Showing papers on "Larva published in 2015"
01 Jan 2015
TL;DR: The life cycle of lampreys typically begins in streams where fertilized eggs hatch into small, wormlike larvae which burrow into soft stream bottoms where they filter feed on organic matter until the onset of metamorphosis, which begins during the summer months, and is completed by winter or early spring.
Abstract: The life cycle of lampreys typically begins in streams where fertilized eggs hatch into small, wormlike larvae (ammocoetes) which burrow into soft stream bottoms where they filter feed on organic matter until the onset of metamorphosis. The relative importance of habitat variables can change with ammocoete size (and depending on the spatial scale measured), but habitat must provide adequate substrate for burrowing and a regular supply of the suspended organic matter upon which larval lampreys feed. Larval movement occurs significantly more often at higher densities and in warmer temperatures, and typically occurs in a downstream direction at night. Sex ratio of some lamprey species is often related to differences in larval density, with the proportion of males increasing with relative density. Larval mortality is thought to be high in the egg phase, immediately following hatching, and at metamorphosis. The duration of the larval period in the life cycle of lampreys has been found to vary among and within species, but generally ranges from 3 to 7 years. However, analyses of larval growth and duration of larval life have been hampered by the unreliability of age assessment methods for larval lampreys. Metamorphosis begins during the summer months, when water temperatures are the most favorable, and is completed by winter or early spring.
111 citations
TL;DR: It is suggested that low concentrations of road salt can have positive effects on larval growth yet negative effects on juvenile survival, and the importance of testing for effects of contaminants acting through food webs and across multiple life stages as well as the potential for population-level consequences in natural environments.
Abstract: Road salt runoff has potentially large effects on wetland communities, but is typically investigated in short-term laboratory trials. The authors investigated effects of road salt contamination on wood frogs (Rana sylvatica) by combining a field survey with 2 separate experiments. The field survey tested whether wood frog larval traits were associated with road salt contamination in natural wetlands. As conductivity increased, wood frog larvae were less abundant, but those found were larger. In the first experiment of the present study, the authors raised larvae in outdoor artificial ponds under 4 salt concentrations and measured larval vital rates, algal biomass, and zooplankton abundance. Salt significantly increased larval growth, algal biomass, and decreased zooplankton abundance. In the second experiment, the authors raised larvae to metamorphosis in the presence and absence of salt contamination and followed resulting juvenile frogs in terrestrial pens at high and low densities. Exposure to road salt as larvae caused juvenile frogs to have greater mortality in low-density terrestrial environments, possibly because of altered energy allocation, changes in behavior, or reduced immune defenses. The present study suggests that low concentrations of road salt can have positive effects on larval growth yet negative effects on juvenile survival. These results emphasize the importance of testing for effects of contaminants acting through food webs and across multiple life stages as well as the potential for population-level consequences in natural environments.
59 citations
TL;DR: Melanin-based trade-off across metamorphosis provides a new pathway by which effects of larval stressors are carried over to the adult stage and thereby advances the understanding of the still largely enigmatic mechanisms of carryover effects of larvae stressors across meetamorphosis.
Abstract: Summary
Despite the strong impact of ultraviolet (UV) radiation on invertebrates, it is unknown whether it affects immune function across metamorphosis. More generally, the mechanisms on how larval stressors bridge metamorphosis and shape adult fitness in animals with a complex life cycle remain poorly understood.
We studied whether cuticular melanin content is upregulated under UV exposure in the larval stage of the damselfly Coenagrion puella and whether this is traded off across metamorphosis against a key component of the invertebrate immune response, the melanotic encapsulation response, in the adult stage.
Larvae exposed to UV increased the melanin content in their exoskeleton and metamorphosed later and at a smaller mass than animals reared without UV. Across metamorphosis, this was associated with a reduced melanotic encapsulation response, thereby constituting the first proof for a UV-driven impaired immune response in an invertebrate. The demonstrated costs of UV exposure in terms of age and mass at metamorphosis and reduced adult immune response likely translate into reduced adult fitness.
Path analysis indicated that the immunosuppressive property of larval UV exposure was not mediated by age and mass at metamorphosis, but instead that the adult immune response was traded off against larval cuticular melanin investment.
Melanin-based trade-off across metamorphosis provides a new pathway by which effects of larval stressors are carried over to the adult stage and thereby advances our understanding of the still largely enigmatic mechanisms of carryover effects of larval stressors across metamorphosis. Given the mechanistic basis, this carryover effect of larval UV exposure on adult immune function is expected to be general and may constitute a widespread and important cost of UV exposure in invertebrates.
45 citations
TL;DR: It is demonstrated that microsatellite markers are a highly powerful tool for studying amphibian populations on an individual basis and the ability to individually track amphibian tadpoles throughout metamorphosis until adulthood will be of substantial value for future studies on amphibian population ecology and evolution.
