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Symbioses with fungi are important and ubiquitous on dry land but underexplored in the sea. As yet only one seagrass has been shown to form a specific root-fungus symbiosis that resembles those occurring in terrestrial plants, namely the dominant long-lived Mediterranean species Posidonia oceanica (Alismatales: Posidoniaceae) forming a dark septate (DS) endophytic association with the ascomycete Posidoniomyces atricolor (Pleosporales: Aigialaceae). Using stereomicroscopy, light and scanning electron microscopy, and DNA cloning, here we describe a novel root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum (Alismatales: Cymodoceaceae) from a site in the Gulf of Aqaba in the Red Sea. Similarly to P. oceanica, the mycobiont of T. ciliatum occurs more frequently in thinner roots that engage in nutrient uptake from the seabed and forms extensive hyphal mantles composed of DS hyphae on the root surface. Contrary to P. oceanica, the mycobiont occurs on the roots with root hairs and does not colonize its host intraradically. While the cloning revealed a relatively rich spectrum of fungi, they were mostly parasites or saprobes of uncertain origin and the identity of the mycobiont thus remains unknown. Symbioses of seagrasses with fungi are probably more frequent than previously thought, but their functioning and significance are unknown. Melanin present in DS hyphae slows down their decomposition and so is true for the colonized roots. DS fungi may in this way conserve organic detritus in the seagrasses' rhizosphere, thus contributing to blue carbon sequestration in seagrass meadows. [ABSTRACT FROM AUTHOR]

Epiphytism is a common phenomenon in macroalgal aquaculture worldwide. This problem can affect the productivity and quality of the farmed species which may have socioeconomic consequences for the human communities that depend on this activity. In southern Chile, the aquaculture of the red macroalga Agarophyton chilense in the area of Maullín River has suffered losses in local production (> 90%) due to the proliferation of the filamentous green epiphyte Rhizoclonium sp. This epiphyte becomes entangled with A. chilense fronds, diminishing its quality and preventing its sale as raw material. Thus, the aim of this study was to investigate the effects of light intensity (90 and 180 μmol photons m−2 s−1) on the competitive interaction between the epiphyte Rhizoclonium sp. and the basiphyte A. chilense co-cultured at different initial biomass proportions in a replace series experiment. At the end of the experiment, the presence of Rhizoclonium sp. did not affect negatively the growth of A. chilense, but both species showed stress responses (i.e. reduced Fv/Fm and C:N ratio, suggesting nutrient limitation) in co-culture compared with monocultures. The epiphyte-basiphyte interaction was not modulated by light availability at any initial co-culture proportion and could have been related to nutrient availability during experimentation. Using the replacement series approach, an interspecific competition was observed at all initial co-culture proportion under 180 μmol photons m−2 s−1 while competition was found at the initial co-culture 1:1 under 90 μmol photons m−2 s−1. Our results suggest that the interaction in co-culture between both A. chilense and Rhizoclonium sp. seems to be regulated by nutrient availability as well as it demands utilization rather than light availability. [ABSTRACT FROM AUTHOR]

Primary hemiepiphytism was documented in Pleopeltis bradeorum (Polypodiaceae) at the La Selva Biological Station, Heredia, Costa Rica. Multiple sporophytes and gametophytes were observed, photographed, and collected. Gametophytes were found on the trunks of trees and lianas within 2.5 m of the ground. Mature sporophytes with fertile fronds were observed growing ca. 2.5 m above the ground with feeder roots descending to the soil. Additional sterile mature sporophytes were observed ca. 4 m up, on small- and medium-sized branches; though these individuals did not appear to be connected to the ground by roots; that is, they were holoepiphytic. Our findings indicate that P. bradeorum conforms to many of the features characteristic of primary hemiepiphytic ferns. Corresponding to expectation, sporophytes exhibited long-creeping, dorsiventrally flattened rhizomes with dimorphic clasping and feeder roots. The clasping and feeder roots, however, were not strongly differentiated as in other primary hemiepiphytic ferns. Gametophytes departed from expectation by having a cordate thallus. The life history and habit of P. bradeorum documented here indicates that it is both a primary hemiepiphyte and holoepiphyte. [ABSTRACT FROM AUTHOR]

