scholarly journals Complete metamorphosis of insects

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190063 ◽  
Author(s):  
Jens Rolff ◽  
Paul R. Johnston ◽  
Stuart Reynolds
Keyword(s):  
Adult Stage ◽  
Pupal Stage ◽  
Life Stages ◽  
Micro Ct ◽  
Larval Form ◽  
Theme Issue ◽  
The Cost ◽  
Ephemeral Resources ◽  
Complete Metamorphosis

The majority of described hexapod species are holometabolous insects, undergoing an extreme form of metamorphosis with an intercalated pupal stage between the larva and adult, in which organs and tissues are extensively remodelled and in some cases completely rebuilt. Here, we review how and why this developmental strategy has evolved. While there are many theories explaining the evolution of metamorphosis, many of which fit under the hypothesis of decoupling of life stages, there are few clear adaptive hypotheses on why complete metamorphosis evolved. We propose that the main adaptive benefit of complete metamorphosis is decoupling between growth and differentiation. This facilitates the exploitation of ephemeral resources and enhances the probability of the metamorphic transition escaping developmental size thresholds. The evolution of complete metamorphosis comes at the cost of exposure to predators, parasites and pathogens during pupal life and requires specific adaptations of the immune system at this time. Moreover, metamorphosis poses a challenge for the maintenance of symbionts and the gut microbiota, although it may also offer the benefit of allowing an extensive change in microbiota between the larval and adult stages. The regulation of metamorphosis by two main players, ecdysone and juvenile hormone, and the related signalling cascades are now relatively well understood. The mechanics of metamorphosis have recently been studied in detail because of the advent of micro-CT and research into the role of cell death in remodelling tissues and organs. We support the argument that the adult stage must necessarily have preceded the larval form of the insect. We do not resolve the still contentious question of whether the larva of insects in general originated through the modification of existing preadult forms or through heterochrony as a modified embryonic stage (pronymph), nor whether the holometabolous pupa arose as a modified hemimetabolous final stage larva. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

scholarly journals The innovation of the final moult and the origin of insect metamorphosis

2019 ◽  
Vol 374 (1783) ◽  
pp. 20180415 ◽  
Author(s):  
Xavier Belles
Keyword(s):  
Common Ancestor ◽  
Adult Stage ◽  
Postembryonic Development ◽  
Prothoracic Gland ◽  
Last Common Ancestor ◽  
Early Devonian ◽  
Final Moult ◽  
Insect Metamorphosis ◽  
Complete Metamorphosis

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’.

scholarly journals Antipredator strategies of pupae: how to avoid predation in an immobile life stage?

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190069 ◽  
Author(s):  
Carita Lindstedt ◽  
Liam Murphy ◽  
Johanna Mappes
Keyword(s):  
Life Stage ◽  
Pupal Stage ◽  
Future Research ◽  
Theme Issue ◽  
Antipredator Strategies ◽  
Individual Fitness ◽  
Cryptic Coloration ◽  
Wide Range ◽  
Common Strategy ◽  
Complete Metamorphosis

Antipredator strategies of the pupal stage in insects have received little attention in comparison to larval or adult stages. This is despite the fact that predation risk can be high during the pupal stage, making it a critical stage for subsequent fitness. The immobile pupae are not, however, defenceless; a wide range of antipredator strategies have evolved against invertebrate and vertebrate predators. The most common strategy seems to be ‘avoiding encounters with predators' by actively hiding in vegetation and soil or via cryptic coloration and masquerade. Pupae have also evolved behavioural and secondary defences such as defensive toxins, physical defences or deimatic movements and sounds. Interestingly, warning coloration used to advertise unprofitability has evolved very rarely, even though the pupal stage often contains defensive toxins in chemically defended species. In some species, pupae gain protection from conspecifics or mimic chemical and auditory signals and thereby manipulate other species to protect them. Our literature survey highlights the importance of studying selection pressures across an individual's life stages to predict how ontogenetic variation in selective environments shapes individual fitness and population dynamics in insects. Finally, we also suggest interesting avenues for future research to pursue. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

scholarly journals Navigating infection risk during oviposition and larval foraging in a holometabolous insect

