Showing papers on "Larva published in 2011"

Common and Distinct Roles of Juvenile Hormone Signaling Genes in Metamorphosis of Holometabolous and Hemimetabolous Insects

Abstract: Insect larvae metamorphose to winged and reproductive adults either directly (hemimetaboly) or through an intermediary pupal stage (holometaboly). In either case juvenile hormone (JH) prevents metamorphosis until a larva has attained an appropriate phase of development. In holometabolous insects, JH acts through its putative receptor Methoprene-tolerant (Met) to regulate Kruppel-homolog 1 (Kr-h1) and Broad-Complex (BR-C) genes. While Met and Kr-h1 prevent precocious metamorphosis in pre-final larval instars, BR-C specifies the pupal stage. How JH signaling operates in hemimetabolous insects is poorly understood. Here, we compare the function of Met, Kr-h1 and BR-C genes in the two types of insects. Using systemic RNAi in the hemimetabolous true bug, Pyrrhocoris apterus, we show that Met conveys the JH signal to prevent premature metamorphosis by maintaining high expression of Kr-h1. Knockdown of either Met or Kr-h1 (but not of BR-C) in penultimate-instar Pyrrhocoris larvae causes precocious development of adult color pattern, wings and genitalia. A natural fall of Kr-h1 expression in the last larval instar normally permits adult development, and treatment with an exogenous JH mimic methoprene at this time requires both Met and Kr-h1 to block the adult program and induce an extra larval instar. Met and Kr-h1 therefore serve as JH-dependent repressors of deleterious precocious metamorphic changes in both hemimetabolous and holometabolous juveniles, whereas BR-C has been recruited for a new role in specifying the holometabolous pupa. These results show that despite considerable evolutionary distance, insects with diverse developmental strategies employ a common-core JH signaling pathway to commit to adult morphogenesis.

The Effects of Larval Nutrition on Reproductive Performance in a Food-Limited Adult Environment

Abstract: It is often assumed that larval food stress reduces lifetime fitness regardless of the conditions subsequently faced by adults. However, according to the environment-matching hypothesis, a plastic developmental response to poor nutrition results in an adult phenotype that is better adapted to restricted food conditions than one having developed in high food conditions. Such a strategy might evolve when current conditions are a reliable predictor of future conditions. To test this hypothesis, we assessed the effects of larval food conditions (low, improving and high food) on reproductive fitness in both low and high food adults environments. Contrary to this hypothesis, we found no evidence that food restriction in larval ladybird beetles produced adults that were better suited to continuing food stress. In fact, reproductive rate was invariably lower in females that were reared at low food, regardless of whether adults were well fed or food stressed. Juveniles that encountered improving conditions during the larval stage compensated for delayed growth by accelerating subsequent growth, and thus showed no evidence of a reduced reproductive rate. However, these same individuals lost more mass during the period of starvation in adults, which indicates that accelerated growth results in an increased risk of starvation during subsequent periods of food stress.

Amphibians at risk? Susceptibility of terrestrial amphibian life stages to pesticides.

Abstract: Current pesticide risk assessment does not specifically consider amphibians. Amphibians in the aquatic environment (aquatic life stages or postmetamorphic aquatic amphibians) and terrestrial living juvenile or adult amphibians are assumed to be covered by the risk assessment for aquatic invertebrates and fish, or mammals and birds, respectively. This procedure has been evaluated as being sufficiently protective regarding the acute risk posed by a number of pesticides to aquatic amphibian life stages (eggs, larvae). However, it is unknown whether the exposure and sensitivity of terrestrial living amphibians are comparable to mammalian and avian exposure and sensitivity. We reviewed the literature on dermal pesticide absorption and toxicity studies for terrestrial life stages of amphibians, focusing on the dermal exposure pathway, that is, through treated soil or direct overspray. In vitro studies demonstrated that cutaneous absorption of chemicals is significant and that chemical percutaneous passage, P (cm/h), is higher in amphibians than in mammals. In vivo, the rapid and substantial uptake of the herbicide atrazine from treated soil by toads (Bufo americanus) has been described. Severe toxic effects on various amphibian species have been reported for field-relevant application rates of different pesticides. In general, exposure and toxicity studies for terrestrial amphibian life stages are scarce, and the reported data indicate the need for further research, especially in light of the global amphibian decline.

Similarity and specialization of the larval versus adult diet of European butterflies and moths.

