Showing papers on "Larva published in 2014"
TL;DR: The use of Anopheles stephensi mosquitoes and the rodent malaria to investigate whether quality of larval habitat influenced vectorial capacity of adult mosquitoes led to a relative reduction invectorial capacity in the low food treatment of 70%.
Abstract: Adult traits of holometabolous insects such as reproduction and survival can be shaped by conditions experienced during larval development. These “carry-over” effects influence not only individual life history and fitness, but can also impact interactions between insect hosts and parasites. Despite this, the implications of larval conditions for the transmission of human, wildlife and plant diseases that are vectored by insects remain poorly understood. We used Anopheles stephensi mosquitoes and the rodent malaria, Plasmodium yoelii yoelii, to investigate whether quality of larval habitat influenced vectorial capacity of adult mosquitoes. Larvae were reared under two dietary conditions; one group received a diet commonly used for colony maintenance (0.3 mg/individual/day of Tetrafin fish food) while the other group received a reduced food diet (0.1 mg/individual/day). Upon emergence, adults were provided an infectious blood feed. We assessed the effects of diet on a range of larval and adult traits including larval development times and survival, number of emerging adults, adult body size and survival, gonotrophic cycle length, and mating success. We also estimated the effects of larval diet on parasite infection rates and growth kinetics within the adult mosquitoes. Larval dietary regime affected larval survival and development, as well as size, reproductive success and survival of adult mosquitoes. Larval diet also affected the intensity of initial Plasmodium infection (oocyst stage) and parasite replication, but without differences in overall infection prevalence at either the oocyst or sporozoite stage. Together, the combined effects led to a relative reduction in vectorial capacity (a measure of the transmission potential of a mosquito population) in the low food treatment of 70%. This study highlights the need to consider environmental variation at the larval stages to better understand transmission dynamics and control of vector-borne diseases.
112 citations
TL;DR: Early life stages of mytilid mussels are largely tolerant to a broad range of [O2 ] reflective of their environment, indicating that the role of pH variability should be recognized as an important feature in coastal oceans that has the capacity to modulate the effects of ocean acidification on biological responses.
Abstract: Natural variation and changing climate in coastal oceans subject meroplanktonic organisms to broad ranges of pH and oxygen ([O2]) levels. In controlled-laboratory experiments we explored the interactive effects of pH, [O2], and semidiurnal pH fluctuations on the survivorship, development, and size of early life stages of two mytilid mussels, Mytilus californianus and M. galloprovincialis. Survivorship of larvae was unaffected by low pH, low [O2], or semidiurnal fluctuations for both mytilid species. Low pH (<7.6) resulted in delayed transition from the trochophore to veliger stage, but this effect of low pH was absent when incorporating semidiurnal fluctuations in both species. Also at low pH, larval shells were smaller and had greater variance; this effect was absent when semidiurnal fluctuations of 0.3 units were incorporated at low pH for M. galloprovincialis but not for M. californianus. Low [O2] in combination with low pH had no effect on larval development and size, indicating that early life stages of mytilid mussels are largely tolerant to a broad range of [O2] reflective of their environment (80–260 lmol kg � 1 ). The role of pH variability should be recognized as an important feature in coastal oceans that has the capacity to modulate the effects of ocean acidification on biological responses.
106 citations
TL;DR: Both food web studies and contaminant management and mitigation strategies need to consider how metamorphosis affects the movement of materials between habitats and ecosystems, with special regard for aquatic-terrestrial linkages.
Abstract: Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development, and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and fractionation of chemical tracers used to establish contaminant biomagnification in food webs, but no framework exists for predicting and managing these effects. We analyzed data from 39 studies of 68 analytes (stable isotopes and contaminants), and found that metamorphosis effects varied greatly. δ15N, widely used to estimate relative trophic position in biomagnification studies, was enriched by ∼1‰ during metamorphosis, while δ13C used to estimate diet, was similar in larvae and adults. Metals and polycyclic aromatic hydrocarbons (PAHs) were predominantly lost during metamorphosis leading to ∼2 to 125-fold higher larval concentrations and higher exposure risks fo...
106 citations
TL;DR: It is proposed that insect postembryonic development is initially independent of JH, and only later, when larvae gain competence to enter meetamorphosis, JH signaling becomes necessary to prevent precocious metamorphosis and to optimize growth.
92 citations
TL;DR: Death during metamorphosis may be a key mechanism explaining how stream metal contamination can impact terrestrial communities by reducing aquatic insect emergence, particularly in contaminated streams.