Abstract: Reliably marking larvae and reidentifying them after metamorphosis is a challenge that has hampered studies on recruitment, dispersal, migration and survivorship of amphibians for a long time, as conventional tags are not reliably retained through metamorphosis. Molecular methods allow unique genetic fingerprints to be established for individuals. Although microsatellite markers have successfully been applied in mark–recapture studies on several animal species, they have never been previously used in amphibians to follow individuals across different life cycle stages. Here, we evaluate microsatellites for genetic across-stages mark–recapture studies in amphibians and test the suitability of available software packages for genotype matching. We sampled tadpoles of the dendrobatid frog Allobates femoralis, which we introduced on a river island in the Nature Reserve ‘Les Nouragues’ in French Guiana. In two subsequent recapture sessions, we searched for surviving juveniles and adults, respectively. All individuals were genotyped at 14 highly variable microsatellite loci, which yielded unique genetic fingerprints for all individuals. We found large differences in the identification success of the programs tested. The pairwise-relatedness-based approach, conducted with the programs kingroup or ML-Relate, performed best with our data set. Matching ventral patterns of juveniles and adult individuals acted as a control for the reliability of the genetic identification. Our results demonstrate that microsatellite markers are a highly powerful tool for studying amphibian populations on an individual basis. The ability to individually track amphibian tadpoles throughout metamorphosis until adulthood will be of substantial value for future studies on amphibian population ecology and evolution.
40 citations
TL;DR: The evolution of the intracapsular Schmidt’s larva involved the loss of the typical feeding structures of the planktotrophic pilidium and a precocious formation of the imaginal discs, as also observed in other pelagic lecithotrophic forms.
Abstract: The life cycle of many animals includes a larval stage, which has diversified into an astonishing variety of ecological strategies. The Nemertea is a group of spiralians that exhibits a broad diversity of larval forms, including the iconic pilidium. A pelagic planktotrophic pilidium is the ancestral form in the Pilidiophora, but several lineages exhibit deviations of this condition, mostly as a transition to pelagic lecithotrophy. The most extreme case occurs, however, in the Pilidiophoran Lineus ruber, which exhibits an adelphophagic intracapsular pilidium, the so-called Schmidt’s larva. We combined confocal laser scanning microscopy and gene expression studies to characterize the development and metamorphosis of the Schmidt’s larva of L. ruber. The larva forms after gastrulation, and comprises a thin epidermis, a proboscis rudiment and two pairs of imaginal discs from which the juvenile will develop. The cells internalized during gastrulation form a blind gut and the blastopore gives rise to the mouth of the larva and juvenile. The Schmidt’s larva eats other siblings that occupy the same egg capsule, accumulating nutrients for the juvenile. A gradual metamorphosis involves the differentiation of the juvenile cell types from the imaginal discs and the shedding of the larval epidermis. The expression of evolutionarily conserved anterior (foxQ2, six3/6, gsc, otx), endomesodermal (foxA, GATA456-a, twi-a) and posterior (evx, cdx) markers demonstrate that the juvenile retains the molecular patterning of the Schmidt’s larva. After metamorphosis, the juveniles stay over 20 days within the egg masses, until they are fully mature and hatch. The evolution of the intracapsular Schmidt’s larva involved the loss of the typical feeding structures of the planktotrophic pilidium and a precocious formation of the imaginal discs, as also observed in other pelagic lecithotrophic forms. However, no special adaptations are observed related to adelphophagy. As in planktotrophic pilidium, the molecular mechanism patterning the juvenile is only active in the imaginal discs and not during the early development of the larva, suggesting two separate molecular programs during nemertean embryogenesis. Our results illuminate the diversification of larval forms in the Pilidiophora and Nemertea, and thus on the developmental mechanisms underlying metazoan larval evolution.
38 citations
Journal Article•
TL;DR: Though they may be a nuisance, soldier flies do not have functional mouthparts, so they do not bite and are not known to transmit any diseases, and this species has the beneficial effect of rendering the breeding media less suitable for the production of houseflies.
Abstract: Black Soldier Flies (Hermetia illucens) are common in the western hemisphere as inhabitants of nutrient rich ecosystems such as manur piles and compost heaps. They pass through a five stage lifecycle i.e. larva, prepupae, pupa, and adult. The adults, 15 to 20 mm in length) have no mouth parts and therefore do not bite nor do they sting and are not known to transmit any diseases. The larva, are voraceous consumers and have been shown to be an effective maneur management tool. In this study a Scanning Electron Microscope is used to analyze and document the anatomy of both the larval and adult for of this insect. Changes in each step of their life cycle were noted as the insect grew and matures.
