Fish recruitment in a large,temperate floodplain: the importance of annual flooding,temperature and habitat complexity

1. Large river floodplains are considered key nursery habitats for many species of riverine fish. The lower Volga River floodplains (Russian Federation) are still relatively undisturbed, serving as a suitable model for studying the influence of flooding and temperature on fish recruitment in floodplain rivers. 2. We examined the interannual variability in recruitment success of young‐of‐the‐year (YOY) fish in the lower Volga floodplain in relation to flood pulse characteristics and rising water temperatures in the spring. We sampled four areas with different flooding regimes, in three consecutive years (2006–2008). 3. Extensive areas with a long duration of flooding accommodated high densities of young fish. This suggests that extended inundation improves the recruitment success of river fish. In areas with extensive flooding, the biomass of YOY of most fish species was about three times higher in 2006 and 2007 than in 2008. We hypothesise that low spring temperatures in 2008 may have caused this reduced recruitment and that a flood synchronised with rising temperature enhances recruitment success. 4. Extensive flooding was particularly favourable for species characterised by large body size, delayed maturation, high fecundity and low parental investment, such as pike Esox lucius, roach Rutilus rutilus and ide Leuciscus idus. Gibel carp Carassius gibelio, a species tolerant of high temperature and hypoxia, did particularly well in small waterbodies in the driest parts of the floodplain. 5. Structural characteristics of floodplain waterbodies explained much of YOY fish density. These species–environment associations varied from year to year, but some species such as common bream Abramis brama, roach and gibel carp showed consistent relationships with structural habitat characteristics in all years, despite large interannual fluctuations in flood pulse and spring temperature.     

Incorporation of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) into hair of mice

The incorporation of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) into hair of newborn mice was investigated in order to contribute to the validation of PhIP in hair as a suitable biomarker for human dietary exposure. Black mice (C57BL/6J; 7-9 days old) were given graded doses of [³H]-PhIP subcutaneously during the start of the hair growth period. The distribution of [³H]-PhIP and incorporation into hair were investigated by tape-section autoradiography. Almost all the radioactivity in hair represented PhIP as shown by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). A dose-response proportionality of incorporation into hair was found when incorporation was determined by liquid scintillation counting. Autoradiography showed that PhIP was rapidly cleared from the skin, but remained for at least 28 days in the part of the hair shafts which was formed during the exposure period. The present results obtained using the mouse as a model, further support the suggestion that PhIP in hair may be a suitable biomarker for human exposure to dietary PhIP.     

Phytochrome‐mediated regulation of plant respiration and photorespiration

The expression of genes encoding various enzymes participating in photosynthetic and respiratory metabolism is regulated by light via the phytochrome system. While many photosynthetic, photorespiratory and some respiratory enzymes, such as the rotenone‐insensitive NADH and NADPH dehydrogenases and the alternative oxidase, are stimulated by light, succinate dehydrogenase, subunits of the pyruvate dehydrogenase complex, cytochrome oxidase and fumarase are inhibited via the phytochrome mechanism. The effect of light, therefore, imposes limitations on the tricarboxylic acid cycle and on the mitochondrial electron transport coupled to ATP synthesis, while the non‐coupled pathways become activated. Phytochrome‐mediated regulation of gene expression also creates characteristic distribution patterns of photosynthetic, photorespiratory and respiratory enzymes across the leaf generating different populations of mitochondria, either enriched by glycine decarboxylase (in the upper part) or by succinate dehydrogenase (in the bottom part of the leaf).     

