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In fiddler crabs, molting and its stage wise characteristics remain poorly understood. This study demonstrated the programming of molting in male fiddler crab, Gelasimus hesperiae inhabiting mangroves along estuaries of Kerala, India by adopting ecological and biochemical approach. By the onset of premolt, epidermal retraction and sign of setogenesis was microscopically visible in epipodite matrix of third maxilliped. Hemocyte count in the epipodite matrix was maximum during premolt (D2) stage, then it showed a significant decrease (P < 0.05) as the premolt stage attained late stages (D3/D4). The hemolymph total protein increased significantly from intermolt to early premolt (D0/D1) (P < 0.001) stage, then showed a substantial decrease towards late premolt (D3/D4) (P < 0.05); contrary to this, hemolymph ecdysteroid titre was found maximum (20.67 ± 1.00 ng/mL) at late premolt stages. The recorded average annual molting rate ranged 12.5–68.5%. May–June showed high (>55%) molting rate and least (<15%) in August–September. Season wise difference in molting rate was also significant (P < 0.05). The molting was high, when the rainfall between 0–617.0 mm, salinity 12–34‰ and water temperature 28–30.2°C. Overall results from the present studies provide insights to address the questions how fiddler crabs are adapted to their habitat. [ABSTRACT FROM AUTHOR]

Simple Summary: Ecdysis triggering hormone (ETH) synthesized and secreted from peripheral Inka cells on the tracheal surface play a vital role in the triggering and orchestration of ecdysis in insects and other arthropod species. Binding of ETH to the ETH receptor (ETHR) located on the peptidergic neurons in the central nervous system (CNS) facilitates synthesis of ecdysis-related neuropeptides. Although the role of ETH on ecdysis has been well-studied in various holometabolous insects, only very little information is available in hemimetabolous insects. Recent studies in hemimetabolous insects have identified and characterized diverse features of ETH precursors, ETH and ETH receptors. In addition to this, the involvement of ETH in Juvenile hormone (JH) mediated courtship short-term memory (STM) retention and long-term courtship memory regulation and retention has also been shown recently. Here, we extensively studied ETH signaling cascades in various insects and their roles in triggering diverse functions in the adults and juvenile insects including development and reproductive regulation. Understanding the intricate details of ETH signaling in diverse insect species could lead to the identification of novel targets and chemicals, as well as the development of various sustainable pest management solutions. Insect growth is interrupted by molts, during which the insect develops a new exoskeleton. The exoskeleton confers protection and undergoes shedding between each developmental stage through an evolutionarily conserved and ordered sequence of behaviors, collectively referred to as ecdysis. Ecdysis is triggered by Ecdysis triggering hormone (ETH) synthesized and secreted from peripheral Inka cells on the tracheal surface and plays a vital role in the orchestration of ecdysis in insects and possibly in other arthropod species. ETH synthesized by Inka cells then binds to ETH receptor (ETHR) present on the peptidergic neurons in the central nervous system (CNS) to facilitate synthesis of various other neuropeptides involved in ecdysis. The mechanism of ETH function on ecdysis has been well investigated in holometabolous insects such as moths Manduca sexta and Bombyx mori, fruit fly Drosophila melanogaster, the yellow fever mosquito Aedes aegypti and beetle Tribolium castaneum etc. In contrast, very little information is available about the role of ETH in sequential and gradual growth and developmental changes associated with ecdysis in hemimetabolous insects. Recent studies have identified ETH precursors and characterized functional and biochemical features of ETH and ETHR in a hemimetabolous insect, desert locust, Schistocerca gregaria. Recently, the role of ETH in Juvenile hormone (JH) mediated courtship short-term memory (STM) retention and long-term courtship memory regulation and retention have also been investigated in adult male Drosophila. Our review provides a novel synthesis of ETH signaling cascades and responses in various insects triggering diverse functions in adults and juvenile insects including their development and reproductive regulation and might allow researchers to develop sustainable pest management strategies by identifying novel compounds and targets. [ABSTRACT FROM AUTHOR]

In aquaculture, high mortality in crustacean larvae during the moulting process restricts the larviculture's productivity. This study aimed to determine the bioactive components in the methanolic extract of fiddlehead ferns, Diplazium esculentum, and their effects on the growth of Microbrachium rosenbergii postlarvae (PL). Hormonal analysis revealed a high level of 20-hydroxyecdysteroid (20E) hormone in both leaves and shoot parts (4733 pg/ml) with the presence of phenols, tannins, saponins, flavonoids, terpenoids, alkaloids, and steroids during the phytochemical screening. GC–MS analysis discovered the presence of thirty-two bioactive compounds, including 1-(2,6-dichlorobenzoyl)-2,5-dimethylpyrrole, decyl sulfide, beta-amyrin, and cyclotetrasiloxane, octamethyl- with the peak area of 12.60%, 10.81%, 10.46%, and 8.48%, respectively. During a pilot study, prawn PL were fed diets containing D. esculentum extracts, namely diet 1–diet 5, with concentrations of 0.5, 1.0, 2.0, 4.0, and 10.0 gkg−1, respectively. Results showed high survival in PL fed with diet 4 and diet 5 (75.56% and 77.22%, respectively; p = 0.049). Next, a 60-day feeding trial was conducted to determine the moulting and growth performance of PL fed with 0 gkg−1 (control), 4.0 gkg−1 (diet 4), and 10.0 gkg−1 (diet 5) fern extracts. Results showed that prawns fed with diet 5 significantly showed the highest moulting frequency (112 ± 1.32 moults) and moulting rate (2.04 ± 0.02 moults per prawn). The findings demonstrated that a higher concentration of 20E with the highest inclusion of D. esculentum in diets could have enhanced the moulting performance in M. rosenbergii. We suggest an experiment on nutrient-dose response to determining the optimum level for growth performance in M. rosenbergii. [ABSTRACT FROM AUTHOR]