Abstract: Many herbivorous insects feed on plant tissues as larvae but use other resources as adults. Adult nectar feeding is an important component of the diet of many adult herbivores, but few studies have compared adult and larval feeding for broad groups of insects. We compiled a data set of larval host use and adult nectar sources for 995 butterfly and moth species (Lepidoptera) in central Europe. Using a phylogenetic generalized least squares approach, we found that those Lepidoptera that fed on a wide range of plant species as larvae were also nectar feeding on a wide range of plant species as adults. Lepidoptera that lack functional mouthparts as adults used more plant species as larval hosts, on average, than did Lepidoptera with adult mouthparts. We found that 54% of Lepidoptera include their larval host as a nectar source. By creating null models that described the similarity between larval and adult nectar sources, we furthermore showed that Lepidoptera nectar feed on their larval host more than...

Agricultural intensity in ovo affects growth, metamorphic development and sexual differentiation in the Common toad ( Bufo bufo )

Abstract: Pollution was cited by the Global Amphibian Assessment to be the second most important cause of amphibian decline worldwide, however, the effects of the agricultural environment on amphibians are not well understood. In this study, spawn from Bufo bufo was taken from four sites in England and Wales with varying intensities of arable agriculture. Spawn was either placed in tanks containing aged tap water (ex-situ, five replicates) or in cages at the native site (caged, five replicates). Hatching success, abnormal tadpoles, and forelimb emergence were recorded during the larval stage. Individuals were also sampled at five time points (TP) during development (5-, 7-, 9-, 12-, 15-weeks post-hatch) and analysed for morphological parameters. The thyroids (TP2) and the gonads (TP3,4,5) were also analysed histologically. With the exception of the thyroid histopathology, all analysed endpoints were significantly different between ex-situ individuals reared under identical conditions from the different sites. In addition, intensity of arable agriculture had a negative effect on growth and development. At one site, despite distinct rearing conditions, a high level of intersex (up to 42%) and similar sex ratios were observed in both ex-situ and caged individuals. Taken together, these data suggest that maternal exposure and/or events in ovo had a much larger effect on growth, metamorphic development, and sexual differentiation in B. bufo than the ambient environment. This could have important implications for traditional exposure scenarios that typically begin at the larval stage. Intersex is reported for the first time in European amphibians in situ, highlighting the potential use of distinct populations of amphibians in fundamental research into the aetiology of specific developmental effects in wild amphibians.

Influence of two methods of dietary restriction on life history features and aging of the cricket Acheta domesticus

Abstract: Studying aging is constrained using vertebrates by their longevity, size, ethical restrictions, and expense. The key insect model, Drosophila melanogaster, is holometabolous. Larvae feed on yeast in moist media and adults sponge food. Most aging studies are restricted to adults. Another key model, the nematode Caenorhabditis elegans, feeds on bacteria in moist media. For either invertebrate refreshing test materials, preventing degradation and obtaining accurate dosing are difficult even with synthetic media. The cricket Acheta domesticus has a short lifespan (∼120 days at 30°C) and is omnivorous. Age-matched cohorts are easily obtained from eggs. The life cycle is hemimetabolous and nymphs eat the same foods as adults. Growth is easily monitored, gender can be differentiated before maturity, and maturation is indicated by wings and mature genitalia. Crickets can be reared in large numbers at low cost. Test materials can be mixed into food and ingestion rates or mass budgets easily assessed. Here, we validate the cricket as a model of aging by testing two fundamental methods of restricting food intake: time-restricted access to food and dietary dilution. Growth, maturation, survivorship, and longevity varied with treatments and genders. Intermittent feeding (which is ineffective in flies) significantly extended longevity of crickets. Dietary dilution also extended longevity via remarkable prolongation of the juvenile period.

Movement of Spodoptera frugiperda Adults (Lepidoptera: Noctuidae) in Maize in Brazil

Abstract: The fall armyworm, Spodoptera frugiperda (J. E. Smith), is one of the most important maize pests in the Americas and particularly in South America. With the adoption of genetically modified plants expressing Bacillus thuringiensis toxins for lepidopterous pest control, there is a need for establishing strategies to delay the development of insect resistance (e.g. refuge areas). Thus, information on target insects' dispersal is essential to improve pest management techniques. The objective of this work was to evaluate the dispersal capacity of S. frugiperda adults using mark-release-recapture techniques. Insects were marked using red oil-soluble dye in the larval artificial diet. Marked adults were released twice in each growing season (dry and wet) in southeastern Brazil in 2006 and 2007. Recapture of marked insects was performed using light and pheromone traps. Males are more attracted to light traps than females and the recapture rate was higher in the dry season than in the rainy season. The m...

