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Biology Letters Aug 2023Palaeoecological deductions are vital for understanding the evolution and diversification of species within prehistoric environments. This review highlights the... (Review)
Review
Palaeoecological deductions are vital for understanding the evolution and diversification of species within prehistoric environments. This review highlights the multitude of ways in which the microanatomy and microscopic structure of bones enables palaeoecological deductions. The occurrence of growth marks in bones is discussed, and their usefulness in deducing the ontogenetic status and age of individuals is considered, as well as how such marks in bones permit the assessment of the growth dynamics of individuals and species. Here osteohistology is shown to provide insight into the structure of past populations, as well as ecological relationships between individuals. In addition, the response of bones to trauma, disease and moulting is considered. Finally, I explore how osteohistology can give insight into ecomorphological adaptations, such as filter feeding, probe feeding and saltatorial locomotion. Methodological advances in three-dimensional microtomography and synchrotron scanning bodes well for future studies in osteohistology and despite some compromises in terms of tissue identity, circumvents the crucial issue of destructive analyses.
Topics: Humans; Locomotion; Molting
PubMed: 37607578
DOI: 10.1098/rsbl.2023.0245 -
WormBook : the Online Review of C.... Mar 2007The nematode cuticle is an extremely flexible and resilient exoskeleton that permits locomotion via attachment to muscle, confers environmental protection and allows... (Review)
Review
The nematode cuticle is an extremely flexible and resilient exoskeleton that permits locomotion via attachment to muscle, confers environmental protection and allows growth by molting. It is synthesised five times, once in the embryo and subsequently at the end of each larval stage prior to molting. It is a highly structured extra-cellular matrix (ECM), composed predominantly of cross-linked collagens, additional insoluble proteins termed cuticlins, associated glycoproteins and lipids. The cuticle collagens are encoded by a large gene family that are subject to strict patterns of temporal regulation. Cuticle collagen biosynthesis involves numerous co- and post-translational modification, processing, secretion and cross-linking steps that in turn are catalysed by specific enzymes and chaperones. Mutations in individual collagen genes and their biosynthetic pathway components can result in a range of defects from abnormal morphology (dumpy and blister) to embryonic and larval death, confirming an essential role for this structure and highlighting its potential as an ECM experimental model system.
Topics: Animals; Caenorhabditis elegans; Collagen; Molting
PubMed: 18050497
DOI: 10.1895/wormbook.1.138.1 -
Cell Death and Differentiation Jan 2020The removal of superfluous and unwanted cells is a critical part of animal development. In insects the steroid hormone ecdysone, the focus of this review, is an... (Review)
Review
The removal of superfluous and unwanted cells is a critical part of animal development. In insects the steroid hormone ecdysone, the focus of this review, is an essential regulator of developmental transitions, including molting and metamorphosis. Like other steroid hormones, ecdysone works via nuclear hormone receptors to direct spatial and temporal regulation of gene transcription including genes required for cell death. During insect metamorphosis, pulses of ecdysone orchestrate the deletion of obsolete larval tissues, including the larval salivary glands and the midgut. In this review we discuss the molecular machinery and mechanisms of ecdysone-dependent cell and tissue removal, with a focus on studies in Drosophila and Lepidopteran insects.
Topics: Animals; Cell Death; Drosophila; Ecdysone; Lepidoptera; Metamorphosis, Biological; Molting
PubMed: 31745213
DOI: 10.1038/s41418-019-0456-9 -
Scientific Reports Jan 2023The ability of animals to sync the timing and location of molting (the replacement of hair, skin, exoskeletons or feathers) with peaks in resource availability has...
