Crossing experiments with Enteromorpha intestinalis and E. compressa from different European localities

Sexual compatibility in the marine algae Enteromorpha intestinalis and E. compressa has been studied using laboratory cultures from various geographical areas in Europe. The two species are found to be totally separated by a sterility barrier. Well branched plants always fall in the same of the two genetically isolated groups and should be called E. compressa s.str., while most other plants should be referred to E. intestinalis s.l. The early development of sporophyte germlings may follow two different patterns, both of which have been observed in a single combination of parental plants, though not at the same time.     

Species-specific oligonucleotide probes for macroalgae: molecular discrimination of two marine fouling species of Enteromorpha (Ulvophyceae)

The green seaweeds Enteromorpha intestinalis and E. compressa are important fouling organisms commonly found in polluted and nutrient-enriched marine and brackish water habitats, where they are used in environmental monitoring. Discrimination of the two species is extremely difficult because of overlapping morphological characters. In this study a quick molecular method for species identification was developed based on the nuclear rDNA ITS2 sequence data of 54 E. intestinalis samples and 20 E. compressa samples from a wide geographical range. Oligonucleotide probes were designed for species-specific hybridization to dot-blots of the PCR-amplified ITS1, 5.8S gene and ITS2 fragment of both E. intestinalis and E. compressa. Specificity of the oligonucleotide probes was confirmed by tests with taxonomically diverse species that could morphologically be confused with E. intestinalis or E. compressa. This is the first use of species-specific probes for macroalgae. The restriction endonuclease NruI digested specifically the amplified PCR product from E. compressa into two fragments detectable on agarose gels, but no suitable restriction sites were identifiable in the PCR product of E. intestinalis.     

Phylogeographical structure, distribution and genetic variation of the green algae Ulva intestinalis and U. compressa (Chlorophyta) in the Baltic Sea area

The marine algae Ulva intestinalis and U. compressa are morphologically plastic with many overlapping characters and are therefore difficult to distinguish from each other. The present distribution of U. intestinalis and U. compressa is investigated along the salinity gradient in the Baltic Sea area through analyses of internal transcribed spacer (ITS) sequence data. Also, the amount and distribution of intraspecific genetic polymorphism in the ITS region is studied allowing inferences on the phylogeographical pattern and postglacial recolonization of the Baltic Sea area. The data show that of the two species only U. intestinalis occurs in the Baltic Sea. The distribution of U. compressa is more restricted than previously reported, and it was not found in salinities lower than 15 ppt. All of Scandinavia and the Baltic Sea were covered with ice during the last ice age and the organisms in the Baltic Sea must have colonized the area after the ice had started to melt. The genetic diversity of U. intestinalis and U. compressa in the Baltic Sea and the neighbouring area was found to be reduced compared to that in the British Isles. This reduction may be the result of either a historical reduction of diversity or an adaptation of specific clones to the northern environmental conditions.     

The nucleotide sequences of 5S rRNAs from two red algae, Gracilaria compressa and Porphyra tenera

The nucleotide sequences of 5S rRNA from two red algae, Gracilaria compressa and Porphyra tenera have been determined. The two 5S rRNAs are fairly dissimilar to each other in their sequences (65% identity), although they are both composed of 121 nucleotides. Their secondary structures are generally of the eukaryotic with a prokaryotic characteristic. Judged from the 5S rRNA sequence data, the red algae are phylogenically distinct from green and brown algae, and they, Porphyra in particular, are evolutionally most ancient among the eukaryotes of which 5S rRNA sequence has been determined.     

Chlorophyll and peptide compositions in the two photosystems of marine green algae.

The molar ratios of chlorophyll a to b in the thalli of marine green algae were between 1.5 and 2.2, being appreciably lower than the ratio between 2.8 and 3.4 found for the leaves of higher plants and the cells of fresh-water green algae. The ratio of chlorophylls to P-700 in these marine algae was also lower than that in higher plants. The a/b ratios in the pigment proteins of Photosystems 1 and 2 separated by polyacrylamide-gel electrophoresis from sodium dodecyl sulfate-solubilized chloroplasts of four species of marine green algae, Bryopsis maxima, Cheatomorpha spiralis, Enteromorpha compressa and Ulva conglobata, were approximately 5 and 1, which are considerably smaller than the ratios, 7 and 2, respectively, found for the pigment proteins of the two photosystems of higher plants separated by the same technique. The chloroplasts of Bryopsis maxima and Cheatomorpha spiralis lacked two of the peptides associated with Photosystem II, which are present in the chloroplasts of Spinacia oleracea and Taraxacum officinale.     