Abstract: The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to explain this pattern is that insects exposed to elevated metal in their larval stages have a reduced ability to successfully complete metamorphosis. To test this hypothesis we exposed late-instar larvae of the mayfly, Centroptilum triangulifer, to an aqueous Zn gradient (32–476 μg/L) in the laboratory. After 6 days of exposure, when metamorphosis began, larval survival was unaffected by zinc. However, Zn reduced wingpad development at concentrations above 139 μg/L. In contrast, emergence of subimagos and imagos tended to decline with any increase in Zn. At Zn concentrations below 105 μg/L (hardness-adjusted aquatic life criterion), survival between the wingpad and...
71 citations
TL;DR: Although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage.
Abstract: Metamorphosis is common in animals, yet the genetic associations between life cycle stages are poorly understood Given the radical changes that occur at metamorphosis, selection may differ before and after metamorphosis, and the extent that genetic associations between pre- and post-metamorphic traits constrain evolutionary change is a subject of considerable interest In some instances, metamorphosis may allow the genetic decoupling of life cycle stages, whereas in others, metamorphosis could allow complementary responses to selection across the life cycle Using a diallel breeding design, we measured viability at four ontogenetic stages (embryo, larval, juvenile and adult viability), in the ascidian Ciona intestinalis and examined the orientation of additive genetic variation with respect to the metamorphic boundary We found support for one eigenvector of G: (gobsmax ), which contrasted larval viability against embryo viability and juvenile viability Target matrix rotation confirmed that while gobsmax shows genetic associations can extend beyond metamorphosis, there is still considerable scope for decoupled phenotypic evolution Therefore, although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage
49 citations
TL;DR: It is found that tea plants infested by E. obliqua caterpillars for 24 h were more attractive to both virgin male and female E. ObliquA adults than were intact, uninfested tea plants; moreover, mated femaleE.
Abstract: Herbivore-induced plant volatiles have been reported to play a role in the host-searching behavior of herbivores. However, next to nothing is known about the effect of volatiles emitted from tea plants infested by Ectropis obliqua larvae on the behavior of conspecific adults. Here, we found that tea plants infested by E. obliqua caterpillars for 24 h were more attractive to both virgin male and female E. obliqua adults than were intact, uninfested tea plants; moreover, mated female E. obliqua moths were more attracted by infested tea plants and preferentially oviposited on these plants, whereas male moths were repelled by infested plants once they had mated. Volatile analysis revealed that the herbivore infestation dramatically increased the emission of volatiles. Among these volatiles, 17 compounds elicited antennal responses from both male and female virginal moths. Using a Y-tube olfactometer, we found that 3 of the 17 chemicals, benzyl alcohol, (Z)-3-hexenyl hexanoate, and (Z)-3-hexenal, were attractive, but two compounds, linalool and benzyl nitril, were repellent to virgin male and female moths. One chemical, (Z)-3-hexenyl acetate, was attractive only to virgin males. Mated females were attracted by three compounds, (Z)-3-hexenyl hexanoate, (Z)-3-hexenyl acetate, and (Z)-3-hexenal; whereas mated males were repelled by (Z)-3-hexenol. The findings provide new insights into the interaction between tea plants and the herbivores, and may help scientists develop new measures with which to control E. obliqua.
42 citations
TL;DR: Analyzing the experimental data with one-way analysis of variance showed that the single hexaflumuron application had significant effects on C. septempunctata, suggesting potential risks to beneficial arthropods.
Abstract: Studying the toxic risk of pesticide exposure to ladybird beetles is important from an agronomical and ecological perspective since larval and adult ladybirds are dominant predators of herbivorous pest insects (e.g., aphids) in various crops in China. This article mainly deals with the long-term effects of a single application of the insect growth regulator hexaflumuron on Coccinella septempunctata. A 72-h and a 33-day toxicity test with hexaflumuron (single application) were performed, starting with the second instar larvae of C. septempunctata. Exposure doses in the long-term experiment were based on the estimated 72-h acute LR50 (application rate causing 50 % mortality) value of 304 g active ingredient (a.i.) ha−1 for second instar larvae of C. septempunctata. The long-term test used five hexaflumuron doses as treatment levels (1/50, 1/100, 1/200, 1/400, and 1/800 of the 72-h acute LR50), as well as a solvent control and blank control treatment. The measurement endpoints used to calculate no observed effect application rates (NOERs) included development time, hatching, pupation, adult emergence, survival, and number of eggs produced. Analyzing the experimental data with one-way analysis of variance showed that the single hexaflumuron application had significant effects on C. septempunctata endpoints in the 33-day test, including effects on development duration (NOER 1.52 g a.i. ha−1), hatching (NOER 3.04 g a.i. ha−1), pupation (NOER 3.04 g a.i. ha−1), and survival (NOER 1.52 g a.i. ha−1). These NOERs are lower than the reported maximum field application rate of hexaflumuron (135 g a.i. ha−1) in cotton cultivation, suggesting potential risks to beneficial arthropods.
