Differential vulnerability determines the diet of a slow-moving predatory stream insect

1. We investigated the diet and prey electivity of Rhyacophila obliterata, a slow‐moving invertebrate predator capable of hunting in high‐flow microhabitats, and quantified the components of the predation sequence of fifth‐instar larvae foraging on mobile (Baetis mayflies, Amphinemura stoneflies) versus semi‐sessile (larval blackflies) prey. 2. In the field, fifth‐instar Rhyacophila consistently took more larval blackflies than more mobile prey. In behavioural trials, the number of attacks by Rhyacophila differed significantly between prey types, mobile prey being attacked more often than blackflies. Capture success, by contrast, was highest for blackflies, whereas Amphinemura and Baetis were rarely captured. In mixed‐prey feeding trials, Rhyacophila showed strong preference for blackflies and equally strong avoidance of Amphinemura and Baetis. 3. For mobile prey, the risk of being captured by this sluggish predator is very low, so they can afford to be in close contact with it. Rhyacophila was almost unable to capture any other prey but blackflies, resulting in strong passive selection for blackflies. 4. Therefore, the diet of fifth‐instar Rhyacophila can be predicted from laboratory observations and prey behaviour is the major determinant of the diet of this invertebrate predator.     

The articulation of annelids

The aim of this paper is to assess the monophyly of the Annelida. Also, recent cladistic analyses of metazoan taxa, using a variety of data, have shown incongruities with regards to annelids and associated taxa that should be resolved. The Platyhelminthes is selected as the taxon to root our minimal length trees and polarise our characters in a parsimony analysis; ingroup taxa being Mollusca, Nemertea, Sipuncula, Echiura, Pogonophora, Vestimentifera, Euarthropoda, Onycho-phora, and the groups most commonly regarded as true ‘annelids’, the Clitellata and Polychaeta. We use 13 characters and a total of 33 states. This results in 18 minimal length trees of 23 steps. The consensus tree has the topology (Platyhelminthes (Nemertea (Sipuncula Mollusca (Echiura (Polychaeta (Vestimcntifera Pogonophora) Clitellata (Euarthropoda Onychophora)))))). The name Articulata is applied to the Clitellata, Euarthropoda, Onychophora, Pogonophora, Polychaeta, and Vestimentifera. The Vestimentifera is the sister group to, or more likely a clade within, the frenulate pogonophores, and the name Pogonophora is retained for this group. In half of the 18 minimal length trees, the traditionally formulated Annelida, i.e. Polychaeta and Clitellata, is paraphyletic if the Pogonophora are excluded. In the remaining minimal length trees, a monophyletic Annelida cannot be formulated. The name Annelida should not be used unless relationships within the Articulata are resolved to show it is a monophyletic taxon. The taxon name Articulata, originally formulated to include the Annelida and Arthropoda by Cuvier, is defined as the clade stemming from the first ancestor to show repetition of homologous body structures derived by teloblastic growth with a pygidial growth zone (segmentation) and longitudinal muscles broken into bands. The Articulata is considered, on current evidence, to consist of four monophyletic groups; the Arthropoda, Clitellata, Polychaeta, and Pogonophora, though the latter group may be a clade of polychaetes. If this is shown, the Pogonophora should revert to the original family name Lamellisabellidae Uschakov, 1933. An indented classification reflective of the cladistic pattern is provided. Other recent hypotheses about metazoan systematics arc analysed.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.     

A phylogenetic analysis of the genus Eunice (Eunicidae, polychaete, Annelida)

Species of Eunice are distributed worldwide, inhabiting soft and hard marine bottoms. Some of these species play significant roles in coral reef communities and others are commercially important. Eunice is the largest and most poorly defined genus in Eunicidae. It has traditionally been subdivided in taxonomically informal groups based on the colour and dentition of subacicular hooks, and branchial distribution. The monophyly of Eunice and of its informal subgroups is tested here using cladistic analyses of 24 ingroup species based on morphological data. In the phylogenetic hypothesis resulting from the present analyses Eunice and its subgroups are paraphyletic; the genus may be divided in at least two monophyletic groups, Eunice s.s. and Leodice , but several species do not fall inside these two groups. Most of the traditional characters used in the taxonomy of Eunice are homoplasies; however, characters used for the first time in this study, such as certain jaw characters and characters derived from a close examination of chaetal variation along the body, are promising sources of phylogenetic signal.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 150 , 413–434.     

