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PubMed2003

Lipid peroxidation and antioxidant defence status during larval development and metamorphosis of giant prawn, Macrobrachium rosenbergii.

In the present communication we studied the involvement of reactive oxygen species and alteration in antioxidant defence status during larval development and metamorphosis of giant prawn, Macrobrachium rosenbergii. Overall results indicate that there was a decline in endogenous lipid peroxidation level during larval development. Activity of superoxide dismutase was the lowest in early larval stages (Zoea-I and II) and thereafter increased in V and VI stages, followed by a decrease in the subsequent larval stages. Catalase and glutathione peroxidase did not exhibit specific pattern of changes during development. Reduced glutathione content exhibited an incremental increase during larval progression until metamorphosis. Ascorbic acid content of the larval tissue remained unaltered during development but a sharp fall was marked in its content in the post-larvae. Hence it is concluded that early larvae face high oxidative stress as evident from the high content of thiobarbituric acid reactive substances. This may be due to direct exposure of larvae to ambient oxygen of the water as well as their low antioxidant potential. However, during development with the augmentation in antioxidant reserve of the larval tissues a diminution in the oxidative stress was recorded. Thus it is presumed that antioxidant defences play an important role in providing protection to the developing larvae from oxidative assault during larval progression and metamorphosis.

Animals↗
PubMed1992

Duration of larval development of Simulium yahense (Diptera: Simuliidae) under natural conditions.

The duration of Simulium yahense Vajime & Dunbar larval development on a dam spillway in Harbel, Liberia, was observed to make accurate decisions regarding the frequency of larvicide treatments against this onchocerciasis vector. Larval development required a minimum of 10-12 d from eclosion to first pupation. Initial larvicidal treatment for S. yahense control would require a treatment cycle of 7 d. Once suppression of adult and larval populations is achieved, a 9-12-9-12 day treatment cycle could be adopted.

Animals↗
PubMed2002

DAF-9, a cytochrome P450 regulating C. elegans larval development and adult longevity.

The daf-9 gene functions to integrate transforming growth factor-beta and insulin-like signaling pathways to regulate Caenorhabditis elegans larval development. Mutations in daf-9 result in transient dauer-like larval arrest, abnormal reproductive development, molting defects and increased adult longevity. The phenotype is sterol-dependent, and dependent on the activity of DAF-12, a nuclear hormone receptor. Genetic tests show that daf-9 is upstream of daf-12 in the genetic pathways for larval development and adult longevity. daf-9 encodes a cytochrome P450 related to those involved in biosynthesis of steroid hormones in mammals. We propose that it specifies a step in the biosynthetic pathway for a DAF-12 ligand, which might be a steroid. The surprising cellular specificity of daf-9 expression (predominantly in two sensory neurons) supports a previously unrecognized role for these cells in neuroendocrine control of larval development, reproduction and life span.

Amino Acid Sequence↗
PubMed2004

Efficacy of benzimidazole anthelmintics in goats and sheep in the Philippines using a larval development assay.

The negative effects of nematodes in small ruminants can be reduced by use of dewormers but their effectiveness is increasingly limited by the emergence of anthelmintic resistance. The efficacy of benzimidazole (BZ) anthelmintics in the Philippines was estimated by an in vitro larval development assay using worm eggs recovered from faeces collected from goats and sheep. Two hundred and eighteen farms were selected to represent areas of the country with high goat and sheep populations and the full range of farm sizes, from smallholders with just a few animals to commercial and institutional farms with several hundred. Initial surveys of worm control advisers indicated that BZs have been in continuous widespread use for up to 20 years with little use of other chemical groups. A larval development assay (LDA: DrenchRite) was modified for use with BZs alone to allow up to five samples to be analysed on a single microtitre plate. The assay was validated by comparison with the faecal egg count reduction test (FECRT). The dominant nematode genera were Haemonchus and Trichostrongylus with small numbers of Oesophagostomum. The range of BZ efficacy estimated from the LDA results was 0-100% and the distribution of efficacy levels was continuous, with mean efficacy of 82 and 64% for goats and sheep, respectively. There were significant associations between efficacy and parameters measured to characterize the sampled farms: size of animal management group, FEC of sample, recent importation of stock and no access to common grazing were all correlated with decreased efficacy. Likewise, low efficacy was associated with reported frequency and number of years that BZ drenches had been used. The LDA was found to be highly suited to estimate efficacy in nematode populations from small farms where performance of a FECRT for even one chemical would be impractical. Using a larval development assay, we have demonstrated a wide efficacy range for BZs against nematodes from all sizes of goat and sheep farms in the tropics.