37 citations
TL;DR: A detailed staging scheme of rudiment development in the purple urchin using soft structures of the rudiment and the primordia of these juvenile skeletal elements is presented, and evidence is provided that this scheme is robust and applicable across a range of temperature and feeding regimes.
Abstract: Background
The purple sea urchin, Strongylocentrotus purpuratus, has long been the focus of developmental and ecological studies, and its recently-sequenced genome has spawned a diversity of functional genomics approaches. S. purpuratus has an indirect developmental mode with a pluteus larva that transforms after 1–3 months in the plankton into a juvenile urchin. Compared to insects and frogs, mechanisms underlying the correspondingly dramatic metamorphosis in sea urchins remain poorly understood. In order to take advantage of modern techniques to further our understanding of juvenile morphogenesis, organ formation, metamorphosis and the evolution of the pentameral sea urchin body plan, it is critical to assess developmental progression and rate during the late larval phase. This requires a staging scheme that describes developmental landmarks that can quickly and consistently be used to identify the stage of individual living larvae, and can be tracked during the final two weeks of larval development, as the juvenile is forming.
34 citations
Journal Article•
TL;DR: S. thermophilum as well as the nematode's symbiotic bacteria applied separately have the potential to be developed as biocontrol agents for key lepidopteran insect pests.
Abstract: Under laboratory conditions, the biocontrol potential of Steinernema thermophilum was tested against eggs and larval stages of two important lepidopteran insect pests, Helicoverpa armigera and Spodoptera litura (polyphagous pests), as well as Galleria mellonella (used as a model host). In terms of host susceptibility of lepidopteran larvae to S. thermophilum, based on the LC50 36 hr after treatment, G. mellonella (LC50 = 16.28 IJ/larva) was found to be more susceptible than S. litura (LC50 = 85 IJ/larva), whereas neither host was found to be significantly different from H. armigera (LC50 = 54.68 IJ/larva). In addition to virulence to the larval stages, ovicidal activity up to 84% was observed at 200 IJ/50 and 100 eggs of H. armigera and S. litura, respectively. To our knowledge this is the first report of entomopathogenic nematode pathogenicity to lepidopteran eggs. Production of infective juvenile (IJ) nematodes/insect larva was also measured and found to be positively correlated with rate of IJ for H. armigera (r = 0.990), S. litura (r = 0.892), as well as G. mellonella (r = 0.834). Both Phase I and Phase II of symbiotic bacteria Xenorhabdus indica were tested separately against neonates of H. armigera and S. litura by feeding assays and found to be virulent to the target pests; phase variation did not affect the level of virulence. Thus S. thermophilum as well as the nematode’s symbiotic bacteria applied separately have the potential to be developed as biocontrol agents for key lepidopteran pests.
33 citations
TL;DR: Under these conditions, any soluble cues emanating from a biofilm do not affect settlement behavior, and after 24 h close to 100 % of larva in the two accessible biofilm treatments had metamorphosed and <15 % in treatments that included a bio film under a clean screen and no biofilm at all, strongly suggesting that soluble cues for settlement were not produced by the biofilms over the longer time period.
Abstract: Larvae of many sessile marine invertebrates settle in response to surface microbial communities (biofilms), but the effects of soluble compounds from biofilms in affecting larval behavior prior to settlement, attachment, and metamorphosis have been little studied. This question was addressed by videotaping the behavior of competent larvae of the serpulid, Hydroides elegans, above settlement-inducing biofilms. Adult worms were collected in Pearl Harbor, Hawaii, USA in November 2012 and spawned almost immediately. Six-day old larvae were placed in five replicated treatments in small cups: (1) with a natural biofilm; (2) with a natural biofilm on an 8-µm screen, 1 mm above the bottom of a clean cup; (3) with a natural biofilm beneath a clean screen; (4) in a clean cup; and (5) in a clean cup with a clean screen. Using the videotapes, larval swimming speeds and trajectories were quantified within 5 min of the larvae being placed in a treatment. Only larvae that touched a biofilm, i.e., in treatments (1) and (2), slowed their swimming speed and increased the amount of time spent crawling rather than swimming. This shows that under these conditions, any soluble cues emanating from a biofilm do not affect settlement behavior. Furthermore, after 24 h close to 100 % of larva in the two accessible biofilm treatments had metamorphosed and <15 % in treatments that included a biofilm under a clean screen and no biofilm at all, strongly suggesting that soluble cues for settlement were not produced by the biofilms over the longer time period.