Fascioliasis Control: In Vivo and In Vitro Phytotherapy of Vector Snail to Kill Fasciola Larva

Abstract: Snail is one of the important components of an aquatic ecosystem, it acts as intermediate host of Fasciola species. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. Life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria in the snail body. In vivo and in vitro toxicity of the plant products and their active component such as citral, ferulic acid, umbelliferone, azadirachtin, and allicin against larva of Fasciola in infected snail Lymnaea acuminata were tested. Mortality of larvae were observed at 2 h, 4 h, 6 h, and 8 h, of treatment. In in vivo treatment, azadirachtin caused highest mortality in redia and cercaria larva (8 h, LC50 0.11, and 0.05 mg/L) whereas in in vitro condition allicin was highly toxic against redia and cercaria (8 h, LC50 0.01, and 0.009 mg/L). Toxicity of citral was lowest against redia and cercaria larva.

An unprecedented role reversal: ground beetle larvae (Coleoptera: Carabidae) lure amphibians and prey upon them.

Abstract: Amphibians often feed on beetle larvae, including those of ground beetles (Carabidae). Preliminary reports have detailed an unusual trophic interaction in which, in contrast, larvae of the ground beetle Epomis prey upon juvenile and adult amphibians. While it is known that these larvae feed exclusively on amphibians, how the predator-prey encounter occurs to the advantage of the beetle larvae had been unknown to date. Using laboratory observations and controlled experiments, we recorded the feeding behavior of Epomis larvae, as well as the behavior of their amphibian prey. Here we reveal that larvae of two species of Epomis (E. circumscriptus and E. dejeani) lure their potential predator, taking advantage of the amphibian's predation behavior. The Epomis larva combines a sit-and-wait strategy with unique movements of its antennae and mandibles to draw the attention of the amphibian to the presence of a potential prey. The intensity of this enticement increases with decreasing distance between the larva and the amphibian. When the amphibian attacks, the larva almost always manages to avoid the predator's protracted tongue, exploiting the opportunity to attach itself to the amphibian's body and initiate feeding. Our findings suggest that the trophic interaction between Epomis larvae and amphibians is one of the only natural cases of obligatory predator-prey role reversal. Moreover, this interaction involves a small insect larva that successfully lures and preys on a larger vertebrate. Such role reversal is exceptional in the animal world, extending our perspective of co-evolution in the arms race between predator and prey, and suggesting that counterattack defense behavior has evolved into predator-prey role reversal.

Prey Suitability and Phenology of Leucopis spp. (Diptera: Chamaemyiidae) Associated with Hemlock Woolly Adelgid (Hemiptera: Adelgidae) in the Pacific Northwest

Abstract: Leucopis spp. (Diptera: Chamaemyiidae) from the Pacific Northwest previously were identified as potential biological control agents for the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in the eastern United States. We collected Leucopis spp. larvae from A. tsugae infested western hemlocks in Oregon and Washington and reared them on an unidentified Pineus spp., Pineus strobi (Hartig), Adelges cooleyi (Gillette), Adelges piceae (Ratzeburg), and A. tsugae in three no-choice tests. Leucopis spp. survival on A. tsugae was significantly higher than on A. piceae during the 2010 progrediens generation test and significantly higher than on P. strobi and A. cooleyi during the 2010 sistens generation test. However, across all three tests, some larvae completed development to adult on all four of the alternative adelgid species. Larvae that survived to the adult stage were identified as Leucopis argenticollis Zetterstedt and Leucopis piniperda Malloch. These results suggest that populations of L. argenticollis and L. piniperda in the Pacific Northwest may not be specific to A. tsugae. We also studied the phenology of Leucopis spp. on fourteen A. tsugae infested western hemlock trees in Oregon and Washington over a period of 14 mo. Leucopis spp. larvae were collected year-round, but highest densities coincided with the presence of progrediens and sistens eggs and adults of A. tsugae. There was a positive correlation between Leucopis spp. and A. tsugae abundance.

Growth- and size-selective mortality in pelagic larvae of a common reef fish

Abstract: Larvae of most aquatic species experience high mortality in the plankton and where traits are naturally variable, mortality can be selective. We tested the hypothesis that reef fish lar- vae with faster growth rates and larger size-at-age will be more likely to survive the pelagic larval period. We examined the otolith microstructure of larval bluehead wrasse Thalassoma bifasciatum collected across the Straits of Florida to obtain daily growth rates and relative size-at-age. Using a cross-sectional approach, we compared these traits between 2 larval age groups (young larvae: 18 to 26 d old, survivors: 27 to 36 d old) to determine whether mean traits varied with age. In contrast to expectations, survivors had slower early growth and were smaller-at-age than the young lar- vae, suggesting that faster growing, larger individuals were selectively removed from the popula- tion over time. To examine the role of water masses, we estimated maximum upstream larval posi- tions. Differential current speeds across the Straits of Florida resulted in substantial overlap in back-estimated upstream locations of larvae at younger ages, suggesting that differences in early growth environments were unlikely the cause of the observed patterns. Instead, the most parsimo- nious explanation is the selective loss of fast-growing, large-at-age larvae in the plankton. Shifts in the direction of selective pressures across stages may contribute to the maintenance of high plasticity in the early life history traits of this species.

