phycopeltis. It is consistent in age with other known fossils of the order that, when combined with molecular evidence, suggests a terrestrial radiation far more recent than that of land plants.

The chloroplast haplotypes, ecology, growth, and reproduction of the introduced Japanese green alga Codium fragile were evaluated in four salt marsh pannes from Brave Boat Harbor, Kittery, Maine. All chloroplast haplotypes were identical and they matched the subsp. fragile delineated by Provan et al. Frond stature was seasonally variable and showed a pronounced increase in length from summer to early fall. Residual (i.e., overwintering) spring fronds were highly variable in stature compared to previous fall values, with some fronds only being ~ 0.5–1.0 cm. Frond stature and frequency patterns in the different pannes were related to their proximity to tidal channels, plus patterns of storm damage. Thus, one panne, which was closest to a tidal channel and had the lowest tidal level, exhibited the largest population frequency and smallest mean frond stature. The highest percent occurrence of gametangia occurred during late summer to early fall when the largest fronds were present. The reproductive p...

Aglaomorpha cornucopia (Copel.) M.C. Roos is an endemic and rare epiphytic fern from the Philippines. Ex situ germplasm storage and growth are important complementary tools for conserving this rare fern. This study was conducted to document the reproductive biology of this species. Mature sporophylls of A. cornucopia were collected in May, 2012 from Mt. Apo, the Philippines. Each sporangium bore 64 yellow, monolete spores. The average spore size was 49.3±3.7 µm. Fresh spores germinated 100% within one week of sowing (mean germination time (MGT)

Gelidium canariense is a canopy-forming endemic macroalga from the Canary Islands. Vegetative and reproductive characteristics of all phases in its life cycle are examined. Key macromorphological features are its blackish color and the corymbose-to-subfastigiate branching pattern that differentiates G. canariense from the nearest species confirmed with molecular data. The length of individuals has notably decreased over the last three decades. Internal vegetative morphology is consistent with the pattern in most species of Gelidium. The distinctive characteristics of tetrasporophytes are their morphology, the arrangement of tetrasporangial branches and the absence of a sterile margin around mature sori. Male and female gametophytes, gametangia and carposporophytes are described here for the first time. Spermatangial sori develop at the tips of axes and branches and lack a sterile margin. Gelidium canariense exhibits the classic Gelidium-type cystocarp. Tetrasporophytes of G. canariense are dominant in populations, with a ratio 4:1:1 (tetrasporophyte: male gametophyte: female gametophyte). The phenological study showed significant evidence that fertile individuals (tetrasporophyte or gametophyte) develop a more leafy morphotype than non-fertile individuals. Individuals collected in July are significantly different from November and March because they show this characteristic morphotype.

Morphologically interesting charophytes were found from Chapai-Nawabgonj and Rajshahi districts in Bangladesh. These are: swollen branchlet of Lamprothamnium papulosum (Wallr.) J. Groves, long stalked gametangia and twin antheridia of Nitella hyalina (DC.) Agardh, bifid bract cells of Chara flaccida A. Braun and bifid end cell of Nitellopsis obtusa (Desv.) J. Groves. DOI: http://dx.doi.org/10.3329/jles.v7i0.20124 J. Life Earth Sci., Vol. 7: 71-77, 2012

The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type – within a cell size range of 7–36 µm – were mixed together. Two binucleate gametes were formed in each gametangium and ga...

This paper addresses the phenology of a Dictyota dichotoma population from the North Patagonian coasts of Argentina. The morphology of the individuals was characterized, and analyses of the temporal variations of vegetative features, diploid and haploid life cycle generations and sex ratios are provided. Individuals, represented by growing sporophytes and gametophytes, occurred simultaneously throughout the year. Morphological variables showed temporal variation, except the width and height of medullary cells, which did not vary between seasons. All vegetative variables were significantly correlated with daylength. Besides, frond length, frond dry mass and apical and basal branching angles were significantly correlated with seawater temperatures. Vegetative thalli were less abundant than haploid and diploid thalli. Sporophytes were less abundant than male and female gametophytes. Male gametophytes dominated in May, August, October and January, and female gametophytes were more abundant in September, November, December, February and March. The formation of female gametangia showed a significant correlation with daylength, and the highest number of gametangia was registered in spring. In general, the male/female sex ratio varied between 1:2 and 1:1. Apical regions were more fertile than basal regions. Our data about frequency in the formation of reproductive structures and male/female ratios are the first recorded in the Dictyota genus and thus could not be compared with populations from other regions of the world. Significant morphological variation was observed in thalli of both life cycle generations, regarding length and dry mass, number of primary branches and branching basal angle. In general, all variables analyzed varied seasonally except cortical cell width. Fil: Gauna, Maria Cecilia. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología Acuática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina Fil: Caceres, Eduardo Jorge. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina Fil: Parodi, Elisa Rosalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología Acuática; Argentina

