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Current Biology : CB Jun 2019Many animals undergo a transition during their lifetime from a larval to an adult form, a major developmental change known as metamorphosis. This developmental process,...
Many animals undergo a transition during their lifetime from a larval to an adult form, a major developmental change known as metamorphosis. This developmental process, which involves behavioural, morphological, physiological and biochemical changes, has a broad phylogenetic distribution, occurring in diverse branches of the animal kingdom, from invertebrates (molluscs, arthropods, tunicates) to certain classes of vertebrates, including amphibians (Figure 1). This phenomenon, which has fascinated biologists for centuries, remains an attractive experimental model for studying mechanisms of post-embryonic development as well as molecular mechanisms underlying hormonal regulation.
Topics: Amphibians; Animals; Larva; Locomotion; Metamorphosis, Biological; Nerve Net; Neuronal Plasticity; Respiration
PubMed: 31211970
DOI: 10.1016/j.cub.2019.05.005 -
ELife Dec 2023Experiments exploring the role of juvenile hormone during the life cycle of firebrat insects provide clues about the evolution of metamorphosis.
Experiments exploring the role of juvenile hormone during the life cycle of firebrat insects provide clues about the evolution of metamorphosis.
Topics: Animals; Metamorphosis, Biological; Insecta; Life Cycle Stages; Juvenile Hormones
PubMed: 38126357
DOI: 10.7554/eLife.94410 -
Environmental Pollution (Barking, Essex... Oct 2022Both amphibian metamorphosis assay (AMA) and larval amphibian growth and development assay (LAGDA) can detect thyroid-mediated modality and adversity on the basis of... (Review)
Review
Both amphibian metamorphosis assay (AMA) and larval amphibian growth and development assay (LAGDA) can detect thyroid-mediated modality and adversity on the basis of morphological changes during the thyroid hormone-dependent metamorphosis. They are used for identification of thyroid hormone system disrupting chemicals (TDCs) for non-target organisms or the environment. The EU Guidance recommends that the AMA and the LAGDA should be used to address sufficient investigation of the thyroid-mediated modality and adversity, respectively. In the EU discussions over identification of TDCs, the necessity of using LAGDA as a follow-up of positive results of the AMA has been questioned because of the overlap between the endpoints and the exposure of both tests. This study analyzed similarities, differences, and sensitivity of these two assays in detection of TDCs. For agonists and most of antagonists of the hypothalamic-pituitary-thyroid (HPT) axis, both AMA and LAGDA can detect the thyroid-mediated modality and adversity. The LAGDA, as a follow-up of the positive results of the AMA, may not be needed because the results of AMA are considered enough for identification of TDCs. For chemicals like inhibitors of iodotyrosine deiodinase, the LAGDA is considered necessary for identification of TDCs because the thyroid-mediated adversity cannot be detected until Nieuwkoop and Faber (NF) stage 62. Incorporation of mechanistic endpoints into existing test guidelines and the use of Xenopus Eleutheroembryo Thyroid Assay (XETA), extended amphibian metamorphosis assay (EAMA) and adverse outcome pathways (AOPs) for testing and identification of TDCs are further discussed.
Topics: Animals; Endocrine Disruptors; Larva; Metamorphosis, Biological; Thyroid Gland; Thyroid Hormones; Xenopus laevis
PubMed: 35998776
DOI: 10.1016/j.envpol.2022.120006 -
Current Opinion in Neurobiology Oct 2023The transition from larval to adult locomotion in the anuran, Xenopus laevis, involves a dramatic switch from axial to appendicular swimming including intermediate... (Review)
Review
The transition from larval to adult locomotion in the anuran, Xenopus laevis, involves a dramatic switch from axial to appendicular swimming including intermediate stages when the tail and hindlimbs co-exist and contribute to propulsion. Hatchling tadpole swimming is generated by an axial central pattern generator (CPG) which matures rapidly during early larval life. During metamorphosis, the developing limbs are controlled by a de novo appendicular CPG driven initially by the axial system before segregating to allow both systems to operate together or independently. Neuromodulation plays important roles throughout, but key modulators switch their effects from early inhibitory influences to facilitating locomotion. Temperature affects the construction and operation of locomotor networks and global changes in environmental temperature place aquatic poikilotherms, like amphibians, at risk. The locomotor control strategy of anurans differs from other amphibian groups such as salamanders, where evolution has acted upon the thyroid hormone pathway to sculpt different developmental outcomes.
Topics: Animals; Spinal Cord; Larva; Locomotion; Swimming; Anura; Metamorphosis, Biological
PubMed: 37549591
DOI: 10.1016/j.conb.2023.102753 -
Developmental Biology Jul 2022External environmental cues can have significant impacts on the timing and outcomes of animal development. For the swimming larvae of many marine invertebrates, the...