36 citations
TL;DR: Examination of variation in size at metamorphosis in the Neotropical red-eyed treefrog, Agalychnis callidryas, affects post-metamorphic growth, foraging, and behavior in the lab as well as growth and survival in the field suggests that size-specific differences in physiology and behavior influence these trends.
Abstract: Most animals have complex life histories, composed of a series of ecologically distinct stages, and the transitions between stages are often plastic. Anurans are models for research on complex life cycles. Many species exhibit plastic timing of and size at metamorphosis, due to both environmental constraints on larval growth and development and adaptive plastic responses to environmental variation. Models predicting optimal timing of metamorphosis balance cost/benefit ratios across stages, assuming that size affects growth and mortality rates in each stage. Much research has documented such effects in the larval period, but we lack an equal understanding of juvenile growth and mortality. Here, we examine how variation in size at metamorphosis in the Neotropical red-eyed treefrog, Agalychnis callidryas, affects post-metamorphic growth, foraging, and behavior in the lab as well as growth and survival in the field. Surprisingly, many individuals lost mass for weeks after metamorphosis. In the lab, larger metamorphs lost more mass following metamorphosis, ate similar amounts, had lower food conversion efficiencies, and grew more slowly after mass loss ceased than did smaller ones. In field cages larger metamorphs were more likely to survive than smaller ones; just one froglet died in the lab. Our data suggest that size-specific differences in physiology and behavior influence these trends. Comparing across species and studies, large size at metamorphosis generally confers higher survival; size effects on growth rates vary substantially among species, in both magnitude and direction, but may be stronger in the tropics.
33 citations
TL;DR: It is inferred that the toxicity of AZA extends beyond its known actions in molting processes to redox homeostasis.
Abstract: The insecticidal effects, specifically, changes in hemolymph total protein and malondialdehyde (MDA) levels, and antioxidant enzyme activities of azadirachtin (AZA) given to the wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae via force feeding were investigated. Bioassays showed that the LD50 and LD99 (lethal dose) values of AZA were 2.1 and 4.6 μg/larva, respectively. Experimental analyses were performed with five doses of AZA (0.5, 1, 1.5, 2, and 3 μg/larva). Total protein level in larval hemolymph increased at all AZA doses at 24 h whereas a considerable decrease was observed at 2 and 3 μg/larva doses, and only an increase displayed at 1.5 μg/larva at 72 h. The level of MDA increased at 2 and 3 μg/larva doses at 24 h compared with controls. This trend was also observed at 1.5, 2, and 3 μg/larva doses at 72 h and MDA levels were lower when compared with those of 24 h at all doses except for 1.5 μg/larva dose. Catalase activity decreased at 1, 1.5, and 2 μg/larva doses at 24 h whereas increased at all doses except for 0.5 μg/larva at 72 h compared with controls. AZA led to a decline in superoxide dismutase activity at all experimental doses at 24 and 72 h except for 3 μg/larva doses at 72 h. An increase in glutathione-S-transferase (GST) activity was evident at all AZA doses at 24 h. AZA displayed 68% decline in GST activity at 72 h post treatments when compared to 24 h. Consequently, We infer that the toxicity of AZA extends beyond its known actions in molting processes to redox homeostasis.
32 citations
TL;DR: While larval food restriction profoundly affected body size in larvae and frogs, time to metamorphosis was highly constrained, which suggests that the physiology and development of this ephemeral pond-breeding amphibian is adapted for rapid meetamorphosis despite large potential variation in nutrient availability.
Abstract: The extent to which interactions between environmental stressors and phenotypic variation during larval life stages impose carry-over effects on adult phenotypes in wildlife are not clear. Using semi-natural mesocosms, we examined how chronically low food availability and size-specific phenotypes in larval amphibians interact and carry over to influence frog growth, resource allocation, endocrine activity and survival. We tagged three cohorts of larvae that differed in body size and developmental stage at 3 weeks after hatching, and tracked them through 10 weeks after metamorphosis in high and low food conditions. We found that growth and development rates during the early tadpole stage not only affected metamorphic rates, but also shaped resource allocation and stress responsiveness in frogs: the slowest growing larvae from low-food mesocosms exhibited a suppressed glucocorticoid response to a handling stressor; reduced growth rate and fat storage as frogs. We also show for the first time that larval developmental trajectories varied with sex, where females developed faster than males especially in food-restricted conditions. Last, while larval food restriction profoundly affected body size in larvae and frogs, time to metamorphosis was highly constrained, which suggests that the physiology and development of this ephemeral pond-breeding amphibian is adapted for rapid metamorphosis despite large potential variation in nutrient availability. Taken together, these results suggest that larval phenotypic variation significantly influences multiple dimensions of post-metamorphic physiology and resource allocation, which likely affect overall performance. J. Exp. Zool. 323A: 191–201, 2015. © 2015 Wiley Periodicals, Inc.