Aboard a spider—a complex developmental strategy fossilized in amber

Abstract: Mantid flies (Mantispidae) are an unusual group of lacewings (Neuroptera). Adults markedly resemble mantids in their general appearance and predatory behavior. The larvae of most mantispids exclusively prey on spider eggs, whereby the first instar larva is highly mobile and active and the other two larval stages immobile and maggot like. One of the larval strategies to pursue spider eggs is spider-boarding. Here, I report on the first record of a fossil mantispid larva. It was found in Middle Eocene Baltic amber, and it is the first record of Mantispidae from this deposit. The larva is attached to a clubionoid spider in a position typical for most mantispid larvae, and, thus, it is also the first fossil record of this complex larval behavior and development.

Predator mediated selection and the impact of developmental stage on viability in wood frog tadpoles ( Rana sylvatica )

Abstract: Complex life histories require adaptation of a single organism for multiple ecological niches. Transitions between life stages, however, may expose individuals to an increased risk of mortality, as the process of metamorphosis typically includes developmental stages that function relatively poorly in both the pre- and post-metamorphic habitat. We studied predator-mediated selection on tadpoles of the wood frog, Rana sylvatica, to identify this hypothesized period of differential predation risk and estimate its ontogenetic onset. We reared tadpoles in replicated mesocosms in the presence of the larval odonate Anax junius, a known tadpole predator. The probability of tadpole survival increased with increasing age and size, but declined steeply at the point in development where hind limbs began to erupt from the body wall. Selection gradient analyses indicate that natural selection favored tadpoles with short, deep tail fins. Tadpoles resorb their tails as they progress toward metamorphosis, which may have led to the observed decrease in survivorship. Path models revealed that selection acted directly on tail morphology, rather than through its indirect influence on swimming performance. This is consistent with the hypothesis that tail morphology influences predation rates by reducing the probability a predator strikes the head or body.

Can we use the tadpoles of Australian frogs to reduce recruitment of invasive cane toads

Abstract: Summary 1. Native to the Americas, cane toads Bufo marinus are an invasive species causing substantial ecological impacts in Australia. We need ways to control invasive species such as cane toads without collateral damage to native fauna. 2. We explored the feasibility of suppressing survival and growth of cane toad tadpoles via competition with the tadpoles of native frogs. Compared to the invasive toads, many native frogs breed earlier in the season and their tadpoles grow larger and have longer larval periods. Hence, adding spawn or tadpoles of native frogs to toad-breeding sites might increase tadpole competition, and thereby reduce toad recruitment. 3. Our laboratory trials using tadpoles of eight native frog species gave significant results: the presence of six of these species (Cyclorana australis, C. longipes, Litoria caerulea, L. dahlii, L. rothii and L. splendida) reduced toad tadpole survival and ⁄ or size at metamorphosis. Litoria caerulea also increased the duration of the larval period of cane toad tadpoles. Tadpoles of the other two frog species (Litoria rubella and Litoria tornieri) did not affect survival or growth of larval cane toads any more than did an equivalent number of additional toad tadpoles. Native frog species with larger tadpoles exerted greater negative effects on toad tadpoles than did native species with smaller tadpoles. 4. Synthesis and applications. Encouraging the general public to construct and restore waterbodies in peri-urban areas to build up populations of native frogs – especially the much-loved green tree frog Litoria caerulea – could help to reduce recruitment rates of invasive cane toads in Australia.

