Chilean high-altitude hot-spring sinters: a model system for UV screening mechanisms by early Precambrian cyanobacteria

Before the build‐up of stratospheric ozone, Archean and early Proterozoic phototrophs existed in an environment subjected to highly elevated levels of ultraviolet (UV) radiation. Therefore, phototrophic life would have required a protective habitat that balanced UV attenuation and photosynthetically active radiation (PAR) transmission. Here we report on aspects of the phototroph geomicrobiology of El Tatio geothermal field, located at 4300 m in the Andes Mountains of northern Chile (22 °S), as an analogue system to early Precambrian environments. El Tatio microbes survive in a geochemical environment of rapidly precipitating amorphous silica (sinter) and unusually high solar radiation (including elevated UV‐B flux) due to the high‐altitude, low‐latitude location. Cyanobacteria produce 10‐mm‐thick surface mats containing filaments encased in amorphous silica matrices up to 5 µm thick. Relative radiation absorbance of these silica matrices was UV‐C > UV‐B > UV‐A > PAR, suggesting the silica provides a significant UV shield to the cyanobacteria. Cyanobacteria also occur in cryptoendolithic communities 1–10 mm below siliceous sinter surfaces, and in siliceous stromatolites, where viable cyanobacteria are found at least ～10 mm below the sinter surface. UV‐B was dramatically attenuated within ～1 mm of the sinter surface, whereas UV‐C (a frequency range absent today but present in the early Precambrian) was attenuated even more efficiently. PAR was attenuated the least, and minimum PAR levels required for photosynthesis penetrated 5–10 mm into the sinter. Thus, a favourable niche occurs between approximately 1–10 mm in siliceous sinters where there is a balance between PAR transmission and UV attenuation. These deposits also would have strongly attenuated Archean and early Precambrian levels of UV and thus, by analogy, cyanobacteria of early Precambrian shallow aquatic environments, inhabiting silicified biofilms and silica stromatolites, would have similarly been afforded protection against high‐intensity UV radiation.     

Incidence of endophytes in seeds from collections of Lolium and Festuca species

Seeds from 53 of 64 collections of Lolium perenne from its centre of origin or from old pastures in Europe were found to be infected with endophyte whereas only four of 16 commercial cultivars had infected seed. Almost two thirds of seed samples of L. multiflorum, Festuca arundinacea and F. pratensis collected from plants growing in the wild in Italy contained endophyte but none of the eight commercial cultivars of L. multiflorum and only two of five cultivars of Festuca spp. produced by the Welsh Plant Breeding Station were infected. At least one seed sample from each of six species and varieties of annual ryegrasses contained endophyte mycelium. Endophytes in annual ryegrasses could not be cultured axenically and are probably a different species to the Acremonium lolii present in L. perenne. A correction to the spelling of the specific epithet of A. lolii is explained.     

The germination of grass seeds after storage at different temperatures in aluminium foil and manilla paper packets

The germination of seeds of three species of forage grasses, Lolium perenne, Festuca pratensis and Dactylis glomerata, was studied after storage for 3–5 years under five different storage conditions: in aluminium foil packets at —25°C, 0°C and laboratory temperature (c. 18°C), and in manilla paper packets at 0°C and laboratory temperature. With Lolium perenne and Festuca pratensis high germination values at 3 and 7 days were obtained from seed stored at — 25 °C and 0°C in foil packets (5% moisture), but at laboratory temperatures, seed from foil packets gave lower germination values than those from manilla paper packets. At all three temperatures Dactylis glomerata germination after 7 and 14 days was higher in seed stored in foil than in manilla packages. With all three species stored in manilla packets, germination was higher after laboratory than cold storage.     

