Larval Developmental Period Research Articles

Insecticidal and growth inhibitory potential of Streptomyces hydrogenans DH16 on major pest of India, Spodoptera litura(Fab.) (Lepidoptera: Noctuidae)

BackgroundDestructive impacts of insecticides on non targeted populations necessitate the development of an eco friendly pest control method. Streptomyces spp. are rich source of bioactive secondary metabolites which may provide valuable alternatives to chemical insect-control agents as they can be less toxic and readily biodegradable. Because of its potent biocontrol attributes, ethyl acetate extract of Streptomyces hydrogenans DH16, a soil isolate, was tested to assess its anti-insect potential against polyphagous noctuid, Spodoptera litura.ResultsThe secondary metabolites in the ethyl acetate extract of S. hydrogenans DH16 exhibited larvicidal and growth inhibitory activities. The results indicated that highest concentration of 1600 μg/ml was significantly effective as 70% larval, 66.66% prepupal and 100% pupal mortality was noticed. The metabolites also prolonged the larval developmental period. The LC50 and LC90 values were 1337.384 and 2070.516 μg/ml, respectively for the insect. Negative effects of S. hydrogenans were also observed on development of the insect. Significant decline in adult emergence, adult longevity, fecundity and % hatching was recorded at higher concentrations along with morphological abnormalities as compared to control. Significant decrease in relative growth and consumption rate, efficiency of ingested and digested food and increase in approximate digestibility in larvae reared on diet supplemented with ethyl acetate extract accounts for the toxic as well as anti-nutritive nature of extract.ConclusionSecondary metabolites in the fermentation broth from S. hydrogenans were toxic to the larvae at higher concentrations whereas lower concentrations significantly reduced the reproductive potential of S. litura. Therefore, these metabolites show considerable potential for incorporation in pest management programmes as new biopesticidal formulation.

Biology of common rose butterfly, Pachliopta aristolochiae Fabricius (Lepidoptera: Papilionidae) on the host plant, Aristolochia indica L. (Aristolochiaceae)

To study the biology of Pachliopta aristolochiae on its host plant Aristolochia indica singly laid eggs on the host plant were collected from the field and reared in the laboratory under optimum conditions of temperature (28 ± 3 °C) and relative humidity (70 ± 5% RH). Incubation period of the egg was 5.0 ± 0.6 days, larval developmental period was 11 ± 0.3 days, pre?pupal period was 0.87 ± 0.08 day, and the pupation took 12 ± 0.63 days. The length of 1st, 2nd, 3rd and 4th instar larvae were 4.0 ± 0.63, 9 ± 0.63, 22.6 ± 5.2 and 38.2 ± 4.70 mm, respectively. The feeding potential rate of 1st, 2nd, 3rd and 4th instar larvae were 11.4 ± 5.04, 29.6 ± 5.12, 51.4 ± 6.0 and 72.8 ± 4.9%, respectively. The weight of the faeces of 1st, 2nd, 3rd and 4th instar larvae were 0.012 ± 0.004, 0.047 ± 0.018, 0.0114 ± 0.023 and 0.274 ± 0.045 gm, respectively. DOI: http://dx.doi.org/10.3329/dujbs.v23i2.20090 Dhaka Univ. J. Biol. Sci. 23(2): 109-117, 2014

Effects of light intensity on activity in four sympatric anuran tadpoles.

Though light conditions are known to affect the development and anti-predation strategies of several aquatic species, relatively little is known about how different species react to light, or how light can affect these species during different points in their life-cycle. In this study, we used four sympatric anuran tadpoles (Bufo gargarizans, B. melanostictus, Pelophylax nigromaculatus and Microhyla fissipes) as animal system to examine species-specific activities of the underdoing different light intensity treatments, so as to better understand how they respond to light. We exposed four different species of tadpoles to 1660 and 14 lux light intensity treatments and then measured several parameters including development stage, body length and tail length, and as well as their basic activities. The results of this observation and analysis showed that the activities of tadpoles were significantly greater in B. gargarizans and B. melanostictus than in P. nigromaculatus and M. fissipes; and were also significantly greater during times of high light intensity as compared to during low light intensity. Moreover, the observed relationship between species and light intensity was significant. The activities of B. gargarizans and B. melanostictus tadpoles were greater in high light, while the activity of P. nigromaculatus tadpoles was greater in low light intensity, while M. fissipes tadpoles showed no differences in either low or high intensity light. Furthermore, the activities of B. gargarizans, B. melanostictus and M. fissipes tadpoles in terms of developmental stage, body size or tail length did not seem to differ with light intensity, but during early larval developmental period of P. nigromaculatus, the activity of tadpoles was negatively correlated with development stage, but irrelevant to either body size or tail length in different light intensities. These results lead us to conclude the observed activities of the four sympatric anuran tadpoles are closely correlated with their specific anti-predation strategies.