29 citations
01 Apr 2015
TL;DR: This review assesses a naturally occurring plant matrix and pure compounds of the Piper species, which have been shown to be active against Aedes aegypti, which is one of the most important mosquito-borne viral diseases in the world.
Abstract: The mosquito, Aedes aegypti, is the principal vector of the viruses responsible for dengue and dengue hemorrhagic fevers. The mosquito is widespread throughout tropical and sub-tropical regions; its prevalence makes dengue one of the most important mosquito-borne viral diseases in the world occurring annually in more than 100 endemic countries. Because blood is essential to their development cycle, the Aedes species maintains a close association with humans and their dwellings. Fittingly, the most widely adopted strategy to decrease the incidence of these diseases is the control of the mosquito larvae population. The emergence of insecticide-resistant mosquitoes has amplified the interest in finding natural products effective against Aedes aegypti adults, as well as larvae. Plantderived compounds have played an important role in the discovery of new active entities for vector management as they are safer and have lower toxicity to humans in comparison to conventional insecticides. This review assesses a naturally occurring plant matrix and pure compounds of the Piper species, which have been shown to be active against Aedes aegypti.
28 citations
TL;DR: Results show that brain morphology is a developmentally plastic trait that is responsive to ecologically relevant natural and anthropogenic factors and whether these effects on brain morphology are linked to performance or fitness is unknown.
Abstract: Naturally occurring environmental factors shape developmental trajectories to produce variable phenotypes. Such developmental phenotypic plasticity can have important effects on fitness, and has been demonstrated for numerous behavioral and morphological traits. However, surprisingly few studies have examined developmental plasticity of the nervous system in response to naturally occurring environmental variation, despite accumulating evidence for neuroplasticity in a variety of organisms. Here, we asked whether the brain is developmentally plastic by exposing larval amphibians to natural and anthropogenic factors. Leopard frog tadpoles were exposed to predator cues, reduced food availability, or sublethal concentrations of the pesticide chlorpyrifos in semi-natural enclosures. Mass, growth, survival, activity, larval period, external morphology, brain mass, and brain morphology were measured in tadpoles and after metamorphosis. Tadpoles in the experimental treatments had lower masses than controls, although developmental rates and survival were similar. Tadpoles exposed to predator cues or a high dose of chlorpyrifos had altered body shapes compared to controls. In addition, brains from tadpoles exposed to predator cues or a low dose of chlorpyrifos were narrower and shorter in several dimensions compared to control tadpoles and tadpoles with low food availability. Interestingly, the changes in brain morphology present at the tadpole stage did not persist in the metamorphs. Our results show that brain morphology is a developmentally plastic trait that is responsive to ecologically relevant natural and anthropogenic factors. Whether these effects on brain morphology are linked to performance or fitness is unknown.
TL;DR: This study focused on the development of larvae with peculiar external morphology that could be linked to a described species established from adult specimens and the use of DNA barcoding was possible to link the stages observed to a known species.
Abstract: The life cycles of many marine taxa are still unknown, especially those species with indirect development and long-lived larval stages. Life cycles of cnidarians are relatively well known for most groups except Ceriantharia. This taxon presents taxonomic problems stemming from the lack of association between planktonic larval forms, often described as distinct species, with the corresponding adult benthic stages. Our study focused on the development of larvae with peculiar external morphology that could be linked to a described species established from adult specimens. Through cultivation of these larvae to juveniles with adult-like morphology and also with the use of DNA barcoding, it was possible to link the stages observed to a known species, Isarachnanthus nocturnus. Based on life span of the larva in the plankton (63–118 days), the larvae could potentially drift for about 2000–4000 km along the coast. Because rearing larvae in the laboratory may be complex and time-consuming and also because morphological data may have limited distinguishing power for specific identification of larvae collected in the field, we suggest and discuss the use of DNA barcoding as a tool to connect life stages of species of cerianthids and invertebrates in general.
TL;DR: Results from this study may bolster efforts to control WNV in urban landscapes by exploring water quality conditions of Culex larval habitats that produce adult mosquitoes.