We give a detailed account of sexual reproduction and auxospore development in the diatom genus Diploneis, principally from clonal cultures of the marine benthic Diploneis papula. Sexual reproduction of D. papula was apparently homothallic. After pairing side to side, cells entered meiosis, and each gametangium produced two gametes. Fertilization was physiologically anisogamous, and both gametes of one gametangium were active and those of the other gametangium passive so that the two zygotes were formed within or close to the ‘passive’ gametangium. Each gamete contained a single chloroplast. The zygote became surrounded by delicate incunabula that contained circular or elliptical scales; this confirmed recent observations that scales (or apparently homologous strips or plates) are quite commonly formed by the zygotes of raphid diatoms. Subsequently, a robust transverse perizonium was built up as the auxospore expanded, and the perizonium was comprised of a closed primary band at the centre and open secondary bands towards each pole. The ends of the secondary bands, which met along one side of the auxospore to form a suture as in other pennate diatoms, were curved inwards towards the centre of the auxospore. Novel features were the extension of the transverse perizonium to cover the tips of the auxospores (in other diatoms it stopped short of the poles, leaving an apical dome covered only by the incunabula) and a differentiation of the ends of the transverse bands into truncated and prolonged variants, which alternated along the suture. The longitudinal perizonium possessed the same highly conserved configuration as in other pennate diatoms, with a wide bifacial central band flanked by two other bands, which here differed in shape and structure. All the perizonial bands were fimbriate. The possible homology of the longitudinal perizonium to the thecae of vegetative cells was discussed. During formation of the initial cell, the protoplast contracted away from the perizonium, but the latter nevertheless moulded the outline shape of the initial valves, which were more strongly constricted than preauxospore cells and gametangia. Other Diploneis species produced either one or two gametes per gametangium.

Summary The infection cycle of five Cephaleuros species – C. aucubae, C. biolophus, C. japonicus, C. microcellularis, and C. virescens – was clarified by investigating seasonal development and gamete and zoospore behavior at study sites in Matsue, Shimane Prefecture, Japan. Fresh thalli or lesions appeared on the leaves of various woody plants from August and continued to develop in general from April to September in the following year. Gametangia and zoosporangia matured on 2- and 3-year-old leaves. Gametes were released in C. microcellularis samples collected from late March to late May and in samples of the other four species collected from late April to late July. Zoospores were released in C. biolophus, C. japonicus, and C. virescens samples collected from mid-May to early August. In the present study, gametes did not conjugate but germinated like zoospores to produce new plants. After inoculation with zoospores and gametes that behave as asexual spores, fresh thalli or lesions became evident in 2–5 months following inoculation and gametes and zoospores were produced on the developed thalli or lesions the following year; one cycle of the infection was completed per year in the study area.

Several specimens of a new fungal reproductive unit, Halifaxia taylorii nov. gen. et spec., occur within the tracheids of a structurally preserved fern axis from the Lower Pennsylvanian of Great Britain. The reproductive units, which appear to be lateral outgrowths of tubular hyphae, consist of a mantled sphere (80–90 μm in diameter) borne terminally on an inflated subtending structure, which may also be mantled. A smaller element clasps the proximal portion of the subtending structure; one arm of this element extends further up along and appears to eventually fuse laterally with the subtending structure. The reproductive units are interpreted as zygosporangium-apposed gametangia complexes of a zygomycetous fungus. Although several structural features of H. taylorii resemble features seen in the zygosporangium-gametangia complexes of certain modern zygomycetes, the precise systematic affinities of the fossils remain unresolved. Nevertheless, the discovery is important because it provides new information o...