Laboratory evaluation of azadirachtin isolated from Melia azedarach L. fruits against Anopheles pulcherrimus Theobald (Diptera: Culicidae)

Efficacy of different concentration of azadirachtin isolated from fruits of Melia azedarach was investigated on the different stages of Anopheles pulcherrimus under lab. condition. Results showed that there was non-significant reduction in eggs hatching rate. There were high significant in larval mortalities which were depending on concentration. Different larval deformities were found. Second instars larvae were more sensitive then fourth larva instar , LC50 and LC90 for the second instars larvae were 35.99 and 67.99 ppm respectively and for the fourth instars larvae it was 63.09 and 139.8 respectively, significant prolongation in larval development period.

Inhibition of Phenoloxidase Activity Delays Development inBactrocera dorsalis(Diptera: Tephritidae)

Abstract Phenoloxidase (PO) is a multicopper enzyme, which plays an important role in melanin synthesis. PO is necessary for defense against intruding microorganisms and parasites, and is important in wound healing and cuticle pigmentation. As a specific inhibitor of PO, kojic acid (KA) is commonly used to characterize the functional properties of PO. In this study, we investigated the effect of KA on PO activity during the development of the oriental fruit fly, Bactrocera dorsalis, which is a destructive pest of many horticultural crops. After feeding on a KA-containing artificial diet, the larval and pupal developmental periods were significantly prolonged. In addition, the larvae did not grow to normal size and rates of pupation and emergence were decreased when B. dorsalis larvae had been fed with KA-containing diet for 6 days. Compared to the control, PO activities from whole bodies of B. dorsalis were inhibited, so did in larval cuticles. Consistent with these, kinetic analysis showed that the catal...

Anthelmintic activity in vitro and in vivo of Baccharis trimera (Less) DC against immature and adult worms of Schistosoma mansoni

Although its efficiency against all Schistosoma species, praziquantel (PZQ) shows low efficacy against schistosomula and juvenile stages. The potential for development of resistance to PZQ has justified the search for new alternative chemotherapies. In this scenario, studies to new formulations, more comprehensive and without adverse effects, are being conducted. One viable and promising treatment is the study of medicinal plants as a new approach to the experimental treatment for Schistosomiasis. Amongst all the variety of the medicinal species studied, we can highlight Baccharis trimera (Less) DC, known as “Carqueja-amarga”. This paper not only describes the effect of crude dichloromethane extract (DE) and aqueous fraction (AF) obtained from B. trimera, in vitro but also is the first one that investigates the in vivo efficacy of B. trimera against schistosomula, juvenile and adult worms of Schistosoma mansoni BH strain. In the experiment, mice were treated with DE, AF and PZQ (40 and 200mg/kg) over the period of larval development (3 and 30 post-infection; pi), and adult worms (60days post-infection; pi). The in vitro results show that the DE and AF effects are dose-dependents, being the 130μg/mL the most effective one in a shorter period of incubation. The exposure of the in vitro samples over adult parasites were able to inhibit 100% of the oviposition in females. Likewise caused the mortality of the parasites with morphological alterations on the tegument, on the suckers, oral and acetabulum, in both males and females after 6–72h of exposure. Additionally, the in vivo treatments against juvenile and adult infection were more effective compared to the control group untreated. Administrations of AF and DE in day 30pi (juvenile worms) show female worm total burden reductions of 75% and 68% respectively. At the same period of infection reductions of respectively 98% and 97% egg/g in the faeces were seen. In relation to the different egg developmental stages (oogram), the results showed significant reductions, due to the reduction in the number of worms, especially the females. In conclusion, B. trimera exhibits major schistosomicidal effects in vivo against immature and adult worms of S. mansoni, opening up perspectives for future researches on substance or compound isolation and the elucidation of its mechanisms of action.

