Pre-adult Stages Research Articles

Prey-stage preference and population increase of the predaceous mite Kampimodromus aberrans (Oudemans) (Acari: Phytoseiidae) on Tetranychus urticae Koch (Acari: Tetranychidae) under laboratory conditions

ABSTRACT The developmental time, survival, and fecundity of Kampimodromus aberrans (Oudemans) (Acari: Phytoseiidae) when feeding on Tetranychus urticae Koch (Acari: Tetranychidae) plus birch pollen were investigated at 16, 20, 25 and 30 ± 1°C, 65 ± 10% relative humidity, and 16:8 light:dark photoperiod in the laboratory. Also, the prey-stage preference of adult female K. aberrans was assessed at constant densities of different stages of T. urticae and T. urticae plus birch pollen. Experiments were carried out using bean leaf discs as substrate. Total developmental times of K. aberrans were 37.1, 26.6, 8.0, and 7.4 days for females and 32.1, 24.6, 7.4, and 7.3 days for males at 16, 20, 25, and 30 ± 1°C, respectively. The total egg production was highest (17.2 eggs) at 25°C, while the daily egg production was at its highest (1.1 eggs) at 30°C. The female longevity of K. aberrans was determined as 75.6, 58.8, 25.8, and 17.4 days at 16, 20, 25, and 30 ± 1°C, respectively. The development threshold of the eggs and pre-adult stages were 13.75 and 13.55°C for females, and 13.58 and 12.92°C for males, respectively. Total effective temperature was 33.78 and 112.35 degree-days for females and 33.44 and 113.63 for males. The mite had the highest intrinsic rate of increase, (r m ) 0.129 ♀/♀/day at 30°C, followed by 0.108 ♀/♀/day at 25°C and 0.034 ♀/♀/day at 20°C, while at 16°C, K. aberrans displayed the lowest r m value (0.023 ♀/♀/day). In the prey-stage preference experiments, the adult female K. aberrans consumed significantly more prey larvae of T. urticae alone, but, when the predatory mite was offered T. urticae plus birch pollen, they consumed significantly more eggs.

The effect of sea lice (Lepeophtheirus salmonis) on juvenile pink salmon (Oncorhynchus gorbuscha) swimming endurance

The swimming endurance of naturally and experimentally infected juvenile pink salmon ( Oncorhynchus gorbuscha ) was measured to determine the effects of sea lice ( Lepeophtheirus salmonis ). Salmon naturally infected with adult male and preadult stage lice did not appear to have a reduced swim performance, but when experimentally infected with adult female lice, juvenile salmon showed a reduced ability to swim compared with uninfected control fish, and this effect increased with lice load. A reduced swimming endurance is not only likely to influence predation risk for salmon, but may have other ecological implications, such as slower seaward migration.

Changed crystallinity of mebendazole solid dispersion: Improved anthelmintic activity

To improve the efficacy of mebendazole (MBZ), a poorly water-soluble drug, MBZ solid dispersions containing different proportions of low-substituted hydroxypropylcellulose (L-HPC) were prepared by lyophilization process. The physical characteristics of recrystallized MBZ, and solid dispersions (SD) at different MBZ:L-HPC proportions were investigated in terms of morphology (scanning electron microscopy, SEM), powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dissolution rate. The in vivo performance was assessed by anthelmintic activity studies against enteral (pre-adult) stage of Trichinella spiralis in mice. The XRD, DSC and SEM revealed a characteristic decrease in crystallinity when increasing the L-HPC proportions in the solid dispersions. The dissolution studies demonstrated a marked increase in the dissolution rate in comparison with recrystallized drug. The considerable improvement in the dissolution rate of MBZ from solid dispersions was attributed to decreased drug crystallinity and altered surface morphology (major) and to the wetting effect of L-HPC (minor). The in vivo studies revealed that the anthelmintic effects of solid dispersions in mice were significantly increased in comparison with recrystallized MBZ (1.74-fold for SD-1:1, 3.20-fold for SD-1:2.5 and 3.80-fold for SD-1:5). These results have shown the suitability of MBZ:L-HPC solid dispersions for the treatment of enteral helmintic diseases at low doses.