Paedogamy (fusion of gametes produced within the same gametangium following meiosis) has rarely been reported in diatoms, with fewer than 10 confirmed examples. One of these, reported by L. Geitler, was in a diatom from Illmitz, Lake Neusiedl (Austria), identified as ‘Nitzschia frustulum var. perpusilla'. We observed uniparental auxosporulation in two Nitzschia clones isolated from the lower Ebro River (Catalonia, Spain), morphologically similar to Geitler's material and belonging to the N. inconspicua species complex. We established that the auxospores were formed paedogamously by Feulgen staining of the nuclei and time-lapse microscopy of living cells. However, reinvestigation of Geitler's original cytological preparations revealed differences between the Illmitz and Ebro material with respect to the length of the initial cells, the structure of the perizonium, and the timing of degeneration of superfluous haploid nuclei during gametogenesis, indicating a genetic and possibly a taxonomic separation. Sca...

This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the genus Oedogonium, from androspore germination to the liberation of mature male gametes. The ultrastructure of the process in O. macrandrium Wittrok is similar to that of Bulbochaete hiloensis (Nordstedt) Tiffany, but with two remarkable differences. In O. macrandrium: 1) instead of a true transverse wall, only condensed mucilage appears between the gametes of each antheridial cell, and 2) the cell wall between the basal cell and the basal most antheridial cell has simple plasmodesmata similar to those present in the transverse walls of vegetative cells, which are absent in B. hiloensis. Fil: D'Amico, Silvana L.. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina; Fil: Leonardi, Patricia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina; Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina; Fil: Caceres, Eduardo Jorge. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina; Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina

Plagiospora gracilis, a mucilaginous crustose red alga growing on subtidal pebbles on\ud both coasts of the North Atlantic Ocean, forms distinctive tetrasporangia (red algal\ud meiotic structures that release haploid tetraspores) but gametophytes have never been\ud reported. In the absence of gametangia, the taxonomic position of this monotypic genus\ud has always been uncertain; it is currently placed provisionally in the Gloiosiphoniaceae\ud (Gigartinales) by comparison with sporophytes of Gloiosiphonia obtained in culture.\ud Dioecious gametophytic crusts of P. gracilis are now reported for the first time, forming\ud gametangia in inconspicuous superficial sori. There is no evidence that fertilization ever\ud occurs in the field although fertile males and female were collected together. In culture,\ud tetraspores grew into tetrasporophytes for three successive generations, by presumed\ud apomictic sporophyte recycling. The life history of P. gracilis may represent a late stage\ud in the loss of sexual reproduction leading to tetraspore-to-tetrasporophyte life histories\ud such as that in Hildenbrandia. Phylogenetic analysis of sequences of the rbcL, LSU\ud (28S) rDNA and coxI (COI-5P) genes for P. gracilis with other Gigartinales resolved P.\ud gracilis as a distinct lineage in a well-supported clade of the families Sphaerococcaceae,\ud Gloiosiphoniaceae, Endocladiaceae, Nizymeniaceae and Phacelocarpaceae. We here\ud propose the monotypic Plagiosporaceae fam. nov. to accommodate P. gracilis.

In-vitro studies of the ontogeny and mating system of the gametophytes of Lepisorus nudus were carried out through multispore and isolate cultures lasting 23 weeks. Spore germination begins early, on day 5–6. Spore germination pattern was Vittaria type and the germination percentage reached 82.69% (± 3.20%). Filamentous gametophyte did not branch and never produce separate prothalli. Occasionally the branching and separate prothalli were produced from mature and cordate gametophytes. Prothallial development was Drynaria type (cordate gametophytes with notched apex) contrary to other known species of Lepisorus, where gametophyte development was Kaulinia type (strap gametophytes without apical notch). Gametophyte production in multispore cultures reached up-to 75.6% (± 18.85%). All isolates initially produced archegonia and antheridia only after a prolonged cessation of production in archegonia. In contrast, only 37.2% (±12.63%) of individuals in multispore culture exhibited the same pattern with 29.8% (±7.56%) developing as males that did not produce archegonia by the end of the study. Only 37.2% (±12.63%) of archegoniate gametophytes developed antheridia by the end of the study and only once archegonia had degenerated; i.e., a temporal gap existed in expression of female and male gametangia. In multispore culture, only 26.21% (±5.70%) sporophytes developed on 160th day by fusion of female and male gametes that were derived from matings between sib gametophytes. In contrast, isolated gametophytes did not produce sporophytes. In isolate gametophytes, mature archegonia could not take delivery of male gametangia because antheridia were produced sequentially. This study suggests that the sequential expression of gametangia and absence of the intragametophytic selfing may also be a possible cause of reproductive barriers. Lepisorus nudus promotes inter-gametophytic selfing as an adaptive mechanism for reproductive success in multispore culture. This study presents a detailed account on reproductive biology of the taxa whose population is decreasing at distressing rate.