Journal Article•
TL;DR: Ecological study on aquatic insects can provide information about ecology of insects in an area for any decision making and play an important role for transmission of human and animal diseases.
Abstract: Background: Aquatic insects are the major groups of arthropods that spend some parts of their life cycle in the water. These insects play an important role for transmission of some human and animal diseases. There is few information about the aquatic insects fauna of Iran. Methods: To study the aquatic insects fauna, adult, nymphal and larval collections were carried out from different habitats using the standard technique in Zayandeh Roud River, Isfahan Province,central Iran, during summer 2011. Results: In total, 741 speimens of aquatic insects were collected and morphologically identi fied. They include 7 families and 12 genera representing 2 Orders. The order of Diptera (92.31%) and Coleoptera (7.69%). The families Culicidae, Syrphidae and Chironomidae from Diptera order, Gyrinidae, Dytisc idae, Haliplidae, Hydrophilidae from Coleoptera order were identified. Conclusion: Some aquatic insects play an important role for transmission of human and animal diseases. These insects also are important for biological control. Therefore ecological stu dy on aquatic insects can provide information about ecology of insects in an area for any decision making.
TL;DR: Results from the experiment suggest that chronic effects of strobilurin fungicides on development, growth, and mortality to B. cognatus are apparent at environmentally relevant concentrations.
Abstract: Agricultural fungicide application has increased tenfold since 2005 in the United States. Active ingredients and formulations of strobilurin fungicides at environmentally relevant concentrations cause mortality to larval and metamorph amphibians; however, little is known about chronic exposure effects in amphibians. We exposed larval amphibians (Bufo cognatus) throughout metamorphosis to the common fungicide formulations Headline®, Stratego®, Quilt®, and a control to determine effects on development and growth. Formulations were tested at 1.7, 50, and 400 μg/L of the active strobilurin ingredient for Headline®, Stratego®, and Quilt®, respectively. Fungicide exposure did not affect body mass or snout–vent length at metamorphosis. However, exposure to Headline® at 1.7 μg/L increased the development rate of tadpoles by approximately 5 days compared to the control, an effect not observed for Stratego® and Quilt®. Stratego® also caused approximately 35 % cumulative mortality. Results from the experiment suggest that chronic effects of strobilurin fungicides on development, growth, and mortality to B. cognatus are apparent at environmentally relevant concentrations.
TL;DR: Results show that early developmental stages (nauplii and cope podids) are generally more tolerant than adults, contrast with the widely accepted generalization that larval forms are more sensitive to physical stressors than adults.
Abstract: Author(s): Tangwancharoen, S; Burton, RS | Abstract: Because of their complex life histories, different life stages of many marine invertebrates may be exposed to varying environmental challenges. Ultimately, the life stage that is least tolerant of its environment will determine the species' abundance and distribution. The intertidal copepod Tigriopus californicus lives in high intertidal pools along the Pacific coast of North America. Unlike most other invertebrates, the different life stages of T. californicus all share the same tidepool habitat. To determine physiological tolerances of various life history stages of this species, we examined responses to acute heat stress in nauplii, copepodids, and adults from 6 populations along a latitudinal gradient. Results show that early developmental stages (nauplii and copepodids) are generally more tolerant than adults. Our results contrast with the widely accepted generalization that larval forms are more sensitive to physical stressors than adults. As previously observed in adults, nauplii and copepodids from southern populations survive higher temperatures than those from northern populations. Acute heat stress was found to delay development but did not affect adult size. We hypothesize that variation in the thermal tolerance of early life stages among intertidal species reflects ecological differences in larval habitats: where larvae remain in the intertidal zone and experience the same high temperatures as adults, selection will favor high larval thermal tolerance, while in species with planktonic larvae, the buffered temperature regime of the water column might relax such selection, and thermal tolerance will be highest in the more exposed intertidal adults.
TL;DR: Organogenesis and changes of body proportions in burbot larvae were more rapid and complex during the yolk sac and preflexion phase of development as larvae developed most of their sensorial, feeding, respiratory and swimming systems and after notochord flexion, when most morphological changes were related to the progressive transformation from pelagic larva to demersal larva/juvenile.