Cloning and Expression Analysis of cDNA Encoding Or83b-Like Receptor from Helicoverpa assulta

An Or83b-like receptor gene was cloned from antennae of Helicoverpa assulta (Guenée) by using reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). Sequence analysis revealed that the transcript of the Or83b-like receptor gene from H. assulta consists of 1 946 nucleotides and the open reading frame (ORF) encodes a peptide of 473 amino acids with 7 putative transmembrane domains. Alignment analysis suggested that amino acid sequence of Or83b-like receptor from H. assulta shares high identity with other Or83b family receptors and this gene was hence named as HassOr83b. Tissues expression analysis showed that the HassOr83b transcript is clearly observed in the antennae, labial palps and proboscises, but not in bodies, wings and legs. The further development expression analysis suggested HassOr83b is also expressed in several preadult stages, including early-stage larvae, late-stage larvae and pupae, but not in embryos. Locked nucleic acid (LNA)-based in situ hybridization of antennal section indicated that HassOr83b is expressed in a very large number of antennal cells, which suggests that HassOr83b may play a special role in olfaction in H. assulta.

Habitat features of settlement areas used by floaters of Bonelli’s and Golden Eagles

SummaryBonelli’s EagleHieraaetus fasciatusand Golden EagleAquila chrysaetosare two declining species, in which floaters tend to be located outside of breeding territories during the dispersal period, in so-called settlement areas. We studied settlement areas for both these long-lived raptors in the southern Iberian Peninsula, to gain a better understanding of the ecological requirements of the eagles during their long pre-adult stage, a period accounting for around 80% of the species’ mortality. Eagle abundance was calculated by road censuses, and habitat characteristics of settlement and non-settlement areas compared by General Discriminant Analysis (GDA) and Logistic Regression (LR). The best model of GDA and LR incorporated the abundance of main prey for eagles (rabbits, partridges) and orchard surface area, and explained 100% of eagle presence; the best model selected by GDA also included habitat heterogeneity. Both eagles tended to share settlement areas in the southern Iberian Peninsula and, when they did not, the mean annual temperature and slope appeared to explain the segregation between the two species. Management measures for the conservation of both threatened species during the dispersal period should be focused on identifying settlement areas, maintaining high prey densities and maximum habitat heterogeneity.

Synergistic/potentiation interaction between nematostatic constituents from Azadirachta indica, Madhuca indica and Sapindus mukorossi

Triterpenic saponins isolated from seeds of Madhuca indica and fruit pericarp from Sapindus mukorossi exhibited inhibitory effect against two phyto-parasitic nematodes. Azadirachtin and salanin-nimbin-desacetylnimbin (SND) was extracted from seeds and oil of Azadirachta indica A. Juss, respectively. M. indica and S. mukorossi saponins were found to inhibit the movement of pre-adult (J4) stage of Rotylenchulus reniformis with LC50 of 168.8 and 181.9 µg/mL. Azadirachtin and SND affected the mobility of secondary juvenile stage (J2) of Meloidogyne incognita by 83.3 and 80.1% respectively, at 0.5 mg m/L. M. indica saponin (LC50 220 µg/mL) exhibited a potentiation effect in the presence of azadirachtin in a 1:3 ratio (LC50 120.1 µg/mL). A binary mixture (1:1) of azadirachtin and SND was found to show significant nematicidal activity against M. incognita (LC50 70.9 µg/mL) and R. reniformis (LC50 91.2 µg/mL).

Developmental stages and growth of Pseudocaligus fugu Yamaguti, 1936 (Copepoda: Siphonostomatoida: Caligidae) host-specific to Puffer

The post-embryonic development of the copepod Pseudocaligus fugu is described. This sea louse only parasitizes toxic pufferfish, and causes commercial loss of cultured Takifugu rubripes in Japan. Two naupliar, one copepodid and four chalimus stages preceding the adult are recognized in the species. The development pattern is similar to that of Caligus except for the suppression of leg 4 in the early chalimus phase. Pseudocaligus fugu lacks any preadult stage, as in Caligus, but contrasts with Lepeophtheirus species in which two preadult stages are reported. The nature of the metamorphic changes in size and even in degree of expression of articulations can occur without moulting. The validity of some chalimus stages recognized in Lepeophtheirus species is questioned. Growth and egg production in P. fugu were obtained in the laboratory. Pseudocaligus fugu attained adulthood 9 days after the infective copepodid attached to the host.

