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Parasitology International Feb 2015The salmon louse (Lepeophtheirus salmonis) is an ectoparasitic copepod causing severe problems to the fish farming industry and to wild salmonids. Morphologically, all...
The salmon louse (Lepeophtheirus salmonis) is an ectoparasitic copepod causing severe problems to the fish farming industry and to wild salmonids. Morphologically, all stages in the life cycle of L. salmonis have been described in detail based on successive samples from host populations. However, the rate of development differs between males and females as well as between individuals. It has therefore been difficult to observe development within stages, and this has led to a longstanding misinterpretation of the number of chalimus stages. Here samples of chalimi obtained for 12 consecutive days were observed daily in incubators. Chalimus 1 was able to molt in incubators only when fully grown and close to molting, whereas chalimus 2 was able to molt at about 60% of total instar growth. Total length instar growth was about 35% in both chalimus 1 and chalimus 2 and about equal among males and females; the cephalothorax increased by about 12% and the posterior body by about 80%. Instar growth was probably the main factor that led to the former belief that L. salmonis had four chalimus stages. Relative total length increase at molting was at the same order of magnitude as instar growth, but total length of females increased significantly more than that of males at molting. Consequently, a sexual size dimorphism was established upon molting to chalimus 2 and males were about 10% smaller than females. While growth by molting was mainly caused by cephalothorax increase, instar growth was mainly due to increase of the posterior body. The cephalothorax/total length ratio decreased from beginning to end of the instar phase suggesting that it may be used as an instar age marker. Male and female chalimus 2 can almost uniquely be identified by cephalothorax length. Chalimus 1 lasted between 5 and 6 days for males and between 6 and 7 days for females at 10°C. Chalimus 2 males lasted between 6 and 7 days and females between 7 and 8 days.
Topics: Animals; Copepoda; Ectoparasitic Infestations; Female; Fish Diseases; Larva; Life Cycle Stages; Male; Molting; Salmo salar; Sex Characteristics
PubMed: 25451218
DOI: 10.1016/j.parint.2014.10.006 -
The FEBS Journal Nov 2009The molting process in arthropods is regulated by steroid hormones acting via nuclear receptor proteins. The most common molting hormone is the ecdysteroid,... (Review)
Review
The molting process in arthropods is regulated by steroid hormones acting via nuclear receptor proteins. The most common molting hormone is the ecdysteroid, 20-hydroxyecdysone. The receptors of 20-hydroxyecdysone have also been identified in many arthropod species, and the amino acid sequences determined. The functional molting hormone receptors consist of two members of the nuclear receptor superfamily, namely the ecdysone receptor and the ultraspiracle, although the ecdysone receptor may be functional, in some instances, without the ultraspiracle. Generally, the ecdysone receptor/ultraspiracle heterodimer binds to a number of ecdysone response elements, sequence motifs that reside in the promoter of various ecdysteroid-responsive genes. In the ensuing transcriptional induction, the ecdysone receptor/ultraspiracle complex binds to 20-hydroxyecdysone or to a cognate ligand that, in turn, leads to the release of a corepressor and the recruitment of coactivators. 3D structures of the ligand-binding domains of the ecdysone receptor and the ultraspiracle have been solved for a few insect species. Ecdysone agonists bind to ecdysone receptors specifically, and ligand-ecdysone receptor binding is enhanced in the presence of the ultraspiracle in insects. The basic mode of ecdysteroid receptor action is highly conserved, but substantial functional differences exist among the receptors of individual species. Even though the transcriptional effects are apparently similar for ecdysteroids and nonsteroidal compounds such as diacylhydrazines, the binding shapes are different between them. The compounds having the strongest binding affinity to receptors ordinarily have strong molting hormone activity. The ability of the ecdysone receptor/ultraspiracle complex to manifest the effects of small lipophilic agonists has led to their use as gene switches for medical and agricultural applications.
Topics: Animals; Arthropods; DNA-Binding Proteins; Drosophila Proteins; Ligands; Molecular Conformation; Molting; Receptors, Cytoplasmic and Nuclear; Receptors, Steroid; Response Elements; Transcription Factors
PubMed: 19796154
DOI: 10.1111/j.1742-4658.2009.07347.x -
BMC Developmental Biology Nov 2020Molting is an essential biological process occurring characteristic times throughout the life cycle of holometabolous insects. However, it is not clear how insects...