Abstract: This study analyzed the morphological development and allometric growth patterns of Lota lota L. (burbot) larvae reared under controlled laboratory conditions. From hatching to day 50, twenty larvae were sampled each [between 1 and 14 days post-hatch (DPH)] or every second day (between 14 and 50 DPH) and measured under a stereoscopic microscope using analytic software. Based on the external morphology, the different stages during early development of burbot were identified: yolk sac larva 0–8 DPH [3.92–4.37 mm total length (TL)]; preflexion larva 9–26 DPH (4.57–12.06 mm TL); flexion larva (between notochord degradation and its replacement with rays) 28–34 DPH (14.00–16.34 mm TL) and postflexion larva/juvenile 36–50 DPH (18.20–29.27 mm TL). Allometric growth patterns of some parameters (e.g., total length, head length, body length, tail length, head depth, body depth, eye diameter) were modeled by a power function and described by the growth coefficient. Organogenesis and changes of body proportions in burbot larvae were more rapid and complex during the yolk sac and preflexion phase of development as larvae developed most of their sensorial, feeding, respiratory and swimming systems and after notochord flexion, when most morphological changes were related to the progressive transformation from pelagic larva to demersal larva/juvenile.
TL;DR: These adrenergic agonists can be used as non-toxic and promising inducers of larval metamorphosis in this species, and to improve M. coruscus larval production for aquaculture.
TL;DR: An exceptionally preserved larval stage of the short great appendage arthropod (SGA) Leanchoilia illecebrosa from the early Cambrian Chengjiang biota of China is described, demonstrating that niche differentiation during ontogeny was developed in this species of megacheiran.
Abstract: Modern arthropods present niche differentiation between larvae and adult stages. Here, Liu et al. describe a larval fossil of Leanchoilia illecebrosa, an early Cambrian arthropod from China, and show a feeding appendage, unknown in adults, that suggests that niche differentiation originated in the early Cambrian.
TL;DR: It is found that both adult females and larvae actively choose their hosts and that the larval preference toward the hosts is related to the females’ preference in both herbivore species.
Abstract: It is expected that females preferentially oviposit on plant hosts that allow for optimal larval performance. However, this expectation contradicts empirical evidence where adults do not always choose the best host for their descendants. Recent evidence suggests that females’ host selection depends on the number of potential hosts. Females from oligophagous species seem to be able to choose an appropriate host in terms of larval performance, whereas in polyphagous species, adult oviposition preference is not related with larval performance. This suggests that larvae in polyphagous species could be taking a more active role in host selection than their mothers. Here, we evaluated the oviposition preference and the larval preference and performance of two polyphagous species of economic importance, Copitarsia decolora (Guenee) (Lepidoptera: Noctuidae: Cuculliinae) and Peridroma saucia (Hubner) (Lepidoptera: Noctuidae: Noctuinae), on eight species of cultivated plants. In laboratory and greenhouse choice assays, we tested adult preference for oviposition and larval preference at 1 and 24 h. Larval performance was measured in terms of survival to adulthood, length of larval period, and pupal weight. We found that both adult females and larvae actively choose their hosts and that the larval preference toward the hosts is related to the females’ preference in both herbivore species. However, the females and larvae did not preferentially select the host with the best larval performance, indicating that larval performance is not related to female or larval preference and that other selective pressures are influencing the choice of the host plant in these two species.
TL;DR: It is suggested that future investigations include more species with a range of life history traits and also consider host ecology, particularly if conspicuous anti-parasite behaviours are more likely in amphibian species that experience a relatively low risk of predation.
Abstract: Along with immune defences, many animals exhibit effective anti-parasite behaviours such as parasite avoidance and removal that influence their susceptibility to infection. Host ecology and life history influence investment into comparatively fixed defences such as innate immunity but may affect the strength of anti-parasite behaviours as well. We investigated activity levels in five different species of larval amphibian with varying life histories and ecology in control, novel food stimulus, and trematode parasite (Echinoparyphium sp.) threat conditions. There was a significant interaction of species and treatment given that American toad (Bufo americanus), wood frog (Lithobates sylvaticus), and bullfrog (Lithobates catesbeianus) tadpoles generally increased their activity when parasite infectious stages were present while grey tree frogs (Hyla versicolor) and northern leopard frogs (Lithobates pipiens) did not, even though activity was negatively related to infection. In addition, there was considerable variation among species in their susceptibility to parasitism, with infection prevalence ranging from 17% in bullfrog tadpoles to 70% in wood frogs. However, amphibian life history (larval and adult traits) was not related to parasitism or level of anti-parasite behaviour at the species level. Consequently, we suggest that future investigations include more species with a range of life history traits and also consider host ecology, particularly if conspicuous anti-parasite behaviours are more likely in amphibian species that experience a relatively low risk of predation.
TL;DR: The present study suggests that the composition of the parasite community is associated with the host feeding habits because 18/21 of the recorded species are trophically transmitted.