Sea lice and salmon population dynamics: effects of exposure time for migratory fish

The ecological impact of parasite transmission from fish farms is probably mediated by the migration of wild fishes, which determines the period of exposure to parasites. For Pacific salmon and the parasitic sea louse, Lepeophtheirus salmonis, analysis of the exposure period may resolve conflicting observations of epizootic mortality in field studies and parasite rejection in experiments. This is because exposure periods can differ by 2-3 orders of magnitude, ranging from months in the field to hours in experiments. We developed a mathematical model of salmon-louse population dynamics, parametrized by a study that monitored naturally infected juvenile salmon held in ocean enclosures. Analysis of replicated trials indicates that lice suffer high mortality, particularly during pre-adult stages. The model suggests louse populations rapidly decline following brief exposure of juvenile salmon, similar to laboratory study designs and data. However, when the exposure period lasts for several weeks, as occurs when juvenile salmon migrate past salmon farms, the model predicts that lice accumulate to abundances that can elevate salmon mortality and depress salmon populations. The duration of parasite exposure is probably critical to salmon-louse population dynamics, and should therefore be accommodated in coastal planning and management where fish farms are situated on wild fish migration routes.

Demographic Traits of <I>Tetranychus urticae</I> (Acari: Tetranychidae) on Leaf Discs and Whole Leaves

Life tables of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), were studied on leaf discs and whole leaves of the common bean plant, Phaseolus vulgaris L. Data were analyzed based on the age-stage, two-sex life table theory. Durations of deutonymph stage, total preadult stage, and preoviposition period of mites reared on whole leaves (1.22, 7.6, and 0.29 d, respectively) were significantly shorter than those reared on leaf discs (1.73, 8.2, and 0.89 d, respectively). The lifetime fecundities were 22.81 and 12.05 offspring on whole leaves and leaf discs, respectively. Although hooked trichomes on the lower surface of the bean leaf contribute to adult mortality, spider mites successfully survive and reproduce on bean plants. The intrinsic rate of increase on whole leaves (0.235 d(-1)) was higher than that on leaf discs (0.159 d(-1). Higher intrinsic rate and fecundity found in mites reared on whole leaves may be due to the higher nutritional quality of whole leaves over leaf discs. We suggest that whole leaves should be used in future studies to better simulate realistic life history characteristics. The advantages of using age-stage, two-sex life tables over female age-specific life tables are discussed.

Identification of Genes Encoding Atypical Odorant-Binding Proteins inAedes albopictus(Diptera: Culicidae)

Insect odorant-binding proteins (OBPs) are a diverse gene family that encode proteins thought to function as molecular chaperones by binding semiochemicals and transporting them through the aqueous lymph of insect sensilla. Between 66 and 68 genes have been classified as OBPs in both Anopheles gambiae (Giles) and Aedes aegypti L. based on bioninformatics criteria. We have cloned and sequenced from a subtracted cDNA library three OBPs in Aedes albopcitus (Skuse). BLASTP and phylogenetic analysis of deduced amino acid sequences identified a unique putative ortholog in Ae. aegypti for each Ae. albopictus OBP. Comparison of these putative Ae. aegypti orthologs with the results of previous bioinformatics analyses of OBP genes in Ae. aegypti highlight the potential variability of bioinformatics analyses and suggest that the OBP gene family of Culicids is even more diverse than previously described. Alignment of deduced amino acid sequences and phylogenetic analysis identified the N-terminal region of Culicid OBPs that is associated with aedine-specific diversification. Analysis of tissue-specific expression indicates that two of the Ae. albopictus OBPs are expressed both in preadult stages and in the hemolymph of adults, suggesting that the proteins encoded by these genes may be involved in the transport of hydrophobic ligands in the hemolymph. The other Ae. albopictus OBP is expressed exclusively in antennae and leg, suggesting a chemosensory function. These results are discussed within the context of the evolution and functional diversification of OBPs in mosquitoes.

