Females of the weevil Zabrotes subfasciatus manipulate the size and number of eggs according to the host seed availability

In some insects, the finding of oviposition substrate triggers the uptake into oocytes of yolk proteins that are stored in the fat body during post-embryonic development. The main host of the bean weevil Zabrotes subfasciatus (Coleoptera; Chrysomelidae; Bruchinae; Amblycerini), in which larval resources are the sole source for future egg maturation, is Phaseolus vulgaris. Despite not feeding as adults, females of this species are able to lay eggs after encountering host seeds but it is not known how females react to changes in the availability of bean seeds. In the present study, the behaviour of Z. subfasciatus facing two very different environments for oviposition is investigated, as well as how this influences offspring fitness. The results obtained show that females of Z. subfasciatus react to variations in the availability of seeds belonging to the same host species by adjusting egg size and number. Females on low bean seed density lay larger and fewer eggs than those on high bean seed density, demonstrating a trade-off between these reproductive traits. Moreover, females can adjust egg size to changing levels of host availability during the first 4 days of their oviposition period. Although no difference in offspring weight is found, those from small eggs (low competition environment) result in larger adults. No response to selection on these traits after rearing beetles on the same host for 40 generations is observed. This unresponsiveness may indicate that beetle populations behave according to their reaction norm that already allows rapid adaptation to a varying amount of host-seed availability and better exploitation of the environments of this widespread stored-seed pest.

A non-invasive method for silencing gene transcription in honeybees maintained under natural conditions

in the Apis mellifera post-genomic era, RNAi protocols have been used in functional approaches. However, sample manipulation and invasive methods such as injection of double-stranded RNA (dsRNA) can compromise physiology and survival. To circumvent these problems, we developed a non-invasive method for honeybee gene knockdown, using a well-established vitellogenin RNAi system as a model. Second instar larvae received dsRNA for vitellogenin (dsVg-RNA) in their natural diet. For exogenous control, larvae received dsRNA for GFP (dsGFP-RNA). Untreated larvae formed another control group. Around 60% of the treated larvae naturally developed until adult emergence when 0.5 mu g of dsVg-RNA or dsGFP-RNA was offered while no larvae that received 3.0 mu g of dsRNA reached pupal stages. Diet dilution did not affect the removal rates. Viability depends not only on the delivered doses but also on the internal conditions of colonies. The weight of treated and untreated groups showed no statistical differences. This showed that RNAi ingestion did not elicit drastic collateral effects. Approximately 90% of vitellogenin transcripts from 7-day-old workers were silenced compared to controls. A large number of samples are handled in a relatively short time and smaller quantities of RNAi molecules are used compared to invasive methods. These advantages culminate in a versatile and a cost-effective approach. (c) 2008 Elsevier Ltd. All rights reserved.

Host preference of the bean weevil Zabrotes subfasciatus

It is largely known that the range of an insect diet is mostly determined by oviposition behavior, mainly in species with endophytic larvae such as Zabrotes subfasciatus. However, the proximate factors determining host choice and the subsequent steps leading to the expansion or reduction of the host number and occasional host shifts are largely unknown. We analyzed various factors determining host preference of Z. subfasciatus through the evaluation of: (i) oviposition preference of a wild population of Z subfasciatus on the usual host (bean) and unusual hosts (lentil, chickpea and soy), and the performance of the offspring; (ii) artificial selection for increasing preference for hosts initially less frequently chosen; (iii) comparison of oviposition behavior between two different populations (reared for similar to 30 generations in beans or chickpeas, respectively); (iv) oviposition timing on usual and unusual hosts; and (v) identification of preference hierarchies. We found that when using unusual hosts, there is no correlation between performance and preference and that the preference hierarchy changes only slightly when the population passes through several generations on the less frequently accepted host. We also found a positive response to artificial selection for increasing oviposition on the less preferred host; however, when the host-choice experiment involved two varieties of the usual host, the response was faster than when the choice involved usual and unusual hosts. Finally, beetles reared on an unusual host (chickpea) for 26 generations showed similar good fitness on both usual and unusual hosts, indicating that the use of a new host does not necessarily result in the loss of performance on the original host. Nevertheless, this population showed lower fitness on the usual host than that of the original population, suggesting an underlying partial trade-off phenomenon which may contribute to a broadening of diet of this insect species.

