Temperature,taxonomic technique and the zoogeography of lugworms (Arenicolidae,Polychaeta)

Summary 1. The surface of the world may be divided into three great zones, each with a completely distinct lugworm fauna on its shores. The boundaries correspond roughly with the summer surface-water isotherms at 20° C, and they separate a northern cool-water, a warm-water and a southern cool-water zone. The third zone shows a subdivision of minor importance along the line of the 10° C isotherm.2. The main zones are characterized by endemic clusters of forms which seem to have evolved and differentiated within the zones. The temperature barriers must therefore have persisted for long enough to allow a considerable degree of intrazonal evolutionary differentiation to take place.3. Until ten years ago, our classification of the Arenicolidae was based almost entirely on museum material, the samples being mostly small and sometimes ill-preserved. In the circumstances, taxonomists could use only very obvious characters, and they tended to make their groups too large.4. Recent work with large samples of worms, combining field with laboratory study, has split several of the older taxa. The number of named species and subspecies of lugworms has risen in ten years, mainly as a result of splitting, from 10 to 24.5. The importance of temperature barriers, and of other isolating factors, in controlling lugworm distribution is now more clearly seen. It may be that similar studies, carried out on other families, would substantially reduce the number of polychaetes supposed to have wide (bipolar or cosmopolitan) distributions.

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Temperatur, taxonomische Technik und die Zoogeographie der Wattwürmer (Arenicolidae, Polychaeta)

Kurzfassung Die Erdoberfläche läßt sich in drei große Zonen einteilen, von denen jede an ihren Küsten eine vollständig unterschiedliche Wattwurmfauna aufweist. Die Zonengrenzen entsprechen in Annäherung dem Verlauf der Sommer-20°-C-Oberflächenisothermen und trennen eine nördliche und eine südliche Kaltwasserzone von einer mittleren Warmwasserzone. Die südliche Kaltwasserzone läßt einige Unterteilungen von geringer Bedeutung erkennen, und zwar entlang der 10°-C-Isotherme. Die Hauptzonen sind charakterisiert durch endemische Formengruppen. Offenbar haben die heutigen Temperaturschranken daher seit langer Zeit bestanden. Bis vor etwa 10 Jahren war die Klassifizierung der Arenicolidae nahezu ausschließlich auf Museumsmaterial begründet. Oft waren die Proben nur klein und nicht selten schlecht fixiert. Die Systematiker konnten daher nur sehr augenfällige Merkmale verwenden und kamen so oftmals zu Gruppen, von denen wir heute auf Grund von kombinierten Untersuchungen im Habitat und im Laboratorium wissen, daß sie zu weit gefaßt waren. In den letzten 10 Jahren ist die Zahl der Arten und Unterarten — hauptsächlich als Ergebnis einer verfeinerten Einteilung — von 10 auf 24 gestiegen. Die Bedeutung der Temperaturschranken und anderer isolierender Faktoren wird jetzt klarer erkannt. Möglicherweise werden ähnliche Studien an anderen Familien die Anzahl der Polychaetenarten, von denen bipolare oder kosmopolitische Verbreitung angenommen wird, erheblich reduzieren.

     

Effects of green algal mats on bivalves in a New England mud flat

Concurrent with the spread of green algal mats on tidal flats, reports of macrofauna dieoffs under dense algal mats have increased in numbers. Bivalves seem to be particularly affected by persistent dense algal mats. Bivalve species with a long extendible siphon seem to be less affected underneath algal mats, but no distinction has been made in the past between species with short and those with long siphons,Mya arenaria andMacoma balthica, on an intertidal mudflat in New England. Abundances ofM. arenaria declined substantially during the study period when a thick green algal mat covered the mudflat for several months. Numbers of the small bivalveGemma gemma also decreased substantially, whereas abundances ofM. balthica showed minimal variation during the time of algal coverage. In algae removal/addition experiments numbers ofM. arenaria decreased, but effects were only significant in an algal addition to previously algal-free mudflat areas. Abundance ofM. balthica did not change significantly in the algal removal/additition experiments. Over the time period of the experiment (9 weeks),M. arenaria showed measurable size increase in uncovered mudflat areas, but not underneath algal mats. Similarly,M. balthica only increased in size in the uncovered mudflat area. From these results it is concluded thatM. balthica can survive time periods of dense algal coverage because it is able to penetrate through the algal mat with its long extendible siphon, and thus can reach well-oxygenated water layers above the mat.M. arenaria with its thick, less extendible, siphon cannot push through dense algal mats and therefore is more likely to die underneath persistent algal mats.     

