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Insect Biochemistry and Molecular... Oct 2022The insect cuticle is a key component of their success, being important for protection, communication, locomotion, and support. Conversely, as an exoskeleton, it also...
The insect cuticle is a key component of their success, being important for protection, communication, locomotion, and support. Conversely, as an exoskeleton, it also limits the size of the insect and must be periodically molted and a new one synthesized, to permit growth. To achieve this, the insect secretes a solution of chitinases, proteases and other proteins, known collectively as molting fluid, during each molting process to break down and recycle components of the old cuticle. Previous research has focused on the degradative enzymes in molting fluid and offered some characterization of their biochemical properties. However, identification of the specific proteins involved remained to be determined. We have used 2D SDS-PAGE and LC/MS-based proteomic analysis to identify proteins in the molting fluid of the tobacco hornworm, Manduca sexta, undergoing the larval to pupal molt. We categorized these proteins based on their proposed functions including chitin metabolism, proteases, peptidases, and immunity. This analysis complements previous reported work on M. sexta molting fluid and identifies candidate genes for enzymes involved in cuticle remodeling. Proteins classified as having an immune function highlight potential for molting fluid to act as an immune barrier to prevent infections during the cuticle degradation and ecdysis processes. Several proteins known to function in melanin synthesis as an immune response in hemolymph were present in molting fluid. We demonstrated that the bacterium Micrococcus luteus and the entomopathogenic fungus Beauveria bassiana can stimulate activation of phenoloxidase in molting fluid, indicating that the recognition proteins, protease cascade, and prophenoloxidase needed for melanin synthesis are present as a defense against infection during cuticle degradation. This analysis offers insights for proteins that may be important not only for molting in M. sexta but for insects in general.
Topics: Animals; Chitin; Chitinases; Endopeptidases; Insect Proteins; Larva; Manduca; Melanins; Molting; Monophenol Monooxygenase; Peptide Hydrolases; Proteomics; Pupa
PubMed: 36115517
DOI: 10.1016/j.ibmb.2022.103844 -
The Journal of Experimental Biology Mar 2022Allocation of energy to thermoregulation greatly contributes to the metabolic cost of endothermy, especially in extreme ambient conditions. Weddell seal (Leptonychotes...
Allocation of energy to thermoregulation greatly contributes to the metabolic cost of endothermy, especially in extreme ambient conditions. Weddell seal (Leptonychotes weddellii) pups born in Antarctica must survive both on ice and in water, two environments with very different thermal conductivities. This disparity likely requires pups to allocate additional energy toward thermoregulation rather than growth or development of swimming capabilities required for independent foraging. We measured longitudinal changes in resting metabolic rate (RMR) for Weddell seal pups (n=8) in air and water from one to seven weeks of age, using open-flow respirometry. Concurrently, we collected molt, morphometric and dive behavior data. Absolute metabolic rate (MR) in air followed the expected allometric relationship with mass. Absolute MR in water was not allometric with mass, despite a 3-fold increase in mass between one and seven weeks of age. Developmental stage (or molting stage), rather than calendar age, determined when pups were thermally capable of being in the water. We consistently observed post-molt pups had lower RMR in air and water (6.67±1.4 and 7.90±2.38 ml O2 min-1 kg-1, respectively) than pre-molt (air: 9.37±2.42 ml O2 min-1 kg-1, water: 13.40±3.46 ml O2 min-1 kg-1) and molting pups (air: 8.45±2.05 ml O2 min-1 kg-1, water: 10.4±1.63 ml O2 min-1 kg-1). RMR in air and water were equivalent only for post-molt pups. Despite the increased energy cost, molting pups spent three times longer in the water than other pups. These results support the idea of an energetic trade-off during early development; pups expend more energy for thermoregulation in water, yet gain experience needed for independence.
Topics: Animals; Body Temperature Regulation; Caniformia; Molting; Seals, Earless; Water
PubMed: 35217875
DOI: 10.1242/jeb.242773 -
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 -
Physiological and Biochemical Zoology :... 2021AbstractHarbor seals () live in cold temperate or polar seas and molt annually, renewing their fur over a period of approximately 4 wk. Epidermal processes at this time...
AbstractHarbor seals () live in cold temperate or polar seas and molt annually, renewing their fur over a period of approximately 4 wk. Epidermal processes at this time require a warm skin; therefore, to avoid an excessive energy cost at sea during the molt, harbor seals and many other pinnipeds increase the proportion of time they are hauled out on land. We predicted that metabolic rate during haul-out would be greater during the molt to sustain an elevated skin temperature in order to optimize skin and hair growth. To examine this, we measured post-haul-out oxygen consumption () in captive harbor seals during molt and postmolt periods. We recorded greater of seals while they were molting than when the molt was complete. Post-haul-out increased faster and reached a greater maximum during the first 40 min. Thereafter, decreased but still remained greater, suggesting that while metabolic rate was relatively high throughout haul-outs, it was most pronounced in the first 40 min. Air temperature, estimated heat increment of feeding, and mass also explained 15.5% of variation over 180 min after haul-out, suggesting that the environment, feeding state, and body size influenced the metabolic rate of individual animals. These results show that molting seals have greater metabolic rates when hauled out, especially during the early stages of the haul-out period. As a consequence, human disturbance that changes the haul-out behavior of molting seals will increase their energy costs and potentially extend the duration of the molt.