Variable effects of larval size on post-metamorphic performance in the field

Larval quality may be capable of explaining much of the variation in the recruitment and subsequent population dynamics of benthic marine invertebrates. Whilst the effects of larval nutritional condition on adult performance have received the most attention, recent work has shown that larval size may also be an important and ubiquitous source of variation in larval quality. We examined the effects of variation in larval size on the post-metamorphic survival and growth of Watersipora subtorquata in 2 very different habitats - experimental substrata and pier pilings. We found strong effects of larval size on colony performance, although these varied among experiments. For colonies on experimental substrata, larval size positively affected adult survival and, initially, growth. However, after 3 wk in the field, there was no relationship between larval size and colony size, possibly because colonies were completely surrounded by newly settled organisms. Larval size also positively affected post-metamorphic growth of colonies on pier pilings, but, surprisingly, colonies that came from larger larvae had lower survival than colonies from smaller larvae. Overall, variation in larval size will strongly affect the recruitment and subsequent performance of adults in this species, although this may vary among different habitats. This study highlights the importance of examining the effects of larval quality on adult performance in as realistic conditions as possible, because of the strong interaction between larval size effects and the environment.

Closely related Symbiodinium spp. differ in relative dominance in coral reef host communities across environmental, latitudinal and biogeographic gradients

The diversity and community structures of symbiotic dinoflagellates are described from reef invertebrates in southern and central provinces of the Great Barrier Reef (GBR), Australia, and Zamami Island, Okinawa, Japan. The symbiont assemblages from region to region were dominated by Clade C Symbiodinium spp. and consisted of numerous host-specific and/or rare types (specialists), and several types common to many hosts (generalists). Prevalence in the host community among certain host-generalist symbionts differed between inshore and offshore environments, across latitudinal (central versus southern GBR) gradients, and over wide geographic ranges (GBR versus Okinawa). One particular symbiont (C3h) from the GBR had a dramatic shift in dominance. Its prevalence ranged from being extremely rare, or absent on high-latitude reefs to dominating the scleractinian diversity on a mid-latitude inshore reef. These changes occurred among coral fauna whose larvae must acquire symbionts from environmental sources (horizontal symbiont acquisition). Such differences did not occur among 'vertical transmitters' such as Porites spp., Montipora spp. and pocilloporids (corals that directly transmit symbionts to their offspring) or among those hosts displaying 'horizontal acquisition', but that associate with specific symbionts. Most host-specialized types were found to be characteristic of a particular geographic region (i.e. Okinawa versus Central GBR versus Southern GBR). The mode of symbiont acquisition may play an important role in how symbiont composition may shift in west Pacific host communities in response to climate change. There is no indication that recent episodes of mass bleaching have provoked changes in host-symbiont combinations from the central GBR.

Geographical variation in offspring size effects across generations

Offspring size is thought to strongly affect offspring fitness and many studies have shown strong offspring size/fitness relationships in marine and terrestrial organisms. This relationship is strongly mitigated by local environmental conditions and the optimal offspring size that mothers should produce will vary among different environments. It is assumed that offspring size will consistently affect the same traits among populations but this assumption has not been tested. Here I use a common garden experiment to examine the effects of offspring size on subsequent performance for the marine bryozoan Bugula neritina using larvae from two very different populations. The local conditions at one population (Williamstown) favour early reproduction whereas the other population (Pt. Wilson) favours early growth. Despite being placed in the same habitat, the effects of parental larval size were extremely variable and crossed generations. For larvae from Williamstown, parental larval size positively affected initial colony growth and larval size in the next generation. For larvae from the other population, parental larval size positively affected colony fecundity and negatively affected larval size in the next generation. Traditionally, exogenous factors have been viewed as the sole source of variation in offspring size/fitness relationship but these results show that endogenous factors (maternal source population) can also cause variation in this crucial relationship. It appears offspring size effects can be highly variable among populations and organisms can adapt to local conditions without changing the size of their offspring.