BACKGROUND: Early life stages of macroalgae, especially from polar species, can be highly vulnerable to physical stressors, leading to important consequences for the fate of the whole population in scenarios of changing environmental variability. In the present study, tolerance to UV and temperature stress, as measured by rapid adjustment of photochemistry, Fv/Fm, and photosynthetic characteristics based on P-E curves (ETRmax, α and Ek), was assessed in the early life stages of six Antarctic macroalgal species from eulittoral (Pyropia endiviifolia, Iridaea cordata, Adenocystis utricularis and Monostroma hariotii) and sublittoral (Ascoseira mirabilis and Gigartina skottsbergii. RESULTS: Reproductive cells of eulittoral species showed the highest light demands (Ek >45 μmol photon m-2 s-1) when compared to those from sublittoral species (Ek30 % inhibition in Fv/Fm in the same condition. Enhanced temperature (7 and 12 °C) improved the tolerance of I. cordata compared to 2 °C, but exacerbated the detrimental effects of UV on A. mirabilis. CONCLUSION: Results showed that photosynthetic characteristics varied among reproductive cells of different species, reflecting the vertical zonation of parental thalli. Otherwise, these differences appear to underlie biogeographical and evolutionary components. In addition, UV tolerance was modulated by temperature increase, while temperature increase, in turn, ameliorated the detrimental effects of stress treatments in some eulittoral species (I. cordata tetraspores). In sublittoral A. mirabilis gametangia, temperature exacerbated the reduction of photosynthetic efficiency.

For decades, the diatom genus Haslea has been known to comprise both "colorless" species and one species containing a blue pigment, the latter being known as H. ostrearia. Recently, a new blue diatom named H. karadagensis has been isolated from the Black Sea. The mating compatibility of the two species has been tested, and their reproductive isolation confirmed. We provide a detailed description of the heterothallic sexual reproduction process in this new species. Cells from clones which are sexually compatible arrange gametangial pairs. Each gametangium in the pair produces two gametes, which to a large extent are morphologically and behaviorally isogamous. No mucilage or mucilage structures are observed. Zygotes and auxospores have no contact with parental frustules, and their orientation is rather irregular though they tend to lie parallel to each other. Evaluation of the position of cardinal points in the life cycle of the species, and the rate of cell size decrease in culture are presented. In the breeding system of this species both homo- and heterothallic ways of reproduction are realized. The latter is basic and predominant. Among the 36 clones investigated, 16 were sexually compatible with the other 20. Homothallic behavior was extremely rare; only one clone displayed a homothallic mode of reproduction.

An assemblage of distinctive fungal reproductive units occurs in a fragment of permineralized xylem from the Lower Coal Measures (Carboniferous) of Great Britain. Specimens are spherical to irregular in outline, 70–95 μm in diameter, and consist of a central cavity surrounded by an investment of tightly interlaced hyphae. Clusters of specimens may additionally be enveloped in a confluent hyphal meshwork. This complement of features is quite similar to the morphology seen in mantled zygosporangia/zygospores of certain extant zygomycetous fungi. Closely associated with several of the reproductive units are single or paired smaller spherical to elongate structures, which we interpret as apposed gametangia. This discovery represents only the third record of zygomycetous fungi from the Carboniferous. Moreover, the reproductive units resemble certain Carboniferous microfossils termed fungal sporocarps in the genus Mycocarpon, and thus indirectly support the hypothesis that the systematic affinities of these sporocarps may lie with the zygomycetous fungi.

Morphological characters of 10 species of Chara from different localities in northern, western and central Iran have been analyzed, with Nitella hyalina and Tolypella glomerata as outgroups. Phenetic and cladistics analyses of populations belonging to the 10 Chara species were undertaken to reveal their inter-population morphological variation and inter-specific relationships. Clustering was based on 54 characters (41 qualitative and 13 quantitative). This produced two major clusters, grouping Chara crassicauliss, C. vulgaris var. longibracteata, C. vulgaris var. vulgaris and C. contraria separate from C. grovesii, C. gymnophylla var. gymnophylla, C. gymnophylla var. rohlenae, C. kirghisorum and C. tomentosa. A smaller cluster of C. socotrensioides, C. fibrosa and Chara sp. was separate from these two clusters. A factor analysis identified the most variable morphological characters as type of cortification, prescence and length of the spine cells, stipulode length, type of branchlet cortication, bract cells length, placement of the gametangia, character of end segment, length of branchlet and internode, development of posterior bract cells, oogonia length and width, oospore length, width and length/width ratio, fossa breath, and number of striae.