Low levels of ribosomal RNA partly account for the very high photosynthetic phosphorus‐use efficiency of Proteaceae species

Proteaceae species in south‐western Australia occur on phosphorus‐ (P) impoverished soils. Their leaves contain very low P levels, but have relatively high rates of photosynthesis. We measured ribosomal RNA (rRNA) abundance, soluble protein, activities of several enzymes and glucose 6‐phosphate (Glc6P) levels in expanding and mature leaves of six Proteaceae species in their natural habitat. The results were compared with those for Arabidopsis thaliana. Compared with A. thaliana, immature leaves of Proteaceae species contained very low levels of rRNA, especially plastidic rRNA. Proteaceae species showed slow development of the photosynthetic apparatus (‘delayed greening’), with young leaves having very low levels of chlorophyll and Calvin–Benson cycle enzymes. In mature leaves, soluble protein and Calvin–Benson cycle enzyme activities were low, but Glc6P levels were similar to those in A. thaliana. We propose that low ribosome abundance contributes to the high P efficiency of these Proteaceae species in three ways: (1) less P is invested in ribosomes; (2) the rate of growth and, hence, demand for P is low; and (3) the especially low plastidic ribosome abundance in young leaves delays formation of the photosynthetic machinery, spreading investment of P in rRNA. Although Calvin–Benson cycle enzyme activities are low, Glc6P levels are maintained, allowing their effective use.     

Effects of tree mortality caused by a bark beetle outbreak on the ant community in the San Bernardino National Forest

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The most ancient bark beetle known: a new tribe,genus and species from Lebanese amber (Coleoptera,Curculionidae, Scolytinae)

Abstract Cylindrobrotus pectinatus gen. et sp.n. , a new scolytine species from Cretaceous Lebanese amber, is described. A new tribe, Cylindrobrotini trib.n. , is proposed for this unique species, which demonstrates an unusual combination of some archaic and many advanced characters. This finding suggests that the Scolytinae became a distinct lineage of Curculionoidea from the Lower Cretaceous. Fossil records are reviewed, and some remarks on the origin and taxonomic position of bark and ambrosia beetles are made. Some comments on the various phylogenetic interpretations of the last 30 years are given, particularly in respect of their correspondence with the fossil record. The early appearance of Scolytinae in the fossil record before other Curculionidae (which appeared in the Upper Cretaceous) can be used as evidence against the hypothesis of bark beetles as offspring of weevils. The question of the taxonomic rank of bark beetles (separate subfamily or family) and their placement among other groups of the superfamily remains unsolved.     

ENDOSYMBIONTS OF DREISSENA POLYMORPHA IN IRELAND: EVIDENCE FOR THE INTRODUCTION OF ADULT MUSSELS

Although zebra mussels (Dreissena polymorpha) have invaded watersacross Europe for over 200 years, they colonized Ireland onlywithin the past decade. To test the hypothesis that Irelandwas colonized by adult D. polymorpha, we examined mussels fromdifferent sites along the Lower Shannon River system in Irelandfor the presence of host specific and generalist endosymbionts.Withinthe mantle cavity and/or associated with zebra mussel tissueswe found species specific-ciliates (Conchophthirus acuminatusand Ophryoglena hemophaga) and generalist symbionts (the ciliateAncistrumina limnica, nematodes, oligochaetes and chironomids).We found a significant difference in the prevalence of symbiontsamong sites, but all mussels at all sites harboured one specialistspecies C. acuminatus, and all of the mussels at three of thefour sites also had the second specialist, O. hemophaga. Thus,with the introduction of D. polymorpha into Ireland, at leasttwo additional species, their host-specific symbionts C. acuminatusand O. hemophaga, have also been introduced. The presence ofthese symbionts in Ireland supports the hypothesis that adultzebra mussels were introduced into Ireland, rather than larvalstages. This contrasts with the introduction of zebra musselsto North America, where adult zebra mussels are devoid of host-specificsymbionts. (Received 8 June 2005; accepted 7 November 2005)     

Isotopic randomness as a biological factor

We discuss an alternative source of randomness originating at the atomic level due to the diversity of stable isotopes. This randomness could contribute to mutation mechanisms through atomic scale variations of bond lengths and strengths, differences in the reaction rates, etc. In terms of purposeful experimentation, isotopic replacements in living organisms give an independent parametrization which allows correlation of global biological variables with the level of individual atoms. We review the work done so far, and suggest some further experimental possibilities by analogy with some isotopic effects and isotopic structuring in solid state physics.