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Integrative and Comparative Biology Sep 2021Ascidians are invertebrate chordates, with swimming chordate tadpole larvae that have distinct heads and tails. The head contains the small brain, sensory organs,... (Review)
Review
Ascidians are invertebrate chordates, with swimming chordate tadpole larvae that have distinct heads and tails. The head contains the small brain, sensory organs, including the ocellus (light) and otolith (gravity) and the presumptive endoderm, while the tail has a notochord surrounded by muscle cells and a dorsal nerve cord. One of the chordate features is a post-anal tail. Ascidian tadpoles are nonfeeding, and their tails are critical for larval locomotion. After hatching the larvae swim up toward light and are carried by the tide and ocean currents. When competent to settle, ascidian tadpole larvae swim down, away from light, to settle and metamorphose into a sessile adult. Tunicates are classified as chordates because of their chordate tadpole larvae; in contrast, the sessile adult has a U-shaped gut and very derived body plan, looking nothing like a chordate. There is one group of ascidians, the Molgulidae, where many species are known to have tailless larvae. The Swalla Lab has been studying the evolution of tailless ascidian larvae in this clade for over 30 years and has shown that tailless larvae have evolved independently several times in this clade. Comparison of the genomes of two closely related species, the tailed Molgula oculata and tailless Molgula occulta reveals much synteny, but there have been multiple insertions and deletions that have disrupted larval genes in the tailless species. Genomics and transcriptomics have previously shown that there are pseudogenes expressed in the tailless embryos, suggesting that the partial rescue of tailed features in their hybrid larvae is due to the expression of intact genes from the tailed parent. Yet surprisingly, we find that the notochord gene regulatory network is mostly intact in the tailless M. occulta, although the notochord does not converge and extend and remains as an aggregate of cells we call the "notoball." We expect that eventually many of the larval gene networks will become evolutionarily lost in tailless ascidians and the larval body plan abandoned, with eggs developing directly into an adult. Here we review the current evolutionary and developmental evidence on how the molgulids lost their tails.
Topics: Animals; Biological Evolution; Larva; Notochord; Tail; Urochordata
PubMed: 33881514
DOI: 10.1093/icb/icab022 -
Scientific Reports Jun 2021Chemosensory signals allow vertebrates and invertebrates not only to orient in its environment toward energy-rich food sources to maintain nutrition but also to avoid...
Chemosensory signals allow vertebrates and invertebrates not only to orient in its environment toward energy-rich food sources to maintain nutrition but also to avoid unpleasant or even poisonous substrates. Ethanol is a substance found in the natural environment of Drosophila melanogaster. Accordingly, D. melanogaster has evolved specific sensory systems, physiological adaptations, and associated behaviors at its larval and adult stage to perceive and process ethanol. To systematically analyze how D. melanogaster larvae respond to naturally occurring ethanol, we examined ethanol-induced behavior in great detail by reevaluating existing approaches and comparing them with new experiments. Using behavioral assays, we confirm that larvae are attracted to different concentrations of ethanol in their environment. This behavior is controlled by olfactory and other environmental cues. It is independent of previous exposure to ethanol in their food. Moreover, moderate, naturally occurring ethanol concentration of 4% results in increased larval fitness. On the contrary, higher concentrations of 10% and 20% ethanol, which rarely or never appear in nature, increase larval mortality. Finally, ethanol also serves as a positive teaching signal in learning and memory and updates valence associated with simultaneously processed odor information. Since information on how larvae perceive and process ethanol at the genetic and neuronal level is limited, the establishment of standardized assays described here is an important step towards their discovery.
Topics: Animals; Behavior, Animal; Drosophila melanogaster; Ethanol; Larva; Learning; Neurons; Odorants; Smell
PubMed: 34112872
DOI: 10.1038/s41598-021-91677-3 -
Journal of Insect Science (Online) Jul 2020Mosquito-transmitted diseases pose a threat for a great portion of the world population. Chemical insecticides are the main tool for mosquito control. Heavy dependence... (Review)
Review
Mosquito-transmitted diseases pose a threat for a great portion of the world population. Chemical insecticides are the main tool for mosquito control. Heavy dependence on chemicals created several problems such as resistance development in many mosquito species, environmental effects, and human health issues. Other tools for mosquito control were developed and used in some parts of the world. Ribonucleic acid interference (RNAi) is a reverse genetic mechanism that was recently introduced as a new tool for pest control. Regarding mosquito, RNAi was used to study gene function and to discover genes that can be used as targets for control purposes. Several delivery methods are used to induce RNAi in mosquito larvae. Some methods such as injection and soaking are used routinely in RNAi research but have no application in the field. Other methods such as nanoparticles and microbes have some characteristics that make them good candidates for field application. In this report, we will focus on delivery methods for RNAi in mosquito larvae and will give examples for each method.