SUMMARY Female gametogenesis was studied in the dioecious siphonous green alga Codium fragile subsp. novae-zelandiae (J. Agardh) P. C. Silva using light and electron microscopy. Early during gametogenesis the protoplasm was uniform; then it separated in portions, while fusiform chloroplasts and nuclei increased in numbers. Some features of the nuclear divisions were similar to those of other Bryopsidophyceae. They were acentric and semi-open. Pairs of parallel electron-dense lines resembling synaptonemic complexes were observed in several prophase nuclei indicating meioses. In metaphase the nuclear envelope showed polar fenestrae from which the spindle emerged. No spindle microtubule nucleating material was visible and chromosome kinetochores were evident. Mature female gametes were pyriform with a hyaline anterior end from which the two flagella emerged. Mature gametes had a spherical nucleus surrounded by a mitochondrion and numerous discoid chloroplasts. Female gametes germinated parthenogenetically in culture and also inside gametangia, involving loss of flagella, rounding and lengthening of cells, multiplication of chloroplasts with well developed thylakoid systems, vacuolization and synthesis of a fibrillar cell wall.

Documented fossil evidence of zygomyce- tous fungi is rare. A conspicuous fungal fossil, Jimwhitea circumtecta gen. et sp. nov., occurs in permineralized peat from the Middle Triassic of Antarctica. The fossil is interpreted as a mantled zygosporangium that buds from a macrogametan- gium subtended by a sac-like macrosuspensor. The macrogametangium is united at its tip with a microgametangium which is subtended by a micro- suspensor. This configuration is strikingly similar to the zygosporangium-gametangia complexes seen in certain modern Endogonaceae. Co-occurring with J. circumtecta are isolated propagules closely resembling the zygosporangium of J. circumtecta and a portion of a sporocarp containing zygosporangia embedded in a gleba. Several of the sporangia are borne on ovoid or elongate structures, which we interpret as gametan- gia. These fossils offer an exceptionally detailed view of the morphology and reproductive biology of early Mesozoic zygomycetes.

Sargassum vulgare C. Agardh shows androgynous receptacles, each bearing on an average 12 unisexual conceptacles which open outside by ostiole, and wherein gametangia (antheridia or oogonia) lie interspersed with paraphyses. Since out-put of eggs is extremely low, 4 - 6 per female conceptacle, Sargassum sp. ensures its survival under all eco-physiological conditions. The released oogonium is “wrapped” in sulphated polysaccharide-rich wall layer known to provide protection against desiccation. Oogonia after being “extruded” out of ostiole, are “incubated” on receptacle, where they grow into eggs that are easily contacted by spermatozoids. Gamete release is synchronous and almost simultaneous ensuring high rates of fertilization. The release occurs on days falling near a full moon or new moon, during low tides when conceptacles lie exposed. Gamete release occurs first from upper conceptacles, which “house” mature gametangia while lower ones are still developing. This results in gamete release over an extended period of time. The zygote dispersal and propagule recruitment also show adaptations selectively advantageous for the alga.

Uniparental auxosporulation was observed in a monoclonal culture of a Sellaphora clone isolated from the epipelon of a fishpond in the Czech Republic. The cox1 sequence for the clone confirmed that it belonged to the Sellaphora pupula-bacillum species complex but showed significant differences from all previously characterized Sellaphora species, and it is therefore described as S. marvanii sp. nov. Protoplast, valve, and girdle structure resembled those of other Sellaphora species, but a novel finding for all diatoms was a change in girdle structure during the life cycle: the most advalvar girdle band (valvocopula) bore a single line of pores in enlarged postauxospore cells but was entirely plain in small cells and gametangia. The young auxospores were covered by incunabula containing large, delicate, ± circular scales, resembling those of centric diatom auxospores; similar scales have been reported in a few other raphid diatoms (Pseudo-nitzschia multiseries, Diploneis sp.) but contrast with the strip incunabula of some Nitzschia and Pinnularia and the helmet-like caps of Neidium. The scales persisted during auxospore expansion, mostly as two caps over the auxospore poles. The transverse perizonium comprised a very wide, closed primary band, flanked by numerous secondary bands whose open ends were strongly incurved toward the center. Initial valves were differentiated from their immediate descendants by the very strong external demarcation of the raphe sternum, irregular shape, and curved transapical profile.