The ability of animals to sync the timing and location of molting (the replacement of hair, skin, exoskeletons or feathers) with peaks in resource availability has important implications for their ecology and evolution. In migratory birds, the timing and location of pre-migratory feather molting, a period when feathers are shed and replaced with newer, more aerodynamic feathers, can vary within and between species. While hypotheses to explain the evolution of intraspecific variation in the timing and location of molt have been proposed, little is known about the genetic basis of this trait or the specific environmental drivers that may result in natural selection for distinct molting phenotypes. Here we take advantage of intraspecific variation in the timing and location of molt in the iconic songbird, the Painted Bunting (Passerina ciris) to investigate the genetic and ecological drivers of distinct molting phenotypes. Specifically, we use genome-wide genetic sequencing in combination with stable isotope analysis to determine population genetic structure and molting phenotype across thirteen breeding sites. We then use genome-wide association analysis (GWAS) to identify a suite of genes associated with molting and pair this with gene-environment association analysis (GEA) to investigate potential environmental drivers of genetic variation in this trait. Associations between genetic variation in molt-linked genes and the environment are further tested via targeted SNP genotyping in 25 additional breeding populations across the range. Together, our integrative analysis suggests that molting is in part regulated by genes linked to feather development and structure (GLI2 and CSPG4) and that genetic variation in these genes is associated with seasonal variation in precipitation and aridity. Overall, this work provides important insights into the genetic basis and potential selective forces behind phenotypic variation in what is arguably one of the most important fitness-linked traits in a migratory bird.
Topics: Animals; Molting; Genome-Wide Association Study; Songbirds; Passeriformes; Feathers; Seasons
PubMed: 36646769
DOI: 10.1038/s41598-022-26973-7 -
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 2021A pair of Y-organs (YOs) are the molting glands of decapod crustaceans. They synthesize and secrete steroid molting hormones (ecdysteroids) and their activity is... (Review)
Review
A pair of Y-organs (YOs) are the molting glands of decapod crustaceans. They synthesize and secrete steroid molting hormones (ecdysteroids) and their activity is controlled by external and internal signals. The YO transitions through four physiological states over the molt cycle, which are mediated by molt-inhibiting hormone (MIH; basal state), mechanistic Target of Rapamycin Complex 1 (mTORC1; activated state), Transforming Growth Factor-β (TGFβ)/Activin (committed state), and ecdysteroid (repressed state) signaling pathways. MIH, produced in the eyestalk X-organ/sinus gland complex, inhibits the synthesis of ecdysteroids. A model for MIH signaling is organized into a cAMP/Ca-dependent triggering phase and a nitric oxide/cGMP-dependent summation phase, which maintains the YO in the basal state during intermolt. A reduction in MIH release triggers YO activation, which requires mTORC1-dependent protein synthesis, followed by mTORC1-dependent gene expression. TGFβ/Activin signaling is required for YO commitment in mid-premolt. The YO transcriptome has 878 unique contigs assigned to 23 KEGG signaling pathways, 478 of which are differentially expressed over the molt cycle. Ninety-nine contigs encode G protein-coupled receptors (GPCRs), 65 of which bind a variety of neuropeptides and biogenic amines. Among these are putative receptors for MIH/crustacean hyperglycemic hormone neuropeptides, corazonin, relaxin, serotonin, octopamine, dopamine, allatostatins, Bursicon, ecdysis-triggering hormone (ETH), CCHamide, FMRFamide, and proctolin. Contigs encoding receptor tyrosine kinase insulin-like receptor, epidermal growth factor (EGF) receptor, and fibroblast growth factor (FGF) receptor and ligands EGF and FGF suggest that the YO is positively regulated by insulin-like peptides and growth factors. Future research should focus on the interactions of signaling pathways that integrate physiological status with environmental cues for molt control.
Topics: Animals; Decapoda; Ecdysteroids; Gene Expression Regulation; Insect Proteins; Molting; Signal Transduction
PubMed: 34234741
DOI: 10.3389/fendo.2021.674711 -
PloS One 2021The crustacean molting process is regulated by an interplay of hormones produced by the eyestalk ganglia and Y-organs (YO). Molt-inhibiting hormone and crustacean...
Understanding molt control switches: Transcriptomic and expression analysis of the genes involved in ecdysteroidogenesis and cholesterol uptake pathways in the Y-organ of the blue crab, Callinectes sapidus.