BACKGROUND
Molting is an essential biological process occurring characteristic times throughout the life cycle of holometabolous insects. However, it is not clear how insects determine the direction of molting to remain status quo or to initiate metamorphosis. To explore the functional factors that determine the direction of molts, liquid chromatography-mass spectrometry was used to identify the molecules involved in larval and metamorphic molting, and the differentially expressed proteins (DEPs) were compared in the two processes.
RESULTS
There were 321 and 1140 DEPs identified in larval and metamorphic molting process, respectively. Bioinformatics analyses show that the amino sugar pathway was up-regulated in both processes. The up-regulated protease contributed to the metamorphosis. In addition, several proteins with different expression patterns in larval-larval and larval-pupal transitions, including Endochitinase, GRIM-19 (Genes associated with retinoid-IFN-induced mortality-19), IDE (Insulin-degrading enzyme), Sorcin (Soluble resistance related calcium binding protein), OBP (Odorant-binding protein-2 precursor), TRAP1(Tumor necrosis factor receptor associated protein-1), etc., were further identified by parallel reaction monitoring, which may play diverse functions in larval-larval and larval-pupal transitions.
CONCLUSIONS
These results provide a proteomic insight into molecules involved in larval and metamorphic molts, and will likely improve the current understanding of determination of direction of molts.
Topics: Animals; Gene Expression Regulation, Developmental; Insect Proteins; Larva; Lepidoptera; Metamorphosis, Biological; Molting; Proteomics; Pupa; Reproducibility of Results
PubMed: 33234135
DOI: 10.1186/s12861-020-00227-z -
Neuro-Signals 2004Insect neural networks have been widely and successfully employed as model systems in the study of the neural basis of behavior. The insect frontal ganglion is a... (Review)
Review
Insect neural networks have been widely and successfully employed as model systems in the study of the neural basis of behavior. The insect frontal ganglion is a principal part of the stomatogastric nervous system and is found in most insect orders. The frontal ganglion constitutes a major source of innervation to foregut muscles and plays a key role in the control of foregut movements. Following a brief description of the anatomy and development of the system in different insect groups, this review presents the current knowledge of the way neural networks in the insect frontal ganglion generate and control behavior. The frontal ganglion is instrumental in two distinct and fundamental insect behaviors: feeding and molting. Central pattern-generating circuit(s) within the frontal ganglion generates foregut rhythmic motor patterns. The frontal ganglion networks can be modulated in-vitro by several neuromodulators to generate a variety of motor outputs. Chemical modulation as well as sensory input from the gut and input from other neural centers enable the frontal ganglion to induce foregut rhythmic patterns under different physiological conditions. Frontal ganglion neurons themselves are also an important source of neurosecretion. The neurosecretory material from the frontal ganglion can control and modulate motor patterns of muscles of the alimentary canal. The current and potential future importance of the insect stomatogastric nervous system and frontal ganglion in the study of the neural mechanisms of behavior are discussed.
Topics: Animals; Behavior, Animal; Digestive System; Electric Stimulation; Feeding Behavior; Ganglia, Invertebrate; Insecta; Molting; Nerve Net; Nervous System Physiological Phenomena; Neural Networks, Computer; Neurons
PubMed: 15004423
DOI: 10.1159/000076156 -
PloS One 2013Crustacean calcium bodies are epithelial sacs which contain a mineralized matrix. The objectives of this study were to describe the microscopic anatomy of calcium bodies...
Crustacean calcium bodies are epithelial sacs which contain a mineralized matrix. The objectives of this study were to describe the microscopic anatomy of calcium bodies in the terrestrial isopod Hyloniscus riparius and to establish whether they undergo molt-related structural changes. We performed 3D reconstruction of the calcium bodies from paraffin sections and analyzed their structure with light and electron microscopy. In addition, we analyzed the chemical composition of their mineralized matrices with micro-Raman spectroscopy. Two pairs of these organs are present in H. riparius. One pair is filled with bacteria while the other pair is not. In non-molting animals, the bacteria-filled calcium bodies contain apatite crystals and the bacteria-free calcium bodies enclose CaCO3-containing concretions with little organic matrix. During preparation for molt, an additional matrix layer is deposited in both pairs of calcium bodies. In the bacteria-filled calcium bodies it contains a mixture of calcium carbonate and calcium phosphate, whereas only calcium carbonate is present in bacteria-free calcium bodies. After ecdysis, all mineral components in bacteria-free calcium bodies and the additional matrix layer in bacteria-filled calcium bodies are completely resorbed. During calcium resorption, the apical surface of the calcium body epithelium is deeply folded and electron dense granules are present in spaces between epithelial cells. Our results indicate that the presence of bacteria might be linked to calcium phosphate mineralization. Calcium bodies likely provide a source of calcium and potentially phosphate for the mineralization of the new cuticle after molt. Unlike other terrestrial isopods, H. riparius does not form sternal CaCO3 deposits and the bacteria-free calcium bodies might functionally replace them in this species.