Animal Husbandry↗
PubMed1980

Levels of the RNA polymerases during the early larval development of Artemia.

Artemia nauplii contain three forms of RNA polymerase. RNA polymerases I and II have the common pattern of alpha-amanitin sensitivity of the eukaryotic enzymes, but RNA polymerase III is insensitive to high concentrations of the drug. The determination of the levels of the RNA polymerases during early larval development is affected by the increase of proteolytic activity during this stage, which produces the inactivation of RNA polymerases I and III in vitro. Protease B has been identified to be the enzyme responsible for the inactivation of RNA polymerase I. The culture conditions of Artemia larvae also affect the levels of the RNA polymerases. The maintenance of the larvae in the absence of food produces a decrease of RNA polymerases I and III several hours after hatching. In contrast, fed nauplii contain almost stable levels of the three forms of RNA polymerases during the studied period of larval development. The decrease of the levels of RNA polymerases I and III in starved nauplii could be the molecular mechanism responsible for the drop in RNA synthesis observed during the larval development in cultures of nauplii in the absence of an external source of food.

Amanitins↗
PubMed1990

Joint larval development of Cystocaulus ocreatus/Muellerius capillaris and C. ocreatus/Neostrongylus linearis (Nematoda) in six species of Helicidae (Mollusca) experimentally infected).

This is the first study on the experimental susceptibility of the following species of molluscs: Cernuella (X.) cespitum arigonis, Helicella (H.) itala, Helicella ordunensis, Cochlicella barbara, Cepaea nemoralis and Helix (C.) aspersa, as intermediate hosts for the combination of both C. ocreatus and M. capillaris, pulmonary parasites in ruminants. Furthermore, the larval development of C. ocreatus and N. linearis, the two taken together, has been followed in Cernuella (X.) cespitum arigonis, H. ordunensis and C. nemoralis. Approximately 40 specimens of each of the above-mentioned species of molluscs were infected with the parasites listed. Bearing in mind the results obtained, we believe that while Cernuella (X.) cespitum arigonis, H. ordunensis, C. nemoralis, C. barbara and Helicella (H.) itala are suitable intermediate hosts for the larval combination of C. ocreatus and M. capillaris, the same cannot be said of Helix (C.) aspersa. Likewise, the first 3 species of molluscs quoted are ideal for the joint larval development of C. ocreatus and N. linearis. It seems that double infections favour larval development.

Analysis of Variance↗
PubMed2002

The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus.

The in vivo effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus were examined over time after anthelmintic treatment of sheep. Twenty merino sheep, (12 months old) were allocated to five treatment groups and infected with ivermectin-resistant H. contortus. Thirty one days later, the sheep were treated with intraruminal ivermectin capsules, oral ivermectin, oral moxidectin or injectable moxidectin at the manufacturer's recommended dosages, or left untreated. At various times up to 112 days after treatment, faecal egg counts (FEC) were determined and development rates of infective larvae (L3) cultured in faeces or on agar were measured. Eggs in faecal cultures from ivermectin capsule treated sheep showed reduced L3 development percentages in comparison to faecal cultures from untreated sheep. Eggs from ivermectin capsule treated sheep, isolated from faeces, and cultured on agar showed similar L3 development to eggs from control sheep. These results demonstrate an inhibitory effect of excreted ivermectin in faeces on larval development of ivermectin-resistant H. contortus. L3 development in faecal culture from animals receiving oral ivermectin were reduced for only 3 days after treatment. Faecal egg counts and development of L3 larvae in both culture systems from moxidectin treated sheep were low, due to the high efficacy of the drug. Egg counts in moxidectin treated sheep were reduced by approximately 90% 24h after treatment, before decreasing to almost 100% at 48h, suggesting that the current quarantine recommendation of holding sheep off pasture for 24h after treatment may still lead to some subsequent pasture contamination with worm eggs.

Animals↗
PubMed2006

Discrete pulses of molting hormone, 20-hydroxyecdysone, during late larval development of Drosophila melanogaster: correlations with changes in gene activity.

Periodic pulses of the insect steroid molting hormone 20-hydroxyecdysone (20E), acting via its nuclear receptor complex (EcR/USP), control gene expression at many stages throughout Drosophila development. However, during the last larval instar of some lepidopteran insects, subtle changes in titers of ecdysteroids have been documented, including the so-called "commitment peak." This small elevation of 20E reprograms the larva for metamorphosis to the pupa. Similar periods of ecdysteroid immunoreactivity have been observed during the last larval instar of Drosophila. However, due to low amplitude and short duration, along with small body size and staging difficulties, their timing and ecdysteroid composition have remained uncertain. Employing a rigorous regimen of Drosophila culture and a salivary gland reporter gene, Sgs3-GFP, we used RP-HPLC and differential ecdysteroid RIA analysis to determine whole body titers of 20E during the last larval instar. Three small peaks of 20E were observed at 8, 20, and 28 hr following ecdysis, prior to the well-characterized large peak around the time of pupariation. The possible regulation of 20E levels by biosynthetic P450 enzymes and the roles of these early peaks in coordinating gene expression and late larval development are discussed.