Preferential expulsion of dividing algal cells as a mechanism for regulating algal-cnidarian symbiosis

A wide range of both intrinsic and environmental factors can influence the population dynamics of algae in symbiosis with marine cnidarians. The present study shows that loss of algae by expulsion from cnidarian hosts is one of the primary regulators of symbiont population density. Because there is a significant linear correlation between the rate of algal expulsion and the rate of algal division, factors that increase division rates (e.g., elevated temperature) also increase expulsion rates. Additionally, 3H-thymidine is taken up to a greater extent by algae destined to be expelled than by algae retained in the host cnidarians. Taken together, data for rates of expulsion, rates of division at different temperatures, and uptake of 3H-thymidine suggest that dividing algal cells are preferentially expelled from their hosts. The preferential expulsion of dividing cells may be a mechanism for regulation of algal population density, where the rate of expulsion of algae may be an inverse function of the ability of host cells to accommodate new algal daughter cells. This kind of regulation is present in some cnidarian species (e.g., Aiptasia pulchella, Pocillopora damicornis), but not in all (e.g., Montipora verrucosa, Porites compressa, and Fungia scutaria).     

Topographic cues guide the attachment of diatom cells and algal zoospores

Surface topography plays a key role in the colonization of substrata by the colonizing stages of marine fouling organisms. For the innovation of marine antifouling coatings, it is essential to understand how topographic cues affect the settlement of these organisms. In this study, tapered, spiked microstructures and discrete honeycombs of varying feature dimensions were designed and fabricated in order to examine the influence of topography on the attachment of zoospores of the green macroalga Ulva linza and cells of the diatom (microalga) Navicula incerta. Contrasting results were obtained with these two species of algae. Indeed, the preferred location of cells of N. incerta was dominated by attachment point theory, which suggested a positive correlation between the density of cells adhering and the amount of available attachment points, while the settlement of spores of U. linza was mainly regulated by both Wenzel roughness and local binding geometry.     

Experimental analyses of patch selection by foraging black surfperch (Embiotoca jacksoni Agazzi)

The dynamics of microhabitat use by foraging adult and juvenile black surfperch (Embiotocajacksoni Agazzi) were explored. Detailed observations of black surfperch feeding at Santa Catalina Island, California, revealed that adults and young-of-year juveniles co-occurred in the same habitat but used different algal substrata as foraging sites. Juveniles selected invertebrate prey almost exclusively from the surface of foliose algae. The occurrence of young E. jacksoni was highly correlated with that of foliose algae. Adults tended to bite most frequently from turf, a low-growing matrix of plants, colonial animals, and debris covering the rocky substratum. The abundance of adults was negatively correlated with the occurrence of foliose algae. Adults and juveniles showed marked, but different, preferences in their utilization of taxa of algae as foraging substrata. Certain algae (e.g., Zonaria farlowii Setchell & Gardner) were preferred while other taxa (e.g., Sargassum palmeri Grun) were avoided by both age groups. However, most types of algae were preferred by one group but not the other. To test the hypothesis that knowledge of algal substratum composition allows prediction of fish occurrence and foraging behavior in a patch, algal cover on 2 × 2 m² areas of bottom was manipulated creating plots dominated by turf, Zonaria farlowii, or Sargassum palmeri. Fish occurrence could be accurately predicted on the basis of abundance of foliose algae, but foraging activity of fish was highly dependent on the algal taxon that dominated the patch. Differential prey availabilities among foraging substrata provided some insight into the patterns of foraging patch preferences displayed by adult and juvenile Embiotoca jacksoni.     

Basic biology and small-scale rearing of Celatoria compressa(Diptera: Tachinidae), a parasitoid of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)

The tachinid Celatoria compressa Wulp has been evaluated as a candidate biological control agent for the western corn rootworm, Diabrotica virgifera virgiferaLeConte, in Europe, where it is an invasive alien pest of maize. Special emphasis has been placed on understanding aspects of the parasitoid basic biology and on developing a rearing technique for a small-scale production of C. compressapuparia. The age of C. compressa adults was found to be the most crucial factor in achieving mating. Only newly emerged, 1-h-old females, mated successfully with 2- to 5-day-old males, achieving a success rate of 74%. After mating, a prelarviposition period of 4 days occurred. The 5-day-old C. compressa females inserted their eggs containing fully-developed first instars directly into adults of D. v. virgifera. Total larval and pupal developmental time, including a pre-larviposition period of 4 days, was 29 days under quarantine laboratory conditions (25 degrees C daytime, 15 degrees C at night, L:D 14:10, 50% +/- 10% r.h). Females of C. compressa were capable of producing on average 30 puparia throughout a female's mean larviposition period of 15 days. A large number of host attacks by C. compressa were unsuccessful, resulting in a mean larviposition success rate of 24% per female. Parasitoid females appear to have difficulties inserting the egg through the intersegmental sutures or membranes around leg openings of the host adults. Although the small-scale rearing technique of C. compressa presented is both time and labour intensive, C. compressa has been reared successfully for at least 20 successive generations without shifting the 1 male : 1 female sex ratio using a non-diapause strain of D. v. virgifera.     