A short-term study of the effects of algal mats on the distribution and behavioural ecology of estuarine birds

The effects of algal mats on wintering wading bird distribution and behaviour were studied at two sites during 1998/99 to identify changes that occurred during the winter breakdown of the algal mat. Numbers of Black-tailed Godwit Limosa limosa did not increase as the algal mat reduced in extent but a significantly greater number of birds were observed in areas without algal cover than in areas with mats in most months. The use of clear spaces, created between the algal patches as the mat broke down, by Black-tailed Godwit increased across the winter. We suggest that algal mats may physically interfere with the deep probing action of this wader. In contrast, when algal mats were most dense in November 1998, significantly greater numbers of Redshank Tringa totanus were observed in algal areas at one site. Redshank appeared not to be deterred by algal cover and, at times, preferentially utilized the algal infauna as prey.     

Cultivable bacteria from ancient algal mats from the McMurdo Dry Valleys, Antarctica

The McMurdo Dry Valleys in Antarctica are a favorable location for preservation of dormant microbes due to their persistent cold and dry climate. In this study, we examined cultivable bacteria in a series of algal mat samples ranging from 8 to 26539 years old. Cultivable bacteria were found in all samples except one (12303 years old), but abundance and diversity of cultivable bacteria decreased with increasing sample age. Only members of the Actinobacteria, Bacteroidetes, and Firmicutes were found in the ancient samples, whereas bacteria in the 8-year-old sample also included Cyanobacteria, Proteobacteria, and Deinococcus-Thermus. Isolates of the Gram-positive spore-forming bacterium Sporosarcina were found in 5 of 8 samples. The growth of these isolates at different temperatures was related to the phylogenetic distance among genotypes measured by BOX-PCR. These findings suggest that adaptation to growth at different temperatures had occurred among Sporosarcina genotypes in the Dry Valleys, causing the existence of physiologically distinct but closely related genotypes. Additionally, fully psychrophilic isolates (that grew at 15°C, but not 25°C) were found in ancient samples, but not in the modern sample. The preservation of viable bacteria in the Dry Valleys could potentially represent a legacy of bacteria that impacts on current microbial communities of this environment.     

An investigation of the relationship between sediment particles size and the development of green algal mats (Ulva prolifera) on the intertidal flats of Muan, Korea

The relationship between median grain size of sediments and the abundance in the wild of green algal mats (Ulva prolifera) on the intertidal flats of Muan, Korea, were investigated. The impact of substratum particle size on the growth and survival of germlings was examined in the laboratory. In the wild, the average annual density of algal mats was 7,950 ind m⁻². The algal mats mainly occurred in sands and exhibited patchy distribution. Statistical analysis indicates significant spatial analysis differences and a significant relationship between density and the ratio of sands to silts, suggesting that the distribution and density of this species were related to particle size. In laboratory experiments, the survival rate of U. prolifera germlings was the lowest value (22%) on sediments with a median grain size of 63–125 μm. Laboratory experiments have generally shown a positive relationship between attachment or survival of the alga and substratum particles size. Our laboratory results indicate a clear link between germling settlement/survival and substratum particle size. These results explain the spatial differences in abundance observed in the field in relation to the distribution and ratio of sands to silt on the Muan flats.     

The effects of brefeldin A upon the Golgi apparatus of the green algal flagellate, Gloeomonas kupfferi

The fungal-derived derivative, brefeldin A, was used to disruptthe Golgi apparatus (GA) of the green alga, Gloeomonas kupfferi.Upon short treatments (10 µg ml^–1 for 10 min orless), the Golgi bodies maintain their perinuclear positioning.However, the medial locus transforms from a tight stack of elongatecisternae to a network of swollen tubules. Upon longer treatments(60 min), swelling and vesiculation of cis face cisternae becomeapparent. Likewise, the edges of several trans face cisternaemay fuse with those of adjacent Golgi bodies leading to theformation of multiGolgi complexes. Key words: Brefeldin A, Golgi apparatus, Gloeomonas kupfferi     

Grain trapping by filamentous cyanobacterial and algal mats: implications for stromatolite microfabrics through time