Residues of spinosad in the tissues of sheep after aerosol treatment of blowfly myiasis

Objective To measure the residues of spinosad and chlorhexidine in the tissues of sheep after treatment of blowfly strike. Procedure Fourteen sheep with natural myiasis and 12 with artificial infestations of Lucilia cuprina larvae had the wool removed over their infestations and were treated with an aerosol wound dressing containing spinosad and chlorhexidine. Sheep were killed up to 14 days after treatment and residues of the chemicals measured in tissues. Results Chlorhexidine was not detected in any tissue. Residues of spinosad were highest in fat, lowest in muscle and intermediate in liver and kidney. The highest residue detected was 0.2 mg/kg spinosad in perirenal fat 7 days after generous treatment of a sheep with a large fly strike. Residues of spinosad in fat peaked 3 to 7 days after treatment and 1 to 3 days after treatment in liver and kidney. Conclusion These studies present a realistic worst-case in struck sheep and at the highest dose studied, equivalent to 5.8 mg spinosad per kg body weight, the maximum residue detected of 0.2 mg/kg in peri-renal fat was 20% of the Australian maximum residue limit. Muscle, liver and kidney residues of spinosad were also below the Australian maximum residue limits at all times.

Effect of estradiol benzoate microinjection into the median raphe nucleus on contextual conditioning

Estrogen deficiency has been associated with stress, anxiety and depression. Estrogen receptors have been identified in the median raphe nucleus (MRN). This structure is the main source of serotonergic projections to the hippocampus, a forebrain area implicated in the regulation of defensive responses and in the resistance to chronic stress. There is reported evidence indicating that estrogen modulates 5-HT(1A) receptor function. In the MRN, somatodendritic 5-HT(1A) receptors control the activity of serotonergic neurones by negative feedback. The present study has evaluated the effect of intra-MRN injection of estradiol benzoate (EB, 600 or 1200 ng/0.2 mu l) on the performance of ovariectormized rats submitted to contextual conditioning. Additionally, the same treatment was given after intra-MRN injection of Way 100635 (100 ng/0.2 mu l). a 5-HT(1A) receptor antagonist. Both doses of EB decreased freezing and increased rearing, indicating an anxiolytic effect. Pretreatment with Way 100635 antagonized the anxiolytic effect of estradiol. On the basis of these results, it may be suggested that estrogens modulate anxiety by acting on 5-HT(1A) receptors localized in the MRN. (C) 2009 Elsevier B.V. All rights reserved.

Neonatal exposure to LPS leads to heightened exploratory activity in adolescent rats

Although several reports have demonstrated physiological and behavioral changes in adult rats due to neonatal immune challenges, little is known about their effects in adolescence. Since neonatal exposure to lipopolysaccharide (LPS) alters the neural substrates involved in cognitive disorders, we tested the hypothesis that it may also alter the response to novel environments in adolescent rats. At 3 and 5 days of age, male Wistar rats received intraperitoneal injections of either vehicle solution or E. coli LPS (0.05 mg/kg) or were left undisturbed. In the mid-adolescent period, between 40 and 46 days of age, the rats were exposed to the following behavioral tests: elevated plus-maze, open-field, novel-object exploration task, hole-board and the modified Porsolt forced swim test. The results showed that, in comparison with control animals, LPS-treated rats exhibited (1) less anxiety-related behaviors and enhanced patterns of locomotion and rearing in the plus-maze and the open-field tests, (2) high levels of exploration of both objects in the novel-object task and of corner and central holes in hole-board test, and (3) more time spent diving, an active behavior in the forced swim test. The present findings suggest that neonatal LPS exposure has long-lasting effects on the behavior profile adolescent rats exhibit in response to novelty. This behavioral pattern, characterized by heightened exploratory activity in novel environments, also suggests that early immune stimulation may contribute to the development of impulsive behavior in adolescent rats. (C) 2010 Elsevier B.V. All rights reserved.

