Influence of quantity and lability of sediment organic matter on the biomass of two isoetids,Littorella uniflora and Echinodorus repens

1. Despite real improvement in the water quality of many previously eutrophic lakes, the recovery of submerged vegetation has been poor. This lack of recovery is possibly caused by the accumulation of organic matter on the top layer of the sediment, which is produced under eutrophic conditions. Hence, our objective was to study the combined effects of quantity and lability of sediment organic matter on the biomass of Echinodorus repens and Littorella uniflora and on the force required to uproot plants of L. uniflora. 2. Lake sediments, rich in organic matter, were collected from four lakes, two with healthy populations of isoetids and two from which isoetids had disappeared. The four lake sediments were mixed with sand to prepare a range of experimental sediments that differed in quantity and lability of sediment organic matter. Two isoetid species, E. repens and L. uniflora, were grown in these sediments for 8 weeks. Sediment quality parameters, including elemental composition, nutrient availability and mineralisation rates, were determined on the raw sources of sediment from the lakes. Porewater and surface water were analysed for the chemical composition in all mixtures. At the end of the experiment, plants were harvested and their biomass, tissue nutrient concentration and (for L. uniflora) uprooting force were measured. 3. For both species, all plants survived and showed no signs of stress on all types of sediment. The biomass of E. repens increased as the fraction of organic matter was increased (from 6 to 39% of organic content, depending upon sediment type). However, in some of the sediment types, a higher fraction of organic matter led to a decline in biomass. The biomass of L. uniflora was less responsive to organic content and was decreased significantly only when the least labile sediment source was used to create the gradient of organic matter. The increase in shoot biomass for both species was closely related to higher CO₂ concentrations in the porewater of the sediment. The force required to uproot L. uniflora plants over a range of sediment organic matter fitted a Gaussian model; it reached a maximum at around 15% organic matter and declined significantly above that. 4. Increasing organic matter content of the sediment increased the biomass of isoetid plants, as the positive effects of higher CO₂ production outweighed the negative effects of low oxygen concentration in more (labile) organic sediments. However, sediment organic matter can adversely affect isoetid survival by promoting the uprooting of plants.     

Back from the dead: Thyreophora cynophila (Panzer, 1798) (Diptera: Piophilidae) ‘globally extinct’ fugitive in Spain

We report on a sensational find in central Spain of six specimens of Thyreophora cynophila ( Panzer, 1798 ), a colourful, strange‐looking piophilid fly living on carcasses of big mammals in advanced stages of decay. Published data suggest that the species is known exclusively from central western Europe (Germany, Austria and France), and was observed last near Paris, France, in the late 1840s, i.e. more than 160 years ago. Accordingly, T. cynophila was placed in 2007 as the only dipteran on a list of recent European animals considered to be globally extinct. Collection‐based data from all 16 known extant specimens found in seven European natural history museums revealed a specimen without date of T. cynophila from Algiers, Algeria. The status of the three thyreophorine piophilids known from Europe is summarized. For the smallest species we reinstate the name Centrophlebomyia anthropophaga ( Robineau‐Desvoidy, 1830 ) with Centrophlebomyia orientalis Hendel, 1907 as a subjective junior synonym ( syn.n. ). We speculate as to why thyreophorines, and T. cynophila in particular, have evaded detection for so long.     

Dietary Overlap Between Huemul and Livestock in Los Alerces National Park,Argentina

ABSTRACT We evaluated the potential for interspecific competition for forage between huemul (Hippocamelus bisulcus) and livestock in Los Alerces National Park, Argentina. We studied winter diets based on microhistological analysis of fecal samples. Huemul selected herbs and shrubs, sheep showed preference for herbs and grasses, and cattle selected grasses. As predicted for small-bodied species, huemul had a narrower dietary niche than did larger bodied cattle. Competition for forage would be more likely between huemul and sheep than between huemul and cattle. Our results might be helpful to managers in areas where domestic and wild ungulates live in sympatry in order to reduce competition, especially in wintering areas where food is scarce.     

A Sarcocystid Misidentified as Hepatozoon didelphydis: Molecular Data from a Parasitic Infection in the Blood of the Southern Mouse Opossum (Thylamys elegans) from Chile

ABSTRACT. The blood of 21 adult South American mouse opossums (Thylamys elegans) captured from April through August of 2005 in central Chile was examined for parasites. Light microscopic analysis of blood smears initially suggested that a highly pleomorphic Hepatozoon species typical of American opossums was infecting erythrocytes. Unexpectedly, amplification by PCR and sequencing of a DNA fragment of the small subunit rDNA combined with phylogenetic analyses indicated that the parasite is not a member of the suborder Adeleorina, which includes the Haemogregarina and Hepatozoon species, but that it is a clearly distinct member of the suborder Eimeriorina, which includes the cyst‐forming family Sarcocystidae. Therefore, a reclassification of this unusual intraerythrocytic apicomplexan will require additional life cycle, microscopic, and molecular analyses.     

