Volume 55, Issue 6

A few recent investigations have established that marine-derived fungi associated with sponges are an excellent source of novel bioactive metabolites with the potential to function as drugs or drug leads. Given the high species diversity and wide distribution of sponges, it is reasonable to expect that they harbour marine-derived fungi with the ability to produce diverse secondary metabolites. For a more complete realisation of their technological potential, a thorough knowledge of the different taxa of marine-derived fungi associated with sponges is essential. There is scarce information on the interplay between sponges and associated marine-derived fungi and between the marine-derived fungi and other sponge endosymbionts. Unravelling such interactions could be useful in recreating the sponge microcosm conditions in vitro for harvesting novel fungal metabolites. This is essential as many genes of fungal secondary metabolism are inactive in axenic cultures. This review addresses these issues by focusing on the isolation, identification, nature of association, secondary metabolites and potential interactions of marine-derived fungi of sponges and presents some future prospects regarding the bioprospecting of these fungi.

We report on (i) in vitro growth conditions for different growth stages of Heterosigma akashiwo and (ii) isolation, purification and structural investigation of the exopolysaccharide fraction (EXO). Cell polysaccharide fractions were analyzed for chemical composition, and we performed a comparison of the lipid components between cultures subjected to either a light/dark cycle of 12 h/12 h or 24 h of light. Man, Rha and Gal were the main monosaccharides in the EXO fraction. Following the purification step, the EXO fraction yielded EXO1.0 and EXO1.5 fractions. A linkage analysis of the EXO1.0 fraction indicated the presence of a highly branched polysaccharide with a (1→4)-linked mannan backbone, and analysis of EXO1.5 indicated the presence of a complex rhamnan consisting mainly of 2- and 4-linked Rha units with the non-reducing end of Gal and Rha. In cultures subjected to a 12 h/12 h light/dark cycle, palmitic and myristic acids were the most abundant lipids, and no polyunsaturated acid was detected. However, in cultures subjected to 24 h of light, no myristic acid was detected, and stearic and palmitic acids were the most abundant fatty acids. A polyunsaturated fatty acid and fatty acids with 20 or more carbon atoms also occurred in this fraction.

We analyzed Gayralia oxysperma (Monostromataceae, Ulvales) from coastal waters in India for nutrients and biochemicals including nutritionally important fatty acids and active radical scavenging properties. This seaweed had moderately high lipid and other biochemical components, which were comparable to levels in other nutritionally rich seaweeds. The species is an important source of Ca (2.74 mg g -1 ) and other essential elements with sufficiently low (below permissible limits) contaminant trace metals. There were four major fatty acids: palmitic acid (PA, C16; 34.6%), linoleic acid (LA, C18:2n-6; 15.8%), gamma-linolenic acid (GLA, C18:3n-6; 15%) and stearic acid (SA, C18; 9.6%). Totally saturated fatty acids predominated (TSFA, 57%), followed by polyunsaturated acids (PUFA, 39%); the monounsaturated fraction (MUFA) was smallest (3.8%). Antioxidant potential assessed through phenolic content, di(phenyl)-(2,4,6-trinitrophen­yl) iminoazanium (DPPH), hydrogen peroxide (H 2 O 2 ), reducing potential and metal chelating ability indicated a dose-dependent relationship of increasing activity with increased concentration. Thus, G. oxysperma has essential properties of nutritional, antioxidant and medicinal value for its use in dietary and pharmaceutical applications.

In vitro germinated seedlings of ­Cymodocea nodosa were used as a source of young embryonic tissue for cell culture. Histological study of the cotyledon revealed the presence of meristematic tissue that gave rise to the first leaf of the plantlet, which released large numbers of cells after enzymatic digestion and thus indicated great growth potential. An effective enzymatic digestion protocol for C. nodosa meristem tissue was developed; this consisted of a 24-h digestion period at 28°C using a 0.6- m enzymatic solution (plasmolysis medium containing 1% (w:v) cellulase and hemicellulase). It was necessary to add citric acid (0.02 m ) as an antioxidant to the enzymatic solution to obtain the highest cell yield and viability (mean±SE: 371.6±30.1×10 5 cells g -1 fw and 97.8±0.6%, respectively). NaCl and other salt components of the seawater were key factors in the establishment of axenic cell cultures and their further progress; their absence in the medium inhibited contaminant overgrowth. Nevertheless, cells maintained growth for 90 days, even without hormones and deprived of salts, although these salts might be necessary to allow the development of morphogenetic programmes desired for plant production. In this manner, we generated a basic tool for the future of C . nodosa in vitro culture that will allow the establishment and maintenance of hormone-autonomous cell cultures with strong potential in future biotechnology for marine higher plants.