Do tadpoles affect leaf decomposition in neotropical streams

Abstract: SUMMARY 1. Of the relatively few studies that have examined consequences of amphibian declines on stream ecosystems, virtually all have focused on changes in algae (or algal-based food webs) and little is known about the potential effects of tadpoles on leaf decomposition. We compared leaf litter decomposition dynamics in two neotropical streams: one with an intact community of tadpoles (with frogs) and one where tadpoles were absent (frogless )a s a result of a fungal pathogen that had driven amphibians locally extinct. The stream with tadpoles contained a diverse assemblage (23 species) of larval anurans, and we identified five species of glass frog (Centrolenidae) tadpoles that were patchily distributed but commonly associated with leaf detritus and organic sediments in pools. The latter reached total densities of 0–318 tadpoles m )2 . 2. We experimentally excluded tadpoles from single-species leaf packs incubated over a 40-day period in streams with and without frogs. We predicted that decomposition rates would be higher in control (allowing access of tadpoles) treatments in the study stream with frogs than in the frogless stream and, in the stream with frogs, in the control than in the tadpole exclusion treatment. 3. In the stream with frogs, Centrolene prosoblepon and Cochranella albomaculata tadpoles were patchily distributed in leaf packs (0.0–33.3 m )2 ). In contrast to our predictions, leaf mass loss and temperature-corrected leaf decomposition rates in control treatments were almost identical in our stream with frogs (41.01% AFDM lost, kdegree day = )0.028 day )1 ) and in the frogless stream (41.81% AFDM lost, kdegree day = )0.027 day )1 ) and between control and tadpole exclusion treatments within each stream. Similarly, there were no significant differences in leaf pack bacterial biomass, microbial respiration rates or macroinvertebrate abundance between treatments or streams. Invertebrate assemblages on leaf packs were similar between treatments (SIMI = 0.97) and streams (SIMI = 0.95) and were dominated by larval Chironomidae, Simuliidae (Diptera) and larval Anchytarsus spp. (Coleoptera). 4. In contrast to dramatic effects of grazing tadpoles on algal communities observed previously, tadpoles had no major effects on decomposition. While centrolenid tadpoles were common in the stream with frogs, their patchy distribution in both experimental and natural leaf packs suggests that their effects on detrital dynamics and microbes are probably more localised than those of grazing tadpoles on algae.

Nidicolous tadpoles rather than direct development in Malagasy frogs of the genus Gephyromantis

Abstract: Frogs in the genus Gephyromantis from Madagascar were assumed to have a direct developmental mode, i.e. the complete embryonic and larval development within the egg, but recently free-swimming, exotrophic tadpoles of a few species have been found. Herein we provide detailed morphological descriptions of the tadpoles of five more species of this genus, indicating a developmental mode other than direct development in species of Gephyromantis. Tadpoles of Gephyromantis granulatus, G. sculpturatus, G. tschenki, and G. ventrimaculatus were found free-swimming in streams, and tadpoles of G. sp. aff. blanci were raised after hatching from clutches found in the leaf litter. All tadpoles were identified by DNA barcoding. The oral discs of all five species are characterized by the lack of many typical morphological traits of exotrophic tadpoles (such as oral papillae and keratodonts). This indicates that these tadpoles are either non-feeding (endotrophic) or only facultatively feeding tadpoles. We classify these ta...

Nutritional and biochemical evaluation of the protein quality of four popular insects consumed in Southern Nigeria

Abstract: The nutritional and biochemical evaluation of the protein quality of some popular insects consumed in Southern Nigeria was investigated. Thirty six (36) young weanling male albino rats (Wistar strain) of about 23 days old, grouped into six (6) groups of six (6) animals per group, were fed separate diets containing 10% protein by weight of the test diets, casein diet and a protein free (corn starch) diet for twenty eight (28) days. The diets contained adequate amounts of all other required nutrients. Results showed that the PER of the insects expressed as percentage of that obtained for casein were 94.26%, 71.31%, 96.72% and 107.38% respectively for Oryctes rhinoceros (OR) larva, Imbrasia belina (IBL) larva, Macrotermis belicosus (MB) and Rhynchophorus pheonicis (RP) larva, while the BV for the different insects were 87.94±4.14, 86.82±3.89, 88.55±7.89, and 88.95±8.14 respectively for OR, IBL, MB and RP. Results obtained for the net protein ratio (NPR), protein retention efficiency (PRE), and true digestibility (TD) for the insects show that they were comparable to values observed for the casein control and the observed slight differences were not significant at 95% confidence limit. The relative weights (g/kg live weight) of the organs namely liver, spleen, heart, kidney and lungs were not affected by feeding the animals using the insects as source of protein (P═0.05). Haematological and toxicological parameters assayed for were not significantly different from the control (P>0.05), but the serum ALP and ALT values were slightly higher while AST values were lower than that of the control (P≤0.05) for animals fed IBL diet. The plasma protein and blood urea levels were similar to values observed for the casein standard diet and the slight differences were not significant at 95% confidence limit. These observed results suggest the insects to be good sources of essential nutrients, which could go a long way in helping to solve most nutritional problems in many developing countries. Entomophagy should be encouraged as a good alternative towards solving the PEM problem facing many third world countries.