Animals↗
PubMed2026

Transcriptome sequencing provides novel insights into larval development and sexual dimorphism in the firefly Aquatica leii (Coleoptera: Lampyridae).

Fireflies are regarded as one of the most charismatic beetles due to their bioluminescence and ecological importance as bioindicators of freshwater quality. However, molecular mechanisms of larval development and sexual dimorphism in aquatic species remain poorly understood. Here, we performed multi-stage transcriptomic analysis of the aquatic firefly Aquatica leii across larval instars from L2 to L6, together with adult females and males, with three biological replicates per stage. Using time-series expression clustering, differential expression analysis, and weighted gene co-expression network analysis (WGCNA), we characterized the transcriptional dynamics of continuous larval development and the onset of sex-biased gene expression. We identified a critical transcriptional transition occurred at L5-L6, marked by downregulation of early morphogenetic genes and upregulation of juvenile hormone metabolism, oxidoreductase activity, and muscle contraction genes, indicating a shift from growth to metamorphic preparation. WGCNA identified a module strongly correlated with L6 (R = 0.97) enriched for the same functions, confirming a coordinated late-larval program. Notably, genes exhibiting sex-biased expression in adults were already expressed during late larval stages (L5 and L6), and 123 genes progressively upregulated from L2 to L6 showed enrichment in chitin biosynthesis, heart contraction, and ion transport; among these, six genes maintained high expression in adults with clear male-biased (Alei052192, Alei006658, and Alei087054) or female-biased (Alei003725, Alei096818, and Alei074026) patterns. These findings establish that transcriptional foundations for sexual dimorphism and adult tissue formation are laid during late larval stages, providing the first multi-stage transcriptomic resource for aquatic firefly conservation and breeding.

Animals↗
PubMed2003

Effect of flavan-3-ols on in vitro egg hatching, larval development and viability of infective larvae of Trichostrongylus colubriformis.

The effects of flavan-3-ols (the monomer units of condensed tannins (CT)) and their galloyl derivatives on the viability of eggs, the development of first stage (L1) larvae, and the viability of the infective larvae of Trichostrongylus colubriformis were investigated under in vitro conditions. Each of the flavan-3-ol gallates showed some inhibition of egg hatching at 100 microg/ml, and 100% inhibition at 1000 microg/ml, with epigallocatechin gallate being the most effective in the egg hatch (EH) assay. In contrast, none of the flavan-3-ols were able to completely inhibit egg hatching. The flavan-3-ols and galloyl derivatives dose-dependently inhibited the development of infective larvae as assessed by the larval development (LD) assay. A larval migration inhibition (LMI) assay was used to assess the effect of flavan-3-ols and their galloyl derivatives on the motility of the infective third-stage (L3) larvae of T. colubriformis. In general, the flavan-3-ol gallates were more effective than the flavan-3-ols at immobilising the infective larvae as evidenced by their ability to inhibit more (P<0.05-0.01) larvae from passing through the LMI sieves. At 500 microg/ml, epigallocatechin gallate inhibited significantly more (P<0.1) larvae from passing through the sieves than did catechin gallate, epicatechin gallate, or gallocatechin gallate. Comparisons were made between the flavan-3-ols and their galloyl derivatives with the in vitro effects of CT extracts from several forage legumes, which have exhibited effects on parasites in vivo. The forage legumes tested at 200-500 microg/ml reduced the proportion of eggs that hatch, with comparable results to those obtained using the flavan-3-ols. The activities may be influenced by the prodelphinidin: procyanidin (PD:PC) ratios: CT extracts from Lotus pendunculatus and sainfoin have PD:PC ratios of 70:30 and 77:23, respectively, whereas the less active CT extract from Lotus corniculatus has a PD:PC ratio of 27:73. The active CT extracts from forage legumes have epigallocatechin as the dominant flavan-3-ol extender unit, and epigallocatechin is the most active flavan-3-ol in both the EH and LD assays.

Animals↗
PubMed1979

Sulfatide content and (Na+ + K+)-ATPase activity of skin and gill during larval development of the Chilean frog, Calyptocephalella caudiverbera.