The relative energetic costs of the larval period, larval swimming and metamorphosis for the ascidian Diplosoma listerianum

Variation in larval quality has been shown to strongly affect the post-metamorphic performance of a wide range of marine invertebrate species. Extending the larval period of non-feeding larvae strongly affects post-metamorphic survival and growth in a range of species. These 'carry-over' effects are assumed to be due to changes in larval energetic reserves but direct tests are surprisingly rare. Here, we examine the energetic costs ( relative to the costs of metamorphosis) of extending the larval period of the colonial ascidian Diplosoma listerianum. We also manipulated larval activity levels and compared the energy consumption rates of swimming larvae and inactive larvae. Larval swimming was, energetically, very costly relative to either metamorphosis or merely extending the larval period. At least 25% of the larval energetic reserves are available for larval swimming but metamorphosis was relatively inexpensive in this species and larval reserves can be used for post-metamorphic growth. The carry-over effects previously observed in this species appear to be nutritionally mediated and even short (< 3 h) periods of larval swimming can significantly deplete larval energy reserves.

Offspring size effects in the marine environment: A field test for a colonial invertebrate

A central tenet of life-history theory is the presence of a trade-off between the size and number of offspring that a female can produce for a given clutch. A crucial assumption of this trade-off is that larger offspring perform better than smaller offspring. Despite the importance of this assumption empirical, field-based tests are rare, especially for marine organisms. We tested this assumption for the marine invertebrate, Diplosoma listerianum, a colonial ascidian that commonly occurs in temperate marine communities. Colonies that came from larger larvae had larger feeding structures than colonies that came from smaller larvae. Colonies that came from larger larvae also had higher survival and growth after 2 weeks in the field than colonies that came from smaller larvae. However, after 3 weeks in the field the colonies began to fragment and we could not detect an effect of larval size. We suggest that offspring size can have strong effects on the initial recruitment of D. listerianum but because of the tendency of this species to fragment, offspring size effects are less persistent in this species than in others.

A new species of Phylloicus Muller, 1880 (Trichoptera: Calamoceratidae), from southeastern Brazil, including descriptions of larval and pupal stages

The cosmopolitan family Calamoceratidae Ulmer, 1906, has 8 living genera, among them Phylloicus Muller, 1880, with species distributed from South to Central America. This genus is characterized by its dark-colored adults (brown to black) with diurnal to crepuscular habits. In this paper, the adults, pupae, and larvae of Phylloicus camargoi n. sp. are described and illustrated. The new species is easily diagnosed by male tergum X bearing a short, digitate, setose, basodorsal process; 2 short, digitate, hairless, lateral processes; and 2 pairs of very short processes on the posterior margin: a pair of digitate, hairless, posterolateral processes, and a pair of posteromesal processes. Additional diagnostic characters are the presence of 3 color bands on the forewings, 2 golden longitudinal bands and a white transversal one.