Fitness Costs Associated With Field-Evolved Resistance to Bt Maize in <I>Spodoptera frugiperda</I> (Lepidoptera: Noctuidae)

Increasing adoption of transgenic crops expressing cry toxin genes from Bacillus thuringiensis (Bt crops) represents an augmented risk for development of insect resistance. While fitness costs can greatly influence the rate of resistance evolution, most available data related to Bt resistance have been obtained from laboratory-selected insect strains. In this article, we test the existence of fitness costs associated with high levels of field-evolved resistance to Bt maize event TC1507 in a strain of Spodoptera frugiperda (JE Smith) originated from maize fields in Puerto Rico. Fitness costs in resistant S. frugiperda were evaluated by comparing biological performance to susceptible insects when reared on meridic diet, maize or soybean leaf tissue, or cotton reproductive tissues. Parameters monitored included larval survival, larval and pupal weights, developmental time (larval and pupal), adult longevity, reproductive traits (fecundity and fertility), and sex ratio. We found that all monitored parameters were influenced to a similar extent by the host, independently of susceptibility to Bt maize. The only parameter that significantly differed between strains for all hosts was a longer larval developmental period in resistant S. frugiperda, which resulted in emergence asynchrony between susceptible and resistant adults. To test the relevance of fitness costs in resistant S. frugiperda, we performed a selection experiment to monitor the stability of resistance in a heterogeneous strain through 12 generations of rearing on meridic diet. Our data demonstrate lack of fitness costs relevant to stability of field-evolved resistance to Bt maize and help explain reported stability of field-evolved resistance in Puerto Rican populations of S. frugiperda.

Survival and development of american bollworm (Helicoverpa armigerahubner) on transgenicBtcotton

A laboratory bioassay was conducted to study the impact of Cry 1 Ac protein on survival and development of Helicoverpa armigera (Hubner.) by feeding larvae with Bt cotton plant parts. During the study, terminal leaves and squares of two Bt hybrids, their corresponding non Bt hybrids and Bunny as check were fed to larvae. Among the plant parts tested, mortality of H.armigera larvae was higher on leaves compared to squares of both the Bt hybrids. Further, the mortality of early larval instars was higher compared to older instar larvae on both leaves and squares of Bt hybrids. Though, the later instar larvae were able to survive when exposed continuously to Bt cotton plant parts, but reduction larval and pupal weight, increase in larval developmental period, malformations in pupae and adults, reduction in adult emergence, less fecundity, low growth and survival indices was observed on both the Bt hybrids compared to their corresponding non Bt hybrids and check hybrid, Bunny.

Altered regulation of sleep and feeding contributes to starvation resistance in Drosophila melanogaster.

Animals respond to changes in food availability by adjusting sleep and foraging strategies to optimize their fitness. Wild populations of the fruit fly, Drosophila melanogaster, display highly variable levels of starvation resistance that are dependent on geographic location, food availability and evolutionary history. How behaviors that include sleep and feeding vary in Drosophila with increased starvation resistance is unclear. We have generated starvation-resistant flies through experimental evolution to investigate the relationship between foraging behaviors and starvation resistance. Outbred populations of D. melanogaster were selected for starvation resistance over 60 generations. This selection process resulted in flies with a threefold increase in total lipids that survive up to 18 days without food. We tested starvation-selected (S) flies for sleep and feeding behaviors to determine the effect that selection for starvation resistance has had on foraging behavior. Flies from three replicated starvation-selected populations displayed a dramatic reduction in feeding and prolonged sleep duration compared to fed control (F) populations, suggesting that modified sleep and feeding may contribute to starvation resistance. A prolonged larval developmental period contributes to the elevated energy stores present in starvation-selected flies. By preventing S larvae from feeding longer than F larvae, we were able to reduce energy stores in adult S flies to the levels seen in adult F flies, thus allowing us to control for energy storage levels. However, the reduction of energy stores in S flies fails to generate normal sleep and feeding behavior seen in F flies with similar energy stores. These findings suggest that the behavioral changes observed in S flies are due to genetic regulation of behavior rather than elevated lipid levels. Testing S-F hybrid individuals for both feeding and sleep revealed a lack of correlation between food consumption and sleep duration, indicating further independence in genetic factors underlying the sleep and feeding changes observed in S flies. Taken together, these findings provide evidence that starvation selection results in prolonged sleep and reduced feeding through a mechanism that is independent of elevated energy stores. These findings suggest that changes in both metabolic function and behavior contribute to the increase in starvation resistance seen in flies selected for starvation resistance.