Intrinsic competition and its effects on the survival and development of three species of endoparasitoid wasps

In natural systems, pre-adult stages of some insect herbivores are known to be attacked by several species of parasitoids. Under certain conditions, hosts may be simultaneously parasitised by more than one parasitoid species (= multiparasitism), even though only one parasitoid species can successfully develop in an individual host. Here, we compared development, survival, and intrinsic competitive interactions amongst three species of solitary larval endoparasitoids, Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae), Microplitis demolitor Wilkinson, and Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), in singly parasitised and multiparasitised hosts. The three species differed in certain traits, such as in host usage strategies and adult body size. Campoletis sonorensis and M. demolitor survived equally well to eclosion in two host species that differed profoundly in size, Pseudoplusia includens (Walker) and the larger Heliothis virescens (Fabricius) (both Lepidoptera: Noctuidae). Egg-to-adult development time in C. sonorensis and M. demolitor also differed in the two hosts. Moreover, adult body mass in C. sonorensis (and not M. demolitor) was greater when developing in H. virescens larvae. We then monitored the outcome of competitive interactions in host larvae that were parasitised by one parasitoid species and subsequently multiparasitised by another species at various time intervals (0, 6, 24, and 48 h) after the initial parasitism. These experiments revealed that M. croceipes was generally a superior competitor to the other two species, whereas M. demolitor was the poorest competitor, with C. sonorensis being intermediate in this capacity. However, competition sometimes incurred fitness costs in M. croceipes and C. sonorensis, with longer development time and/or smaller adult mass observed in surviving wasps emerging from multiparasitised hosts. Our results suggest that rapid growth and large size relative to competitors of a similar age may be beneficial in aggressive intrinsic competition.

Comparative Anatomy and Histology of Developmental and Parasitic Stages in the Life Cycle of the Lined Sea Anemone Edwardsiella lineata

The evolution of parasitism is often accompanied by profound changes to the developmental program. However, relatively few studies have directly examined the developmental evolution of parasitic species from free-living ancestors. The lined sea anemone Edwardsiella lineata is a relatively recently evolved parasite for which closely related free-living outgroups are known, including the starlet sea anemone Nematostella vectensis. The larva of E. lineata parasitizes the ctenophore Mnemiopsis leidyi, and, once embedded in its host, the anemone assumes a novel vermiform body plan. That we might begin to understand how the developmental program of this species has been transformed during the evolution of parasitism, we characterized the gross anatomy, histology, and cnidom of the parasitic stage, post-parasitic larval stage, and adult stage of the E. lineata life cycle. The distinct parasitic stage of the life cycle differs from the post-parasitic larva with respect to overall shape, external ciliation, cnida frequency, and tissue architecture. The parasitic stage and planula both contain holotrichs, a type of cnida not previously reported in Edwardsiidae. The internal morphology of the post-parasitic planula is extremely similar to the adult morphology, with a complete set of mesenterial tissue and musculature despite this stage having little external differentiation. Finally, we observed 2 previously undocumented aspects of asexual reproduction in E. lineata: (1) the parasitic stage undergoes transverse fission via physal pinching, the first report of asexual reproduction in a pre-adult stage in the Edwardsiidae; and (2) the juvenile polyp undergoes transverse fission via polarity reversal, the first time this form of fission has been reported in E. lineata.

Diagnosing declining grassland wader populations using simple matrix models

Abstract Many populations of wader species have shown a strong decline in number in Western-Europe in recent years. The use of simple population models such as matrix models can contribute to conserve these populations by identifying the most profitable management measures. Parameterization of such models is often hampered by the availability of demographic data (survival and reproduction). In particular, data on survival in the pre-adult (immature) stage of wader species that remain in wintering areas outside Europe are notoriously difficult to obtain, and are therefore virtually absent in the literature. To diagnose population decline in the wader species; Black-tailed Godwit, Curlew, Lapwing, Oystercatcher, and Redshank, we extended an existing modelling framework in which incomplete demographic data can be analysed, developed for species with a pre-adult stage of one year. The framework is based on a Leslie matrix model with three parameters: yearly reproduction (number of fledglings per pair), yearly pre-adult (immature) and yearly adult (mature) survival. The yearly population growth rate of these populations and the relative sensitivity of this rate to changes in survival and reproduction parameters (the elasticity) were calculated numerically and, if possible, analytically. The results showed a decrease in dependence on reproduction and an increase in pre-adult survival of the population growth rate with an increase in the duration of the pre-adult stage. In general, adult survival had the highest elasticity, but elasticity of pre-adult survival increased with time to first reproduction, a result not reported earlier. Model results showed that adult survival and reproduction estimates reported for populations of Redshank and Curlew were too low to maintain viable populations. Based on the elasticity patterns and the scope for increase in actual demographic parameters we inferred that conservation of the Redshank and both Curlew populations should focus on reproduction. For one Oystercatcher and the Black-tailed Godwit populations we suggested a focus on both reproduction and pre-adult survival. For the second Oystercatcher population pre-adult survival seemed the most promising target for conservation. And for the Lapwing populations all demographic parameters should be considered.

