Are behavioural responses to predation cues linked across life cycle stages?

1. Prey organisms can perceive cues to predation hazard and adopt low‐risk behaviours to increase survival. Animals with complex life cycles, such as insects, can exhibit such anti‐predatory behaviours in multiple life stages. 2. Cues to predation risk may induce ovipositing females to choose habitats with low predation risk. Cues to predation risk may also induce larvae to adopt facultative behaviours that reduce risk of predation. 3. One hypothesis postulates that anti‐predation behaviours across adult and larval stages may be negatively associated because selection for effective anti‐predator behaviour in one stage leads to reduced selection for avoidance of predators in other stages. An alternative hypothesis suggests that selection by predation favours multi‐component defences, with both avoidance of oviposition and facultative adoption of low‐risk behaviours by larvae. 4. Laboratory and field experiments were used to determine whether defensive responses of adult and larval mosquitoes are positively or negatively associated. The study tested effects of waterborne cues from predatory Toxorhynchites theobaldi on oviposition choices and larval behaviours of three of its common prey: Culex mollis, Limatus durhamii and Aedes albopictus. 5. Culex mollis shows strong anti‐predator responses in both life stages, consistent with the hypothesis of a multi‐component behavioural defence. The other two species showed no detectable responses to waterborne predator cues in either adult or larval stages. Larvae of these unresponsive species were significantly more vulnerable to this predator than was C. mollis. 6. For these mosquitoes, species appear either to have been selected for multi‐component defences against predation or to act in ways that could be called predator‐naïve.     

Single-taxon field measurements of bacterial gene regulation controlling DMSP fate

The ‘bacterial switch'' is a proposed regulatory point in the global sulfur cycle that routes dimethylsulfoniopropionate (DMSP) to two fundamentally different fates in seawater through genes encoding either the cleavage or demethylation pathway, and affects the flux of volatile sulfur from ocean surface waters to the atmosphere. Yet which ecological or physiological factors might control the bacterial switch remains a topic of considerable debate. Here we report the first field observations of dynamic changes in expression of DMSP pathway genes by a single marine bacterial species in its natural environment. Detection of taxon-specific gene expression in Roseobacter species HTCC2255 during a month-long deployment of an autonomous ocean sensor in Monterey Bay, CA captured in situ regulation of the first gene in each DMSP pathway (dddP and dmdA) that corresponded with shifts in the taxonomy of the phytoplankton community. Expression of the cleavage pathway was relatively greater during a high-DMSP-producing dinoflagellate bloom, and expression of the demethylation pathway was greater in the presence of a mixed diatom and dinoflagellate community. These field data fit the prevailing hypothesis for bacterial DMSP gene regulation based on bacterial sulfur demand, but also suggest a modification involving oxidative stress response, evidenced as upregulation of catalase via katG, when DMSP is demethylated.     

Accumulation of rare earth elements by siderophore-forming <Emphasis Type="Italic">Arthrobacter luteolus</Emphasis> isolated from rare earth environment of Chavara,India

In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.     

A database of vertebrate longevity records and their relation to other life‐history traits

Longevity is a major characteristic of animals that has long fascinated scientists. In this work, we present a comprehensive database of animal longevity records and related life‐history traits entitled AnAge, which we compiled and manually curated from an extensive literature. AnAge started as a collection of longevity records, but has since been expanded to include quantitative data for numerous other life‐history traits, including body masses at different developmental stages, reproductive data such as age at sexual maturity and measurements of reproductive output, and physiological traits related to metabolism. AnAge features over 4000 vertebrate species and is a central resource for applying the comparative method to studies of longevity and life‐history evolution across the tree of life. Moreover, by providing a reference value for longevity and other life‐history traits, AnAge can prove valuable to a broad range of biologists working in evolutionary biology, ecology, zoology, physiology and conservation biology. AnAge is freely available online ( http://genomics.senescence.info/species/ ).     

Detection and expression of the phosphonate transporter gene phnD in marine and freshwater picocyanobacteria

We describe a PCR-based assay designed to detect expression of the phosphonate assimilation gene phnD from picocyanobacteria. The phnD gene encodes the phosphonate binding protein of the ABC-type phosphonate transporter, present in many of the picocyanobacterial genome sequences. Detection of phnD expression can indicate a capacity of picoplankton to utilize phosphonates, a refractory form of phosphorus that can represent 25% of the high-molecular-weight dissolved organic phosphorus pool in marine systems. Primer sets were designed to specifically amplify phnD sequences from marine and freshwater Synechococcus spp., Prochlorococcus spp. and environmental samples from the ocean and Laurentian Great Lakes. Quantitative RT-PCR from cultured marine Synechococcus sp. strain WH8102 and freshwater Synechococcus sp. ARC-21 demonstrated induction of phnD expression in P-deficient media, suggesting that phn genes are regulated coordinately with genes under phoRB control. Last, RT-PCR of environmental RNA samples from the Sargasso Sea and Pacific Ocean detected phnD expression from the endemic picocyanobacterial population. Synechococcus spp. phnD expression yielded a depth-dependent pattern following gradients of P bioavailability. By contrast, the Prochlorococcus spp. primers revealed that in all samples tested, phnD expression was constitutive. The method described herein will allow future studies aimed at understanding the utilization of naturally occurring phoshonates in the ocean as well as monitoring the acquisition of synthetic phosphonate herbicides (e.g. glyphosate) by picocyanobacteria in freshwaters.     