There are three carpet-like Codium species with a broadly expanded thallus reported from Korea and Japan: C. latum Suringar, C. tapetum Y. Lee, and C. tenuifolium Shimada, Tadano and J. Tanaka. During surveys of green algal diversity, we encountered a Codium species with carpet-like thalli from several sites on Jeju Island. To confirm the taxonomic identity of these specimens, we studied the morphological features and obtained rbcL gene sequences. The morphological and sequence data indicated that the carpet-like Codium specimens from Jeju are C. tenuifolium from Japan, but distant from Japanese C. latum. We propose that the carpet-like specimens from Jeju should be renamed C. tenuifolium, instead of C. tapetum or C. latum. C. tenuifolium is characterized by a tenuous, carpet-like and erect thallus with a very short and slightly compressed stipe arising from a discal holdfast, sub-pyriform and clavate utricles with a tumid and swollen apical head, and globular or sub-globular gametangia issued at the basal portion of the utricles.

Miravalles A.B., Leonardi P.I. and Caceres E.J. 2011. Male gametogenesis ultrastructure of Codium fragile subsp. novae-zelandiae (Bryopsidophyceae, Chlorophyta). Phycologia 50: 370–378. DOI: 10.2216/10-25.1 Male gametogenesis was studied by light and electron microscopy in the dioecious siphonous green alga Codium fragile subsp. novae-zelandiae. Gametangia were formed on the sides of utricules. Initially, gametangia showed vegetative interphase nuclei and chloroplasts already with a mature structure with few thylakoid lamellae and a single starch granule. Then, mitotic divisions occurred, originating a proliferation of gametic nuclei. Features of the gametangial mitosis were similar to vegetative mitoses of other Bryopsidophyceae. The fusion of minute vesicles clearly delimited uninucleate portions of protoplasm with a large mitochondrion and chloroplasts. Ultimately, the gamete final shape was delimited, and the basal-flagellar apparatus developed. Mature gametes were liberated immersed in a muc...

Morphology and life history of a brown alga Scytosiphon lomentaria (Lyngbye) Link (Scytosiphonaceae, Phaeophyceae) were investigated from 2005 to 2009 in the coastal waters of Dalian, China. The erect thalli collected in the field were tubular, hollow, and commonly constricted at intervals. Ascocysts were presented. Plurilocular gametangia, which were positioned in continuous sori on the erect thallus surface, produced biflagellar gametes. Gametophytes were dioecious and gametes were nearly isogamous. Gametes fusion occurred in three types. Type one, female and male gametes fused directly while swimming; type two, female gamete settled first, with which a male one contacted and fused rapidly; type three, while settling adjacently, a male gamete's entire protoplast moved slowly into the previously settled female one, with only an empty cell membrane left. In culture zygotes developed into crustose sporophytes that formed unilocular sporangia. Biflagellar zoospores developed into erect thalli that formed plurilocular gametangia. The results indicated that a periodical heteromorphic alternation history with haploid gametophyte generation and diploid sporophyte generation exists in S. lomentaria of the Dalian populations.

The gametophyte morphology and development of eight Chinese species of Dryopteris (Dryopteridaceae) were studied and described. Spores of all species were monolete and reniform. The germination pattern was the Vittaria-type. Germinal filaments were uniseriate, sometimes biseriate and the prothallial development was the Aspidium-type. Adult gametophytes in culture were cordiform, elongate-cordiform to cordiform-reniform, having wings with marginal and superficial trichomes. Gametangia belong to leptosporangiate fern type. Spore size, germination time, numbers of trichomes, morphology of rhizoids, formation time of the gametangia and gametophyte margin shape were different among the studied species.

The spores of Ophioglossum pendulum ssp. falcatum germinated after six weeks in the dark on a nutrient medium containing inorganic nutrients and glucose. The gametophytes grew on the same nutrient medium to give globular, teardrop-shaped, and finally cylindrical gametophytes. The mature gametophytes were cylindrical and highly branched. Other aspects of these gametophytes were normal for Ophioglossum gametophytes with sunken antheridia and short-necked archegonia. The gametangia were functional because fertilization took place in older cultures. Mature gametophytes of O. pendulum ssp. falcatum from culture had the same structure as those of O. pendulum ssp. pendulum from nature. The differing conditions under which the gametophytes of both subspecies grew did not alter their stellate form.

