Band 54, Heft 1

No abstract available

This review summarizes increasing evidence for the role of Labyrinthulomycetes in marine ecosystems gathered over the last six decades. It focuses on their diversity, habitats, biomass, productivity and overall role in food webs and remineralization. Earlier studies contributed enormously to the cultured diversity of Labyrinthulomycetes. In recent years, their uncultured diversity has been demonstrated in exotic environments like the deep sea and anoxic waters. These findings emphasize the need for novel culture methods to grow these organisms. Many species seem to be substrate-specific in their occurrence. Their commensalistic or mutualistic occurrence in marine invertebrates deserves attention. The biomass of Labyrinthulomycetes in the water column may often match or even exceed that of bacteria, although such occurrences seem to be seasonal. There is a major knowledge gap on their productivity and turnover in the water column. The high biomass and production of several degradative enzymes indicate their importance as remineralizers in the ocean. However, the mechanisms by which they overcome bacterial competition are not clear. It is likely that they occupy special habitats, such as marine aggregates. One role of the Labyrinthulomycetes suggested in this review, based on preliminary experiments, is that of “left-over scavenging”, following bacterial growth.

Meadows of the seagrass Halodule wrightii occur on shallow subtidal sandy bottoms of euhaline high-energy sites in Paranaguá Bay, Brazil. Close to their southernmost limit in the South Atlantic, local populations are patchy, unstable and most often do not reproduce sexually. We describe morphological and biomass variations of a local H. wrightii meadow off Rasa da Cotinga Island, which deteriorated from a healthy state to subsequently decline and die-off. Leaf width and length, number of leaves per shoot, leaf sheath length, rhizome width, internodal length and biomass, sediment grain size, CaCO 3 and POM contents were measured on six sampling dates between November 2004 and October 2005. Compared to other Halodule meadows along the southwestern Atlantic coastline, local plants had shorter and narrower leaves, shorter leaf sheaths, thinner rhizomes, fewer leaves per shoot, a larger internodal distance, and lower biomass. Local variations in morphology and plant biomass followed a seasonal pattern, but were affected by stressor, such as the lowering of temperature, precipitation, and high turbidity associated with southwesterly winds that increased meadow vulnerability. Life history traits of H. wrightii , a short-lived species with rapid growth and ability to reproduce vegetatively under stress conditions, promote resilience and rapid recovery of local meadows, which exhibit a typically fugitive behavior.

Lagoon environments are particularly subject to the introduction, either accidental or voluntary, of alien species that may cause biological pollution. On the basis of morphological data and molecular analyses ( rbc L and mitochondrial cox 2- cox 3 spacer sequences) we confirmed the taxonomic identity (previously only hypothesised) of Grateloupia turuturu in both the Lagoon of Venice and the Mar Piccolo basin of Taranto, where it was most probably introduced by shellfish transfers. A detailed morphological description of vegetative and reproductive thalli is given, focusing particularly on the encrusting bases. The bases act as resting structures that are able to survive during unfavourable environmental conditions. In both the Lagoon of Venice and the Mar Piccolo of Taranto, G. turuturu does not yet exhibit invasive behaviour.

Sexual structures of Ptilothamnion sphaericum and Pterosiphonia complanata are described for the first time. Spermatangial heads of P. sphaericum are densely clustered in short lateral branchlets, each cell of which bears up to three spermatangial heads. They consist of a stalk cell and 3-4 axial cells bearing a cluster of spermatangial mother cells that cut-off 1–2 spermatangia. The last two cells in female axes of P. sphaericum are relatively short, with the hypogenous cell longer and more similar to vegetative cells. The subapical cell bears three periaxial cells: two sterile and the supporting cell, which bears a four-celled carpogonial branch and one sterile cell. The hypogenous cell bears 1–2 involucral filaments prior to fertilization. These features support the placement of P. sphaericum in the genus Ptilothamnion . Spermatangial branches of Pterosiphonia complanata are borne on unbranched modified trichoblasts. They consist of an elongate suprabasal cell that bears a fertile central axis from which four periaxial cells arise, bearing quadrangular spermatangial mother cells that bear the spermatangia. Spermatangial branches have 1 (-3) apical sterile cells. Procarps of P. complanata consist of a four-celled carpogonial branch and two sterile cells borne on the supporting cell. These features are similar to all Pterosiphonia species for which they have been described.

Metapeyssonnelia milleporoides is newly described based on specimens growing epizoically on corals, primarily Millepora complanata and Porites sp., in shallow-water coral reef environments off Puerto Rico. The new species possesses light hypobasal calcification, sunken tetrasporangial nemathecia and has hypothallial cells arranged in broad flabellules. Both cystoliths and hair cells are present in the perithallus. The species grows sympatrically with M. corallipeda and also kills its host by overgrowth. Peyssonnelia dawsonii is recognized as a member of Metapeyssonnelia and is transferred to this genus.