Topics: Animals; Bacteria; Calcification, Physiologic; Calcium; Calcium Carbonate; Epithelium; Isopoda; Minerals; Molting; Spectrum Analysis, Raman
PubMed: 23554963
DOI: 10.1371/journal.pone.0058968 -
Current Pharmaceutical Design 2020Chitin contributes to the rigidity of the insect cuticle and serves as an attachment matrix for other cuticular proteins. Deficiency of chitin results in abnormal...
Chitin contributes to the rigidity of the insect cuticle and serves as an attachment matrix for other cuticular proteins. Deficiency of chitin results in abnormal embryos, cuticular structural defects and growth arrest. When chitin is not turned over during molting, the developing insect is trapped inside the old cuticle. Partial deacetylation of cuticular chitin is also required for proper laminar organization of the cuticle and vertical pore canals, molting, and locomotion. Thus, chitin and its modifications strongly influence the structure of the exoskeleton as well as the physiological functions of the insect. Internal tendons and specialized epithelial cells called "tendon cells" that arise from the outer layer of epidermal cells provide attachment sites at both ends of adult limb muscles. Membrane processes emanating from both tendon and muscle cells interdigitate extensively to strengthen the attachment of muscles to the extracellular matrix (ECM). Protein ligands that bind to membrane-bound integrin complexes further enhance the adhesion between muscles and tendons. Tendon cells contain F-actin fiber arrays that contribute to their rigidity. In the cytoplasm of muscle cells, proteins such as talin and other proteins provide attachment sites for cytoskeletal actin, thereby increasing integrin binding and activation to mechanically couple the ECM with actin in muscle cells. Mutations in integrins and their ligands, as well as depletion of chitin deacetylases, result in defective locomotion and muscle detachment from the ECM. Thus, chitin in the cuticle and chitin deacetylases strongly influence the shape and functions of the exoskeleton as well as locomotion of insects.
Topics: Animals; Chitin; Humans; Insect Proteins; Insecta; Molting
PubMed: 32445445
DOI: 10.2174/1381612826666200523175409 -
Poultry Science Mar 2005Molting is a common practice used by the commercial egg industry to rejuvenate flocks for a second or third laying cycle. During this time the hens rest from production,...
Molting is a common practice used by the commercial egg industry to rejuvenate flocks for a second or third laying cycle. During this time the hens rest from production, and the reproductive organs are rejuvenated to increase production and quality during the next laying cycle. Although feed withdrawal (FW) is the most popular and effective method of molt induction, it has come under scrutiny due to food safety issues and animal welfare issues. This study involved feeding alfalfa mixed with layer ration at different ratios to hens to determine their ability to induce molt. The treatment ratios were 100% alfalfa (A100), 90% alfalfa and 10% layer ration (A90), and 70% alfalfa and 30% layer ration (A70). In addition, a fully fed (FF) nonmolted control and a FW negative control were used. Alfalfa is an insoluble, high fiber feedstuff with low metabolizable energy. Egg production for A90 and FW treatments ceased completely by d 6, whereas birds fed A100 and A70 ceased egg production by d 8. Ovary and oviduct weight of hens fed all molting diets decreased (P < 0.05) by an average of 1.5 to 2.5% (BW basis) compared with FF control during the 9-d molt induction period. As the percentage of layer ration increased, feed intake also increased and percentage of BW loss decreased during the 9-d molt induction period. Hens molted by FW lost an average of 25.8% BW, whereas A70 hens lost 18.9% BW. Nonmolted hens (FF) and A70 treatment hens had significantly lower (P < 0.05) egg production when compared with all other treatments over the 39-wk postmolt period. FF treatment hens also had lower (P < 0.05) albumen heights when compared with all other treatments. From these results, alfalfa or alfalfa mixed with layer ration appears to be viable alternatives to conventional FW methods for the successful induction of molt and retention of postmolt performance.