The crustacean molting process is regulated by an interplay of hormones produced by the eyestalk ganglia and Y-organs (YO). Molt-inhibiting hormone and crustacean hyperglycemic hormone released by the sinus gland of the eyestalk ganglia (EG) inhibit the synthesis and secretion of ecdysteroid by the YO, hence regulating hemolymph levels during the molt cycle. The purpose of this study is to investigate the ecdysteroidogenesis pathway, specifically genes linked to changes in ecdysteroid levels occurring at early premolt (ePM). To this end, a reference transcriptome based on YO, EG, and hepatopancreas was de novo assembled. Two genes (cholesterol 7-desaturase Neverland and cytochrome p450 307a1-like Spook) involved in ecdysteroidogenesis were identified from the YO transcriptome using sequence comparisons and transcript abundance. Two other candidates, Hormone receptor 4 and probable cytochrome p450 49a1 potentially involved in ecdysteroidogenesis were also identified. Since cholesterol is the ecdysteroid precursor, a putative cholesterol carrier (Apolipoprotein D-like) was also examined to understand if cholesterol uptake coincided with the increase in the ecdysteroid levels at the ePM stage. The expression level changes of the five candidate genes in the YO were compared between intermolt (IM) and induced ePM (iePM) stages using transcriptomic analysis. Expression analysis using qPCR were carried out at IM, iePM, and normal ePM. The increase in Spook and Neverland expression in the YO at the ePM was accompanied by a concomitant rise in ecdysteroid levels. The data obtained from iePM stage were congruent with those obtained from the normal ePM stage of intact control animals. The present findings support the role of Halloween genes in the ecdysteroidogenesis and molt cycle in the blue crab, Callinectes sapidus.
Topics: Animals; Arthropod Proteins; Brachyura; Cholesterol; Ecdysteroids; Gene Expression Regulation, Developmental; Hemolymph; Invertebrate Hormones; Molting; Transcriptome
PubMed: 34478479
DOI: 10.1371/journal.pone.0256735 -
Poultry Science Jun 2003Postnuptial molt is the major molt that occurs in most wild and domestic avian species each year. The process is much more than the replacement of feathers. Studies have... (Review)
Review
Postnuptial molt is the major molt that occurs in most wild and domestic avian species each year. The process is much more than the replacement of feathers. Studies have shown that a significant increase in metabolic rate, increase in whole body protein synthesis, osteoporosis, loss of body fat, and a suppression of the immune system occur during this event of a bird's annual cycle. Several procedures have been developed to initiate feather replacement, and this review addresses hormonal and neuropeptide treatments that effected molt. The administration of thyroxine, progesterone, gonadotropin-releasing hormone agonist, and prolactin were examined. Of the four, the two most effective were thyroxine and prolactin administration. The neural modulators known to release thyroxine and prolactin, respectively, are thyroid hormone releasing hormone (TRH) and vasoactive intestinal polypeptide (VIP). To gain insight into the possible functions of VIP and TRH, the distribution of these neuromodulators and their terminal fields were reviewed in the avian brain. It was found that VIP-containing neurons and fibers identified a neural system in birds comparable to the visceral forebrain system (VFS) described in mammals. The VFS functions to regulate the balance of the autonomic nervous system. The autonomic nervous system and, therefore, the VFS have been proposed to regulate the many behavioral and physiological events in the annual cycle of a bird, including postnuptial molt. In contrast to VIP that has an extensive brain distribution throughout the forebrain and brainstem, TRH is relatively restrictive and has a main concentration in nerve cells in and about the paraventricular nucleus, a key neural component of the VFS. Due to the roll of TRH in regulating the thyroid axis and operating within the framework of the VFS, it is proposed that the peptide functions to shift the balance of the autonomic nervous system in the direction of the sympathetic nervous system. A shift toward the dominance of the sympathetic nervous system appears to be required during this phase of a bird's yearly cycle.