Our present knowledge of marine macroalgal diversity for the Central American Pacific coast is limited by the short history of investigations (ca. 100 years) and few algal specialists through a large geographical area. While recent checklists have emerged for other regions of the eastern Pacific, there have been virtually no attempts to inventory macroalgal diversity for the Pacific of Central America. This checklist of the marine macroalgae was developed based on published scientific literature and unpublished records in student theses. A total of 379 species records are regarded as current valid names of marine macroalgae. The red algae (Rhodophyta) had the highest species number (252 species), followed by green algae (Chlorophyta: 81 species) and brown algae (Phaeophyceae: 46 species). The country with the greatest diversity of marine macroalgae is Costa Rica with 216 species, followed by Panama with 174, El Salvador with 146, Nicaragua with 24, and Guatemala with 16. At present, there are no published records for the Pacific coast of Honduras. Variation in number of species throughout the Pacific coast of Central America is likely due to differences in geomorphology, habitat heterogeneity among national coastal-marine zones, and unbalanced research efforts.

The marine fungus Plectosphaerella sp. strain MF-1 was isolated from sea shells and found to produce a chitinase potentially active at low temperature. The fungal strain was characterized by morphological and molecular features. Chitinase production by Plectosphaerella MF-1 was detected by inoculating the fungus into M9 medium containing 0.5% colloidal chitin at 10°C. Crude chitinase production in culture filtrates reached a maximum 14 days after inoculation. Crude chitinase was purified by ammonium sulfate fractionation, cellulose DEAE anion exchange, and sephadex gel filtration chromatography. Purified marine fungal chitinase had activity at 37°C, the difference in chitinase activities at 10°C and 37°C was less than 0.01 U ml -1 indicating chitinase was active at low temperature. The optimal pH for the low temperature active chitinase was 3–4. The K m was 0.03 m m and V max was 0.095, using p -nitrophenyl N -acetyl-β- d -glucosaminide as a substrate. Among the metal ions tested for inhibitory activity, Ag + , Hg 2+ , and Pb 2+ strongly inhibited enzyme activity, whereas Mg 2+ and Fe 2+ had minimal inhibition. The molecular mass of purified chitinase was determined as 67 kDa by SDS-PAGE. The N-terminal amino acid sequence was determined to be “DNISQTGEHARYXPMVWFIKL”.

We monitored the dominance and species diversity of fungi in hypersaline water bodies and saline depressions in Kuwait in the period February–October, 2007. There were considerable variations in total numbers and species diversity in concert with salinity variation. Among the most dominant isolates in high salinity water were several Cladosporium spp. and two moderately halophilic Acremonium spp. Several Alternaria -like strains were frequently found; they had various morphologies, but with identical ITS-5.8-ITS2 DNA sequences. Halophilic Cladosporium spp. and an undescribed Sporomiella sp. had best growth in 5% NaCl solutions.

Endophytes from marine plants have not been widely explored, and their bioactive compounds are not well-documented. In the present study, 64 endophytic fungi were isolated from Malaysian marine plants and seaweeds. The endophyte extracts were tested for cytotoxic (seven cancer cell lines) and antimicrobial (against four bacteria and two fungi) activities. Out of 64 extracts tested, 49 (77%) were able to inhibit cancer cell lines. Eight of the endophyte extracts that were potent (IC 50 ≤0.1 μg ml -1 ) against colon and lung cancer cell lines were further compared for their effects on a normal human fibroblast cell line. The marine endophytic fungal extracts showed stronger antimicrobial activity against bacteria (72%) than fungi (16%). The bioactivity of a few selected marine endophytic fungal extracts was comparable to a number of current commercial anticancer, antibacterial and antifungal agents. Results from the present study indicate marine endophytic fungi are a promising source for anticancer and antimicrobial agents.

Flowering events of Posidonia oceanica (over two consecutive years) are reported for the first time in meadows located close to its westernmost distribution limit (Málaga, southern Spain). Shoots with inflorescences were found in fragmented meadows (patches between 1–130 m 2 ) at a mean depth of 2.5 m. In March 2009, flowering was only observed in Calaburras (0–28 inflorescences m -2 ) and not in Calahonda. In November 2009, massive flowering events were observed in both Calaburras (4–144 inflorescences m -2 ) and Calahonda (8–184 inflorescences m -2 ). On this occasion, developing fruits were also observed. From 2003 to 2009, mean annual water temperatures increased in this area, with maximum values in late summer and autumn of 2007 and 2008, and these warm waters may have induced the massive flowering events. Flowering in these P. oceanica meadows located close to the Atlantic Ocean may imply favourable environmental conditions and a good health status, which should be considered in improving conservational strategies for these meadows.

This first record of vivipary in the Amaranthaceae is reported for the foredune plant Alternanthera littoralis var. maritima (July 2008, northern coast of Brazil). Vivipary is the precocious and uninterrupted growth of the seedlings while still attached to the maternal body. We propose a hypothesis for the viviparous germination of this species based on field observations. Our record adds new perspectives to the reproductive biology of the Amaranthaceae.

No abstract available