Macro-floral assemblages in upland Welsh streams in relation to acidity, and their importance to invertebrates

SUMMARY 1. Macro-flora (angiosperms. bryophytes and macroscopic algae) and macroinvertebrates were sampled in 1984 at eighty-eight sites on soft-water streams in upland Wales. Assemblage patterns were related to stream chemistry using TWINSPAN, DECORANA and multiple discriminant analysis.
2. Floral assemblages could be related most strongly to pH and aluminium concentration, with Scapania undulata, Nardia compressa and filamentous chlorophytes characterizing streams of mean pH5.2–5.8, whilst Fontinalis squamosa occurred mostly at pH 5.6–6.2 and Lemanea at pH 5.8–7.0. We propose an indicator system based on thesetaxa.
3. Assemblages of invertebrates and flora concorded highly significantly, sites with Scapania and Nardia holding impoverished faunas. Because some acid sensitive invertebrates (e.g. Ecdyonurus and Ancylus ) can feed from acid tolerant plants (e.g. Scapania ), we hypothesize that they are restricted physiologically from acid streams.     

The distribution of Ephemerella ignita (Ephemeroptera) in streams: the role of pH and food resources

SUMMARY. 1. The mayfly Ephemerella ignita does not occur in upland streams of the River Duddon catchment which have waters with low pH values of 4.8-5.2, negative alkalinities and low ionic contents. However, it does occur in lowland streams of the catchment which have waters with higher pH values of 6.6 and above, large positive alkalinities and high ionic contents. This study addresses the question of whether the absence of the animal in the acid water streams is due directly to the water chemistry or to the absence of suitable food.
2. In comparative experiments using unfed animals of several species it was shown that E. ignita has a considerable tolerance of low pH, low ion water. In this it is similar to Amphinemura sulcicollis (Plecoptera), a stonefly which occurs in the acid water streams of the River Duddon catchment.
3. Growth rates in laboratory experiments with E. ignita were equally good whether the food supplied was that available in the low pH water streams (bryophyte Nardia compressa plus filamentous alga Hormidium subtile) or typical of that available in high pH water streams (moss Rhynchostegium riparioides with the epiphytic diatom Cocconeis placentula). However, a consideration of the natural habits of the animal suggests that it is the inaccessibility of the H. subtile algal food, rather than its unsuitability, which is relevant to the exclusion of E. ignita from the low pH streams. In addition, the very limited diversity of other algae in the low pH water streams, in the summer season, may well be influential in inhibiting the establishment of E. ignita.
4. The comparative experiments using unfed animals suggested that, contrary to the findings for E. ignita , the mayflies Baetis muticus and Beatis rhodani are probably excluded from the acid water streams of the Upper Duddon because of water chemistry.     

Developing an in vitro method for Eimeria tenella attachment to its preferred and non-preferred intestinal sites

A frozen section method utilising chicken intestinal tissue was developed to study the Eimeria tenella attachment ex vivo. In order to examine Eimeria-epithelial cell attachment, 10⁵E. tenella sporozoites were incubated with each caecal frozen section (6, 10 and 14 μm) for 1 h in 5% CO₂ incubator at 41 °C. E. tenella sporozoites attached successfully to enterocytes in 14 μm thick of caecal sections. Sporozoite attachment to caecal sections was shown to be dependent on the number of parasites added. To evaluate the method, E. tenella sporozoites were incubated to its preferred (caecum) and non-preferred (duodenum and jejunum) intestinal sites. The number of sporozoites attached to the caecal enterocytes was significantly greater (P < 0.0001) in comparison with the limited number of sporozoites attached to enterocytes of non-preferred intestinal sites. This method was shown to be able to reveal differences in binding capability and allows for comparison of intestinal site attachment.     