Destination‐based seed dispersal homogenizes genetic structure of a tropical palm

As the dominant seed dispersal agents in many ecosystems, frugivorous animals profoundly impact gene movement and fine‐scale genetic structure of plants. Most frugivores engage in some form of destination‐based dispersal, in that they move seeds towards specific destinations, resulting in clumped distributions of seeds away from the source tree. Molecular analyses of dispersed seeds and seedlings suggest that destination‐based dispersal may often yield clusters of maternal genotypes and lead to pronounced local genetic structure. The long‐wattled umbrellabird Cephalopterus penduliger is a frugivorous bird whose lek mating system creates a species‐specific pattern of seed dispersal that can potentially be distinguished from background dispersal processes. We used this system to test how destination‐based dispersal by umbrellabirds into the lek affects gene movement and genetic structure of one of their preferred food sources Oenocarpus bataua, a canopy palm tree. Relative to background dispersal processes, umbrellabird mating behaviour yielded more diverse seed pools in leks that included on average five times more seed sources and a higher incidence of long‐distance dispersal events. This resulted in markedly lower fine‐scale spatial genetic structure among established seedlings in leks than background areas. These species‐specific impacts of destination‐based dispersal illustrate how detailed knowledge of disperser behaviour can elucidate the mechanistic link driving observed patterns of seed movement and genetic structure.     

Abundance and distribution of major groups of diazotrophic cyanobacteria and their potential contribution to N2 fixation in the tropical Atlantic Ocean

The abundances of six N₂‐fixing cyanobacterial phylotypes were profiled at 22 stations across the tropical Atlantic Ocean during June 2006, and used to model the contribution of the diazotrophs to N₂ fixation. Diazotroph abundances were measured by targeting the nifH gene of Trichodesmium, unicellular groups A, B, C (UCYN‐A, UCYN‐B and UCYN‐C), and diatom‐cyanobiont symbioses Hemiaulus–Richelia, Rhizosolenia–Richelia and Chaetoceros–Calothrix. West to east gradients in temperature, salinity and nutrients [NO₃^‐ + NO₂^‐, PO₄^3?, Si(OH)₄] showed the influence of the Amazon River plume and its effect on the distributions of the diazotrophs. Trichodesmium accounted for more than 93% of all nifH genes detected, dominated the warmer waters of the western Atlantic, and was the only diazotroph detected at the equatorial upwelling station. UCYN‐A was the next most abundant (> 5% of all nifH genes) and dominated the cooler waters of the eastern Atlantic near the Cape Verde Islands. UCYN‐C was found at a single depth (200 m) of high salinity and low temperature and nutrients, whereas UCYN‐B cells were widespread but in very low abundance (6.1 × 10¹ ± 4.6 × 10² gene copies l^?1). The diatom‐cyanobionts were observed primarily in the western Atlantic within or near the high Si(OH)₄ input of the Amazon River plume. Overall, highest diazotroph abundances were observed at the surface and declined with depth, except for some subsurface peaks in Trichodesmium, UCYN‐B and UCYN‐A. Modelled contributions of Trichodesmium, UCYN‐B and UCYN‐A to total N₂ fixation suggested that Trichodesmium had the largest input, except for the potential of UCYN‐A at the Cape Verde Islands.     

In vivo uptake of a haem analogue Zn protoporphyrin IX by the human malaria parasite P. falciparum‐infected red blood cells

The cellular traffic of haem during the development of the human malaria parasite Plasmodium falciparum, through the stages R (ring), T (trophozoite) and S (schizonts), was investigated within RBC (red blood cells). When Plasmodium cultures were incubated with a fluorescent haem analogue, ZnPPIX (Zn protoporphyrin IX) the probe was seen at the cytoplasm (R stage), and the vesicle‐like structure distribution pattern was more evident at T and S stages. The temporal sequence of ZnPPIX uptake byP. falciparum‐infected erythrocytes shows that at R and S stages, a time‐increase acquisition of the porphyrin reaches the maximum fluorescence distribution after 60 min; in contrast, at the T stage, the maximum occurs after 120 min of ZnPPIX uptake. The difference in time‐increase acquisition of the porphyrin is in agreement with a maximum activity of haem uptake at the T stage. To gain insights into haem metabolism, recombinant PfHO (P. falciparum haem oxygenase) was expressed, and the conversion of haem into BV (biliverdin) was detected. These findings point out that, in addition to haemozoin formation, the malaria parasite P. falciparum has evolved two distinct mechanisms for dealing with haem toxicity, namely, the uptake of haem into a cellular compartment where haemozoin is formed and HO activity. However, the low Plasmodium HO activity detected reveals that the enzyme appears to be a very inefficient way to scavenge the haem compared with the Plasmodium ability to uptake the haem analogue ZnPPIX and delivering it to the food vacuole.