Cyanobacteria, an increasingly important epiphyte on macroalgae and seagrass, have been shown to have strong effects on its hosts; this association has been identified as a driving mechanism that maintains algal blooms on coral reefs. We examined both the costs and benefits of epiphytism on 2 algal congeners of Halimeda ( H. tuna and H. opuntia), both of which are abundant members of tropical reef communities in the Caribbean. To evaluate potential benefits of an associational defense as well as costs to growth, we manipulated herbivore access to (uncaged/caged) and cyanobacteria presence on (epiphytized/cleaned) 2 species of Halimeda on shallow patch reefs in Belize and measured change in branch length and segment number after 10 ( H. tuna) and 5 ( H. opuntia) days. Cyanobacterial epiphytes did not serve as an associational defense from herbivory as there were no differences between caged and uncaged treatments for either response variable. The presence of cyanobacterial epiphytes did not affect the growth of branches or net generation of new segments, demonstrating there was also no cost to growth. The robustness of both species of Halimeda to epiphytism contrasts strongly with recent research that found strong effects of epiphytes on several other species of tropical algae. Our results may be attributed to the unique characteristics of Halimeda, a heavily physically and chemically defended algal genus, and the shallow nature of the patch reefs reducing the potential for significant light limitation. These findings suggest that close interactions such as epiphytism may not be as generalizable as originally assumed; studies must consider differences among host species, as this may lead to a better understanding of community-wide effects. [ABSTRACT FROM AUTHOR]

The diversity of epiphytes, their temporal abundance variation and the anatomical structure of host-epiphyte interfaces were studied in the agarophyte Gracilaria gracilis from a natural bed in Bahía Bustamante, Chubut Province, Argentina. Twenty-nine algal species were recorded as epiphytes during 2 years of monthly sampling (March 2006-February 2008). Total epiphyte density ranged between 0.037 ind. cm (November 2006) and 39.37 ind. cm (April 2007), with higher density values throughout the second sampling year. Ceramiales species were the most abundant epiphytes. The density of Ceramium rubrum ranged from 0.09 ind. cm (52 % of the total amount) in September 2006 to 17.4 ind. cm (44.18 % of the total amount) in April 2007. Epiphyte infection was more dependent on spore recruitment and sporeling development, especially on thalli derived from fragmentation, than on seasonal environmental variations. The different infections were analysed, taking into account the epiphytic attachment strength and invasiveness and the degree of damage inflicted on the host. Calothrix confervicola was one of the most abundant species. This epiphyte, weakly attached to the host surface, generated no host tissue damage. In contrast, C. rubrum, Polysiphonia abscissa and other Ceramiales were the species that caused more damage to the host because their rhizoids penetrated the cortical portion of the host thallus, sometimes reaching the medullary tissue. Some generalisations and characterisations of the different epiphyte groups in relation to their consequences to Gracilaria spp. are presented. [ABSTRACT FROM AUTHOR]

The red alga Gracilaria chilensis is commercially farmed for the production of agar hydrocolloids, but some susceptible algae in farms suffer from intense epiphyte growth. We investigated the induced chemical defense response of G. chilensis against epiphytes and demonstrated that an extract of an epiphyte-challenged alga can trigger a defense response. The hormonally active metabolites were purified by RP-HPLC. Treatment with the extract or the purified fraction changed the chemical profile of the alga and increased resistance against epiphyte spores. Semi-quantitative RT-PCR and enzyme assays demonstrated that this metabolic response occurs after an increase in lipoxygenase and phospholipase A2 activity. Although this suggests the involvement of regulatory oxylipins, neither jasmonic acid nor the algal metabolite prostaglandin E2 triggers comparable defense responses. [ABSTRACT FROM AUTHOR]

Most species of the paleotropic fern generaAglaomorphaandDrynaria, together constituting a monophyletic clade (drynarioid ferns), possess humus-collecting structures as an adaptation to their epiphytic life form. Humus-collectors are either present as a specialized foliar structure (external leaf dimorphism) or as a specialized leaf part (internal dimorphism). Apart from these basic patterns there are several forms of reduction and an internal fertile - sterile dimorphism inAglaomorpha. We present a phylogeny of drynarioid ferns based on morphological and molecular (cpDNA) markers. The genusAglaomorphawas found to be monophyletic, whereasDrynariais likely to be a paraphyletic assemblage including a grade of Himalayan to Southern Chinese taxa basal toAglaomorpha. The evolution of humus-collectors is reconstructed by plotting their character state changes onto the obtained phylogeny. Despite the complex morphological pattern across species, evolution of drynarioid humus-collecting structures can be reconstructed postulating a simple sequence of character state changes based on only a few elementary processes. [ABSTRACT FROM AUTHOR]

Abiotic and biotic factors affecting seasonal variations in the biomass andreproductive condition of Chondracanthus chamissoi were evaluatedin a population at La Herradura Bay, northern Chile. During spring,increase in temperature, light, and photoperiod favored the reproductiveactivity of C. chamissoi, contributing to its growth and production ofreproductive biomass. During summer, extremes of temperature and lightavailability were accompanied by bleaching of the thalli, followed bydecomposition and biomass loss, significantly lowering production.Epiphytism and herbivory showed were then at their maximum. Analysis offertility showed that C. chamissoi was in reproductive conditionthroughout the year, with maximum for cystocarpic and tetrasporic plantsduring spring, significantly correlated with total biomass production.Production and liberation of spores and other values for reproductivecapacity showed the highest values in spring. The results of the study,coupled with information from the literature, recommend two commercialharvests during spring, at a time when standing crops are the highest, andvalues for reproductive condition predict adequate expression of the sexualphase. The time of the year suggested as adequate for commercial harvestof this alga probably coincides with the highest quality of its carrageenans,and would precede the phase of local growth cycle, where its biomassbegins to deteriorate due to bleaching, epiphytism and herbivory. [ABSTRACT FROM AUTHOR]

