scholarly journals Knockout silkworms reveal a dispensable role for juvenile hormones in holometabolous life cycle

2015 ◽  
Vol 112 (31) ◽  
pp. E4226-E4235 ◽  
Author(s):  
Takaaki Daimon ◽  
Miwa Uchibori ◽  
Hajime Nakao ◽  
Hideki Sezutsu ◽  
Tetsuro Shinoda
Keyword(s):  
Larval Instar ◽  
Status Quo ◽  
Mrna Expression Level ◽  
Larval Life ◽  
Larval Instars ◽  
Larval Stages ◽  
Juvenile Hormones ◽  
Competence Factor ◽  
Mosaic Analysis ◽  
Independent Mechanism

Insect juvenile hormones (JHs) prevent precocious metamorphosis and allow larvae to undergo multiple rounds of status quo molts. However, the roles of JHs during the embryonic and very early larval stages have not been fully understood. We generated and characterized knockout silkworms (Bombyx mori) with null mutations in JH biosynthesis or JH receptor genes using genome-editing tools. We found that embryonic growth and morphogenesis are largely independent of JHs in Bombyx and that, even in the absence of JHs or JH signaling, pupal characters are not formed in first- or second-instar larvae, and precocious metamorphosis is induced after the second instar at the earliest. We also show by mosaic analysis that a pupal specifier gene broad, which is dramatically up-regulated in the late stage of the last larval instar, is essential for pupal commitment in the epidermis. Importantly, the mRNA expression level of broad, which is thought to be repressed by JHs, remained at very low basal levels during the early larval instars of JH-deficient or JH signaling-deficient knockouts. Therefore, our study suggests that the long-accepted paradigm that JHs maintain the juvenile status throughout larval life should be revised because the larval status can be maintained by a JH-independent mechanism in very early larval instars. We propose that the lack of competence for metamorphosis during the early larval stages may result from the absence of an unidentified broad-inducing factor, i.e., a competence factor.

Determination of Larval Instars of Semanotus bifasciatus (Coleoptera: Cerambycidae) Based on Frequency Distributions of Morphological Variables

2020 ◽  
Vol 55 (3) ◽  
pp. 405-415
Author(s):  
Na Li ◽  
Lei Wu ◽  
Yongxin Geng ◽  
Danfeng Wei ◽  
Min Chen
Keyword(s):  
Body Length ◽  
Larval Instar ◽  
Head Capsule ◽  
Larval Instars ◽  
Frequency Distributions ◽  
Larval Stages ◽  
Field Investigations ◽  
Mandible Length ◽  
Morphological Variables

Abstract Semanotus bifasciatus Motschulsky (Coleoptera: Cerambycidae) is one of the most destructive pests of Platycladus trees in China. Morphological measurements, such as head capsule (HC) width, can be very useful and practical indicators for identifying larval instars of coleopteran species. In this study, six morphological variables, including HC width, pronotum width, mandible length and width, and body length and width were measured to determine the instars of field-collected larvae of S. bifasciatus. Both the HC width and pronotum width were reliable parameters for determining the instar and stage. Larvae of S. bifasciatus were divided into eight instars; we detected strong relationships between larval instar and both the HC width (R2 = 0.9640) and pronotum width (R2 = 0.9549). The ranges of body widths and lengths for each instar are provided as reference values for distinguishing among larval stages in field investigations.