Abstract: Population growth and urbanization have increased the potential habitats, and consequently the abundance of Culex quinquefasciatus, the southern house mosquito, a vector of West Nile Virus in urban areas. Water quality is critical in larval habitat distribution and in providing microbial food resources for larvae. A mesocosm experiment was designed to demonstrate which specific components of water chemistry are conducive to larval Culex mosquitoes. Dose-response relationships between larval development and NO3 , NH4 , and PO4 concentrations in stream water were developed through this experiment to describe the isolated effects of each nutrient on pre-adult development. The emergence pattern of Culex mosquitoes was found to be strongly related to certain nutrients, and results showed that breeding sites with higher PO4 or NO3 concentrations had higher larval survival rates. High NO3 concentrations favor the development of male mosquitoes and suppress the development of female mosquitoes, but those adult females that do emerge develop faster in containers with high NO3 levels compared to the reference group. The addition of PO4 in the absence of nitrogen sources to the larval habitat slowed larval development, however, it took fewer days for larvae to reach the pupal stage in containers with combinations of NO3 and PO4 or NH4 and PO4 nutrients. Results from this study may bolster efforts to control WNV in urban landscapes by exploring water quality conditions of Culex larval habitats that produce adult mosquitoes.
TL;DR: The results of the present study imply that the selection of resistant animals could be used as a strategic tool for tick control in production systems, reducing infestation levels on cattle and environment.
TL;DR: The most important thing that should be done by farmers is to avoid the rearing of H. rugulosa tadpoles under food × density conditions greatly reducing larval survival, growth and developmental synchrony rather than to rear them under conditions substantially increasing the costs due to the increased payments for food and space.
TL;DR: Mature larva and pupa of Adosomus (s. str.) roridus (Pallas, 1781) (Curculionidae: Lixinae:Cleonini) are described and compared with ten other taxa of Cleonini with known larvae.
Abstract: Mature larva and pupa of Adosomus (s. str.) roridus (Pallas, 1781) (Curculionidae: Lixinae: Cleonini) are described and compared with ten other taxa of Cleonini with known larvae. This weevil is an oligophagous species on the Asteraceae family. From our observations in Slovakia, we found active adults from April to September in dry sunny places within extensively used or fallow vineyards and in ruderal vegetation with host plants. The weevil is a root borer--larvae, pupae and fresh adults were collected from the root necks and roots of Common Tansy (Tanacetum vulgare L.) and rarely from Mugwort (Artemisia vulgaris L.). Each plant was usually occupied by one larva, or more rarely with two or three larvae. The new generation of adult individuals appeared from early summer to autumn. Both larvae and some of the adults overwinter, which is quite unique within Cleonini.
TL;DR: The results from this study will be helpful to develop the strategy to incorporate Vip 3A containing crops in an integrated pest management programme.
Abstract: The assessment of sub-lethal effects is important to interpret the overall insecticide efficacy in controlling insect pest populations. In addition to the lethal effect, sub-lethal effects may also occur in exposed insects. Vegetative insecticidal proteins (Vips) have shown a broad spectrum of insecticidal activity against many insect pest species. In this study the sub-lethal effects of the Bacillus thuringiensis vegetative insecticidal toxin Vip3A on the development and reproduction of Heliothis virescens F. and Plutella xylostella L. were evaluated in the laboratory. The results indicated that the sub-lethal concentration of Vip3A increased the duration of the larval and pupal stages as compared with the control treatment for both species. The percent pupation and percent adult emergence were significantly lower for Vip3A-treated insects. The proportion of pairs that produced eggs and the longevity of adults were not significantly different between treatments. H. virescens and P. xylostella treated with Vip3A showed an 11 and 17 % decrease in their intrinsic rate of increase (rm) respectively compared with untreated insects. The results from this study will be helpful to develop the strategy to incorporate Vip 3A containing crops in an integrated pest management programme.
TL;DR: Third-stage larvae of the nematode Serpinema trispinosum were collected from the midgut of four of five species of adult damselflies (Zygoptera) from a non-irrigated restored semipermanent wetland located in Stillwater, Oklahoma, USA, and this is the first record of larvae of S. trispinoum from damselfly hosts.
Abstract: Third-stage larvae of the nematode Serpinema trispinosum (Leidy, 1852) were collected from the midgut of four of five species of adult damselflies (Zygoptera) from a non-irrigated restored semipermanent wetland located in Stillwater, Oklahoma, USA. Of the four infected damselfly species, prevalence and mean abundance was highest for the southern spreadwing, Lestes disjunctus australis Walker (10%, 0.2 ± 0.8) and lowest for the familiar bluet, Enallagma civile (Hagen) (2.5%, 0.04 ± 0.3); whereas mean intensities were lowest for the citrine forktail, Ischnura hastata (Say) (1.5 ± 0.5) and the eastern forktail, Ischnura verticalis (Say) (1.0 ± 0). This is the first record of larvae of S. trispinosum from damselflies. Serpinema trispinosum adults have been reported from 18 species of North and Central American freshwater turtles, whereas microcrustaceans such as copepods serve as intermediate hosts and snails, fish and amphibians serve as paratenic hosts in this nematode's life cycle. However, dietary studies of the 18 species of freshwater turtles reported as definitive hosts for S. trispinosum indicate that aquatic insects including damselflies are more commonly reported in turtle diets than are fish or amphibians. Additionally, unlike snails and amphibians, larval damselflies predominantly feed on microcrustaceans, and our observation of S. trispinosum infecting damselflies may reflect the importance of these insects as paratenic hosts. In the present study, we provide new host information and measurements for third-stage larvae of S. trispinosum from damselfly hosts along with measurements for adult male and female S. trispinosum from turtle hosts from Oklahoma, USA.
