Evolution, mitochondrial DNA phylogeny and systematic position of the Macaronesian endemic Hydrotarsus Falkenström (Coleoptera: Dytiscidae)

Abstract.  Hydrotarsus Falkenström (Coleoptera, Dytiscidae) is the only genus of aquatic beetle considered to be endemic to the Atlantic islands of Macaronesia. Its three known species ( H. lundbladi Falkenström from Madeira, and H. compunctus (Wollaston) and H. pilosus Guignot from the Canary Islands) are revised, and their phylogenetic position studied based on sequences of the 16S rRNA and Cytochrome Oxidase I genes of mitochondrial DNA. Our results clearly indicate that the species of Hydrotarsus fall deep within the genus Hydroporus Clairville, in a clade formed by (in addition to Hydrotarsus ) species currently included in the H. fuscipennis , marginatus , nigrita and tessellatus groups, and in consequence a new synonymy is proposed: Hydrotarsus Falkenström =  Hydroporus Clairville syn.n. The origin of the species of ' Hydrotarsus ', based on molecular clock estimations, is late Miocene, relatively recent in the history of the Atlantic islands. They are therefore not palaeoendemics but highly derived, recently evolved elements in the Macaronesian fauna. The estimated ages of divergence among species are much more recent than the emergence of any of the islands on which they are found, suggesting rare long-range dispersal as the mechanism driving the diversification of the lineage. Morphological modifications of the species of ' Hydrotarsus ' are discussed, as well as those of other dytiscids from hygropetric habitats.     

Ferric ion (hydr)oxo clusters in the “Venus flytrap” cleft of FbpA: M?ssbauer, calorimetric and mass spectrometric studies

Isothermal calorimetric studies of the binding of iron(III) citrate to ferric ion binding protein from Neisseria gonorrhoeae suggested the complexation of a tetranuclear iron(III) cluster as a single step binding event (apparent binding constant K(app) (ITC) = 6.0(5) × 10(5) M(-1)). High-resolution Fourier transform ion cyclotron resonance mass spectrometric data supported the binding of a tetranuclear oxo(hydroxo) iron(III) cluster of formula [Fe(4)O(2)(OH)(4)(H(2)O)(cit)](+) in the interdomain binding cleft of FbpA. The mutant H9Y-nFbpA showed a twofold increase in the apparent binding constant [K(app) (ITC) = 1.1(7) × 10(6) M(-1)] for the tetranuclear iron(III) cluster compared to the wild-type protein. M?ssbauer spectra of Escherichia coli cells overexpressing FbpA and cultured in the presence of added (57)Fe citrate were indicative of the presence of dinuclear and polynuclear clusters. FbpA therefore appears to have a strong affinity for iron clusters in iron-rich environments, a property which might endow the protein with new biological functions.     

Global and regional patterns in lotic meiofauna

• 1 Parsimony analysis of endemicity (PAE) was used to assess patterns in the distribution of harpacticoid copepods (all freshwater species and stream species only) at global and regional scales. These analyses provided a focus for reviewing large scale patterns and processes in freshwater meiofauna.
• 2 On a global scale, PAE suggested that large‐scale biogeographical events have been most important in shaping present‐day distributions in the Canthocamptidae. A small proportion (4%) of canthocamptid species were widespread (i.e. occurred in more than one biogegraphical region), suggesting that dispersal may also play a role in determining distribution at the species level. Global distribution patterns for other meiofauna suggest varying roles for dispersal and vicariant events. No consistent latitudinal trends in species diversity were evident, although a lack of distributional data for many regions, and uncertainty over the status of many cosmopolitan species, precludes more robust analyses. Molecular techniques should prove useful in identifying truly cosmopolitan taxa.
• 3 On a regional scale, a PAE within Western Europe demonstrated a clear link between the distribution of canthocamptid species and the extent of the Last (Wiechselian) glaciation. Northern and southern areas of Europe contain distinctive harpacticoid faunas and the recolonisation of northern Europe appears to have been from the Balkans rather than other Mediterranean peninsulae. The high harpacticoid diversity in southern Europe, may reflect a lack of glacial disruption of groundwater habitats.
• 4 A PAE of lotic data for harpacticoid copepods within the Holarctic reflected the global PAE for freshwater harpacticoids as a whole, but not the regional PAE. A high proportion of stream‐dwelling harpacticoids are widespread species, but only one (Bryocamptus zschokkei) was found in streams across the Holarctic. Other cosmopolites were restricted to streams in Europe or North America, suggesting that species‘ niche requirements might differ among regions. There appeared to be some convergence in the composition of lotic copepod communities in terms of the number of species within genera.
• 5 We conclude that large‐scale processes inevitably have a major influence on the local composition of lotic meiofaunal communities, but that the relative importance of small scale vs. large scale processes is unclear at present, largely due to a paucity of suitable data.