Developmental and growth patterns in Xiphinema parasimile and X. simile (Nematoda: Dorylaimida), members of the X. americanum-group

AbstractXiphinema parasimile and X. simile are morphologically and morphometrically very similar, yet molecularly different, species with different developmental and growth patterns, a different number of juvenile developmental stages (four vs three) and a different post-embryonic growth pattern. Body length, body volume and odontostyle and replacement odontostyle lengths served for comparison of the post-embryonic growth patterns in these species. A percentage method was used to make the data sets comparable between one population of X. parasimile and three populations of X. simile. The mean body lengths of the first, second and pre-adult stages in X. simile showed similarity with those of the second, third and pre-adult stages in X. parasimile. In X. simile there was no unique growth pattern of body length and body volume from stage to stage applicable for all populations, just a similar trend with more or less similar values. The difference between replacement odontostyle and functional odontostyle lengths in all juvenile stages was higher in X. simile and lower in X. parasimile, despite the very similar mean odontostyle length in the female stage of both species.

Extreme temperatures increase the deleterious consequences of inbreeding under laboratory and semi-natural conditions

The majority of experimental studies of the effects of population bottlenecks on fitness are performed under laboratory conditions, which do not account for the environmental complexity that populations face in nature. In this study, we test inbreeding depression in multiple replicates of inbred when compared with non-inbred lines of Drosophila melanogaster under different temperature conditions. Egg-to-adult viability, developmental time and sex ratio of emerging adults are studied under low, intermediate and high temperatures under laboratory as well as semi-natural conditions. The results show inbreeding depression for egg-to-adult viability. The level of inbreeding depression is highly dependent on test temperature and is observed only at low and high temperatures. Inbreeding did not affect the developmental time or the sex ratio of emerging adults. However, temperature affected the sex ratio with more females relative to males emerging at low temperatures, suggesting that selection against males in pre-adult life stages is stronger at low temperatures. The coefficient of variation (CV) of egg-to-adult viability within and among lines is higher for inbred flies and generally increases at stressful temperatures. Our results contribute to knowledge on the environmental dependency of inbreeding under different environmental conditions and emphasize that climate change may impact negatively on fitness through synergistic interactions with the genotype.

Life extension in Drosophila maintained under lengthened light/dark regime

In the present study, we investigated whether the length of light/dark cycle could influence the pre-adult developmental time and adult life span in Drosophila melanogaster. Flies were reared to adulthood and maintained as adults under both 24-h (light/dark 12:12 h) and 48-h (light/dark 24:24 h) cycles. The flies reared during pre-adult stages at the 48-h light/dark cycle had significantly prolonged developmental time compared to those in flies reared at normal 24-h cycle. Irrespective of the duration of pre-adult light/dark period, the males maintained as adults at prolonged 48-h cycle had a 13-16% longer mean adult life span than those maintained at normal 24-h cycle (P<0.001 in all cases). In females reared under normal 24-h cycle such differences were lower but also significant (P=0.03); no significant difference in life span was found in females reared under prolonged 48-h cycle. The results are interpreted to demonstrate that pre-adult developmental time and adult life span in Drosophila melanogaster are both influenced by the length of light/dark cycle.