Abstract: A total of 21 helminth species were recovered from 52 specimens of red snapper, Lutjanus campechanus, captured in the reef Santiaguillo, Parque Nacional Sistema Arrecifal Veracruzano, State of Veracruz, in the Southern Gulf of Mexico. These helminths included 9 trematodes (7 adults and 2 metacercariae), 4 nematodes (3 adults and 1 larva), 4 acanthocephalans (1 adult and 3 juvenile), 2 cestodes (both larvae), and 2 monogeneans. Sixteen of the 21 species are new host records; 7 are common species with a prevalence >40% and mean intensity >4.1. The monogenean Euryhaliotrema tubocirrus was the most-prevalent parasite with a prevalence of 78.8%, followed by the intestinal plerocercoids of Tetraphyllidea with a prevalence of 59.6%. The richness (S = 21), and diversity (Shannon index H = 2.17) in the component community, as well as in the infracommunity level (S = 5.1 ± 2.2, H = 0.92 ± 0.4), was similar to those found in other marine fish of temperate and tropical latitudes. The present study suggests...
TL;DR: This study is the first report on the effects of temperature, density and protein level in food on the rearing of the North African green Frog Pelophylax saharicus and suggests new techniques for aquaculture.
TL;DR: It is concluded that even in the absence of genetic variation between colony members, differences in experience levels of brood care may affect performance of sanitary brood care in social insects.
Abstract: Repeated pathogen exposure is a common threat in colonies of social insects, posing selection pressures on colony members to respond with improved disease-defense performance. We here tested whether experience gained by repeated tending of low-level fungus-exposed (Metarhizium robertsii) larvae may alter the performance of sanitary brood care in the clonal ant, Platythyrea punctata. We trained ants individually over nine consecutive trials to either sham-treated or fungus-exposed larvae. We then compared the larval grooming behavior of naive and trained ants and measured how effectively they removed infectious fungal conidiospores from the fungus-exposed larvae. We found that the ants changed the duration of larval grooming in response to both, larval treatment and their level of experience: (1) sham-treated larvae received longer grooming than the fungus-exposed larvae and (2) trained ants performed less self-grooming but longer larval grooming than naive ants, which was true for both, ants trained to fungus-exposed and also to sham-treated larvae. Ants that groomed the fungus-exposed larvae for longer periods removed a higher number of fungal conidiospores from the surface of the fungus-exposed larvae. As experienced ants performed longer larval grooming, they were more effective in fungal removal, thus making them better caretakers under pathogen attack of the colony. By studying this clonal ant, we can thus conclude that even in the absence of genetic variation between colony members, differences in experience levels of brood care may affect performance of sanitary brood care in social insects.
TL;DR: Seed coat extracts of N. nucifera is effective against A. stephensi larvae because it is non-toxic to non-target organisms and environment-friendly, however, the non- target populations were entirely non-responsive to extracts under study.
Abstract: Background and objective : Control of mosquito vector is of paramount significance to reduce disease incidences as proper vaccines against mosquito borne diseases are yet to develop. Standard amalgamation of cost effective, target specific and bio-degradable insecticides is necessary owing to vector resistance, an evolutionary phenomenon and intoxication of nature through indiscriminate use of chemical insecticides. The present study projected larvicidal activities of the crude and solvent extracts of Nelumbo nucifera seed coats against the malarial vector Anopheles stephensi under laboratory conditions.
Methods : Crude extracts of N. nucifera seed coats were scrutinized for larvicidal activity against 1 st to 4 th instars larvae of A. stephensi . Solvent extractions of the same material fractions were carried out by means of petroleum ether, ethyl acetate and water. Dose dependent mortality assay was performed by graded concentrations (from 60 ppm to 180 ppm) of the solvent extracts. Quantifications of LC 50 and LC 90 values were consummated through log-probit analyses. ANOVA analyses were performed for statistical justifications of the larvicidal property. Impacts of the extracts on a non-target water fauna were evaluated under laboratory conditions.
Result: The highest mortality was recorded in 0.5% concentration of crude extracts after 72 hours of post exposure. Ethyl acetate extract was found to be the most potent larvicidal agent exerting efficient larvicidal activity amongst all the three solvent extracts. Following introduction of ethyl acetate extracts, 1 st and 2 nd instars larvae exhibited 100 per cent mortality within 72 hours of post-exposure. The mortality rates for 3 rd and 4 th instars were 96 and 72 per cent respectively with the same observation period. The rate of mortality (Y) was found to be positively correlated with the concentration (X) through regression analyses. ANOVA analyses established the statistical significance of the larvicidal activity of the seed coat extractives. However, the non-target populations were entirely non-responsive to extracts under study.