Biology and Ecology of Pleurotroppopsis podagrica (Waterston) (Hymenoptera: Eulophidae): A Potential Parasitoid of the Oil Palm Pest, Coelaenomenodera Elaeidis (Coleoptera: Chrysomelidae)

Coelaenomenodera elaeidis (Coleoptera: Chrysomelidae) is endemic in almost all oil palm growing areas of West Africa and regarded as the most devastating insect pest of the oil palm. For the purpose of a detailed knowledge of the rearing, life cycle and ecology of the natural enemy of C. elaeidis , field and laboratory studies were conducted in the main station of the Nigerian Institute for Oil Palm Research. Pruned, damaged and infested fronds from the field were cut open and studied for presence of different life stages of C. elaeidis , and their potential parasitoids. Parasitoid larval developmental period averaged 8 d while pupal developmental period had a mean of 7.2 ± 1.48 d. The total developmental period of the parasitoid from larva to adult averaged 23.2 ± 3.56 d. Average longevity of the adult parasitoid was 3.9 ± 3.56 d. Temperature was between 25 - 30oC and relative humidity ranged between 81-86%. The eulophid wasp, Pleurotroppopsis podagrica,/i> was found to parasitize C. elaeidis . Its larva is predominantly whitish, oval and translucent. The larva is averagely 3mm, oblong at the anterior and posterior sections tapering at both ends. The parasitoid emerged from the posterior region of C. elaeidis with the anterior region inside the host. This paper has shown that control of the C. elaeidis in its larval stage seems most promising and P. podagrica offers potential as bio-control agent for the C. elaeidis .

Developmental Response of <i>Pieris brassicae</i> (L.) (Lepidoptera: Pieridae) on Different Cauliflower Cultivars under Laboratory Conditions

Cauliflower is popular vegetable in Pakistan and it is severely attacked by Pieris brassicae (L). There are different cauliflower cultivars available in this area. The aim of this study was to determine the developmental response of Pieris brassicae on ten cauliflower cultivars. An experiment was conducted during 2012-13 at the Entomology section of the Agriculture Research Institute Tarnab Peshawar under laboratory conditions of 20&degC ± 2&degC, 50% ± 5% RH and 12:12h photoperiod. Pieris brassicae eggs were collected from a cauliflower field ARI Tarnab and the larvae placed after hatching on fresh leaves often cauliflower cultivars. The results showed that the larval development of P. brassicae was short (35 days), longer larval length (32.41 mm), larval mortality was low (6.6%) and pupal weight was high (0.50 g) on Clima cultivar. On the other hand, a longer larval developmental period (37 days), higher larval mortality (86.66%), shorter larval length (24.55 mm) and lower pupal weight (0.42 g) were recorded on cultivar AX-2034.

Biology and harmfulness of Planococcus vovae (Nassonov) (Hemiptera: Pseudococcidae) in Belgrade area