TL;DR: Outdoor mesocosm experiment to examine how intraspecific larval density may affect larval performance and oviposition habitat selection in H. savignyi found that gravid H.savignyi females reduce future intrapecific competition for their progeny by choosing to oviposit in mesocOSms with no, or lo...
Abstract: Amphibians breeding in temporary pools may experience strong intraspecific density-dependent effects in the form of larval competition and oviposition site selection. These potential effects are untested for the tree frog, Hyla savignyi, an anuran species of conservation concern in Israel. We conducted an outdoor mesocosm experiment to examine how intraspecific larval density may affect larval performance and oviposition habitat selection in H. savignyi. We added ecologically relevant densities of 0, 10, or 40 early-stage tadpoles into mesocosms (plastic tubs) containing 20 L of water. Each density was replicated with four tubs. Time to and size at metamorphosis were not significantly affected by initial H. savignyi density. However, strong intraspecific competitive effects were observed in the form of reduced size at metamorphosis at the high density. We also found that gravid H. savignyi females reduce future intraspecific competition for their progeny by choosing to oviposit in mesocosms with no, or lo...
TL;DR: Exposure to Batrachochytrium dendrobatidis did not influence larval development, terrestrial growth, or survival, and exposure to malathion appears to not have altered the effects of B. d endrobatidis exposure in a biologically significant way.
Abstract: Effects of pathogens on host life-history characteristics can be influenced by changes in the immune system that occur during development as well as by environmental factors that negatively affect immune system function. Amphibians worldwide are experiencing population declines from chytridiomycosis caused by the fungal pathogen Batrachochytrium dendrobatidis. Disease outbreaks can be influenced by timing of exposure to B. dendrobatidis and by abiotic factors, such as pesticides, that could influence susceptibility. To examine the effects of larval pesticide exposure and timing of B. dendrobatidis exposure during development, we exposed Cope’s Gray Treefrogs (Hyla chrysoscelis) to the insecticide malathion throughout larval development and to B. dendrobatidis at 1 or 3 wk posthatching, or after metamorphosis. We reared tadpoles through metamorphosis and then for 28 d in the terrestrial environment to examine treatment effects on larval survival, time to metamorphosis, and mass at metamorphosis,...
TL;DR: The aim was to study the preferences for pupation substrates of Notofenusa surosa larvae, leaf-miners of Nothofagus obliqua, in relation to soil properties and to determine the probability of individuals to choose a particular option depending on its preferences and substrates’ properties.
Abstract: The choices made by insects at different stages of their life cycle are critical for the individual and progeny success. In the case of leaf-miners, during larval development they are not able to make choices until the emergence from the leaf, after which the larva falls to the ground and begins pupation. According to needs, preferences and soil properties, the larva could achieve a suitable substrate for the development of the pupa. Our aim was to study the preferences for pupation substrates of Notofenusa surosa larvae, leaf-miners of Nothofagus obliqua, in relation to soil properties. We selected different types of substrates (including volcanic ash) and conducted paired preference tests. The substrate was considered chosen when the larva selected it and formed the pupa (response variable). According to data obtained, several models were performed to determine the probability of individuals to choose a particular option depending on its preferences and substrates’ properties. These larvae are able to discriminate the different options offered and choose their pupation substrate according to the percentage of organic matter.
01 Jan 2015
TL;DR: Frogs, toads and tadpoles are significant fractions of the ecosystem for their parts for predating on various life stages of insects including mosquitoes to fulfil vector's control task, but frogs or toads cannot be used alone as an independent intervention for vector borne disease control in surroundings and more research is needed to use them effectively for mosquito control.