SUMMARY Brief treatment with hypertonic solutions induced gamete discharge from gametangia in the coenocytic green alga Bryopsis plumosa (Hudson) C. Agardh. It is known that gamete discharge in this alga is triggered by a change from darkness to light. However, in this study mature gametangia, incubated for 30–120 s in artificial seawater (ASW) with an additional 0.4–0.6 M NaCl and then transferred into pure ASW, discharged gametes in darkness. The treatment did not affect the motility of the gametes. Addition of sucrose (1.0–1.2 M) to ASW also induced gamete discharge in darkness. Similar results were obtained by adding KCl (0.4 M) or mannitol (1.2 M) to ASW. Continuous incubation of gametangia in such hypertonic solutions also induced gamete discharge but led to a delay and a reduction in the rate of gamete discharge, and a loss of gamete motility. In gametangia treated with the hypertonic solutions, as well as in those exposed to light, shortening of the gametangial length was observed before gamete discharge.

The gametophyte of Argyroschosma nivea was studied, mainly focusing in its morphological development, and in the apogamous production of sporophytes. Some observations on the spores were also made. As far as it is known, this is the second species of the genus whose gametophytes are studied. The germination pattern followed the Vittaria type. The subsequent developmental processes followed the Ceratopteris type. Some of the gametophytes reached an adult stage with a cordate, symmetric shape, but most of them developed as irregular, lobed prothalli. The sporophyte emerged from the anterior part of the prothallus, without formation of gametangia. First, a cell became active and originated a proliferating area of small cells. From this area, long glandular hairs were formed followed by a projected conical cluster of cells. The cluster elongated into a sporophytic structure and its apex became progressively spatulate and finally trilobulate, with marginal, glandular hairs, stomata and tracheids continuously produced. This sporophyte secreted granules of white farina from its beginnings. The production of farina in the sporophyte but not in the gametophyte could help to support the idea of the segregation of this species from its traditional location in Notholaena to Argyrochosma, as farinose gametophytes seem to be a synapomorphy of the notholenoids, group that includes Notholaena but not Argyroschoma.

Asplenium auritum Sw. is a sexual fern that produces 64 spores per sporangium, while A. monodon Liebm. is an apogamous species that produces 32 spores. The hybrid between them, A. × lellingerianum Sanchez & Regalado, also shows an apogamous life cycle, with mainly abortive spores. The scope of this work was to study the sexual and apogamous behavior in these taxa. We studied spore germination and gametophyte development of the three species, a process that followed the Adiantum type. Afterward, we observed morphological apogamous characters in A. monodon and A. × lellingerianum. Apogamous sporophytes arose from apical and basal regions of gametophytes, lacking feet and roots in the first instance, but developing other normal sporophytic structures, such as tracheids, stomata, glandular hairs, and scales. Finally, we studied the gametangia production in all three taxa, finding that the scarce production of antheridia in A. monodon is indicative of the Braithwaite apogamous life cycle scheme, and this scheme has probably been inherited by A. × lellingerianum.

Sexual behaviour, pattern of auxosporulation, and breeding system of the araphid diatom Tabularia fasciculata were studied using 64 clones derived from two natural populations from the Canadian Atlantic seashore and the Black Sea. Both inter- and intraclonal reproductions were observed. Heterothallic reproduction was morphologically and behaviourally heterogamous. The heterothallic nature of sexual reproduction in this species allowed the determination of sex ratio in the population, which was 1:1 male:female. A novel type of active movement of gametes designated as male was described and pathways traced and recorded. A few male clones could reproduce intraclonally, but this was not abundant compared to interclonal reproduction. The advantages and inferred significance of each mode of reproduction are discussed. In the semi-natural population of T. fasciculata, two size classes were detected among sexualized individuals, and they gave rise to two size groups of initial cells. Sexual compatibility of all derived clones was independent of cell size class. In cultures, the apical length of initial cells was also strongly correlated to the size of parental gametangia. Cell sizes corresponding to cardinal points in the life cycle were established. Interbreeding of clones derived from the Canadian Atlantic and the Black Sea suggests a pan-Atlantic reproductive compatibility of populations of diatoms conforming to current morphological delineation of T. fasciculata.