Plastic wastes deposited in canals running through Thiruvananthapuram city have created stagnant waters providing breeding sites for mosquitoes. In the present study, plastic waste–derived bisphenol A (BPA) was quantified from four mosquito breeding sites. During summer rain, the concentration of BPA in the stagnant water samples was found to be between 0.86 and 1.14 mg/L, and hence 1 mg/L BPA was considered as the environmentally relevant concentration. In the present study, the effect of BPA on the life cycle and metamorphosis of filarial vector, Culex quinquefasciatus Say was elucidated by rearing larvae in water added with BPA at and above the environmentally relevant concentration viz., 1, 2, and 4 mg/L. The duration required for adult emergence was reduced from 10 to 8.5 days, when the concentration of BPA was increased from 1 to 4 mg/L respectively. Our study revealed that embryonic and larval developments were shortened by BPA treatment. BPA also caused a dose-dependent advancement of 20-hydroxyecdysone (20-E) peaks; phospholipase A2 induction; and upregulation of ecdysone receptor gene, EcRA, and ecdysone inducible gene E75A, which culminated in early pupation. No significant difference in sanguivory and fecundity was observed in adult mosquitoes treated with 1 mg/L of BPA. Our study reveals that BPA is a developmental agonist of C. quinquefasciatus. [ABSTRACT FROM AUTHOR]

[Objectives] To obtain the full-length cDNA sequence of the Mythimna separata chitin synthase B (CHSB) gene, and investigate the effect of 20 E and validamycin on the mRNA expression levels of this gene in different developmental stages and tissues. [Methods] A full-length cDNA sequence of the M. separata CHSB genet was obtained by highthroughput sequencing and its mRNA expression levels in different developmental stages and tissues quantified with RT-qPCR. mRNA expression levels after treatment with 20 E and validamycin were also measured with RT-qPCR. [Results] The cDNA sequence of the M. separata CHSB gene is 4 617 bp with an open reading frame encoding a polypeptide of 1 538 amino acids, an estimated molecular mass of 175.629 ku, and an estimated pI of 5.96. It has 17 transmembrane helices, 4 tag sequences (CHS, CATMWHET, DGD, EDR and QRRRW), and one putative catalytic domain. Its cDNA sequence was designated MsCHSB and has been deposited in GenBank (accession No. KY348776). Sequencing indicated > 52% shared identity between MsCHSB and CHSB from other insect species, and 92% and 83% similarity with Mamestra configurata and Helicoverpa armigera CHSB. Real-time PCR indicated that MsCHSB mRNA transcripts were expressed in all developmental stages and in tissues but were most highly expressed in the early 3rd larval instar and in the midgut. MsCHSB expression was significantly higher than that of the control group 6 h and 12 h after treatment with 10 µg/µL of 20 E. The relative expression of MsCHSB after validamycin treatment was significantly lower than in the control group, and this was most apparent 48 h after treatment with 20 µg/µL validamycin. [Conclusion] A novel CHSB cDNA sequence was obtained from M. separata. The expression of MsCHSB was increased by 20 E and inhibited by validamycin. These results provided a foundation for further research on the biological function of CHSB in insects. [ABSTRACT FROM AUTHOR]

Morphogenetic signaling by small terpenoid hormones is a common feature of both vertebrate and invertebrate development. Most attention on insect developmental signaling by small terpenoids has focused on signaling by juvenile hormone through bHLH-PAS proteins (e.g., the MET protein), especially as that signaling axis intersects with ecdysteroid action through the receptor EcR. However, a series of endocrine and pharmacological studies on pupariation in cyclorrhaphous Diptera have remained persistently refractory to explanation with the above two-axis model. Recently, the terpenoid compound methyl farnesoate has been physicochemically demonstrated to exist in circulation at physiological concentrations, in several mecopterid orders, including Diptera. In addition, it has also been recently demonstrated that the receptor to which methyl farnesoate binds with nanomolar affinity (ultraspiracle, an ortholog of retinoid X receptor) requires a functioning ligand binding pocket to sustain the morphogenetic transition to puparium formation. This review evaluates endocrine and pharmacological evidence for developmental pathways reached by methyl farnesoate action, and assesses the participation of the retinoid X receptor ligand pocket in signal transduction to those developmental endpoints., (Copyright © 2013 Elsevier Inc. All rights reserved.)