Frontal glands and frontal sensory structures in the Macrostomida (Turbellaria)

The ultrastructure of the frontal gland complex of six species of Macrostomida is investigated. In all species it comprises an array of discretely emerging gland necks of at least two gland types, including one with rhammite secretion granules and one with rhahdite granules. Moreover, mucous glands and glands containing other secretion granules are found in Microstomum sp. No intermeditate form which would allow bridging of the present lack of ultrastructural, histochemical and positional similarities between the Macrostomida and the Acoela is found in the examined species. Therefore, the probability of homology between the frontal organs of the Acoela and the frontal glands of the Macrostomida remains low. Even though two or three tyes of sensory receptors are found distributed over the anterior end of all examined species, the frontal gland complex does not appear to be sensory. Because of the uniformity in frontal gland ultrastructure. relationships within the Macrostomida based on this character alone cannot be detected.     

A neglected lineage of North American turtles fills a major gap in the fossil record

Abstract: The fossil record of the two primary subclades of softshell turtles (Trionychidae) is exceedingly asymmetric, as a result of a ghost range of total clade Cyclanorbinae that is estimated at 80 Ma. Herein, we present the first phylogenetic analysis of Trionychidae that includes a representative of the poorly studied taxon Plastomenidae, which is known from the Campanian to Eocene of North America. The analysis reveals that plastomenids are stem cyclanorbines, thus significantly reducing the apparent ghost range of total group Cyclanorbinae to approximately 30 Ma. Plastomenids are either an early branching clade of stem Cyclanorbinae, or they represent a paraphyletic grade that gave rise to modern cyclanorbines. Although abundant, the fossil record is still too poorly understood to distinguish between these two primary hypotheses. The previously persistent extremely long ghost range of total clade Cyclanorbinae appears to have been the result of a research bias.     

Individuality in Corncrake Crex crex vocalizations

Vocal individuality has potential for the monitoring of bird species that are otherwise difficult to observe. In this study we assessed the potential of this technique for the monitoring of the globally threatened Corncrake Crex crex based on the analysis of calls recorded in Ireland and Scotland in 1993 and 1994. Discriminant function analysis correctly attributed >80% of individual calls based on five temporal parameters. A high level of individual distinctiveness was also found in the fine temporal structure of calls. When information on fine structure was added to the discriminant function analysis, classification of calls to individuals was improved to 100%. The structure of an individual's call was found to be consistent over the 2-year period. This study highlighted the problemsassociated with setting criteria for re-identifying individuals by calls. The consequences of these problems and the potential of vocal individuality for providing monitoring information in this species are discussed.     

Nutrient loading and grazing by the minnow Phoxinus erythrogaster shift periphyton abundance and stoichiometry in mesocosms

1. Anthropogenic activities in prairie streams are increasing nutrient inputs and altering stream communities. Understanding the role of large consumers such as fish in regulating periphyton structure and nutritional content is necessary to predict how changing diversity will interact with nutrient enrichment to regulate stream nutrient processing and retention. 2. We characterised the importance of grazing fish on stream nutrient storage and cycling following a simulated flood under different nutrient regimes by crossing six nutrient concentrations with six densities of a grazing minnow (southern redbelly dace, Phoxinus erythrogaster) in large outdoor mesocosms. We measured the biomass and stoichiometry of overstory and understory periphyton layers, the stoichiometry of fish tissue and excretion, and compared fish diet composition with available algal assemblages in pools and riffles to evaluate whether fish were selectively foraging within or among habitats. 3. Model selection indicated nutrient loading and fish density were important to algal composition and periphyton carbon (C): nitrogen (N). Nutrient loading increased algal biomass, favoured diatom growth over green algae and decreased periphyton C : N. Increasing grazer density did not affect biomass and reduced the C : N of overstory, but not understory periphyton. Algal composition of dace diet was correlated with available algae, but there were proportionately more diatoms present in dace guts. We found no correlation between fish egestion/excretion nutrient ratios and nutrient loading or fish density despite varying N content of periphyton. 4. Large grazers and nutrient availability can have a spatially distinct influence at a microhabitat scale on the nutrient status of primary producers in streams.