Evaluating the use of predatory insects as bioindicators of metals contamination due to sugarcane cultivation in neotropical streams

Streams located in areas of sugarcane cultivation receive high concentrations of metal ions from soils of the adjacent areas causing accumulation of metals in the aquatic sediment. This impact results in environmental problems and leads to bioaccumulation of metal ions in aquatic organisms. In the present study, metal concentrations in different predatory insects were studied in streams near sugarcane cultivation and compared to reference sites. Possible utilisation of predatory insects as bioindicators of metal contamination due to sugarcane cultivation from 13 neotropical streams was evaluated. Ion concentrations of Al, Cd, Cr, Cu, Zn, Fe, and Mn in adult Belostomatidae (Hemiptera) and in larvae of Libellulidae (Odonata) were analysed. Nine streams are located in areas with sugarcane cultivation, without riparian vegetation (classified as impacted area) and four streams were located in forested areas (reference sites). Metal concentrations in insects were higher near sugarcane cultivations than in control sites. Cluster analysis, complemented by an ANOSIM test, clearly showed that these insect groups are good potential bioindicators of metal contamination in streams located in areas with sugarcane cultivation and can be used in monitoring programmes. We also conclude that Libellulidae appeared to accumulate higher concentrations of metals than Belostomatidae.

Constituents of glandular trichomes of Tithonia diversifolia: Relationships to herbivory and antifeedant activity

The herbivory activity of the bordered patch larvae (Chlosyne lacinia, Lepidoptera) on leaves of a Brazilian population of Tithonia diversifolia and the antifeedant potential of its leaf rinse extract were investigated. The caterpillars fed only on the adaxial face, where the density of glandular trichomes is very low, and avoided the abaxial face, which contains high levels of trichomes. Deterrent activity against the larvae was observed in leaf discs treated with leaf rinse extract at concentrations of 1-5% of fresh leaf weight. High-performance liquid chromatography (HPLC) analysis indicated that sesquiterpene lactones are the main constituents of the glandular trichomes. Dichloromethane rinse extracts of the leaves and inflorescences were chemically investigated, and 16 compounds were isolated and identified: 14 sesquiterpene lactones, a flavonoid and a diterpenoid. In this study, five sesquiterpene lactones are described for the first time in the genus, including two lactones, one of which has an unusual seco-guaianolide skeleton. Our findings indicate that the caterpillars avoid the sesquiterpene-lactone-rich glandular trichomes, and provide evidence for the antifeedant activity of the dichloromethane leaf rinse extract. In addition, a study of the seasonal variation of the main constituents from the leaf surface throughout a year demonstrated that a very low qualitative but a very high quantitative variation occurs. The highest level of the main metabolite tagitinin C was observed between September and October and the lowest was from March to June, the later corresponding to the period of highest infestation by the larvae. (C) 2008 Elsevier Ltd. All rights reserved.

The origin of the metazoan biphasic life cycle: New insights from an ancient phylum

The biphasic life cycle, characterised by metamorphosis from a pelagic larva to a benthic adult, is found throughout the Metazoa. So is sexual reproduction via eggs and sperm. Amidst a tangled web of hypotheses on the origin of metazoan biphasy, current weight of opinion lies with a simple, larva-like holopelagic ancestor that independently settled multiple times to incorporate a benthic phase into the life cycle. This school of thought derives from Haeckel's interpretation of the gastrula as the recapitulation of a gastrean ancestor that evolved via selection on a simple, planktonic hollow ball-of-cells to develop the capacity to feed. We suggest that a paradigm shift is required to accomodate accumulating evidence of the genomic and developmental complexity of the metazoan last common ancestor, which was likely to have already possessed a biphasic lifecycle. Here we incorporate recent evidence from basal metazoans, in particular poriferans, to argue that a more parsimonious theory of the origin of biphasy is as a direct consequence of sexual reproduction in an ancestral benthic adult form. The metazoan embryo can itself be considered the precursor to a biphasic life cycle, wherein the embryo represents one phase and the adult another. Embryos in the water column are subject to natural selection for longeveity and dispersal, which sets them on the evolutionary trajectory towards the crown metazoan planktonic larvae. This alternate view considers the conserved use of regulatory genes in disparate metazoans as a reflection of both the complexity of the LCA and the antiquity of the biphasic life cycle. It does not require that extant embryogenesis, including gastrulation, recapitulates evolution.