Conclusion: Seed coat extracts of N. nucifera is effective against A. stephensi larvae . It is non-toxic to non-target organisms and environment-friendly.
TL;DR: The results suggest that the direct consumption of larvaldetritus can support the production of adults in larval habitats that lack allochthonous detritus inputs or where such organic inputs are insufficient.
Abstract: The utilization of detritus sources by mosquito larvae during development may significantly affect adult life history traits and mosquito population growth. Many studies have shown invertebrate carcasses to be an important detritus source in larval habitats, but little is known regarding how invertebrate carcasses are utilized by mosquito larvae. We conducted two studies to investigate the rate of detritus consumption and its effect on larval development and life history traits. Overall, we found that Aedes aegypti and Aedes albopictus larvae rapidly consumed larval detritus, while pupal detritus was consumed at a significantly slower rate. We also found that the consumption of larval detritus significantly increased larval survivorship and decreased male development time but did not significantly influence female development time or pupal cephalothorax length for either sex. Our results suggest that the direct consumption of larval detritus can support the production of adults in larval habitats that lack allochthonous detritus inputs or where such organic inputs are insufficient. These studies indicate that different forms of invertebrate detritus are utilized in distinct ways by mosquito larvae, and therefore different forms of invertebrate detritus may have distinct effects on larval development and adult life history traits.
TL;DR: This work identifies a difference in metamorphic gene expression that is associated with neoteny, and thus provides insights into the relationship between metamorphics and neotenic development.
Abstract: Derived members of the endoparasitic order Strepsiptera have acquired an extreme form of sexual dimorphism whereby males undergo metamorphosis and exist as free-living adults while females remain larviform, reaching sexual maturity within their hosts. Expression of the transcription factor, broad (br) has been shown to be required for pupal development in insects in which both sexes progress through metamorphosis. A surge of br expression appears in the last larval instar, as the epidermis begins pupal development. Here we ask if br is also up-regulated in the last larval instar of male Xenos vesparum Rossi (Stylopidae), and whether such expression is lost in neotenic larviform females. We clone three isoforms of br from X. vesparum (Xv’br), and show that they share greatest similarity to the Z1, Z3 and Z4 isoforms of other insect species. By monitoring Xv’br expression throughout development, we detect elevated levels of total br expression and the Xv’Z1, Xv’Z3, and Xv’Z4 isoforms in the last larval instar of males, but not females. By focusing on Xv’br expression in individual samples, we show that the levels of Xv’BTB and Xv’Z3 in the last larval instar of males are bimodal, with some males expressing 3X greater levels of Xv’br than fourth instar femlaes. Taken together, these data suggest that neoteny (and endoparasitism) in females of Strepsiptera Stylopidia could be linked to the suppression of pupal determination. Our work identifies a difference in metamorphic gene expression that is associated with neoteny, and thus provides insights into the relationship between metamorphic and neotenic development.
TL;DR: Limited support is provided to the hypothesis that pesticides can alter the response of tadpoles to isolates of Bd and that the insecticide carbaryl can alter developmental decisions.
Abstract: Pesticides are detectable in most aquatic habitats and have the potential to alter host-pathogen interactions. The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has been associated with amphibian declines around the world. However, Bd-associated declines are more prominent in some areas, despite nearly global distribution of Bd, suggesting other factors contribute to disease outbreaks. In a laboratory study, the authors examined the effects of 6 different isolates of Bd in the presence or absence of a pesticide (the insecticide carbaryl or the fungicide copper sulfate) to recently hatched Cope's gray treefrog (Hyla chrysoscelis) tadpoles reared through metamorphosis. The authors found the presence or absence of pesticides differentially altered the mass at metamorphosis of tadpoles exposed to different Bd isolates, suggesting that isolate could influence metamorphosis but not in ways expected based on origin of the isolate. Pesticide exposure had the strongest impact on metamorphosis of all treatment combinations. Whereas copper sulfate exposure reduced the length of the larval period, carbaryl exposure had apparent positive effects by increasing mass at metamorphosis and lengthening larval period, which adds to evidence that carbaryl can stimulate development in counterintuitive ways. The present study provides limited support to the hypothesis that pesticides can alter the response of tadpoles to isolates of Bd and that the insecticide carbaryl can alter developmental decisions.
TL;DR: It was concluded that timing of meetingamorphosis and size at metamorphosis were highly affected by pond duration, and density regulation, acting on the tadpole stage, may be present in the population but was of less short-term importance than abiotic factors.