Comparison of the Activities of Three LdMNPV Isolates in the Laboratory Against the Chinese Strain of Asian Gypsy Moth

Abstract: Three isolates of gypsy moth (Lymantria dispar (L.)) nucleopolyhedrovirus (LdMNPV), from China (LdMNPV-H), Japan (LdMNPV-J) and the registered strain from North America (LdMNPV-D), were bioassayed in the Inner Mongolia Autonomous Region, People's Republic of China, in 2004, using a modified version of the diet plug method, to determine their pathogenicity and virulence based on the dose- and time-response of second-instar larvae of the Chinese strain of the Asian gypsy moth. Results showed that LdMNPV-H and LdMNPV-D did not differ significantly in dose-response. The LD 50 and LD 95 for LdMNPV-H were 211 and 1414 OBs larva -1 , respectively, while LdMNPV-D had a somewhat lower LD 50 (194 OBs larva -1 ) and a higher LD 95 (1705 OBs larva -1 ). LdMNPV-J was the least pathogenic, with a LD 50 of 940 OBs larva -1 and LD 95 of 11 457 OBs larva -1 . Overall, LdMNPV-H and LdMNPV-D had similar pathogenicity against second-instar larvae of the Chinese strain of the Asian gypsy moth, and were considerably more pathogenic than LdMNPV-J. Time-responses were not significantly different among the three virus strains.

The fate of the larval epidermis in the Desor-larva of Lineus viridis (Pilidiophora, Nemertea) displays a historically constrained functional shift from planktotrophy to lecithotrophy

Abstract: Pilidiophora constitutes a clade of nemerteans characterized by a peculiar larval type, the pilidium. A characteristic of this larva is the transitory epidermis in which the juvenile develops from imaginal discs. The primary function of this larval envelope is assumed to be feeding and dispersal. When juvenile development is complete, the larval epidermis is ruptured and swallowed by the juvenile. According to recent cladistic and molecular analyses of the Nemertea, the intracapsular Desor-larva of the sibling species Lineus viridis and L. ruber is thought to have evolved from a pelagic pilidium. The general course of development has been demonstrated to be similar to that of the pilidium, in which the juvenile forms from imaginal discs under the larval epidermis. The two Lineus species, however, differ in their mode of larval feeding: L. ruber being ootrophic and L. viridis being lecithotrophic. In order to elucidate the transition from the planktotrophic pilidum to lecithotrophic development, I studied the early cleavage and metamorphosis from intracapsular Desor-larva to juvenile stages in L. viridis from the island of Sylt, using light microscopical, electron microscopical, and fluorescent staining methods. Due to the specific cleavage pattern with equally sized 1st quartet animal blastomeres and vegetal blastomeres in L. viridis, the larval epidermis later contains a considerable amount of the yolk reserve. During metamorphosis, the larval epidermis is ingested by the juvenile thus displaying behavior similar to that of the pilidium larva. In contrast to the pilidium, the function of the larval epidermis of the Desor-larva has shifted from feeding and dispersal to direct food supply. Thus, the development of L. viridis is a perfect example for strong historical constraints that prevent ancestral larval structures from being lost.

Risk assessment of non-target effects caused by releasing two exotic phytoseiid mites in Japan: can an indigenous phytoseiid mite become IG prey?

Abstract: Two exotic phytoseiid mites, Neoseiulus cucumeris and Amblyseius swirskii, are commercially available in Japan for the control of thrips and other pest insects. As part of a risk assessment of the non-target effects of releasing these two species, we investigated intraguild predation (IGP) between these exotic phytoseiid mites and an indigenous phytoseiid mite Gynaeseius liturivorus, which is promising as an indigenous natural enemy for the control of thrips in Japan. To understand IGP relations between the exotic and indigenous phytoseiid mites after use of the exotic mites for biological control, we investigated IGP between them in the absence of their shared prey. When an IG prey was offered to an IG predator, both exotic and indigenous females consumed the IG prey at all immature stages (egg, larva, protonymph, deutonymph), especially at its larval stages. The propensity for IGP in a no-choice test was measured by the survival time of IG prey corrected using the survival time of thrips offered to the IG predator. There was no significant difference in the propensity for IGP between N. cucumeris and G. liturivorus, but the propensity was significantly higher in A. swirskii than G. liturivorus. The propensity for IGP in a choice test was measured by the prey choice of the IG predator when a conspecific and a heterospecific larva were offered simultaneously as IG prey. Both exotic females consumed the heterospecific larva only. The indigenous female preferentially consumed the heterospecific larva when the heterospecific larva was N. cucumeris, but consumed the conspecific larva when the heterospecific larva was A. swirskii. We concluded that further investigation would be necessary for the exotic mites' risk assessment, since the propensity for IGP of the two exotic females was similar to or higher than that of the indigenous female in both the no-choice and choice tests.