2017 ◽  
Author(s):  
Jonathon A. Siva-Jothy ◽  
Katy M. Monteith ◽  
Pedro F. Vale
Keyword(s):  
Larval Stage ◽  
Developmental Stages ◽  
Adult Stage ◽  
Life Stages ◽  
Holometabolous Insect ◽  
Fitness Consequences ◽  
Risk Of Exposure ◽  
Selection For ◽  
Complete Metamorphosis ◽  
Oviposition Sites

AbstractDeciding where to eat and raise offspring carries important fitness consequences for all animals, especially if foraging, feeding and reproduction increase the risk of exposure to pathogens. In insects with complete metamorphosis, foraging occurs mainly during the larval stage, while oviposition decisions are taken by adult-stage females. Selection for infection avoidance behaviours may therefore be developmentally uncoupled. Using a combination of experimental infections and behavioural choice assays, here we tested if Drosophila melanogaster fruit flies avoid potentially infectious environments at distinct developmental stages. When given conspecific fly carcasses as a food source, larval-stage flies did not discriminate between carcasses that were clean or infected with the pathogenic Drosophila C Virus (DCV), even though scavenging was a viable route of DCV transmission. Adult females however, discriminated between different oviposition sites, laying more eggs near a clean rather than an infectious carcass if they were healthy; DCV-infected females did not discriminate between the two environments. While potentially risky, laying eggs near potentially infectious carcasses was always preferred to sites containing only fly medium. Our findings suggest that infection avoidance can play an important role in how mothers provision their offspring, and underline the need to consider infection avoidance behaviours at multiple life-stages.

scholarly journals Persistence of an extracellular systemic infection across metamorphosis in a holometabolous insect

2018 ◽  
Vol 14 (2) ◽  
pp. 20170771 ◽  
Author(s):  
David F. Duneau ◽  
Brian P. Lazzaro
Keyword(s):  
Larval Stage ◽  
Adult Stage ◽  
A Priori ◽  
Adult Life ◽  
Bacterial Pathogen ◽  
Systemic Infection ◽  
Life Cycles ◽  
Life Stages ◽  
Holometabolous Insect ◽  
Complete Metamorphosis

Organisms with complex life cycles can differ markedly in their biology across developmental life stages. Consequently, distinct life stages can represent drastically different environments for parasites. This difference is especially striking with holometabolous insects, which have dramatically different larval and adult life stages, bridged by a complete metamorphosis. There is no a priori guarantee that a parasite infecting the larval stage would be able to persist into the adult stage. In fact, to our knowledge, transstadial transmission of extracellular pathogens has never been documented in a host that undergoes complete metamorphosis. We tested the hypothesis that a bacterial parasite originally sampled from an adult host could infect a larva, then survive through metamorphosis and persist into the adult stage. As a model, we infected the host Drosophila melanogaster with a horizontally transmitted, extracellular bacterial pathogen, Providencia rettgeri . We found that this natural pathogen survived systemic infection of larvae (L3) and successfully persisted into the adult host. We then discuss how it may be adaptive for bacteria to transverse life stages and even minimize virulence at the larval stage in order to benefit from adult dispersal.

scholarly journals Regulatory mechanisms underlying the specification of the pupal-homologous stage in a hemimetabolous insect

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190225 ◽  
Author(s):  
Yoshiyasu Ishimaru ◽  
Sayuri Tomonari ◽  
Takahito Watanabe ◽  
Sumihare Noji ◽  
Taro Mito
Keyword(s):  
Genetic Interaction ◽  
Pupal Stage ◽  
Regulatory Mechanisms ◽  
Stage Versus ◽  
Nymphal Instar ◽  
Gryllus Bimaculatus ◽  
Theme Issue ◽  
Evolutionarily Conserved ◽  
Hemimetabolous Insect ◽  
Complete Metamorphosis