Identifying footprints of selection in stocked brown trout populations: a spatio‐temporal approach

Studies of interactions between farmed and wild salmonid fishes have suggested reduced fitness of farmed strains in the wild, but evidence for selection at the genic level is lacking. We studied three brown trout populations in Denmark which have been significantly admixed with stocked hatchery trout (19–64%), along with two hatchery strains used for stocking. The wild populations were represented by contemporary samples (2000–2006) and two of them by historical samples (1943–1956). We analysed 61 microsatellite loci, nine of which showed putative functional relationships [expressed sequence tag (EST)‐linked or quantitative trait loci]. F_ST‐based outlier tests provided support for diversifying selection at chromosome regions marked by three loci, two anonymous and one EST‐linked. Patterns of differentiation suggested that the loci were candidates for being under diversifying hitch‐hiking selection in hatchery vs. wild environments. Analysis of hatchery strain admixture proportions showed that in one wild population, two of the loci showed significantly lower admixture proportions than the putatively neutral loci, implying contemporary selection against alleles introduced by hatchery strain trout. In the most strongly admixed population, however, there was no evidence for selection, possibly because of immigration by stocked trout overcoming selection against hatchery‐derived alleles or supportive breeding practices allowing hatchery strain trout to escape natural selection. To our knowledge, this is the first study demonstrating footprints of selection in wild salmonid populations subject to spawning intrusion by farmed fish.     

Actions to alleviate the mental health impact of the economic crisis

The current global economic crisis is expected to produce adverse mental health effects that may increase suicide and alcohol-related death rates in affected countries. In nations with greater social safety nets, the health impacts of the economic downturn may be less pronounced. Research indicates that the mental health impact of the economic crisis can be offset by various policy measures. This paper aims to outline how countries can safeguard and support mental health in times of economic downturn. It indicates that good mental health cannot be achieved by the health sector alone. The determinants of mental health often lie outside of the remits of the health system, and all sectors of society have to be involved in the promotion of mental health. Accessible and responsive primary care services support people at risk and can prevent mental health consequences. Any austerity measures imposed on mental health services need to be geared to support the modernization of mental health care provision. Social welfare supports and active labour market programmes aiming at helping people retain or re-gain jobs can counteract the mental health effects of the economic crisis. Family support programmes can also make a difference. Alcohol pricing and restrictions of alcohol availability reduce alcohol harms and save lives. Support to tackle unmanageable debt will also help to reduce the mental health impact of the crisis. While the current economic crisis may have a major impact on mental health and increase mortality due to suicides and alcohol-related disorders, it is also a window of opportunity to reform mental health care and promote a mentally healthy lifestyle.     

Effects of Extracellular Matrix Molecules on Subepidermal Neural Crest Cell Migration in Wild Type and White Mutant (dd) Axolotl Embryos

Migration of neural crest (NC) derived pigment cells is restricted in the white mutant (dd) axolotl embryo (Ambystoma mexicanum). Transplantations between mutant and wild type embryos show that the extracellular matrix (ECM) of the white mutant is unable to support the migration of prospective pigment cells in wild type embryos (Löfberg et al., 1989, Dev. Biol. 131:168–181). In the present study, we test the effects of various purified ECM molecules on NC cell migration in the subepidermal migratory pathway of wild type (D/-) and white mutant (dd) axolotl embryos. We adsorbed the ECM molecules onto membrane microcarriers, which were then implanted under the epidermis. Fibronectin (FN), tenascin (TN), collagens I and VI, and a chick aggrecan stimulated migration in both types of embryos. Laminin-nidogen, rat chondrosarcoma aggrecan, and shark aggrecan stimulated migration in dd embryos but did not affect migration in D/- embryos. Collagen III, fibromodulin and bovine aggrecan had no effect on migration in either type of embryo. NC cells did not migrate on control micro-carriers, which lacked ECM molecules. Some cells observed contacting, and presumably migrating on, coated microcarriers could be identified as pigment cells by their ultra-structure. Enzymatic digestion in vivo with chondroitinase ABC had no effect on NC cell migration. The neutral or stimulatory effect of the aggrecans is surprising; when tested in vitro they inhibited NC cell migration. The effect of three-dimensionality and other molecules present either in the embryonic ECM or in solution may overcome the inhibitory effect of aggrecans.     

Insulin and Amino-acid Regulation of Polysomes in Perfused,Diabetic Rat Liver

IN normal mammalian liver, protein synthesis and concomitant polyribosome assembly are controlled by amino-acids^1–4. A similar control may be exerted by insulin in liver⁵ and muscle⁶. Both the effect of amino-acids on liver and that of insulin on muscle can be demonstrated with isolated, perfused tissue^4,7, but the interrelationship between these agents has not been clarified either in liver or in muscle. We have used perfused livers from diabetic rats to establish whether amino-acids and insulin promote polysomal assembly independently or in concert.