Topics: Animals; Animals, Wild; Autonomic Nervous System; Birds; Body Composition; Female; Gonadotropin-Releasing Hormone; Immune System; Male; Molting; Neuropeptides; Periodicity; Progesterone; Prolactin; Prosencephalon; Thyroxine
PubMed: 12817454
DOI: 10.1093/ps/82.6.981 -
General and Comparative Endocrinology 2007Insect ecdysis sequence is composed of pre-ecdysis, ecdysis and post-ecdysis behaviors controlled by a complex cascade of peptide hormones from endocrine Inka cells and... (Review)
Review
Insect ecdysis sequence is composed of pre-ecdysis, ecdysis and post-ecdysis behaviors controlled by a complex cascade of peptide hormones from endocrine Inka cells and neuropeptides in the central nervous system (CNS). Inka cells produce pre-ecdysis and ecdysis triggering hormones (ETH) which activate the ecdysis sequence through receptor-mediated actions on specific neurons in the CNS. Multiple experimental approaches have been used to determine mechanisms of ETH expression and release from Inka cells and its action on the CNS of moths and flies. During the preparatory phase 1-2 days prior to ecdysis, high ecdysteroid levels induce expression of ETH receptors in the CNS and increased ETH production in Inka cells, which coincides with expression of nuclear ecdysone receptor (EcR) and transcription factor cryptocephal (CRC). However, high ecdysteroid levels prevent ETH release from Inka cells. Acquisition of Inka cell competence to release ETH requires decline of ecdysteroid levels and beta-FTZ-F1 expression few hours prior to ecdysis. The behavioral phase is initiated by ETH secretion into the hemolymph, which is controlled by two brain neuropeptides-corazonin and eclosion hormone (EH). Corazonin acts on its receptor in Inka cells to elicit low level ETH secretion and initiation of pre-ecdysis, while EH induces cGMP-mediated ETH depletion and consequent activation of ecdysis. The activation of both behaviors is accomplished by ETH action on central neurons expressing ETH receptors A and B (ETHR-A and B). These neurons produce numerous excitatory or inhibitory neuropeptides which initiate or terminate different phases of the ecdysis sequence. Our data indicate that insect ecdysis is a very complex process characterized by two principal steps: (1) ecdysteroid-induced expression of receptors and transcription factors in the CNS and Inka cells. (2) Release and interaction of Inka cell peptide hormones and multiple central neuropeptides to control consecutive phases of the ecdysis sequence.
Topics: Amino Acid Sequence; Animals; Ecdysteroids; Insect Hormones; Molecular Sequence Data; Molting; Neuropeptides; Receptors, Neuropeptide; Receptors, Peptide; Receptors, Steroid; Sequence Homology, Amino Acid; Signal Transduction; Transcription Factors
PubMed: 17507015
DOI: 10.1016/j.ygcen.2007.04.002 -
Poultry Science Jun 2003The initiation of seasonal feather molting in wild avian species frequently coincides with incubation of eggs and brooding of offspring. A period of natural inappetence... (Review)
Review
The initiation of seasonal feather molting in wild avian species frequently coincides with incubation of eggs and brooding of offspring. A period of natural inappetence or anorexia usually accompanies this molt. This is particularly true of the jungle fowl, the wild ancestor of the domestic chicken. Brooding of eggs by the jungle fowl is accompanied by spontaneous anorexia, with little food or water consumed throughout the period of egg incubation. During this time, the reproductive tract regresses, and feather molting is initiated. Selective breeding for a high rate of egg production has blunted the response of the commercial laying hen to exogenous environmental cues and reduced or eliminated the endogenous biological cues that coordinate initiation of seasonal molting. However, commercial layers retain in their physiological repertoire the ability to tolerate prolonged fasting and to undergo a spontaneous regression of the reproductive tract and feather molting. Induction of a coordinated molt, by manipulation of environmental and nutritional cues, or endocrine manipulation, can be used in domestic hens to regress and regenerate the reproductive tract. This improves subsequent egg production and eggshell quality. This process also induces temporary recrudescence of lymphoid tissues and may alter immune function in hens. The process of molting, and the subsequent recovery from the molt, may be viewed as a complex physiological constellation, induced by environmental and nutritional cues, involving endocrine systems, reproductive tissue structure and function, lymphoid structure, and immune function.
Topics: Agriculture; Animal Husbandry; Animals; Animals, Wild; Chickens; Drinking; Eating; Eggs; Endocrine System; Environment; Female; Food Deprivation; Immune System; Molting; Nutritional Status; Seasons
PubMed: 12817453
DOI: 10.1093/ps/82.6.971