External environmental cues can have significant impacts on the timing and outcomes of animal development. For the swimming larvae of many marine invertebrates, the presence of specific surface-bound bacteria are important cues that help larvae identify a suitable location on the sea floor for metamorphosis and adult life. While metamorphosis in response to bacteria occurs in diverse animals from across the animal tree of life, we know little about the signal transduction cascades stimulated at the onset of metamorphosis upon their interaction with bacteria. The metamorphosis of a model tubeworm, Hydroides elegans, is triggered by the bacterium Pseudoalteromonas luteoviolacea which produces a stimulatory protein called Mif1. In this work, we define three key nodes in a signaling cascade promoting Hydroides metamorphosis in response to Mif1. Using metabolomic profiling, we find that the stimulation of Hydroides larvae by P. luteoviolacea leads to an increase in diacylglycerol during the initiation of metamorphosis, and that Mif1 is necessary for this upregulation. Genomic and pharmacological examination suggests that diacylglycerol triggers a phosphotransferase signaling cascade involving Protein Kinase C (PKC) and Mitogen-Activated Protein Kinase (MAPK), to induce Hydroides metamorphosis. Additionally, Mif1 activates the expression of two nuclear hormone receptors, HeNHR1 and HeNHR2 in the cerebral ganglia of Hydroides larvae. Our results define a post-translational signal transduction pathway mediating bacteria-stimulated metamorphosis in a model invertebrate animal.
Topics: Animals; Diglycerides; Larva; Metamorphosis, Biological; Mitogen-Activated Protein Kinases; Polychaeta; Protein Kinase C; Signal Transduction
PubMed: 35500661
DOI: 10.1016/j.ydbio.2022.04.009 -
Genes Dec 2022Metamorphosis is a critical process in the transition from planktonic life to benthic life for marine invertebrates, which is accompanied by a large amount of energy...
Metamorphosis is a critical process in the transition from planktonic life to benthic life for marine invertebrates, which is accompanied by a large amount of energy consumption. Previous studies have proved that AMP-activated protein kinase (AMPK), as a vital energy regulator, plays a prominent role in mediating the growth and development of terrestrial animals. However, its function in the growth and development of marine invertebrates, especially in metamorphosis, remains elusive. This study explored the function of AMPK in the larval metamorphosis of . The full-length cDNA of genes in was cloned and characterized, which is composed of three subunits, , , and . Pharmacological tests demonstrated that through the application of an AMPK activator, AMP substantially enhanced the larval metamorphosis rate ( < 0.05). By contrast, the larval metamorphosis rate decreased significantly after being treated with the AMPK inhibitor Compound C ( < 0.05). gene knock-down resulted in a reduction in gene expression ( < 0.05), and the larval metamorphosis of was significantly restrained ( < 0.05). These results indicated that AMPK signaling is vital in the larval metamorphosis of , which advances further understanding in exploring the molecular mechanisms in the metamorphosis of marine invertebrate larvae.
Topics: Animals; Mytilus; AMP-Activated Protein Kinases; Metamorphosis, Biological; Larva
PubMed: 36553651
DOI: 10.3390/genes13122384 -
Experimental Dermatology Apr 2015Present-day hairs and feathers are marvels of biological engineering perfected over 200 million years of convergent evolution. Prominently, both follicle types coevolved...
Present-day hairs and feathers are marvels of biological engineering perfected over 200 million years of convergent evolution. Prominently, both follicle types coevolved regenerative cycling, wherein active filament making (anagen) is intermitted by a phase of relative quiescence (telogen). Such regenerative cycling enables follicles to “reload” their morphogenetic program and make qualitatively different filaments in the consecutive cycles. Indeed, many species of mammals and birds undergo regenerative metamorphosis, prominently changing their integument between juvenile and adult forms. This phenomenon is inconspicuous in mice, which led to the conventional perception that hair type is hardwired during follicle morphogenesis and cannot switch. A series of recent works by Chi and Morgan change this perception, and show that many mouse follicles naturally switch hair morphologies, for instance from “wavy” zigzag to straight awl, in the second growth cycle. A series of observations and genetic experiments show that back and forth hair type switching depends on the number of cells in the follicle's dermal papilla, with the critical threshold being around 40-50 cells. Pigmentation is another parameter that hair and feather follicles can reload between cycles, and even midway through anagen. Recent works show that hair and feather pigmentation “printing” programs coevolved to rely on pulsed expression of Agouti, a melanocortin receptor-1 antagonist, in the follicular mesenchyme. Here, we discuss broader implications of hair and feather regenerative plasticity.