Topics: Animals; Culicidae; Larva; Mosquito Control; RNA Interference
PubMed: 32725159
DOI: 10.1093/jisesa/ieaa074 -
Philosophical Transactions of the Royal... Oct 2019Many animals depend on microbial symbionts to provide nutrition, defence or other services. Holometabolous insects, as well as other animals that undergo metamorphosis,... (Review)
Review
Many animals depend on microbial symbionts to provide nutrition, defence or other services. Holometabolous insects, as well as other animals that undergo metamorphosis, face unique constraints on symbiont maintenance. Microbes present in larvae encounter a radical transformation of their habitat and may also need to withstand chemical and immunological challenges. Metamorphosis also provides an opportunity, in that symbiotic associations can be decoupled over development. For example, some holometabolous insects maintain the same symbiont as larvae and adults, but house it in different tissues; in other species, larvae and adults may harbour entirely different types or numbers of microbes, in accordance with shifts in host diet or habitat. Such flexibility may provide an advantage over hemimetabolous insects, in which selection on adult-stage microbial associations may be constrained by its negative effects on immature stages, and vice versa. Additionally, metamorphosis itself can be directly influenced by symbionts. Across disparate insect taxa, microbes protect hosts from pathogen infection, supply nutrients essential for rebuilding the adult body and provide cues regulating pupation. However, microbial associations remain completely unstudied for many families and even orders of Holometabola, and future research will undoubtedly reveal more links between metamorphosis and microbiota, two widespread features of animal life. This article is part of the theme issue 'The evolution of complete metamorphosis'.
Topics: Animals; Insecta; Larva; Metamorphosis, Biological; Microbiota; Symbiosis
PubMed: 31438811
DOI: 10.1098/rstb.2019.0068 -
Frontiers in Endocrinology 2020Physiological functions of juvenile hormone (JH) and molting hormone have been demonstrated in insects. JH, molting hormone and their mimics (insect growth regulators,...
Physiological functions of juvenile hormone (JH) and molting hormone have been demonstrated in insects. JH, molting hormone and their mimics (insect growth regulators, IGRs) show endocrine-disrupting effects not only on target pest insects but also on other arthropod species such as crustaceans. However, little is known about the endocrine-disrupting effects of IGRs on benthic crustaceans. In this study, laboratory experiments were conducted to investigate effects of representative innate JH in crustaceans (methyl farnesoate, MF) and molting hormone (20-hydroxyecdysone, 20E, active form of ecdysteroid) on larval stages of the kuruma prawn , which is a decapod crustacean living in warm seawater. Larval development of kuruma prawn progresses in the order of nauplius, zoea, mysis, and then post-larvae with molting and metamorphosis, but it is unknown whether both MF and 20E have crucial roles in metamorphosis and molting of this species. Treatments of either MF or 20E on shrimp larvae were attempted at each developmental stage and those effects were validated. In terms of EC values between mortality and metamorphosis, there were apparent differences in the transition from nauplius to zoea (MF: 7.67 and 0.12 μM; 20E: 3.84 and 0.06 μM in survival and metamorphic rates, respectively). In contrast, EC values in MF and 20E treatments showed high consistency in the transitions between zoea to mysis (EC values for survival; MF: 1.25 and 20E: 0.22 μM), and mysis to post-larvae (EC values for survival; MF: 0.65 and 20E: 0.46 μM). These data suggest that nauplius has strong resistance against exposure to MF and 20E. Moreover, both chemicals induced high mortality triggered by the disruption of molting associated with metamorphosis. To our knowledge, this is the first experimental evidence that investigates physiological functions of MF and 20E in the larval stages of kuruma prawn, shedding light on not only ecotoxicological impacts of IGRs released into nature, but also endocrine mechanisms underlying larval development with metamorphosis in benthic decapod crustaceans.
Topics: Animals; Ecdysterone; Fatty Acids, Unsaturated; Juvenile Hormones; Larva; Metamorphosis, Biological; Penaeidae
PubMed: 32849271
DOI: 10.3389/fendo.2020.00475 -
Current Biology : CB Jan 2022Nervous systems continuously receive environmental signals with distinct behavioral meanings. To process ambiguous sensory inputs, neural circuits rely on hubs with...
Nervous systems continuously receive environmental signals with distinct behavioral meanings. To process ambiguous sensory inputs, neural circuits rely on hubs with compartmentalized synaptic structures. A new study has revealed how, in Drosophila larvae, this architecture with the local release of neuropeptides enables the control of flexible and context-dependent behavioral outcomes.
Topics: Animals; Drosophila; Larva; Nervous System; Neuropeptides
PubMed: 35015994
DOI: 10.1016/j.cub.2021.11.037 -
Cells Oct 2022The zebrafish intestine and liver, as in other vertebrates, are derived from the endoderm. Great effort has been devoted to deciphering the molecular mechanisms...
The zebrafish intestine and liver, as in other vertebrates, are derived from the endoderm. Great effort has been devoted to deciphering the molecular mechanisms controlling the specification and development of the zebrafish intestine and liver; however, genome-wide comparison of the transcriptomes between these two organs at the larval stage remains unexplored. There is a lack of extensive identification of feature genes marking specific cell types in the zebrafish intestine and liver at 5 days post-fertilization, when the larval fish starts food intake. In this report, through RNA sequencing and single-cell RNA sequencing of intestines and livers separately dissected from wild-type zebrafish larvae at 5 days post-fertilization, together with the experimental validation of 47 genes through RNA whole-mount in situ hybridization, we identified not only distinctive transcriptomes for the larval intestine and liver, but also a considerable number of feature genes for marking the intestinal bulb, mid-intestine and hindgut, and for marking hepatocytes and cholangiocytes. Meanwhile, we identified 135 intestine- and 97 liver-enriched transcription factor genes in zebrafish larvae at 5 days post-fertilization. Our findings provide rich molecular and cellular resources for studying cell patterning and specification during the early development of the zebrafish intestine and liver.