Cultivation of the two perennial brown algae Ecklonia cava and E. stolonifera for abalone feeds in Korea

Ecklonia cava and Ecklonia stolonifera are perennial brown algae that form sea forests off the coast of Korea. Both species are cultured to supply a summer feed for the abalone industry. Recent expansion of the abalone industry in Korea has been bringing an increase in demand for fresh algal supply. Zoospores of the two algae were seeded in October 2006 on seed frames coiled with 100 m of seed fibers. After 2 months of indoor culture and 2 months of intermediate culture, growth and production of the two algae were compared during their main cultivation period from March 2007 to June 2008, in the culture ground in Wando, Korea (34°26′18.68″ N, 127°05′43.88″ E), in situ. Growth rate of E. cava and E. stolonifera was 1.058 and 3.089 mm day^?1, respectively. The mean production of E. stolonifera obtained from the culture ropes was ca. 12 kg wet wt. m^?1 of culture rope while production of E. cava was ca. 3 kg wet wt. m^?1 of culture rope. The difference in production was attributed from the different growth strategies of the two algae, with only E. stolonifera being able to regenerate blades from the holdfast. The ability to regenerate blades from the holdfast therefore makes E. stolonifera the preferred species for biomass production for abalone feeds. In a 120-day feeding experiment, growth rate, weight gain, and survival rate of abalone showed that E. cava and E. stolonifera feeds could provide an alternative feed to Saccharina japonica during summer months.     

Mechanisms of bioadhesion of macrophytic algae

During the evolution the benthic macrophytic algae developed effective mechanisms of bioadhesion enabling their attachment to almost any surface in the aqueous medium. The attachment of algal spores and zygotes includes two successive stages: the primary and the secondary (final) adhesion. Analysis of information on the composition of adhesive materials and attachment mechanisms in brown, green, and red marine macrophytes indicates that synthesis and release of adhesive substances by algal cells can be considered as a temporary intensification of cell wall synthesis. The structure of the primary adhesive material comprises a gel phase (alginate, ulvan, and agar gels) and a structuring component, i.e., a flexible network based on branched chains and/or rings of phenolic compounds, polysaccharides, or glycoproteins. Irreversible hardening of the primary adhesive material arises from phenol polymerization catalyzed by different peroxidases (brown algae) or from polymerization of glycoproteins comprising amino acids with phenolic residues (red algae). In parallel with these processes, covalent cross-links are being formed between the adhesive structural components and the gel phase polysaccharides. This results in the formation of the secondary adhesive and in eventual attachment of the organism to the substrate. The attachment mechanisms of benthic algae appear to have some features in common with the mechanisms of bioadhesion of marine invertebrates.     

渤海浒苔属绿藻调查

于2009年至2010年对渤海及其周边10个沿海城市和6个岛屿的浒苔属绿藻进行了调查,初步确定该海区缘管浒苔、肠浒苔、扁浒苔、浒苔、条浒苔5个种类的地理分布情况。并对生物量进行了评估。与历史资料相比,渤海中辽东湾、渤海湾和莱州湾三个湾内的浒苔多样性和生物量下降明显或保持较低水平,湾周边地区则维持较高水平。此外,在近海人工基质上,以浒苔属为主的绿藻相对于红藻、褐藻分布更为广泛。     

STUDIES OF MESOHERBIVORY IN AQUARIA AND IN AN UNBARRICADED MARICULTURE FARM ON THE CHINESE COAST1

The effects upon macrophytic and epiphytic algae of caprellid amphipods, including Caprella irregularis Mayer, and of gammarid amphipods, including Ampithoe lacertosa Bate, Jassa falcata (Montagu) and Pontogeneia rostrata Gurjanova, were studied in aquaria and in a coastal mariculture farm near Qingdao, People's Republic of China. The macrophytic species studied included Enteromorpha linza (L.) J. Agardh, Gracilaria asiatica Zhang & Xia, Gracilaria lemaneiformis (Bory) Weber-van Bosse and Scytosiphon lomentaria (Lyngbye) C. Agardh. These algae and amphipods were selected for study because of their local abundances. Aquarium experiments demonstrated that C. irregularis, J. falcata and P. rostrata feed on ephemeral/epiphytic algae. A. lacertosa (adults and juveniles) ate Gracilaria but preferred E. linza. The different species of amphipods had substantially different patterns of daily activity. Caprellids prevented epiphytic overgrowth of G. asiatica when added to plants in an experimental, openocean, mariculture farm, despite the presence of numerous amphipod predators (e.g. the fishes Hexagrammos otakii Jordan & Starks and Sebastes thompsoni Jordan & Hubbs). Periodic removals of all (naturally colonizing) amphipods from another group of plants in the farm resulted in heavy epiphytic overgrowth. Since these results were obtained in an unbarricaded mariculture farm, we conclude that mesoherbivores may have large effects upon algal community structure in temperate intertidal and subtidal habitats.     