Abstract: The present study in a controlled laboratory setting provided important insights into both the degree of plasticity and the proximal environmental cues operating in the response of green toad tadpoles to pond drying, food level. It was concluded that timing of metamorphosis and size at metamorphosis were highly affected by pond duration. The effects of pond desiccation are reflected by shorter developmental duration and smaller size at metamorphosis as a result of increased crowding in the shallow tanks than tadpoles in the deep tanks. Bufo viridis raised on high food supplements grew faster than those raised on low food in low or high population density. In the tanks with decreased water and food levels, the tadpoles accelerate development and metamorphose earlier than tadpoles in higher food and water levels. The obtained data revealed that tadpoles grew faster under conditions of high population density than low one in either high or low food levels. Actual density had limited but significant effects on tadpole size and development. It also suggested that density regulation, acting on the tadpole stage, may be present in the population but was of less short-term importance than abiotic factors. Environmentally induced variation in developmental rates translated to changes in relative hind leg length. Hind leg length plasticity was positively correlated with growth rate plasticity. Finally, documenting the recent results of this study, B. viridis breed in temporary ponds and exhibited plasticity in developmental duration and growth rate in response to a change in water level.
TL;DR: The results suggest that this haemolymph feeding behavior could play a role in malaria mosquito life history and could provide a novel mechanism for horizontal transmission of pathogens and other micro-organisms between hosts.
Abstract: Adult female mosquitoes need blood to develop their eggs and both sexes use nectar and honeydew as carbohydrate resources for flight, survival and to enhance reproduction. However, there are also a few reports in the literature of mosquitoes feeding on haemolymph of soft-bodied insects such as caterpillars. The frequency and significance of this entomophagous behavior is not well understood, but is thought to be a vestige of ancestral feeding behavior or an opportunistic behavior that has evolved over time. In our current paper we investigated the extent to which the malaria mosquito, Anopheles stephensi, is attracted to, and can successfully feed on, larvae of two common moth species, Manduca sexta and Heliothis subflexa. Using y-tube olfactometer assays we found that female An. stephensi readily flew upwind to and landed on the caterpillars of both moth species. The nature of the volatile cues used in host location remains unclear but respirometer studies suggest a possible role of CO2. Laboratory cage assays further showed that the female mosquitoes were able to actively feed on moth larvae and gain sufficient nutritional benefit to influence survival. The extent to which such an opportunistic behavior occurs in the field has yet to be explored but our results suggest that this haemolymph feeding behavior could play a role in malaria mosquito life history and could provide a novel mechanism for horizontal transmission of pathogens and other micro-organisms between hosts.
TL;DR: Larval cues from both species generally reduced larval attraction and pupariation on food, which was generally—but not always—low, and rarely reflected larval response.
Abstract: Insects use chemosensory cues to feed and mate. In Drosophila, the effect of pheromones has been extensively investigated in adults, but rarely in larvae. The colonization of natural food sources by Drosophila buzzatii and Drosophila simulans species may depend on species-specific chemical cues left in the food by larvae and adults. We identified such chemicals in both species and measured their influence on larval food preference and puparation behaviour. We also tested compounds that varied between these species: (i) two larval volatile compounds: hydroxy-3-butanone-2 and phenol (predominant in D. simulans and D. buzzatii, respectively), and (ii) adult cuticular hydrocarbons (CHs). Drosophila buzzatii larvae were rapidly attracted to non-CH adult conspecific cues, whereas D. simulans larvae were strongly repulsed by CHs of the two species and also by phenol. Larval cues from both species generally reduced larval attraction and pupariation on food, which was generally--but not always--low, and rarely reflected larval response. As these larval and adult pheromones specifically influence larval food search and the choice of a pupariation site, they may greatly affect the dispersion and survival of Drosophila species in nature.
TL;DR: The egg is similar to previously described eggs of other Sarcophagidae but differs in the configuration of the micropyle, and in the first-instar larva, the oral ridges are much more developed than has been described for other species.
Abstract: Flies in the family Sarcophagidae incubate their eggs and are known to be ovoviviparous (i.e., ovolarviparous), but a laboratory-maintained colony of Blaesoxipha plinthopyga (Wiedemann) deposited clutches of viable eggs over 10 generations. A description of the egg and first-instar larva of this species is provided along with genetic data (genome size and cytochrome oxidase I sequences). The egg is similar to previously described eggs of other Sarcophagidae but differs in the configuration of the micropyle. In the first-instar larva, the oral ridges are much more developed than has been described for other species. B. plinthopyga has forensic importance, and the present descriptive information is critical for proper case management.