Morphological and behavioral alterations induced by endocrine disrupters in amphibian tadpoles

Abstract: Developmental toxicity effects of endocrine disrupter chemicals, acephate and cypermethrin were studied in Bufo melanostictus tadpoles. Thirty developing eggs of B. melanostictus were exposed to each concentration (0.01, 0.05, 0.1, 0.5, and 1 µg L−1) of acephate or cypermethrin in the laboratory (temperature: 23 ± 1°C; photoperiod: 11.5–12.5 h). Eggs maintained in conditioned water alone served as controls. After hatching, larvae were fed on boiled spinach until the completion of metamorphosis. In control group, larvae that hatched on 3rd day were heavily pigmented, voracious feeders, and active swimmers; in these tadpoles, hind limb and forelimb-buds emerged on 16th and 24th day and metamorphosis was complete on 32nd day. Eggs exposed to acephate also hatched on 3rd day but larvae exhibited deformities such as, (i) tail distortions, (ii) laterally crooked trunk, (iii) decreased pigmentation, (iv) inactivity, (v) peeling of the skin, and (vi) delay in emergence of limbs and completion of metamorphosis. Cy...

Plasticity in the timing of a major life-history transition and resulting changes in the age structure of populations of the salamander Hynobius retardatus

Abstract: Variation in age and size at life-history transitions is a reflection of the diversifying influence of biotic or abiotic environmental change. Examples abound, but it is not well understood how such environmental changes influence the age structure of a population. I experimentally investigated the effects of water temperature and food type on age and body size at metamorphosis in larvae of the salamander Hynobius retardatus. In individuals grown at a cold temperature (15 °C) or given Chironomidae as prey, the time to metamorphosis was significantly prolonged, and body size at metamorphosis was significantly enlarged, compared with individuals grown at a warmer temperature (20 °C) or fed larvae. I also examined whether larval density (a possible indicator of cannibalism in natural habitats) generated variation in the age structure of natural populations in Hokkaido, Japan, where the climate is subarctic. Natural ponds in Hokkaido may contain larvae that have overwintered for 1 or 2 years, as well as larvae of the current year, and I found that the number of age classes was related to larval density. Although cool water temperatures prolong the larval period and induce later metamorphosis, in natural ponds diet-based enhancement of development translated into a shorter larval duration and earlier metamorphosis. Geographic variation in the frequency of cannibalism resulted in population differences in metamorphic timing in H. retardatus larvae. It is important to understand how environmental effects are ultimately transduced through individual organisms into population-level phenomena, with the population response arising as the summation of individual responses. Without a thorough comprehension of the mechanisms through which population and individual responses to environmental conditions are mediated, we cannot interpret the relationship between population-level and individual-level phenomena. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 100–114.

Responses of toad tadpoles to ammonium nitrate fertilizer and predatory stress: differences between populations on a local scale.

Abstract: Agriculture-related pollution is among the major causes of global amphibian population declines. The multiple stressors to which amphibians are exposed in the field, such as predation pressure, can make agrochemicals far more deadly than when they act in isolation. Even within a small area, diffuse agricultural pollution does not affect all aquatic environments equally, which could account for local differences in amphibian sensitivity to agrochemicals. We examined the combined effects of ammonium nitrate fertilizer (0 to 45.2 mg N-NH þ /L) and predator stress on larval Western spadefoot toad (Pelobates cultripes), using adult caged male marbled newts (Triturus marmoratus) as predators. We compared the interaction between both stressors in tadpoles from two ponds separated by 3 km. No significant mortality was observed (survival > 80% in all cases). Local differences were detected when analyzing larval growth, with a significant interaction between factors for one of the two populations tested (Fornillos de Fermoselle). Although tadpoles exposed to 45.2 mg N-NH þ /L were 7% smaller than controls, the presence of predators from a foreign community resulted in animals 15% larger than those raised without predators after 15 d of experiment. Interestingly, predators from the same community as the tadpoles did not affect larval growth. The length of the tadpoles from a nearby location (Mamoles) was unaffected after exposure to ammonium nitrate and predatory stress. Environ. Toxicol. Chem. 2011;30:1440-1446. # 2011 SETAC

Activities of four enzymes in Galleria mellonella larvae infected with entomopathogenic nematode Heterorhabditis beicherriana n. sp.

Abstract: To investigate the mechanism of Galleria mellonella infected with entomopathogenic nematodes (EPNs), we studied the effects of a new species of EPNs, Heterorhabditis beicherriana n.sp., on the activities of Tyrosinase (TYR), acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione S-transferase (GST) in whole body of G. mellonella. The last instar larvae of G. mellonella (0.18 to 0.20 g/larva) were used as host insects and were randomized into four groups (n = 60 in each group): 0 IJ/larva control group, 20 IJs/larva group, 40 IJs/larva group and 80 IJs/larva group. Infective juveniles (IJs) were injected into each selected G. mellonella larva. At 0, 8, 16, 24, 32 and 40 h post-infection, ten injected larvae were randomly collected from each group, enzymes were extracted, and the enzyme activities of TYR, AChE, CarE and GSTs were assessed following standard methods. We found that the activities of TYR, AChE, CarE and GST were significantly enhanced in a dose-dependent manner in G. mellonella larvae infected with H. beicherriana, which may be the overeactive stress response to the EPNs infection and the overreaction could lead to the death of host insects. Key words: Entomopathogenic nematode, Galleria mellonella, tyrosinase, acetylcholinesterase, carboxylesterase, glutathione S-transferase.