Topics: Agriculture; Animal Feed; Animals; Chickens; Eating; Female; Industry; Medicago sativa; Molting; Organ Size; Oviposition
PubMed: 15782903
DOI: 10.1093/ps/84.3.362 -
Annual Review of Entomology 2014The shedding of the old exoskeleton that occurs in insects at the end of a molt (a process called ecdysis) is typically followed by the expansion and tanning of a new... (Review)
Review
The shedding of the old exoskeleton that occurs in insects at the end of a molt (a process called ecdysis) is typically followed by the expansion and tanning of a new one. At the adult molt, these postecdysial processes include expansion and hardening of the wings. Here we describe recent advances in understanding the neural and hormonal control of wing expansion and hardening, focusing on work using Drosophila melanogaster in which genetic manipulations have permitted detailed investigation of postecdysial processes and their modulation by sensory input. To place this work in context, we briefly review recent progress in understanding the neuroendocrine regulation of ecdysis, which appears to be largely conserved across insect species. Investigations into the neuroendocrine networks that regulate ecdysial and postecdysial behaviors provide insights into how stereotyped, yet environmentally responsive, sequences are generated and how they develop and evolve.
Topics: Animals; Drosophila melanogaster; Insect Hormones; Molting; Neurosecretory Systems; Wings, Animal
PubMed: 24160420
DOI: 10.1146/annurev-ento-011613-162028 -
Frontiers in Endocrinology 2021Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce,... (Review)
Review
Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce, the ability to change color, and multiple strategies for sexual differentiation. Accordingly, the endocrine regulation of these processes involves hormones, receptors, and enzymes that differ from those utilized by vertebrates and other non-arthropod invertebrates. As a result, environmental chemicals known to disrupt endocrine processes in vertebrates are often not endocrine disruptors in crustaceans; while, chemicals that disrupt endocrine processes in crustaceans are often not endocrine disruptors in vertebrates. In this review, we present an overview of the evolution of the endocrine system of crustaceans, highlight endocrine endpoints known to be a target of disruption by chemicals, and identify other components of endocrine signaling that may prove to be targets of disruption. This review highlights that crustaceans need to be evaluated for endocrine disruption with consideration of their unique endocrine system and not with consideration of the endocrine system of vertebrates.
Topics: Animals; Biological Evolution; Crustacea; Endocrine Disruptors; Endocrine System; Fishes; Molting; Reproduction; Water Pollutants, Chemical
PubMed: 33737907
DOI: 10.3389/fendo.2021.587608 -
Poultry Science Jun 2003Induced molting is an important economic tool used by the egg industry to recycle an aging layer flock. It is estimated that approximately 70% of the flocks nationwide... (Review)
Review
Induced molting is an important economic tool used by the egg industry to recycle an aging layer flock. It is estimated that approximately 70% of the flocks nationwide and almost 100% in California are molted annually. Considering that there are approximately 240 million hens in production in the U.S., a rough estimate of the numbers of hens molted every year would be between 144 and 168 million birds, a substantial number. There are many methods to induce molt, but feed removal until hens lose a specific weight is the most prevalent molt strategy in the U.S. However, experimental studies in our laboratory have shown that induced molting via feed removal depresses the immune system of hens and exacerbates a Salmonella enteritidis (SE) problem in a simulated flock situation. Molted hens excreted significantly higher SE numbers in the feces, had higher numbers of SE in internal organs, and exhibited more intestinal inflammation. Molted hens were 100- to 1,000-fold more susceptible to infection by SE and therefore more readily transmitted the organism to uninfected hens in neighboring cages. With the problems identified, solutions were sought, and several were successful in ameliorating the SE issue. Antibiotic therapy, vaccination, and use of low-energy, low-calcium diets to molt hens all dramatically decreased SE shedding during molt. All of the solutions provide the producer with many potential solutions to the SE food safety issue and still allow them to recycle their hens.
Topics: Animal Feed; Animal Husbandry; Animals; Anti-Bacterial Agents; Chickens; Diet; Feces; Female; Food Deprivation; Immune System; Molting; Risk Factors; Salmonella Infections, Animal; Salmonella enterica; Vaccination
PubMed: 12817457
DOI: 10.1093/ps/82.6.1008