Abstract: Dengue is now the most important mosquitoes borne viral disease of humans in terms of both morbidity and mortality, and a lack of an effectual vaccine or treatment for the disease makes control of its vectors as a consideration of primary importance. Mosquito eggs can survive drought conditions while harboring pathogens and perpetuate diseases throughout breeding season. Biological control of mosquitoes using vertebrates mostly birds, mammals, reptiles, fishes and insect predators has been highlighted, but, sufficient scientific evidences through usage of amphibians as predators are few. This article explores the use of frogs, toads and tadpoles (immature frogs) as egg, larva and adult predators for control of dengue disease carrying Aedes vector mosquitoes. Frogs, toads and tadpoles are significant fractions of the ecosystem for their parts for predating on various life stages of insects including mosquitoes to fulfil vector's control task. Since the eggs of mosquitoes are minute, and in some species such as Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) (Diptera: Culicidae), only individual eggs are laid (as opposed to egg rafts in some other mosquito species), so the propensity of egg predation by predators is not apparent. Adult frogs and toads consume adult mosquitoes; however, tadpoles commonly consume mosquito larvae. Even when tadpoles are not interested to eat mosquito larvae, and as these grow up to become toads or frogs, can eat adult mosquitoes. With respect to available information from various studies, one frog or toad can consume about a hundred mosquitoes in a night. Still, the associations of different prey and predator relationships in the environment to assess the feasibility on the use of a species as biocontrol agent for vector control exist. However, frogs or toads cannot be used alone as an independent intervention for vector borne disease control in surroundings and more research is needed to use them effectively for mosquito control. Consequently, before deciding to raise frogs or toads make sure to understand state’s laws on collecting wildlife, and prior to making a wild species as pet, it is also best to read and check with the legality of having a native species a pet as some amphibian types are very fragile and poisonous.
TL;DR: Insight is given into the environments that can select for different plasticities of C. elegans dauer larva arrest phenotypes, suggesting that different combinations of environmental cues can selectfor the diversity of phenotypically plastic responses seen in C. nematode.
Abstract: Organisms can end up in unfavourable conditions and to survive this they have evolved various strategies. Some organisms, including nematodes, survive unfavourable conditions by undergoing developmental arrest. The model nematode Caenorhabditis elegans has a developmental choice between two larval forms, and it chooses to develop into the arrested dauer larva form in unfavourable conditions (specifically, a lack of food and high population density, indicated by the concentration of a pheromone). Wild C. elegans isolates vary extensively in their dauer larva arrest phenotypes, and this prompts the question of what selective pressures maintain such phenotypic diversity? To investigate this we grew C. elegans in four different environments, consisting of different combinations of cues that can induce dauer larva development: two combinations of food concentration (high and low) in the presence or absence of a dauer larva-inducing pheromone. Five generations of artificial selection of dauer larvae resulted in an overall increase in dauer larva formation in most selection regimes. The presence of pheromone in the environment selected for twice the number of dauer larvae, compared with environments not containing pheromone. Further, only a high food concentration environment containing pheromone increased the plasticity of dauer larva formation. These evolutionary responses also affected the timing of the worms’ reproduction. Overall, these results give an insight into the environments that can select for different plasticities of C. elegans dauer larva arrest phenotypes, suggesting that different combinations of environmental cues can select for the diversity of phenotypically plastic responses seen in C. elegans.
TL;DR: It is suggested that Chinese brown frog tadpoles prefer cool a temperature and high food level for longer larval periods to capitalize on the opportunity of entering the terrestrial habitat with a larger body size.
Abstract: Larval amphibians are especially likely to encounter variation in temperature and resource availability because they live in a variety of aquatic habitats. In this study, plasticity in growth rates, survivorship, age and size at metamorphosis were examined in the Chinese brown frog ( Rana chensinensis ) under different combinations of rearing temperature and food level. Tadpoles reared at 23.2°C had larger mass at metamorphosis and a longer larval period than tadpoles reared at 25.3 and 28.1°C. High food level shortened the larval period and produced a larger size at metamorphosis. The interaction of rearing temperature and food level significantly influenced the growth and survival of Chinese brown frog tadpoles. At a low food level, tadpoles reared at 23.2°C displayed faster growth than tadpoles reared at the higher temperatures, and tadpoles had lower survival at 28.1°C than at the lower temperatures. Therefore, global warming or local manipulations of the environment could limit growth and development of Chinese brown frog tadpoles, resulting in low survival, but food availability may mediate effects of temperature. We suggest that Chinese brown frog tadpoles prefer cool a temperature and high food level for longer larval periods to capitalize on the opportunity of entering the terrestrial habitat with a larger body size.
01 Jan 2015
TL;DR: By any criterion, Insecta (as a subtaxon of Hexapoda) is the most successful taxon on the planet, and they are found in almost every ecosystem, forming the major component of animal biomass in most.