Topics: Animals; Energy Metabolism; Feeding Behavior; Male; Molting; Oxygen Consumption; Phoca; Seasons
PubMed: 33710938
DOI: 10.1086/713958 -
Current Biology : CB Feb 2021Animals with exoskeletons molt for further growth. In insects, the number of larval (or nymphal) molts varies inter- and intra-specifically, and it is widely accepted...
Animals with exoskeletons molt for further growth. In insects, the number of larval (or nymphal) molts varies inter- and intra-specifically, and it is widely accepted that the variation in the number of larval molts is an adaptive response to diverse environmental conditions. However, the molecular mechanism that underlies the variety and plasticity in the number of larval molts is largely unknown. In the silkworm, Bombyx mori, there are strains that molt three, four, or five times, and these numbers are determined by allelic variation at a single autosomal locus, Moltinism (M). Here, we demonstrate that the Hox gene Sex combs reduced (Scr) is responsible for the phenotypes of the M locus. Scr is selectively expressed in the larval prothoracic gland (PG), an endocrine organ that produces molting hormones.Scr represses the biosynthesis of molting hormones in the PG, thereby regulating the incremental increase in body size during each larval instar. Our experiments consistently suggest that the differential expression levels of Scr among the three M alleles result in different growth ratios that ultimately lead to the different number of larval molts. Although the role of Hox genes in conferring segmental identity along the body axis and in molding segment-specific structure later in development has been well established, the present study identifies an unexpected role of Hox gene in hormone biosynthesis. This new role means that, in addition to shaping segment-specific morphology, Hox genes also drive the evolution of life history traits by regulating animal physiology.
Topics: Animals; Bombyx; Ecdysone; Larva; Molting; Phenotype
PubMed: 33308417
DOI: 10.1016/j.cub.2020.11.017 -
Current Biology : CB Jan 2021Ecdysis or molting evolved ∼535 mya in Ecdysozoa, the most diverse and species-rich animal superphylum. A cascade of ecdysis-related neuropeptides (ERNs) controls the...
Ecdysis or molting evolved ∼535 mya in Ecdysozoa, the most diverse and species-rich animal superphylum. A cascade of ecdysis-related neuropeptides (ERNs) controls the innate behavioral programs required for cuticle shedding in some ecdysozoan lineages (e.g., arthropods) but is lacking in others (e.g., nematodes). We recently reported on the surprisingly ancient bilaterian origin of key ERNs, such as eclosion hormone (EH), crustacean cardioactive neuropeptide (CCAP), myoinhibitory peptide (MIP), bursicon alpha (Bursα), and bursicon beta (Bursβ). Thus, ERNs far predate the emergence of ecdysis, but the question as to their ancestral functions remains unresolved. Here, we compare the ERN toolkits and temporal expression profiles of six ecdysozoans (tardigrades, crustaceans, and insects), eight lophotrochozoans (planarians, annelids, and mollusks), and five deuterostomes (crinoids, sea urchins, and hemichordates). Our results show that the major, coordinated upregulation of ERNs always coincides with a transition between key life history stages, such as hatching in direct developers and metamorphosis in indirect developers. This implies that ERNs already played an ancestral role in the switch from embryonic or larval ontogeny to juvenile maturation in the last common ancestor of Nephrozoa. Consequently, the transcriptional signature of invertebrate life cycle transitions presented here was already in place in the Precambrian and was only secondarily co-opted into regulating the molting process at the dawn of Ecdysozoa.
Topics: Animals; Biological Evolution; Life Cycle Stages; Molting; Neuropeptides
PubMed: 33125864
DOI: 10.1016/j.cub.2020.10.004 -
Journal of Photochemistry and... Sep 2022Scorpion fluorescence under ultraviolet light is a well-known phenomenon, and its change is also a known biological feature during the scorpion moulting process....
Scorpion fluorescence under ultraviolet light is a well-known phenomenon, and its change is also a known biological feature during the scorpion moulting process. However, the synthesis and transport of fluorescent substances during the moulting stage remain unclear. In this study, in-depth investigations on the global fluorescence changes from the exoskeleton, fluorescence layer, coelomic fluid, and abdomen to the digestive glands indicated that the digestive glands, which occupy most of the space in the abdomen of the scorpion mesosoma segment, were responsible for synthesizing the fluorescent substances. More importantly, these fluorescent substances were produced in advance, before the moulting process, which contributed to the recovery of the fluorescent exoskeleton as early as possible. The synthesized fluorescent substances first entered the coelomic fluid, then successively passed through the inherent epithelial cell layer and two new formed endocuticle and exocuticle layers, and ultimately reached and became enriched in the new formed fluorescent layer, which was protected by the new epicuticle layer. These four new layers were the first to illustrate the structural features of the fluorescent exoskeleton. Due to the very soft body and the inability of the newly moulted scorpion to resist attacks from the predator, this special synthesis and transport strategy of the fluorescent substances could guarantee the rapid formation of the integrated fluorescent exoskeleton during the 24 h after ecdysis, which would be a novel biological feature during the scorpion evolution.