We developed a simple and inexpensive digital image analysis method for measuring leaf area and the length of strapped-shaped seagrass leaves. The method uses specialized software that permits automatic leaf and scale recognition in digital images along with batch image processing. The leaf biometrics of 80 Posidonia oceanica and Cymodocea nodosa leaves were used for the evaluation of the method for accuracy, precision, and speed in comparison to manual measurements. Each leaf was measured 90 times under different combinations of several factors that might affect software estimation. The factors examined included leaf shape, leaf orientation in the image, scale dimensions, image resize, and binary conversion. Estimates of leaf length and leaf area were highly correlated between the new image analysis procedure and manual measurements. Relative error values between the two methods were <10% in 99% of leaf length measures and in 75% of leaf area measures. The factors examined explained <10% of the relative error variance; the remaining variance was mostly attributed to technical issues concerning leaf size and image illumination. The digital method proved to be approximately 2.5 times faster than the manual one.

We examined the environmental and biological factors related to blooms of the toxic dinoflagellate Pyrodinium bahamense in three shallow, restricted subtropical lagoons in the Gulf of California during the rainy summer. In the San José, Yavaros, and El Colorado lagoons, the vegetative stage peaked at 63, 108, and 151 (×10 3 cells l -1 ), respectively. At San José, production of cysts peaked at 9.7×10 3 g -1 of dry sediment mass as the bloom declined. Large diatoms predominated, with P. bahamense the most common dinoflagellate during the blooms. Abundance of P . bahamense at San José was positively correlated with salinity (r=0.50, p=0.0003), seawater temperature (r=0.44, p=0.005), silicates (r=0.45, p=0.003), and ammonium (r=0.32, p=0.005), and negatively correlated with dissolved oxygen (r=-0.34, p<0.0001). No such correlations were found at El Colorado and Yavaros. The environmental window that favors development of blooms is restricted to the summer and is influenced by seawater temperature, salinity, and relative concentrations of ammonium and phosphates that, in turn, depend on rainfall and runoff, which is greater on the eastern side of the Gulf where seawater quality is degraded.

We sampled macroalgal assemblages on 37 rocky outcrops in the northern Adriatic over the last 2 decades by SCUBA. Macroalgal assemblages were rich (173 taxa), but there was high variability in the number of species and coverage. The morphology of the outcrops, the distance from the coast and the depth were identified as the main factors accounting for this variability. Both the mean total algal coverage (14.8%) and encrusting layer coverage (8.0%) were low when compared to typical Mediterranean coralligenous habitats. Four main groups of algal assemblages were distinguished on the basis of their species composition and coverage. Groups 1 and 3 were located inshore off the Lido inlet and south of it, and had, respectively, low or intermediate total algal cover. Group 2 included outcrops situated offshore from the Venice lagoon along with all outcrops off the Grado-Marano lagoon; these had the highest total algal cover. Finally, group 4 included assemblages comprising algae that were widespread on outcrops in the inshore habitats of the Venice lagoon, between Malamocco and Chioggia inlets. Offshore outcrops subject to low turbidity and eutrophication levels had several characteristic Mediterranean coralligenous taxa.

Phototactic movements of Elachista antarctica spores were quantified across a wide range of irradiances from 10 to 800 μmol photons m -2 s -1 using the recently updated version of CellTrak 1.5 motion analysis software. Spores 0–12 h old exhibited phototactic attraction at 80 and 200 μmol photons m -2 s -1 , which contributed to vertical movements up out of the boundary layer to be further dispersed hydrodynamically, but were repelled at 800 μmol photons m -2 s -1 , causing spores to retreat from detrimental irradiances. No significant effects were observed among spores released 24–36 h before measuring phototaxis at 200 and 800 μmol photons m -2 s -1 .

Blackler first recorded Colpomenia peregrina in the Northwest Atlantic based on collections from Nova Scotia, Canada. Five decades later we found large quantities of C. peregrina in Maine, USA, even though it was absent during earlier floristic studies in this region. Thus, C. peregrina has undergone a rapid southern expansion along the Northwest Atlantic coast. While the causes of such an expansion are unknown, it could have a major effect on both shellfish cultivation and native seaweeds within New England because of competitive interactions and increased drag.