Thallium Behavior in Soils Polluted by Pyrite Tailings (Aznalcóllar,Spain)

Thallium content and chemical speciation was studied at 91 sites contaminated by water and tailings spilled from the settling pond of a pyrite mine into the Agrio and Guadiamar rivers in Aznalcóllar (Spain). The contamination was highly heterogeneous, with 15% of the affected area seriously contaminated, 55% moderately contaminated and 30% uncontaminated. The total Tl content in the surface horizon increased with respect to the background level, more than 4-fold in the uppermost 10 cm of the soils, and clearly decreased with depth without contaminating either the subsoil or groundwater. Most of the Tl (approximately 75%) was in non-extractable forms, either as a component of the particles in the tailings or adsorbed to crystalline oxides. The remaining Tl was held on, or occluded in, amorphous or poorly crystallized oxides. In acidic soils, the adsorption of Tl was dominated by iron oxides (Feo) and, in neutral-alkaline soils, by aluminium oxides (Alo). A relatively high amount of the Tl adsorbed by amorphous oxides in the uppermost 10 cm of the soils was extracted with acetic acid, and was presumably bio-available (mean values approximately 15% of the Tlo). The EDTA is a strong extractant of inorganic forms of aluminium and, consequently, the quantity of Tl extracted by EDTA in neutral-alkaline soil (mean values more than 10% of the total Tl) could be higher than the truly bio-available fraction. Approximately 1% of the total Tl was extracted with calcium chloride, but only in the neutral-alkaline soil was the extraction significantly related to the cation-exchange capacity and, thus, adsorbed by the negative charges of the clay and organic matter. The Tl soluble in water (< 0.1%) declined with the pH in the neutral-alkaline soils, and was unrelated to any soil property in the acid soils. Thus, the behavior of Tl is determined by climatic conditions, soils properties and time.     

Quantity versus quality: Endemism and protected areas in the temperate forest of South America

Abstract Identification of biodiversity hotspots is essential to conservation strategies aimed at minimizing the possibility of losing half of the world's species in the next 50 years. The aims of the present study were: (i) to locate and designate zones of endemism in the temperate forest of South America; and (ii) to compare the distribution of these areas with the distribution of existing protected areas in this habitat type. Endemism areas were determined by using parsimonious analysis of endemism, which identified zones of endemism on the basis of sets of endemic species that were restricted to two or more study areas. We used distribution information for five unrelated taxa (ferns, trees, reptiles, birds and mammals) to provide more reliable results and patterns than would work with only a single taxon or related taxa. The northern part of this region has high endemism for all of the taxa considered in this study. We demonstrate that although the temperate forest of South America has more than 30% of its area under some type of protection, correlation between protected areas and the areas of endemism is remarkably low. In fact, less than 10% of protected areas are situated in areas that have the greatest value for conservation (i.e. high endemism). Under the current strategy, biodiversity within South America's temperate forest is in danger despite the large amount of protected area for this forest type.     

Chemical Composition of Viscin Mucilage from Three Mistletoe Species--A comparison

The viscin of mistletoes is a unique tissue which serves toprovide strong adherence of the seed of the parasite to thehost branch. The viscin mucilage of three species, Phoradendroncalifornicum and Arceuthobium americanum (Viscaceae) and Phthirusapyrifolia (Loranthaceae), was analysed. The major componentof the mucilage of Pho. californicum and A. americanum was polysaccharidic;of this, neutral sugars comprised the largest portion, but substantialamounts of uronic acids and proteins were also present. Xyloseand arabinose were the most abundant of the neutral sugars,and analysis showed glycine to be the most abundant amino acidas well as the presence of higher-than-average amounts of histidine.In contrast, in the mucilage of Pht. pyrifolia glucose was themost abundant neutral sugar and the protein content was substantiallyhigher. Based on the differences in composition observed amongthe different species the future use of viscin components astaxonomic markers is suggested. Viscin mucilage, mistletoes, Arceuthobium americanum, Phthirusa pyrifolia, Phoradendron californicum, g.l.c., amino acid analysis     

Influence of bacterial density and water temperature on the grazing activity of two freshwater ciliates

1. The influences of bacterial density and water temperature on the grazing activity of the ciliates Uronema sp. and Colpoda inflata were studied. The conditions assayed were two prey densities (10⁶ and 4 × 10⁷ bacteria ml^?1) and three water temperatures (10, 15 and 22 °C). 2. The response of the ciliates was measured from changes in protistan biovolumes and specific clearance rates. At high prey density, both ciliates showed lower biovolumes as water temperature increased, while at low prey density this tendency was minimized. 3. At the intermediate temperature of 15 °C both ciliates filtered ten times more body volume when bacteria were scarce; however, the ingested bacteria were fewer than at high prey density. At low prey density, a decrease from 15 to 10 °C evidenced different strategies of the two ciliates, which led to a similar ingestion of bacteria: C. inflata reduced its specific clearance rates and increased its biovolume, while Uronema sp. did not show changes. At high prey density, an increase from 15 to 22 °C caused lower biovolumes and a noticeable increase in specific clearance rates in both ciliates, indicating opportunist behaviour.     

Catechol Oxidase in Suspension Cultures of Apple Fruit--The Effects of Growth Regulators

Growth and catechol oxidase activity were followed in suspensioncultures of cells derived from apple fruit. In cultures whichrequired the addition of hormones, enzyme activity was affectedby 2, 4-D (2, 4-dichlorophenoxyacetic acid) and kinetin viatheir effect on growth. Exogenous hormones did not affect catecholoxidase activity of habituated cultures. Ethylene and PCIB (-4-chlorophenoxyisobutyricacid) rapidly depressed enzyme activity in all cell fractions,but only at concentrations which repressed growth. Ethioninecaused an immediate decrease in enzyme activity which precededthe repression of growth. Ethionine did not inhibit enzyme activityin vitro. Possible mechanisms of the action of ethionine arediscussed and the formation of a specific inhibitor is hypothesized.