Juvenile hormones and the genetic interaction between the transcription factors Krüppel homologue 1 ( Kr-h1 ) and Broad ( Br ) regulate the transformation of insects from immature to adult forms in both types of metamorphosis (holometaboly with a pupal stage versus hemimetaboly with no pupal stage); however, knowledge about the exact instar in which this occurs is limited. Using the hemimetabolous cricket Gryllus bimaculatus ( Gb ), we demonstrate that a genetic interaction occurs among Gb ′ Kr-h1 , Gb ′ Br and the adult-specifier transcription factor Gb ′ E93 from the sixth to final (eighth) nymphal instar. Gb ′ Kr-h1 and Gb ′ Br mRNAs were strongly expressed in the abdominal tissues of sixth instar nymphs, with precocious adult moults being induced by Gb ′ Kr-h1 or Gb ′ Br knockdown in the sixth instar. The depletion of Gb ′ Kr-h1 or Gb ′ Br upregulates Gb ′ E93 in the sixth instar. By contrast, Gb ′ E93 knockdown at the sixth instar prevents nymphs transitioning to adults, instead producing supernumerary nymphs. Gb ′ E93 also represses Gb ′ Kr-h1 and Gb ′ Br expression in the penultimate nymphal instar, demonstrating its important role in adult differentiation. Our results suggest that the regulatory mechanisms underlying the pupal transition in holometabolous insects are evolutionarily conserved in hemimetabolous G . bimaculatus , with the penultimate and final nymphal periods being equivalent to the pupal stage. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

scholarly journals The evolution of insect metamorphosis: a developmental and endocrine view

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190070 ◽  
Author(s):  
James W. Truman ◽  
Lynn M. Riddiford
Keyword(s):  
Transcription Factors ◽  
Experimental Treatment ◽  
The Other ◽  
Life Stages ◽  
Developmental Genetic ◽  
Theme Issue ◽  
Insect Metamorphosis ◽  
Krüppel Homolog 1 ◽  
Complete Metamorphosis ◽  
Insight Into

Developmental, genetic and endocrine data from diverse taxa provide insight into the evolution of insect metamorphosis. We equate the larva–pupa–adult of the Holometabola to the pronymph–nymph–adult of hemimetabolous insects. The hemimetabolous pronymph is a cryptic embryonic stage with unique endocrinology and behavioural modifications that probably served as preadaptations for the larva. It develops in the absence of juvenile hormone (JH) as embryonic primordia undergo patterning and morphogenesis, the processes that were arrested for the evolution of the larva. Embryonic JH then drives tissue differentiation and nymph formation. Experimental treatment of pronymphs with JH terminates patterning and induces differentiation, mimicking the processes that occurred during the evolution of the larva. Unpatterned portions of primordia persist in the larva, becoming imaginal discs that form pupal and adult structures. Key transcription factors are associated with the holometabolous life stages: Krüppel-homolog 1 ( Kr-h1 ) in the larva, broad in the pupa and E93 in the adult. Kr-h1 mediates JH action and is found whenever JH acts, while the other two genes direct the formation of their corresponding stages. In hemimetabolous forms, the pronymph has low Broad expression, followed by Broad expression through the nymphal moults, then a switch to E93 to form the adult. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

scholarly journals Cell death during complete metamorphosis

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190065 ◽  
Author(s):  
Gianluca Tettamanti ◽  
Morena Casartelli
Keyword(s):  
Cell Death ◽  
Body Structure ◽  
Theme Issue ◽  
Tissue Remodelling ◽  
Regulatory Pathways ◽  
Adult Transition ◽  
Similarities And Differences ◽  
Cell Death Mechanisms ◽  
Complete Metamorphosis

In insects that undergo complete metamorphosis, cell death is essential for reshaping or removing larval tissues and organs, thus contributing to formation of the adult's body structure. In the last few decades, the study of metamorphosis in Lepidoptera and Diptera has provided broad information on the tissue remodelling processes that occur during larva–pupa–adult transition and made it possible to unravel the underlying regulatory pathways. This review summarizes recent knowledge on cell death mechanisms in Lepidoptera and other holometabolous insects, highlighting similarities and differences with Drosophila melanogaster , and discusses the role of apoptosis and autophagy in this developmental setting. This article is part of the theme issue ‘The evolution of complete metamorphosis'.