The sulfatide content, phospholipid concentration, and (Na+ + K+)-ATPase activity from skin and gills of different stages of larval development of Calyptocephalella caudiverbera (a Chilean frog) were analyzed. Additionally, the short-circuit current in skin was studied. When skin and gills, depending on the stage of larval development, present (Na+ + K+)-ATPase activity, they have a high ratio of sulfatide to amount of membrane and the phosphatidylserine concentration remains unchanged. Sulfatide content and (Na+ + K+)-ATPase activity in skin are in direct relationship with the level of sodium flux present during development. The specific enzymatic hydrolysis of sulfatide with partially purified arylsulfatase of pig kidney inhibits 100% of the ouabain-sensitive (Na+ + K+)-ATPase. The ouabain-insensitive ATPase remains virtually unchanged with the treatment, even with a high concentration of arylsulfatase or with ouabain present in the medium. These experiments strongly suggest a role of sulfatides in the (Na+ + K+)-ATPase activity and, as a consequence, in sodium ion transport.

Animals↗
PubMed1997

Transamination of 3-hydroxykynurenine to produce xanthurenic acid: a major branch pathway of tryptophan metabolism in the mosquito, Aedes aegypti, during larval development.

An electrochemically active compound was detected in the larvae of Aedes aegypti mosquitoes and progressive accumulation of this compound was observed during larval development. The compound was purified from mosquito larvae using various chromatographic techniques and spectral analysis of the purified compound resulted in its identification as xanthurenic acid. Production of xanthurenic acid results from the transamination of 3-hydroxykynuorenine, and analysis of the biochemical pathway in xanthurenic acid production revealed the presence of a particular transaminase that has a much higher specific activity to 3-hydroxykynurenine than to kynurenine in the mosquito larvae. Concentration of xanthurenic acid is closely related to the level of this transaminase activity. Results suggest that this particular transaminase plays an important role in regulating the level of 3-hydroxykynurenine in the mosquito, A. aegypti during larval development.

Aedes↗
PubMed1998

Possible utilization of metallic copper to inhibit Aedes Albopictus (Skuse) larval development.

The effect of metallic copper on development of Aedes albopictus was studied in the laboratory. Multiwire electric cable was used as a source of metallic copper in flower saucers colonized by Ae. albopictus. A linear regression coefficient of 0.68 was obtained between copper concentration in the water during larval development and the relative production of adults. Larval mortality was higher in earlier instars with less evident effect on 4th-instar larvae and pupae. The effect of copper on larval development time and adult weight in both sexes was also observed. The strong algicidal action is presumed to only partially explain the effect of metallic copper on Ae. albopictus larvae. A direct toxic effect also may be involved. The use of metallic copper is suggested as a practical alternative method for preventing development of Ae. albopictus in small containers such as flower saucers found in urban areas.

Aedes↗
PubMedDate not supplied

Larval development of silver sea bream (Sparus sarba): ontogeny of RNA-DNA ratio, GH, IGF-I, and Na(+)-K(+)-ATPase.

To ascertain some of the important biochemical and molecular events that take place during early larval development of silver sea bream (Sparus sarba), we undertook a study of changes in the morphology as well as the ontogeny of the RNA-DNA ratio, growth hormone (GH), insulin-like growth factor I (IGF-I) messenger RNA abundance, Na(+)-K(+)-ATPase subunit mRNA abundance, and Na(+)-K(+)-ATPase enzyme activity. Larvae samples were collected at 1 to 46 days posthatch (dph). At 7 dph the yolk sac was fully absorbed, and from 28 dph onward larvae underwent rapid developmental changes to the juvenile stage. The RNA-DNA ratio was highest at 1 dph, decreased to low levels between 7 and 21 dph, then increased by 28 dph, and then again by 46 dph. The ontogenetic profiles of GH, IGF-I, and Na(+)-K(+)-ATPase alpha1 and beta1 subunits were studied using reverse transcriptase polymerase chain reaction, coupled with radioisotope hybridization of immobilized DNA. Growth hormone abundance reached a constant and high level from 35 dph onward, whereas the IGF-I level reached a peak at 35 dph and then significantly decreased. Both Na(+)-K(+)-ATPase alpha1 and beta1 subunit mRNAs increased up to 35 dph, however, at 46 dph the alpha1 subunit remained high whereas the beta1 subunit decreased. Na(+)-K(+)-ATPase activity was low in 1-dph larvae but increased rapidly as development progressed. The importance of these findings is discussed within the context of larval development.