Topics: Animals; Zebrafish; Larva; Transcriptome; Intestines; Liver; RNA; Transcription Factors
PubMed: 36291156
DOI: 10.3390/cells11203290 -
American Journal of Botany Oct 2016Brood pollination mutualisms-interactions in which specialized insects are both the pollinators (as adults) and seed predators (as larvae) of their host plants-have been... (Review)
Review
Brood pollination mutualisms-interactions in which specialized insects are both the pollinators (as adults) and seed predators (as larvae) of their host plants-have been influential study systems for coevolutionary biology. These mutualisms include those between figs and fig wasps, yuccas and yucca moths, leafflowers and leafflower moths, globeflowers and globeflower flies, Silene plants and Hadena and Perizoma moths, saxifrages and Greya moths, and senita cacti and senita moths. The high reciprocal diversity and species-specificity of some of these mutualisms have been cited as evidence that coevolution between plants and pollinators drives their mutual diversification. However, the mechanisms by which these mutualisms diversify have received less attention. In this paper, we review key hypotheses about how these mutualisms diversify and what role coevolution between plants and pollinators may play in this process. We find that most species-rich brood pollination mutualisms show significant phylogenetic congruence at high taxonomic scales, but there is limited evidence for the processes of both cospeciation and duplication, and there are no unambiguous examples known of strict-sense contemporaneous cospeciation. Allopatric speciation appears important across multiple systems, particularly in the insects. Host-shifts appear to be common, and widespread host-shifts by pollinators may displace other pollinator lineages. There is relatively little evidence for a "coevolution through cospeciation" model or that coevolution promotes speciation in these systems. Although we have made great progress in understanding the mechanisms by which brood pollination mutualisms diversify, many opportunities remain to use these intriguing symbioses to understand the role of biotic interactions in generating biological diversity.
Topics: Animals; Biodiversity; Insecta; Larva; Magnoliopsida; Pollination; Species Specificity; Symbiosis
PubMed: 27765775
DOI: 10.3732/ajb.1600056 -
Biomolecules Jun 2020Due to the sustainable organic matter bioconversion process used as substrate for its development, the (Linnaeus) larvae biomass is considered a source of compounds... (Review)
Review
Due to the sustainable organic matter bioconversion process used as substrate for its development, the (Linnaeus) larvae biomass is considered a source of compounds with high aggregate value and quite a promising market. The materials that can be extracted from larvae have opened the door to a diverse new field of ingredients, mainly for the feed and food industry, but also with potential applicability in cosmetics. In this review we succinctly describe the larval development and rearing cycle, the main compounds identified from different types of extractions, their bioactivities and focus on possible applications in cosmetic products. A search was made in the databases PubMed, ScienceDirect and Web of Science with the terms '', 'bioactives', 'biochemical composition' and 'cosmetics ingredients', which included 71 articles published since 1994.
Topics: Animals; Biological Factors; Biomass; Cosmetics; Diptera; Larva; Life Cycle Stages
PubMed: 32610700
DOI: 10.3390/biom10070976 -
Developmental Dynamics : An Official... Jun 2021Unlike axolotls, the urodele Notophthalmus viridescens completes two metamorphoses and emerges from its aquatic environment to mate as a fully terrestrial adult. Larval...
BACKGROUND
Unlike axolotls, the urodele Notophthalmus viridescens completes two metamorphoses and emerges from its aquatic environment to mate as a fully terrestrial adult. Larval and adult limb regeneration are commonly treated as roughly equivalent processes and, at least in part, as a recapitulation of embryonic development.
RESULTS
We compared larval limb development to regeneration of both larval and adult forelimbs and found that there are substantial differences in developmental pattern among larvae and adults. The larval pattern of preaxial dominance is absent in adult regenerates: adult regenerates instead develop digits synchronously, and they do so before proximal autopodial elements have formed discrete aggregation zones. By contrast, larval regenerates follow a pattern of sequential digit formation from anterior to posterior, like their embryonic limb buds.
CONCLUSIONS
Based upon these morphological clues, we conclude that larval regenerates are unlikely to exhibit features of epimorphic regeneration seen in adults, but are more likely to represent a form of developmental regulation. Furthermore, we confirm that post-metamorphic limb regeneration is not a simple recapitulation of ontology at the morphological level. These distinctions may help to explain and interpret some experiments and observations of regeneration in neotenic or paedomorphic urodeles.
Topics: Animals; Extremities; Larva; Limb Buds; Metamorphosis, Biological; Notophthalmus viridescens; Regeneration
PubMed: 33205502
DOI: 10.1002/dvdy.272