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The data derived from a chloroplast DNA restriction site analysis of subtribe Dendrobiinae ( Orchidaceae) indicate that extreme vegetative diversification is concentrated in two limited parts of this group. Overlaying the vegetative character states onto the chloroplast DNA cladogram suggests that several xeromorphic, vegetative characters evolved in the lines leading to the above-mentioned clades. Several anatomical characters are also associated with xeromorphy. These vegetative and anatomical characters facilitated the establishment of this group in various dry habitats. On the other hand, the modifications of size and number of parenchymatous cells substantially contributed to the vegetative diversification. This fact implies that a simple structural adjustment can result in a major modification of growth habits in the Dendrobiinae. [ABSTRACT FROM AUTHOR]

Achnanthes linearis produces two auxospores from one cell pair by allogamic fusion of migratory and stationary gametes. Unusually little copulation jelly is produced. Pairing occurs by chance in regard to the heteropoly of the transapical axis. The orientation of the primary cells in relation to the substratum and to the mother cells is constant and characteristic. Variation of cell size is much larger than hitherto known; correspondingly the diagnosis is to be completed.-The position and orientation of vegetative cells and partner cells is strongly determined by the relief of the leaves of Fontinalis on which they are fixed with their raphe valve. The same is true for the cells of A. minutissima which usually are fixed at one cell pole only, but exceptionally at both poles; this means that morphological heteropoly of apical axis is lacking, and that the function of the second holdfast-jelly producing structure usually is suppressed. The cells of both species normally creep by means of the raphe mechanism; the direction is very independent of the relief of the Fontinalis leaves. After cell division the moving down of the upper daughter cell follows a different mechanism. A. linearis is the first to settle on Fontinalis leaves, other epiphytes come much later. [ABSTRACT FROM AUTHOR]

The little known epiphytic alga Hydrianum viride was studied and pictured. The morphology and the variability of the vegetative cells are described in detail and compared with the observations of other authors. For the first time typical biflagellate zoospores of the chlorophycean-type have been recognized and the course of the asexual reproduction is studied. The residual protoplasm, that is the proximal half of the zoosporangium protoplast, growth up to the original size, typical for the genus Hydrianum. The life cycle, especially the settling down of the zoospores, is described. Hydrianum viride belongs to the characteristic inhabitants of peaty waters; it belongs together with the host alga, Microspora loefgrenii, to the dominants of algal association of peat-springs. At last the taxonomic position and the synonyma of this organism are discussed. [ABSTRACT FROM AUTHOR]

In a special habitat near Lunz (Mittersee) long time epiphytism of Cocconeis placentula var. tenuistriata and var. klinoraphis on Fontinalis antipyretica leaves causes characteristic, strongly localized alterations in the walls of affected cells. They turn brown, may thicken, and may produce cystolithe-like protuberances into the cell lumina. These reactions obviously are brought about by a specific property of Cocconeis, for other epiphytes do not cause any change. The comparison of the Cocconeis vegetation on younger and older Fontinalis leaves shows a considerable variability of the reactions mentioned, and in another habitat none could be found. Apparently several factors cause these reactions. Altogether, Cocconeis placentula is not a completely harmless epiphyte under certain circumstances. The alterations of the moss cells may be interpreted partly as a premature aging process, partly as a defensive action corresponding to alterations induced by some parasitic fungi. Furthermore, the reactions of Cocconeis on Fontinalis are remarkably parallel to the influence of the dinococcalean alga Raciborskia inermis on Spirogyra grevilleana. [ABSTRACT FROM AUTHOR]

Conchospores from the perennial conchocelis phase of the annual, epiphytic, marine red alga Porphyra nereocystis Anderson, which in nature lives on the large annual kelp Nereocystis luetkeana (Mertens) Postels et Ruprecht, are released in culture only in response to a short-day photoperiod treatment followed by a long-day treatment. Each treatment requires a minimum of three to four weeks and is enhanced by lower temperature during the second photoperiod treatment. To our knowledge P. nereocystis is the first known dualdaylength seaweed and requires a short-day-longday treatment for completion of its life cycle. This stringent environmental control of its reproduction appears to be an adaptation to coordinate conchospore production with the seasonal availability of its host kelp Nereocystis. [ABSTRACT FROM AUTHOR]