Planococcus vovae (Nassonov) (Hemiptera: Pseudococcidae) is an important pest on plants of the family Cupressaceae. Its numerous populations have been present in recent years on Juniperus spp. in Belgrade. Feeding by sap-sucking on all aboveground plant organs, it causes growth stagnation, chlorosis, drying of needles and branches, and even of entire plants under heavy infestation. Additionally, the scale excretes large quantities of honeydew, on which sooty mold develops, reducing photosynthesis and causing faster plant deterioration. Throughout 2007 and 2008, P. vovae was recorded on Juniperus spp. in 12 localities in Belgrade, and on Thuja sp. in a single locality. The pest was found to develop three generations per year and overwinter on branches at the egg or second instar stages. The first generation adults were observed at the end of May, the second generation at the beginning of August, while the third generation was recorded at the beginning of October. Different overwintering modes, and variable oviposition, embryonic and larval development periods led to an overlapping of generations and continuous presence of all developmental stages on plants. In different localities the infestation of plants varied in abundance from a few individual specimens to very large colonies. The highest infestation intensity was recorded in the localities Bezanija, Dorcol and Vozdovac. The predatory species Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and Nephus bipunctatus (Kugelann) (Coleoptera: Coccinelidae) were found in the scale colonies. Regarding N. bipunctatus, this was its first record as a new species in the Serbian fauna.

Occupancy Patterns of Mammals and Lentic Amphibians in the Elwha River Riparian Zone Before Dam Removal

AbstractThe downstream transport of sediments and organics and upstream migration of anadromous fishes are key ecological processes in unregulated riverine ecosystems of the North Pacific coast, but their influence on wildlife habitats and populations is poorly documented. Removal of two large hydroelectric dams in Washington's Elwha Valley provides an unprecedented opportunity to study long‐term responses of wildlife populations to dam removal and restoration of these key ecological processes. We compared pre‐dam removal patterns in the relative abundance and occupancy of mesocarnivores, small mammals and lentic amphibians of the Elwha River riparian zone above, between and below the dams. Occupancy of riparian habitats by three mesocarnivore species diminished upriver but did not appear to be closely linked with the absence of salmon in the upper river. Although the importance of salmon in the lower river cannot be discounted, other gradients in food resources also likely contributed to observed distribution patterns of mesocarnivores. Abundance and occupancy patterns within congeneric pairs of new world mice (Peromyscus spp.) and shrews (Sorex spp.) indicated that closely related species were negatively associated with each other and responded to habitat gradients in the riparian zone. The availability of lentic habitats of amphibians was highly variable, and occupancy was low as a result of rapidly changing flows during the larval development period. We speculate that long‐term changes in habitat conditions and salmon availability following dam removal will elicit long‐term changes in distribution of mesocarnivores, small mammals and amphibians. Long‐term monitoring will enhance understanding of the role of fish and restored ecosystem processes on wildlife communities along salmon‐bearing rivers in the region. Copyright © 2013 John Wiley & Sons, Ltd.

Food utilization and growth of cutworm Spodoptera litura Fabricius larvae exposed to nickel, and its effect on reproductive potential

Food utilization and growth of the 5th and 6th instar Spodoptera litura Fabricius larvae, and its effect on reproduction potential was evaluated by feeding larvae diets with different doses of Ni for 3 generations. Dose-dependent relationships between Ni levels and food consumption and growth were variable with different larval developmental period and Ni exposure duration. RCR, AD and RGR of the 6th instar larvae were much more affected by Ni exposure than those of 5th instar larvae, and the effects were strongest in the 3rd generation. It was found that RCR was significantly stimulated after 1 and 20mgkg−1 Ni exposure, while AD was significantly inhibited after 1, 5, 10 and 40mgkg−1 Ni exposure. However, lower levels of Ni (⩽5mgkg−1) significantly increased and higher levels of Ni (⩾10mgkg−1) significantly decreased RGR. In 3 successive generations, 10mgkg−1 Ni significantly increased the ECI and ECD of the 5th instar larvae, and 5mgkg−1 Ni significantly increased the ECD of the 6th instar larvae. However, ECD were all significantly inhibited with 20mgkg−1 Ni exposure. Results also revealed that durations of larvae were shortened at low levels of Ni, but extended at high levels of Ni. Fecundity was inhibited by the highest Ni doses in each generation, while improved by low Ni doses in the 3rd generation. Hatching rates in all treatments were significantly decreased in a Ni dose-dependent manner. Study indicated that effects of Ni on these parameters were predominant with the increasing Ni exposure period.