     

Respiratory control in aquatic insects dictates their vulnerability to global warming

Forecasting species responses to climatic warming requires knowledge of how temperature impacts may be exacerbated by other environmental stressors, hypoxia being a principal example in aquatic systems. Both stressors could interact directly as temperature affects both oxygen bioavailability and ectotherm oxygen demand. Insufficient oxygen has been shown to limit thermal tolerance in several aquatic ectotherms, although, the generality of this mechanism has been challenged for tracheated arthropods. Comparing species pairs spanning four different insect orders, we demonstrate that oxygen can indeed limit thermal tolerance in tracheates. Species that were poor at regulating oxygen uptake were consistently more vulnerable to the synergistic effects of warming and hypoxia, demonstrating the importance of respiratory control in setting thermal tolerance limits.     

Secondary Bile Acid Induced DNA Damage in HT29 Cells: are Free Radicals Involved?

Increased bile acid secretion, as a consequence of a high fat diet, results in the increased production of bile acids that may escape the enterohepatic circulation, and be subsequently metabolised by the colonic micro-flora to form the co-mutagenic and cwarcinogenic secondary bile acids. The potential of the secondary bile acids lithocholate (LOC) and deoxycholate (DOC), to induce DNA damage, in the colonocyte cell line HT29, at physiological concentrations both individually and in a 2:l ratio was assessed. Results indicated significant levels of DNA damage induced by both bile acids, with LOC having the greater DNA damaging capacity. The potential role of vitamin A, and the antioxidant vitamin E, in reducing this damage was determined, over a range of vitamin concentrations. Both vitamins reduced the bile acid induced DNA damage. Vitamin A displayed a dose response relationship, whereas vitamin E reduced DNA damage close to negative control values at all concentrations above 50 μM. These results indicate a protective role for Vitamins A and E, against the DNA damaging capacity of LOC and DOC.     

Spatio-temporal nested patterns in macroinvertebrate assemblages across a pond network with a wide hydroperiod range

Nestedness has been widely used to measure the structure of biological communities and occurs when species-poor sites contain subsets of species-rich ones. Here, we examine nested patterns across the macroinvertebrate assemblages of 91 ponds in Doñana National Park, Spain, and explore temporal variation of nestedness and species richness in 19 temporary ponds over 2 years with differing rainfall. Macroinvertebrate assemblages were significantly nested; both pond spatial arrangement and environmental variation being important in driving nested patterns. Despite the nested structure observed, a number of taxa and ponds deviate from this pattern (termed idiosyncratic), by occurring more frequently than expected in species-poor sites, or having assemblages dominated by species largely absent from species-rich sites. Aquatic adults of winged insects, capable of dispersal, were more highly nested than non-dispersing taxa and life-history stages. Idiosyncratic taxa were found in ponds spanning a wide range of hydroperiods, although nestedness was higher in more permanent waterbodies. Monthly sampling demonstrated a gradual increase of species richness and nestedness from pond filling to April–May, when the most temporary ponds started to dry. Although the degree of nestedness of individual pond assemblages varied from month to month, the overall degree of nestedness in the two study years was practically identical despite marked differences in hydroperiod. Our results suggest that differential colonization and environmental variation are key processes driving the nested structure of Doñana ponds, that macroinvertebrate assemblages change in a predictable manner each year in response to cycles of pond wetting and drying, and that connectivity and environmental variability maintain biodiversity in pond networks.     

Hydrolytic enzyme substrates. II. A new method for measuring periodate

This report describes an accurate and sensitive method for quantitatively measuring periodate concentration. The substances used to determine periodate are 4(p-nitrophenoxy)1,2-butanediol and 4(2,4-dinitrophenoxy)1,2-butanediol. These substances are readily oxidized by periodate yielding β-nitrophenoxy aldehydes which undergoes a facile β-elimination in base to yield the colored nitrophenolate ion. The concentration of the nitrophenolate ion is thus equivalent to the concentration of periodate. This report documents the validity of this reaction as an analytical method. The method was shown to be capable of accurately measuring periodate in concentrations as low as 10^?8M. Its value in biochemical analyses was demonstrated by quantitatively measuring the amount of periodate used to oxidize small quantities of adenosine 5′-phosphate, d-arabitol and d-glucose. Its accuracy, sensitivity and ease of use was shown by its utility in estimating the molecular weight of yeast transfer RNA using about 6 A₂₆₀ units of this material.