Bacterial Enhancement of Vinyl Fouling by Algae

The role of bacteria in the development of algae on low-density vinyl was investigated. Unidentified bacterial contaminants in unialgal stock cultures of Phormidium faveolarum and Pleurochloris pyrenoidosa enhanced, by 1 to 2 orders of magnitude, colonization of vinyl by these algae, as determined by epifluorescence microscopy counts and chlorophyll a in extracts of colonized vinyl. Colonization by bacteria always preceded that by algae. Scanning electron microscopy of the colonized Phormidium-bacteria mixture revealed the presence of a slime matrix engulfing both bacteria and algae that may have facilitated algal attachment. Slime was not evident in the Pleurochloris-bacteria mixture, suggesting that the attachment mechanisms differ for the two algae.     

Food preference of freshwater invertebrates: comparing fresh and decomposed angiosperm and a filamentous alga

1. Fresh and decomposed Mougeotia sp. (a filamentous green alga) and Elodea nuttallii (a vascular plant) were offered as food to three species of aquatic macroinvertebrates (Lymnaea peregra, Asellus meridianus and Endochironomus albipennis) to test: (i) if filamentous algae are preferred to aquatic higher plants (hereafter, called ‘macrophytes’) and (ii), as is known for higher plants, if decomposition also results in greater palatability of filamentous algae. 2. Compared with the alga, the macrophyte in both states was of higher nutritional value. Conditioning improved the nutritional value of both food types, but especially of the macrophyte. 3. Both fresh alga and fresh macrophyte were eaten little by all animals except A. meridianus feeding upon the macrophyte. Consumption was higher for both plants in their decomposed state. However, L. peregra consumed more decomposed macrophyte than the decomposed alga. Both decomposed plants were eaten most by E. albipennis followed by A. meridianus and L. peregra. 4. Digestibility of both plants, but especially of the macrophyte, increased significantly after decomposition. The assimilation efficiencies of all animals on the fresh E. nuttallii were higher than on fresh Mougeotia sp. After decomposition, the efficiency increased significantly only on the alga. Consequently, both decomposed plants were assimilated with similar efficiency by all test animals. 5. Amongst aquatic macrophytes, the increase of their consumption and digestibility upon decomposition has hitherto been known only for vascular plants but not for filamentous algae.     

Microbial communities associated with skeletal tumors on Porites compressa

Coral tumors are atypical skeletal forms found on coral reefs worldwide. Here we present an analysis of the microbial communities associated with skeletal tumors on the coral Porites compressa. Microbial growth rates on both healthy and tumorous P. compressa were decoupled from the surrounding water column. Microbial communities associated with tumorous colonies had a significantly faster growth rate than those associated with healthy P. compressa. The microbial community associated with the tumors contained more culturable Vibrio spp. and could utilize more carbon sources than the microbes associated with healthy colonies. Presence of tumors affected the composition and dynamics of the microbial population associated with the entire colony.     

Sponge white patch disease affecting the Caribbean sponge Amphimedon compressa

We report on a novel sponge disease, hereafter termed 'sponge white patch' (SWP), affecting the Caribbean sponge species Amphimedon compressa. SWP is characterized by distinctive white patches of variable size that are found irregularly on the branches of diseased sponges. Nearly 20% of the population of A. compressa at Dry Rocks Reef, Florida, USA, showed symptoms of SWP at the time of investigation (November 2007-July 2010). Approximately 21% of the biomass of SWP individuals was bleached, as determined by volume displacement. Scanning electron microscopy analysis showed severe degradation of bleached tissues. Transmission electron microscopy of the same tissues revealed the presence of a spongin-boring bacterial morphotype that had previously been implicated in sponge disease (Webster et al. 2002; Mar Ecol Prog Ser 232:305-309). This particular morphotype was identified in 8 of 9 diseased A. compressa individuals investigated in this study. A close relative of the aforementioned disease-causing alphaproteobacterium was also isolated from bleached tissues of A. compressa. However, whether the spongin-boring bacteria are true pathogens or merely opportunistic colonizers remains to be investigated. Molecular fingerprinting by denaturing gradient gel electrophoresis (DGGE) demonstrated a distinct shift from the microbiota of healthy A. compressa to a heterogeneous mixture of environmental bacteria, including several phylotypes previously implicated in sponge stress or coral disease. Nevertheless, tissue transplantation experiments conducted in the field failed to demonstrate infectivity from diseased to healthy sponges, leaving the cause of SWP in A. compressa to be identified.