Insecticidal activity of pogostone against Spodoptera litura and Spodoptera exigua (Lepidoptera: Noctuidae)

Essential oil of Pogostemon cablin (Blanco) Benth. has been reported to exhibit strong insecticidal activities, but few studies have focused on the insecticidal activity of its main individual constituent, pogostone (PO). The goal of this research was to investigate the insecticidal activity of PO against two harmful noctuid insects, Spodoptera litura (Fabricius) and Spodoptera exigua (Hübner). In a no-choice assay, PO exhibited strong antifeedant activity against S. litura and S. exigua. PO showed pronounced larvicidal activities, including oral toxicity (LC50 986.88 mg L(-1) and 545.61 mg L(-1) respectively) and contact toxicity (LC50 1041.42 mg L(-1) and 519.48 mg L(-1) respectively) against these two noctuid insects. Additionally, PO treatment significantly increased the larval and pupal developmental period. Furthermore, PO showed moderate ovicidal activities and influenced the emergence and deformity of the moth. However, PO failed to exert a potent effect on adult development. These tested parameters proved to be dose dependent for both insect species. PO possesses strong insecticidal activities, especially antifeedant, larvicidal, growth inhibitory and pupicidal activities, against S. litura and S. exigua. PO may partly account for the insecticidal activity of patchouli oil and may be a promising candidate for the control of agricultural insects.

Seasonal and diel changes in the structure of a crustacean decapod assemblage associated to a shallow Cymodocea nodosa meadow in northern Tunisia (Mediterranean Sea). An overview of the Mediterranean decapod taxocoenoses.

A study on the decapod assemblage inhabiting a shallow meadow of Cymodocea nodosa from the bay of La Goulette (Tunisia) was carried from February 2009 to February 2010. Monthly samples (with replicates) were taken in the morning and at night, with a small Agassiz trawl. In total 11699 specimens belonging to 41 species were caught. Significant day-night and seasonal changes are mainly related to movements (feeding) and recruitments. Higher abundance and richness were reported at night. Analyses rendered no significant relationships between the plant phenology and abundances and richness; neither between the total abundance and temperature, but significant correlations with a time lag of 3 - 4 months between these factors exist, which could be related with hatching and larval development period. The nocturnal and diurnal values in the diversity and equitability indexes are quite similar along the year (peaks in spring - early summer, minimum in autumn - early winter). This pattern is mainly due to the strong dominance of a few species, with maximum abundances during their recruitment events, whose seasonal and day-night changes have been determined. Besides, an overview of the decapods assemblage associated to this seagrass for the Mediterranean Sea has been carried out. The species can be divided into two groups (linked to the leaves and to the sediment). The differences in species composition between areas must be related to different sampling methodologies, feeding and reproductive strategies, but also to the layout and influence of the surrounding habitats.

In vivo effect of single oral dose of artemether against early juvenile stages of Schistosoma mansoni Egyptian strain

The current treatment and control of schistosomiasis, rely on a single drug, praziquantel, although, it has minor activity against juvenile stages of the parasite. Studies have shown that artemether (ART) exhibits effects against juveniles of Schistosoma mansoni Liberian and Puerto Rican strains, Schistosoma japonicum and Schistosoma haematobium. Aiming to assess the in vivo activity of single oral dose of ART against early juvenile stages of S. mansoni Egyptian strain, this study was established. Mice were treated with ART (400mg/kg) at two time points evenly spaced over the period of larval development (7 and 21days post-infection; pi), and a third treatment point (day 49 pi) was included to elucidate when susceptibility decreases. Administration of ART on day 7 pi reduced the total worm burden by 85.94%. The greatest reductions were seen when treatment was given on day 21 pi, with total and female worm burden reductions of 91.52% and 90.57%, respectively, and cessation of oviposition. Similar dose given on day 49 pi reduced total worm burden by 55.17% and female worm burden by 66.51%. Moreover, it induced significant reduction in the tissue egg load and significant alterations in the oogram pattern with decreased immature eggs and increased dead eggs. Antipathological activities were evident in significant reductions in granulomata count and diameter. In conclusion, ART exhibits major in vivo schistosomicidal effects against the early larval migratory stages of S. mansoni Egyptian strain, mainly the 21-day old schistosomula, hence preventing disease progression and morbidity.