The molecular and cellular basis of olfactory-driven behavior inAnopheles gambiaelarvae

The mosquito Anopheles gambiae is the principal Afrotropical vector for human malaria. A central component of its vectorial capacity is the ability to maintain sufficient populations of adults. During both adult and preadult (larval) stages, the mosquitoes depend on the ability to recognize and respond to chemical cues that mediate feeding and survival. In this study, we used a behavioral assay to identify a range of odorant-specific responses of An. gambiae larvae that are dependent on the integrity of the larval antennae. Parallel molecular analyses have identified a subset of the An. gambiae odorant receptors (AgOrs) that are localized to discrete neurons within the larval antennae and facilitate odor-evoked responses in Xenopus oocytes that are consistent with the larval behavioral spectrum. These studies shed light on chemosensory-driven behaviors and represent molecular and cellular characterization of olfactory processes in mosquito larvae. These advances may ultimately enhance the development of vector control strategies, targeting olfactory pathways in larval-stage mosquitoes to reduce the catastrophic effects of malaria and other diseases.

Optimization and field use of a bioassay to monitor sea lice Lepeophtheirus salmonis sensitivity to emamectin benzoate

A bioassay for sea lice Lepeophtheirus salmonis sensitivity towards emamectin benzoate (EMB) was validated for field use. A probit regression model with natural responsiveness was used for the number of affected (moribund or dead) sea lice in bioassays involving different concentrations of EMB. Bioassay optimization included an evaluation of the inter-rater reliability of sea lice responsiveness to EMB and an evaluation of gender-related differences in susceptibility. Adoption of a set of bioassay response criteria improved the concordance (evaluated using the concordance correlation coefficient) between raters' assessments and the model estimation of EC50 values (the 'effective concentration' leading to a response of 50% of the lice not prone to natural response). An evaluation of gender-related differences in EMB susceptibility indicated that preadult stage female sea lice exhibited a significantly larger sensitivity towards EMB in 12 of 19 bioassays compared to preadult males. In order to evaluate sea lice sensitivity to EMB in eastern Canada, the intensive salmon farming area in the Bay of Fundy in southwestern New Brunswick was divided into 4 distinct regions based on industry health management practices and hydrographics. A total of 38 bioassays were completed from 2002 to 2005 using populations of preadult stage sea lice collected from Atlantic salmon Salmo salar farms within the 4 described regions. There was no significant overall effect of region or year on EC50 values; however, analysis of variance indicated a significant effect of time of year on EC50 values in 2002 and a potential effect in 2004 to 2005. Although the range of EC50 values obtained in this 3 yr study did not appear sufficient to affect current clinical success in the control of sea lice, the results suggest a seasonal- or temperature-associated variation in sensitivity to EMB. This will need to be considered if changes in EMB efficacy occur in the future.

Temperature-Dependent Development and Demography of &lt;I&gt;Scymnus subvillosus&lt;/I&gt; (Coleoptera: Coccinellidae) Reared on &lt;I&gt;Hyalopterus pruni&lt;/I&gt; (Homoptera: Aphididae)

The development, survival, and fecundity of Scymnus subvillosus (Goeze) (Coleoptera: Coccinellidae) were studied at 20, 25, 30, and 35 degrees C, 60 +/- 5% RH, and a photoperiod of 16:8 (L:D) h (5,000 lux) under laboratory conditions. The total developmental time from egg hatch to adult eclosion ranged from 22.6 d at 20 degrees C to 10.6 d at 35 degrees C. The developmental rates of the egg stage, the larval stage, and total preadult stage at different temperatures increased linearly with increasing temperature. The thermal summation of the egg stage, the larval stage, and the total preadult stage was 77.5, 145.8 and 300 degree-days (DD), respectively. The developmental threshold of the egg stage, the larval stage, and the total preadult stage was 7.4, 4.1, and 7.1 degrees C, respectively. The life history raw data were analyzed using the age-stage, two-sex life table. The intrinsic rate of increase was 0.0845, 0.1138, 0.1395, and 0.0668 d(-1) at 20, 25, 30, and 35 degrees C, respectively. The net reproductive rate was highest at 25 degrees C (R0 = 78.7), and lowest at 35 degrees C (R0 = 4.7). The mean generation time was shortest at 35 degrees C (T = 23.9 d). The life table data can be used for the projection of population growth and designing mass rearing programs.

Juvenility in the context of life history theory

Homo sapiens is unique in having four prolonged and pronounced postnatal pre-adult life history stages: infancy, which lasts for 30–36 months and ends with weaning from breast feeding in traditional...