Abstract: By any criterion, Insecta (as a subtaxon of Hexapoda) is the most successful taxon on the planet (see Chaps. 2 and 3 for the inclusion of the various subtaxa in Hexapoda versus Insecta). The number of described insect species nears one million, and they are found in almost every ecosystem, forming the major component of animal biomass in most. Within the insects, the largest group comprises the holometabolous insects. In the holometabolous insects, the outcome of embryogenesis is a larva, which normally has a relatively simple morphology, with no wings or reproductive organs and either no legs or rudimentary legs. The larva goes through several molts, pupates, and undergoes metamorphosis within the pupa, finally hatching from the pupa as an adult with limbs, wings, and reproductive organs. Most of the remaining species belong to the hemimetabolous insects, a paraphyletic group wherein the outcome of embryogenesis is a nymph, superficially similar to an adult, but with no wings or reproductive organs. The nymph undergoes several molts, each being slightly larger and closer in shape and size to the adult, with the final adult molt developing wings and reproductive organs, without going through a pupal stage or undergoing a dramatic metamorphosis. Finally, a small group of insects undergoes ametabolous development, wherein there is no terminal adult stage, and the animal continues to molt even after developing reproductive organs. These insects are all primitively wingless.
TL;DR: Although tadpoles do not feed on mosquito larvae, there may be other direct or indirect inter-specific interactions that adversely impact the development of larvae in shared habitats with tadpole.
Abstract: Tadpoles are often considered to be predators of mosquito larvae and are therefore beneficial for the control of certain disease vectors. Nevertheless, only a few species have actually been recorded to prey on mosquito larvae. The mosquito larvae predation rates of tadpoles of three common Thai anuran species (Bufo melanostictus, Kaloula pulchra and Hylarana raniceps) were experimentally tested. Tadpoles in varying developmental stages were used to assess a size/age effect on the predation rate. In addition, different instars of Culex quinquefasciatus were used in order to assess a prey size effect on the predation rates. All three species failed to show any evidence of mosquito larvae predation. Neither small nor large tadpoles fed on mosquito larvae. Prey size also did not affect predation. Although tadpoles do not feed on mosquito larvae, there may be other direct or indirect inter-specific interactions that adversely impact the development of larvae in shared habitats with tadpoles.
TL;DR: The narrower salinity tolerance of larvae compared to adults and the ability of zoea I to survive at least some days at 5 psu may be related with an export larval strategy.
TL;DR: Tests showed that larvae sourced from different estuaries did not vary significantly in their metamorphic response to short-term temperature manipulation and epinephrine-induced metamorphosis, and repeatability in outcomes was confirmed.
Abstract: A need to improve larval rearing techniques led to the development of protocols for catecholamine-induced settlement of flat oyster, Ostrea angasi , larvae. To further refine these techniques and optimize settlement percentages, the influence of salinity or temperature on development of O. angasi larvae was assessed using epinephrine-induced metamorphosis. Larvae were reared between salinities of 15–35 and temperatures between 14.5 and 31°C. The greatest percentage survival, growth, development occurred when larvae were reared between 26 and 29°C and between salinities of 30 and 35. Larvae reared outside this salinity and temperature range exhibited reduced growth, survival and/or delayed development. Short-term (1 h) reduction in larval rearing temperature from 26°C to 23.5°C significantly increased larval metamorphosis without affecting larval survival. Short-term (1 h) increase in larval rearing temperature from 26°C to 29 and 31°C decreased larval survival and metamorphosis. To ensure repeatability in outcomes, tests showed that larvae sourced from different estuaries did not vary significantly in their metamorphic response to short-term temperature manipulation and epinephrine-induced metamorphosis.
TL;DR: This work describes the complete development in two lineiform species that are common to the northeast Pacific coast, Micrura wilsoni and Lineus sp.
Abstract: Unique to the phylum Nemertea, the pilidium is an unmistakable planktonic larva found in one group of nemerteans, the Pilidiophora. Inside the pilidium, the juvenile develops from a series of epidermal invaginations in the larval body, called imaginal discs. The discs grow and fuse around the larval gut over the course of weeks to months in the plankton. Once complete, the juvenile breaks free from the larval body in a catastrophic metamorphosis, and often devours the larva as its first meal. One third of nemertean species are expected to produce a pilidium, but the larvae are known for very few species; development from fertilization to metamorphosis has been described in only one species, Micrura alaskensis. Known pilidia include both planktotrophic and lecithotrophic forms, and otherwise exhibit great morphological diversity. Here, we describe the complete development in two lineiform species that are common to the northeast Pacific coast, Micrura wilsoni and Lineus sp. "red." Both species possess typical, cap-shaped planktotrophic pilidia, and the order of emergence of imaginal discs is similar to that which is described in M. alaskensis. The pilidium of Lineus sp. "red" resembles pilidia of several other species, such as Lineus flavescens, and potentially characterizes a pilidiophoran clade. M. wilsoni has relatively transparent oocytes and a pilidium with what appears to be a unique pattern of pigmentation. The adults of both species are more commonly observed in intertidal zones than their larvae are in the plankton.