Hostile Takeovers and Anti-takeover Defenses in the Russian Corporate Market

2007 ◽  
pp. 70-84 ◽  
Author(s):  
E. Demidova
Keyword(s):  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Benefit Analysis ◽  
Costs And Benefits ◽  
Hostile Takeovers ◽  
Russian Market ◽  
Takeover Defenses ◽  
The Cost ◽  
European Markets

This article analyzes definitions and the role of hostile takeovers at the Russian and European markets for corporate control. It develops the methodology of assessing the efficiency of anti-takeover defenses adapted to the conditions of the Russian market. The paper uses the cost-benefit analysis, where the costs and benefits of the pre-bid and post-bid defenses are compared.

Changing Role of Agriculture in Income and Employment, and Trends of Agricultural Worker Productivity in Indian States

2020 ◽  
pp. 183-189
Keyword(s):  
Green Revolution ◽  
Positive Trend ◽  
Worker Productivity ◽  
Indian States ◽  
Agricultural Worker ◽  
The Sixties ◽  
High Level ◽  
The Cost ◽  
Changing Role

The productivity of land has been often discussed and deliberated by the academia and policymakers to understand agriculture, however, very few studies have focused on the agriculture worker productivity to analyze this sector. This study concentrates on the productivity of agricultural workers from across the states taking two-time points into consideration. The agriculture worker productivity needs to be dealt with seriously and on a time series basis so that the marginal productivity of worker can be ascertained but also the dependency of worker on agriculture gets revealed. There is still disguised unemployment in all the states and high level of labour migration, yet most of the states showed the dependency has gone down. Although a state like Madhya Pradesh is doing very well in terms of income earned but that is at the cost of increased worker power in agriculture as a result of which, the productivity of worker has gone down. States like Mizoram, Meghalaya, Nagaland and Tripura, though small in size showed remarkable growth in productivity and all these states showed a positive trend in terms of worker shifting away from agriculture. The traditional states which gained the most from Green Revolution of the sixties are performing decently well, but they need to have the next major policy push so that they move to the next orbit of growth.

Music publications in Galicia in the 19th — beginning of the 20th centuries: production, advertising, pricing

2019 ◽  
pp. 481-499
Author(s):  
Olga Osadtsia
Keyword(s):  
Book Publishing ◽  
Initial Form ◽  
Music Production ◽  
Bibliographic Information ◽  
Financial Factor ◽  
Determining Factors ◽  
Book Selling ◽  
The Cost ◽  
Import Trade

The main forms and methods of distribution of music publications in Galicia in the XIX — early XX centuries are scrutinized. The demand for the relevant music production is one of the determining factors in the formation of the musical publishing repertoire, its structure and special features in the process of the existence of music publications in society. It is noted that export-import trade in books has become especially widespread in Galicia; there are facts about the links between publishers and booksellers in Lviv and Warsaw. The basic types of presentation of book advertising of music products, its regional peculiarities, and ways of its placement are considered. Special emphasis is placed on the role of specialized press in the advertising of music products, typical examples of press advertising. The registration bibliographic information as the initial form of music bibliography and the forms of its compilation are distinguished. The emphasis is placed on the importance of thorough critical articles as a separate typological group of bibliographic publications under the conditions of formation of the Ukrainian bibliography, in which the main importance is given to the disclosure of the content and evaluation of the reviewed work. The combination of article genres and reviews on examples of separate publications by Stanislav Lyudkevych and Ivan Franko is traced. Special book-selling and book-publishing catalogs are characterized. While executing the marketing and advertising function, these directories were addressed primarily to foreign consumers and distributors (the so-called commissioners).One way to distribute music is to subscribe through libraries. A significant financial factor in the distribution of any printed matter was the price that depended primarily on the cost of each process associated with its publication. Keywords: music publications, bookstore, book-trading enterprise, advertising of publications, pricing.

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