Archean and Proterozoic stromatolites are sparry or fine‐grained and finely laminated; coarse‐grained stromatolites, such as many found in modern marine systems, do not appear until quite late in the fossil record. The cause of this textural change and its relevance to understanding the evolutionary history of stromatolites is unclear. Cyanobacteria are typically considered the dominant stromatolite builders through time, but studies demonstrating the trapping and binding abilities of cyanobacterial mats are limited. With this in mind, we conducted experiments to test the grain trapping and binding capabilities of filamentous cyanobacterial mats and trapping in larger filamentous algal mats in order to better understand grain size trends in stromatolites. Mats were cut into squares, inclined in saltwater tanks at angles from 0 to 75° (approximating the angle of lamina in typical stromatolites), and grains of various sizes (fine sand, coarse sand, and fine pebbles) were delivered to their surface. Trapping of grains by the cyanobacterial mats depended strongly on (i) how far filaments protruded from the sediment surface, (ii) grain size, and (iii) the mat's incline angle. The cyanobacterial mats were much more effective at trapping fine grains beyond the abiotic slide angle than larger grains. In addition, the cyanobacterial mats actively bound grains of all sizes over time. In contrast, the much larger algal mats trapped medium and coarse grains at all angles. Our experiments suggest that (i) the presence of detrital grains beyond the abiotic slide angle can be considered a biosignature in ancient stromatolites where biogenicity is in question, and, (ii) where coarse grains are present within stromatolite laminae at angles beyond the abiotic angle of slide (e.g., most modern marine stromatolites), typical cyanobacterial‐type mats are probably not solely responsible for the construction, giving insight into the evolution of stromatolite microfabrics through time.     

Growth of enterobacteria on algal mats in the eastern part of the Gulf of Finland

Model experiments on a possibility that pathogenic enterobacteria Salmonella enteritidis (Gartneri) can grow on decaying algal mats with prevalence of the filamentous algae Cladophora glomerata (L.) Kütz were carried out. Samples of algal mats have been collected in the eastern part of the Gulf of Finland in the Baltic Sea. A bacterial culture of Salmonella enteritidis was placed into tubes containing samples of mats. The intensive growth of salmonella was noted in alga samples collected in the freshwater zone (salinity 0.2–1.5‰); growth was practically absent in the samples of algae collected in a zone with salinity 2–3‰, while salmonella remained viable in the control tubes with water without algae. The growth of coliform enterobacteria initially inhabited in the algal mats was discovered in all experiments. Studies carried out in 2009 show that the thickness of the algal mats in the costal zones of the Gulf of Finland reached 20 cm and their biomass reached a few tons per 1 km². These experiments showed that dead algal mats stimulate the growth of enterobacteria in the littoral zone of the Baltic Sea, especially in the freshwater part, and can promote the development of these pathogenic microorganisms.     

四川黄龙钙华沉积区附生藻垫生物与水环境因子相关性分析

【背景】近年来,四川省黄龙风景区钙华沉积地貌上藻垫大面积滋生,厚度达3-5cm,严重影响了钙华的持续沉积及欣赏价值。【目的】为有效控制藻类过度生长,并提出相关治理方法措施,需要对藻垫的结构特征及滋生原因进行深入分析。【方法】利用PE-250高通量测序平台对黄龙钙华沉积区典型附生藻垫剖面的不同层次进行真核物种组成分析,同时通过场发射扫描电子显微镜对其微观形貌进行表征,并且对藻垫的生长厚度与水环境参数进行了相关性分析。【结果】藻垫内的真核生物有400种左右,优势藻类主要为硅藻门(Diatomea)、轮虫动物门(Rotifera)和链型植物门(Streptophyta),硅藻门主要为桥弯藻属(Cymbella)。非度量多维尺度分析(non-metric multidimensional scaling,NMDS)统计和聚类分析表明,藻垫的中层和底层真核物种组成具有较高的相似性。场发射扫描电子显微镜的结果显示,硅藻主要分布在藻垫上层,中层主要为丝状藻类,底层为钙华颗粒填充在丝状藻构成的网状结构中。水质参数与藻垫生长的相关性分析表明,藻垫厚度主要与水体中的总氮(total nitrogen, T...     