Aging↗
PubMed1999

Investigation of intestinal nematode responses to naphthalophos and pyrantel using a larval development assay.

Responses of several nematode species to naphthalophos and pyrantel/levamisole were examined using a larval development assay in order to determine the potential of this assay for detection of resistance. Haemonchus contortus and Ostertagia circumcincta showed concentration-dependent responses to naphthalophos, however, the assay was unsuitable for Trichostrongylus colubriformis due to the low toxicity of the drug to the larval stages of this nematode. Measurement of concentration-dependent response to pyrantel in susceptible T. colubriformis was limited by a reduced toxicity against larvae at high drug concentrations, resulting in a parabolic response with a development-inhibition maxima of less than 100%. This limits the usefulness of the assay to detect pyrantel resistance in this species as the presence of a small resistant fraction in a field isolate may be indistinguishable from the parabolic susceptible response. On the other hand, responses of susceptible T. colubriformis to levamisole, and susceptible H. contortus to pyrantel and levamisole showed 100% development inhibition over a range of drug concentrations, indicating that the appearance of a resistant fraction in a field population would be readily discernible from the susceptible response, allowing resistance detection for these drug/parasite combinations. This study has highlighted the varied suitability of the larval development assay technique for resistance detection with different combinations of drugs and parasite species.

Animals↗
PubMed2003

Effect of Microcystis aeruginosa and Nodularia spumigena on survival of Eurytemora affinis and the embryonic and larval development of the Baltic herring Clupea harengus membras.

Laboratory experiments were carried out to investigate the effect of two strains of Microcystis aeruginosa and a strain of Nodularia spumigena on the survival of Eurytemora affinis (Copepoda) and on the embryonic and larval development of the Baltic spring-spawning herring Clupea harengus membras. The trials were made in water taken from Pärnu Bay, at a salinity of 3.7-5.1 psu, a constant temperature (15 degrees C +/- 1 degrees C in trials with Eurytemora and herring embryos; 18 degrees C +/- 2 degrees C with herring larvae), and an oxygen concentration of 8.8-10.4 ppm. The strains tested had a negative impact on the survival of Eurytemora, as well as on the embryonic development and hatching regime of the Baltic herring. In Eurytemora the response depended on the sex of the animals: the survival was clearly higher in females. In the embryonic stages of herring, the influence resulted in an increase in deviations from the normal pattern of development and a higher mortality. The impact of the strains on the larval development of herring was rather moderate.

Animals↗
PubMed1991

Effects of juvenile hormone mimics on larval development and metamorphosis of Drosophila melanogaster.

To determine if prolonged larval exposure to juvenile hormone (JH) could influence the decision to metamorphose, Drosophila melanogaster larvae were reared from hatching on medium containing either of the JH mimics, methoprene or 2-[1-methyl-2-(4-phenoxyphenoxy)-ethoxy]-pyridine (S31183). The latter was 23 times more active as a JH mimic in the white puparial assay (ED50 = 0.22 pmole). Larval development and pupariation were unaffected except at 1000 ppm methoprene and 10 ppm or higher S31183 where larval life was prolonged with increased mortality in the second instar. Adult eclosion was prevented by concentrations greater than 1 ppm methoprene and 0.1 ppm S31183. At low concentrations only adult abdominal development was affected, but at the higher concentrations an increasing percentage was blocked at the pupal stage. This latter effect was considerably diminished when the treatment was begun in the mid second instar. The methoprene-resistant mutations, Met1 and Met2, were 10 and 6 times more resistant to S31183 in the white puparial assay and about 20 times more resistant in the larval feeding experiments than the wild-type, indicating that the effects seen are typical of JH. These studies suggest that excess JH may affect adult development of imaginal structures if present at the onset of postembryonic cell proliferation of the imaginal discs or histoblasts. Thus, commitment for adult differentiation must occur early during this proliferative phase.

Abdomen↗
PubMed1990

A larval development test for the detection of anthelmintic resistance in nematodes of sheep.

First stage larvae of a number of species of parasitic nematodes of sheep have been shown to develop to third stage larvae in the presence of a defined medium consisting of Earle's balanced salt solution and yeast extract. A larval development test, based on this culture technique, was used as a screen for detecting the presence of anthelmintic resistance in nematodes of sheep. It was found to be sensitive and simple to use and also appeared capable of detecting resistance to any of the main anthelmintic groups. Available anthelmintic sensitive and resistant strains of Haemonchus contortus and Ostertagia circumcincta showed differences in development when incubated in the presence of either thiabendazole, levamisole and ivermectin. These differences were expressed as the minimum inhibitory concentration required to prevent larval development over the incubation period.

Animals↗