Effects of chronic aluminum and copper exposure on growth and development of wood frog (Rana sylvatica) larvae

Wood frogs (Rana sylvatica) were exposed to aluminum (Al; 10, 100, 500, 1000, or 2000μgL−1) or copper (Cu; 1, 10, 50, 100, 200μgL−1) at a pH of 4.70 from the beginning of the larval period through the completion of metamorphosis (range=43–102 days). Observations on mortality, malformation, time to reach specific developmental stages, body mass at these stages, and metamorphic success were made throughout the larval developmental period. Only one case of malformation was observed and mortality was ≤10% at all concentrations except the highest Cu concentration where the rate was 33%. All larvae that survived the experiment successfully completed metamorphosis, but significant effects on growth and development occurred for both metals and these were most prominent for Cu. At the highest Al concentration (2000μgL−1), body mass of larvae was significantly lower (reduced by 17% compared to the control) at 20 days post hatching (DPH) and the time to reach the hind-limb (HL), front-limb (FL), and tail resorption (TR) stages was significantly increased (9–10 days longer than the control). Body mass of larvae exposed to the three highest concentrations of Cu (50, 100, 200μgL−1) was reduced by 30–34% at 20 DPH. Exposure to these concentrations also resulted in increased time to reach the HL, FL, and TR stages with larvae in the highest concentration taking 21–29 days longer to reach these stages. Larvae exposed to 10μgL−1 Cu also took longer to reach the FL and TR stages of development, and exposure to all Cu concentrations increased tail resorption time by more than two days compared to the control. Although the only observed effects of Al were for a concentration that is probably not ecologically relevant, results demonstrate that environmentally-realistic levels of Cu may have significant biological effects that could influence individual fitness and population-level processes.

Oviposition dynamics and larval development of Helicoverpa armigera on a highly preferred unsuitable host plant, Solanum viarum

AbstractOogenesis and oviposition dynamics of female moths of tomato fruitworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), were compared in a monoculture of tomato (Solanum lycopersicum L.) and in mixtures with a highly preferred but unsuitable host plant, Solanum viarum Dunal. Female H. armigera provided with S. viarum laid many more eggs than those provided with tomato, both in choice and no‐choice experiments. Gravid female moths did not display any preference for oviposition neither between young or old plants of S. viarum or tomato, nor between young and old leaves of S. viarum. Larval mortality and larval developmental period significantly increased, with subsequent reduction in pupal weight, when H. armigera larvae fed on S. viarum leaves compared to a meridic diet. Oviposition of female moths significantly increased in tomato in the presence of S. viarum volatiles. However, in screen cages with an increasing percentage of S. viarum as a trap crop, the number of eggs laid on tomato as the main crop was the same. The results of this study are discussed in light of the possibility of using S. viarum as a ‘dead‐end’ trap crop.

Survival Rate and Development Period of the Larvae of Portunus pelagicus (Decapoda, Brachyura, Portunidae) In Relation to Temperature and Salinity

Berried females of Portunus pelagicus (Blue swimmer crab) were collected from the wild and the zoea 1 obtained from a single berry were stocked in 200 litre tanks at the rate of 25 numbers/mL. In order to study the independent effects of temperature and salinity, the larvae were reared in three different temperatures (26°C, 28°C and 30°C) at a fixed salinity of 35 ppt and in three different salinities (25 ppt, 30 ppt and 35 ppt) at a fixed temperature of 28°C. Feeding was carried out with microalgae, rotifers, moina and formulated shrimp feed, which varied with stage. The survival rates at each stage in all the trials were assessed by random sampling. The most ideal temperature and salinity among those studied were calculated in relation to the overall survival rate and larval development period. The data pertaining to both temperature and salinity manipulated investigations were found to be significant (P < 0.01) when subjected to one-way ANOVA. Among the tested temperatures, the highest average survival (14.12 ? 0.31%) and the lowest average development period (14.67 days) were obtained at 30 ± 0.1°C. Among the salinity values tested, the highest mean survival rate (06.89 ± 0.06%) and the lowest average development period (14.33 days) were obtained at 35 ppt.