Commensals of Mytilus galloprovincialis in the Black Sea: Urastoma cyprinae (Turbellaria) and Polydora ciliata (Polychaeta)

The intensity of infection of the mussel Mytilus galloprovincialis Lamarck in the Black Sea by the turbellarian Urastoma cyprinae (Graff), which lives on its gills, was found to be higher in larger hosts, reaching a maximum in mussels of 50–70 mm length. Greater numbers occured in mussels inhabiting a silty bottom than in cultivated mussels suspended above the bottom. Over the period 1982–1987, U. cyprinae was most numerous in winter and especially so in years that were colder. The spionid polychaete Polydora ciliata (Johnston) also infects M. galloprovincialis, burrowing into the shell. Young spionids of up to 1 mm length occured in mussels with a shell length of 35 mm. Numbers of this commensal reached a maximum in mussels of intermediate size.     

藻毒素的类型、危害和防治

介绍了赤潮藻毒素：麻痹性贝毒、短裸甲藻毒素、溶血性毒素、细胞性毒素和氨毒：水华藻毒素：肝毒素、神经毒素、脂多糖内毒素的化学结构、性质和毒害机理等,以及藻毒素的防治方法。     

Uncoupling of omnivore-mediated positive and negative effects on periphyton mats

The riverine grass shrimp (Palaemonetes paludosus) and eastern mosquitofish (Gambusia holbrooki) consume periphyton and small invertebrates, potentially affecting periphyton through negative effects (i.e., consumption) and/or positive effects such as nutrient regeneration, physical stimulation, and trophic cascades. We performed field experiments in the Everglades in which omnivores and periphyton were maintained in cages, with a fraction of the periphyton held in omnivore-exclusion bags that allowed passage of nutrients but prevented its consumption or physical disturbance. In some instances, periphyton growth rate increased with increasing omnivore biomass. Omnivores probably stimulated periphyton growth through nutrient regeneration, possibly subsidizing periphyton with nutrients derived from ingested animal prey. The net balance of omnivore-mediated negative and positive effects varied among experiments because of seasonal and spatial differences in periphyton characteristics. Consumption of periphyton mats might have been reduced by the arrangement of palatable algae (green algae and diatoms) within a matrix of unpalatable ones (CaCO(3)-encrusting filamentous cyanobacteria). In a laboratory feeding experiment, mosquitofish consumed more green algae and diatoms in treatments with disrupted mat structure than in those with intact mats. No difference in diet was observed for shrimp. Our study underscores the complexity of consumer-periphyton interactions in which periphyton edibility affects herbivory and consumers influence periphyton through multiple routes that cannot be fully appreciated in experiments that only investigate net effects.     

Green land: Multiple perspectives on green algal evolution and the earliest land plants

Green plants, broadly defined as green algae and the land plants (together, Viridiplantae), constitute the primary eukaryotic lineage that successfully colonized Earth's emergent landscape. Members of various clades of green plants have independently made the transition from fully aquatic to subaerial habitats many times throughout Earth's history. The transition, from unicells or simple filaments to complex multicellular plant bodies with functionally differentiated tissues and organs, was accompanied by innovations built upon a genetic and phenotypic toolkit that have served aquatic green phototrophs successfully for at least a billion years. These innovations opened an enormous array of new, drier places to live on the planet and resulted in a huge diversity of land plants that have dominated terrestrial ecosystems over the past 500 million years. This review examines the greening of the land from several perspectives, from paleontology to phylogenomics, to water stress responses and the genetic toolkit shared by green algae and plants, to the genomic evolution of the sporophyte generation. We summarize advances on disparate fronts in elucidating this important event in the evolution of the biosphere and the lacunae in our understanding of it. We present the process not as a step-by-step advancement from primitive green cells to an inevitable success of embryophytes, but rather as a process of adaptations and exaptations that allowed multiple clades of green plants, with various combinations of morphological and physiological terrestrialized traits, to become diverse and successful inhabitants of the land habitats of Earth.     

The effects of nutrient,pH and herbicide levels on algal growth

Growth inhibition of algae increased as herbicide concentrations increased, particularly with prometryn and fluometuron. However, picloram had no effect on algal growth while dinoseb inhibited only Lyngbya. There were no differences in growth rate of algae treated with different levels of potassium or phosphorus. High levels of calcium or magnesium increased growth rate of the algae tested. High levels of nitrogen or pH increased growth rates except when combined with prometryn or fluometuron.     