Topics: Animals; Biological Evolution; Feathers; Hair; Hair Follicle; Metamorphosis, Biological; Regeneration
PubMed: 25557541
DOI: 10.1111/exd.12627 -
Proceedings of the National Academy of... May 2022How larvae of the many phyla of marine invertebrates find places appropriate for settlement, metamorphosis, growth, and reproduction is an enduring question in marine...
How larvae of the many phyla of marine invertebrates find places appropriate for settlement, metamorphosis, growth, and reproduction is an enduring question in marine science. Biofilm-induced metamorphosis has been observed in marine invertebrate larvae from nearly every major marine phylum. Despite the widespread nature of this phenomenon, the mechanism of induction remains poorly understood. The serpulid polychaete Hydroides elegans is a well established model for investigating bacteria-induced larval development. A broad range of biofilm bacterial species elicit larval metamorphosis in H. elegans via at least two mechanisms, including outer membrane vesicles (OMVs) and complexes of phage-tail bacteriocins. We investigated the interaction between larvae of H. elegans and the inductive bacterium Cellulophaga lytica, which produces an abundance of OMVs but not phage-tail bacteriocins. We asked whether the OMVs of C. lytica induce larval settlement due to cell membrane components or through delivery of specific cargo. Employing a biochemical structure–function approach with a strong ecological focus, the cells and OMVs produced by C. lytica were interrogated to determine the class of the inductive compounds. Here, we report that larvae of H. elegans are induced to metamorphose by lipopolysaccharide produced by C. lytica. The widespread prevalence of lipopolysaccharide and its associated taxonomic and structural variability suggest it may be a broadly employed cue for bacterially induced larval settlement of marine invertebrates.
Topics: Animals; Bacteria; Biofilms; Invertebrates; Larva; Lipopolysaccharides; Metamorphosis, Biological
PubMed: 35467986
DOI: 10.1073/pnas.2200795119 -
Frontiers in Bioscience (Landmark... Jan 2020In some adult holometabolous insects, specific epithelial tissues form imaginal discs, small sac-like clusters of cells that form in the larval body. During... (Review)
Review
In some adult holometabolous insects, specific epithelial tissues form imaginal discs, small sac-like clusters of cells that form in the larval body. During metamorphosis, in response to hormones, the discs undergo dramatic changes including cell proliferation and differentiation. In Bombyx mori insects, the cuticular protein (CP) genes, which are expressed at prepupal stage in the wing discs, are divided into six groups according to their developmental expression profile and responsiveness to steroid hormones. In this article, we discuss the expression of CP genes in the wing disc, and examine the molecular mechanisms by which metamorphosis and cell transformations are regulated by hormones in insects.
Topics: Animals; Bombyx; Ecdysone; Gene Expression Regulation, Developmental; Imaginal Discs; Insect Proteins; Larva; Metamorphosis, Biological; Pupa; Wings, Animal
PubMed: 31585879
DOI: 10.2741/4796 -
Developmental Dynamics : An Official... Dec 2021Metamorphosis in marine species is characterized by profound changes at the ecophysiological, morphological, and cellular levels. The cnidarian Clytia hemisphaerica...
BACKGROUND
Metamorphosis in marine species is characterized by profound changes at the ecophysiological, morphological, and cellular levels. The cnidarian Clytia hemisphaerica exhibits a triphasic life cycle that includes a planula larva, a colonial polyp, and a sexually reproductive medusa. Most studies so far have focused on the embryogenesis of this species, whereas its metamorphosis has been only partially studied.
RESULTS
We investigated the main morphological changes of the planula larva of Clytia during the metamorphosis, and the associated cell proliferation and apoptosis. Based on our observations of planulae at successive times following artificial metamorphosis induction using GLWamide, we subdivided the Clytia's metamorphosis into a series of eight morphological stages occurring during a pre-settlement phase (from metamorphosis induction to planula ready for settlement) and the post-settlement phase (from planula settlement to primary polyp). Drastic morphological changes prior to definitive adhesion to the substrate were accompanied by specific patterns of stem-cell proliferation as well as apoptosis in both ectoderm and endoderm. Further waves of apoptosis occurring once the larva has settled were associated with morphogenesis of the primary polyp.
CONCLUSION
Clytia larval metamorphosis is characterized by distinct patterns of apoptosis and cell proliferation during the pre-settlement phase and the settled planula-to-polyp transformation.
Topics: Animals; Apoptosis; Cell Polarity; Cell Proliferation; Hydrozoa; Larva; Life Cycle Stages; Metamorphosis, Biological; Stem Cells
PubMed: 34036636
DOI: 10.1002/dvdy.376