Differential Patterns of Accumulation and Depuration of Dietary Selenium and Vanadium During Metamorphosis in the Gray Treefrog (Hyla versicolor)

Abstract: Selenium (Se) and vanadium (V) are contaminants commonly found in aquatic systems affected by wastes derived from fossil fuels. To examine their effects on a widely distributed species of amphibian, we exposed gray tree frogs (Hyla versicolor) to Se (as SeO2) or V (as NaVO3) in their diet from the early larval period to metamorphosis. Concentrations of Se in Se-enriched food were 1.0 (Se control), 7.5 (Se low), and 32.7 (Se high) μg/g dw. Concentrations of V in V-enriched food were 3.0 (V control), 132.1 (V low), and 485.7 (V high) μg/g dw. Although we observed bioaccumulation of both metals throughout the larval period, no effects on growth, survival, metabolic rate, or lipid content were observed. Se concentrations in tissues did not vary among life stages, neither in Se low nor Se high treatments, such that maximum accumulation had occurred by the mid-larval period. In addition, there was no evidence of depuration of Se in either the Se low or the Se high treatments during metamorphosis. A strikingly different pattern of accumulation and depuration occurred in V-exposed individuals. In treatments V low and V high, maximum body burdens occurred in “premetamorphs” (i.e., animals with developed forelimbs but in which tail resorption had not begun), whereas body burdens in animals having completed metamorphosis were much lower and similar to those in larvae. These results suggest that compared with Se-exposed animals, V-exposed animals were able to depurate a substantial amount of accumulated V during the metamorphic period. In an ecologic context, it appears that amphibians exposed to Se during the larval period may serve as a vector of the metal to terrestrial predators, yet potential transfer of accumulated V to predators would largely be restricted to the aquatic habitat.

The Effect of Root Volatiles on the Orientation Behaviour of Cockchafer Larvae in the Soil

Abstract: The present study investigates the effect of root volatiles on the orientation behaviour of cockchafer larvae Melolontha hippocastani in the soil. Cockchafer larvae are known as severe pests in agriculture and forestry. The present study adresses three relevant aspects of their chemical ecology linked to food choice belowground: Volatile organic compounds (VOCs) of several potential host plant roots and shoots are investigated and analysed by using gas chromatography mass spectrometry (GC-MS). The obtained volatile patterns of damaged roots differ clearly from the undamaged ones. Emitted shoot volatiles differ clearly from the emitted root volatiles. Electrophysiological methods are employed to record sensory reactions of the detached larval antennae to several of the previously identified compounds. Volatile emissions of Quercus sp. are investigated in detail. By using electroantennography (EAG), changes in the receptor potential elicited by odour stimuli are recorded. It turns out that seasonal and maybe also circadian rhythms appear to play an important role in cockchafer larvae antenna physiology. The behavioural response of cockchafer larvae is tested on selected compounds. A dual choice test setup is designed to study the behavioural orientation of the belowground living larvae. Attractive and repellent compounds in host plants are identified. Preparative methods show the antennal lobes (ALs, first central processing unit for olfactory information processing in the insect brain) of 3rd instar of M. hippocastani to contain a high number of glomeruli, which are regarded as the functional subunits of odour discrimination. Therefore, a highly developed odour discrimination ability of the cockchafer larvae is indicated. These findings are, to our knowledge, the first proof that larvae of M. hippocastani are able to perceive volatiles emitted by roots of their host plants Quercus sp. in electrophysiological and behavioural tests.

Extended Parental Care in the Freshwater Shrimp Genus Dugastella Bouvier, 1912 (Decapoda, Atyidae, Paratyinae)

Abstract: D. HUGUET1,4), J. E. GARCÍA MUÑOZ2), J. E. GARCÍA RASO2) and J. A. CUESTA3,5) 1) Département Milieux et Peuplements aquatiques, Muséum national d’Histoire naturelle, 61 rue Buffon, CP 53, F-75253 Paris cedex 05, France 2) Departamento de Biología Animal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, E-29071 Malaga, Spain 3) Instituto de Ciencias Marinas de Andalucía (CSIC), Avenida República Saharaui, 2, E-11519 Puerto Real, Cadiz, Spain