Carotenoid composition and metabolism in green and blue-green algal lichens in the field

The carotenoid composition of 33 species of green algal lichens and 5 species of blue-green algal lichens was examined and compared with that of the leaves of higher plants. As in higher plants, green algal lichen species which were found in both shade and full sunlight exhibited higher levels of the carotenoids involved in photoprotective thermal energy dissipation (zeaxanthin as well as the total xanthophyll cycle pool) in the sun than in the shade. This was particularly true when thalli were moist during exposure to high light, or presumably became desiccated in full sunlight. However, the reverse trend in the carotenoid composition of green algal lichens was also observed in those species which were found predominantly either in the shade or in full sunlight. In this case sun-exposed lichens often possessed lower levels of zeaxanthin and of the components of the xanthophyll cycle than lichens which were found in the shade. In contrast to higher plants, the lichens from all habitats exhibited a relatively high ratio of carotenoids to chlorophylls (more characteristic of sun leaves), very low levels of α-carotene (similar to that found in sun leaves), and a level of β-carotene similar to that found in shade leaves. Zeaxanthin, but not the expoxides of the xanthophyll cycle, was also frequently found in blue-green algal lichens. A trend for increasing levels of zeaxanthin with increasing growth light regime was observed inPeltigera rufescens, the species which was found to occur over the widest range of light environments. The level of zeaxanthin per chlorophylla in these blue-green algal lichens was in a range similar to that per chlorophylla+b in green algal lichens. However, zeaxanthin was also absent in one species,Collema cristatum, in full sunlight. Thus, the zeaxanthin content of the blue-green algal lichens can be similar to that of higher plants, or it can be rather dissimilar, as was also the case in the green algal lichen species. The presence of large amounts of ketocarotenoids in blue-green algal lichens is also noteworthy.     

Metabolism of green tea catechins by the human small intestine

Numerous studies have shown that green tea polyphenols can be degraded in the colon, and there is abundant knowledge about the metabolites of these substances that appear in urine and plasma after green tea ingestion. However, there is very little information on the extent and nature of intestinal degradation of green tea catechins in humans. Therefore, the aim of this study was to examine in detail the microbial metabolism and chemical stability of these polyphenols in the small intestine using a well-established ex vivo model. For this purpose, fresh ileostomy fluids from two probands were incubated for 24 h under anaerobic conditions with (+)-catechin (C), (-)-epicatechin (EC), (-)-epicatechin 3-O-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatchin 3-O-gallate (EGCG) and gallic acid (GA). After lyophilisation and extraction, metabolites were separated, identified and quantified by high performance liquid chromatography-photodiode array detection (HPLC-DAD) and HPLC-ESI-tandem mass spectrometry. Two metabolites of EC and C (3', 4', 5'-trihydroxyphenyl-γ-valerolactone and 3', 4'-dihydroxyphenyl-γ-valerolactone) were identified. In addition, 3', 4', 5'-trihydroxyphenyl-γ-valerolactone was detected as a metabolite of EGC, and (after 24-h incubation) pyrogallol as a degradation product of GA. Cleavage of the GA esters of EGCG and ECG was also observed, with variations dependent on the sources (probands) of the ileal fluids, which differed substantially microbiotically. The results provide new information about the degradation of green tea catechins in the gastrointestinal tract, notably that microbiota-dependent liberation of GA esters may occur before these compounds reach the colon.     

Turbellaria in the lagoon of Ghar-el-Melh. Research on the regenerative ability of Monocelis fusca Oersted (Turbellaria, Monocelididae)

The Turbellarian Monocelis fusca Oersted is abundant in the lagoon of Ghar-el-Melh. Traumatic regeneration in this animal is realised for the first time. Transversal sections through two levels of the body are made, and pointed out the presence or the absence of regeneration ability with the considered fragment.     

Influence of the surface microlayer on nutrients,chlorophyll and algal diversity of a small eutrophic bog pond

Nutrients, chlorophyll, phaeophytin and algal abundances were investigated in the surface microlayer and at subsurface depths in a small eutrophic bog pond. Nutrient levels were consistently higher in the microlayer while algal abundance was sometimes higher but sometimes lower in the microlayer than at near subsurface depths. Algal diversity values were strongly influenced by the depth of flagellate blooms, and in contrast to previous studies, diversity in the microlayer was higher than at near subsurface depths. These results are discussed in terms of weather parameters, affinity of algal species for the surface and differences between microlayer ecology in shallow and deep water systems.