Topics: Animals; Molting; Scorpions
PubMed: 35816856
DOI: 10.1016/j.jphotobiol.2022.112511 -
The Journal of Experimental Biology Apr 2023In many taxa, the subsocial route is considered the main pathway to permanent sociality, but the relative contribution of offspring interactions and parental care to the...
In many taxa, the subsocial route is considered the main pathway to permanent sociality, but the relative contribution of offspring interactions and parental care to the maintenance of cohesion and tolerance at advanced developmental stages remains poorly studied. Spiders are relevant models for this question because they all show a transient gregarious phase before dispersal, and the transition to permanent sociality, which concerns approximately 20 of the ∼50,000 species, is assumed to rely on the subsocial route. Using spiderlings of the solitary species Agelena labyrinthica, we manipulated the social context to demonstrate that tolerance in aggressive juveniles can be restored when exposed to siblings after moulting. We propose that moulting can reopen closed critical periods and renew the imprinting to social cues and thus lead to the reacquisition of tolerance. Our study highlights the critical role of contacts between juveniles in the expression of tolerance, which opens novel avenues for understanding social transitions.
Topics: Animals; Molting; Social Behavior; Aggression; Cues; Spiders
PubMed: 36939384
DOI: 10.1242/jeb.245387 -
Philosophical Transactions of the Royal... Oct 2019The three modes of insect postembryonic development are ametaboly, hemimetaboly and holometaboly, the latter being considered the only significant metamorphosis mode....
The three modes of insect postembryonic development are ametaboly, hemimetaboly and holometaboly, the latter being considered the only significant metamorphosis mode. However, the emergence of hemimetaboly, with the genuine innovation of the final moult, represents the origin of insect metamorphosis and a necessary step in the evolution of holometaboly. Hemimetaboly derives from ametaboly and might have appeared as a consequence of wing emergence in Pterygota, in the early Devonian. In extant insects, the final moult is mainly achieved through the degeneration of the prothoracic gland (PG), after the formation of the winged and reproductively competent adult stage. Metamorphosis, including the formation of the mature wings and the degeneration of the PG, is regulated by the MEKRE93 pathway, through which juvenile hormone precludes the adult morphogenesis by repressing the expression of transcription factor E93, which triggers this change. The MEKRE93 pathway appears conserved in extant metamorphosing insects, which suggest that this pathway was operative in the Pterygota last common ancestor. We propose that the final moult, and the consequent hemimetabolan metamorphosis, is a monophyletic innovation and that the role of E93 as a promoter of wing formation and the degeneration of the PG was mechanistically crucial for their emergence. This article is part of the theme issue 'The evolution of complete metamorphosis'.
Topics: Animals; Biological Evolution; Insecta; Molting
PubMed: 31438822
DOI: 10.1098/rstb.2018.0415 -
Fish & Shellfish Immunology Mar 2022The widespread occurrence and accumulation of plastic waste have been globally recognized as a critical issue. However, few researches have evaluated the adverse effects...
The widespread occurrence and accumulation of plastic waste have been globally recognized as a critical issue. However, few researches have evaluated the adverse effects of nanoplastics to freshwater organisms. Thus, here, the effects of polystyrene nanoplastics (PS-NP) on the physiological changes (i.e., molting) and enzyme activity of oxidative stress were investigated in the adult freshwater prawn Macrobrachium nipponense. Based on a previous study and environmental microplastic concentrations, the prawn was exposed to 0, 0.04, 0.4, 4, and 40 mg/L waterborne PS-NP for 21 days. The results showed that growth and survival-related parameters were not affected by all PS-NP groups, while the molting rate were significantly decreased in the 4 and 40 mg/L PS-NP group. Meanwhile, the expression of molting-related gene (calcium-calmodulin-dependent protein kinase I, ecdysteroid receptor, and leucine-rich repeat-containing G-protein-coupled receptor 2) were significantly decreased. HO content was significantly increased in all PS-NP groups relative to the control. Lower concentrations of PS-NP increased the activity of superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GSH-Px), whereas increased concentrations, decreased SOD, GST, and GSH-Px activity. These results suggest that chronic exposure to PS-NP at an environmental concentration impaired molting and induced oxidative stress in the adult river prawn Macrobrachium nipponense. The findings provided basic information for assessing the risk assessment of nanoplastics and revealing the molecular mechanisms of nanoplastics toxicity.
Topics: Animals; Hydrogen Peroxide; Microplastics; Molting; Oxidative Stress; Palaemonidae; Plastics; Polystyrenes; Water Pollutants, Chemical
PubMed: 35182722
DOI: 10.1016/j.fsi.2022.02.028