Morphological and molecular identification of all developmental stages of four whitefly species (Hemiptera: Aleyrodidae) commonly intercepted in quarantine

Zootaxa ◽  
2009 ◽  
Vol 2118 (1) ◽  
pp. 1-29 ◽  
Author(s):  
CHRISTOPHER MALUMPHY ◽  
KATHERINE WALSH ◽  
M. BELEN SUAREZ ◽  
DOMINIQUE W. COLLINS ◽  
NIEL BOONHAM
Keyword(s):  
Developmental Stages ◽  
Larval Instar ◽  
Life Stage ◽  
Morphological Characters ◽  
Trialeurodes Vaporariorum ◽  
Accurate Identification ◽  
Larval Instars ◽  
Larval Stages ◽  
Set Up ◽  
Simple Character

Whiteflies are inadvertently, but commonly, transported in international plant trade. Rapid, accurate identification is the essential first step when such insects are intercepted by quarantine authorities. Whitefly taxonomy, and identification, is almost entirely based on the fourth-larval instar or puparium, but often only the eggs, early larval instars or adults are detected. Morphological descriptions of the egg, first three larval stages and adult are presented for four species commonly detected in trade, Bemisia afer (Priesner & Hosny), B. tabaci (Gennadius), Trialeurodes ricini (Misra) and Trialeurodes vaporariorum (Westwood). Morphological characters are provided that enable most life stage/species combinations in these four species to be distinguished. The structure of the antenna is a reliable and simple character for separating the four larval instars. Phenotypic plasticity, previously only reported in the puparial stage, also occurs in the second and third-larval instars. Where morphological separation of two species is sometimes inconclusive, or impossible, identification can be achieved using four real-time PCR assays, designed and validated to distinguish between the four species. The assays are generic in their set-up and can be multiplexed to form two reactions allowing discrimination of B. afer and B. tabaci in one well, and T. ricini and T. vaporariorum in another.

Neurogenesis in the thoracic neuromeres of two crustaceans with different types of metamorphic development

1998 ◽  
Vol 201 (17) ◽  
pp. 2465-2479 ◽  
Author(s):  
S Harzsch ◽  
J Miller ◽  
J Benton ◽  
RR Dawirs ◽  
B Beltz
Keyword(s):  
Embryonic Development ◽  
Larval Development ◽  
Neuronal Development ◽  
Temporal Patterns ◽  
Homarus Americanus ◽  
Spider Crab ◽  
Larval Life ◽  
Larval Stages ◽  
Metamorphic Development ◽  
Embryonic And Larval Development

The mode of embryonic and larval development and the ethology of metamorphosis in the spider crab and the American lobster are very different, and we took advantage of this to compare neuronal development in the two species. The goals of this study were to discover whether the differences in the maturation of the neuromuscular system in the pereopods and the metamorphic changes of motor behavior between the two species are reflected at the level of the developing nervous system ('neurometamorphosis'). Furthermore, we wanted to broaden our understanding of the mechanisms that govern neuronal development in arthropods. Proliferation of neuronal stem cells in thoracic neuromeres 4-8 of the lobster Homarus americanus and the crab Hyas araneus was monitored over the course of embryonic and larval development using the in vivo incorporation of bromodeoxyuridine (BrdU). Neuropil structure was visualized using an antibody against Drosophila synapsin. While proliferation of neuronal precursors has ceased when embryogenesis is 80 % complete (E80%) in the lobster thoracic neuromeres, proliferation of neuroblasts in the crab persists throughout embryonic development and into larval life. The divergent temporal patterns of neurogenesis in the two crustacean species can be correlated with differences in larval life style and in the degree of maturation of the thoracic legs during metamorphic development. Several unusual aspects of neurogenesis reported here distinguish these crustaceans from other arthropods. Lobsters apparently lack a postembryonic period of proliferation in the thoracic neuromeres despite the metamorphic remodeling that takes place in the larval stages. In contrast, an increase in mitotic activity towards the end of embryonic development is found in crabs, and neuroblast proliferation persists throughout the process of hatching into the larval stages. In both E20% lobster embryos and mid-embryonic crabs, expression of engrailed was found in a corresponding set of neurons and putative glial cells at the posterior neuromere border, suggesting that these cells have acquired similar specific identities and might, therefore, be homologous. None of the BrdU-labeled neuroblasts (typically 6-8 per hemineuromere over a long period of embryogenesis) was positive for engrailed at this and subsequent stages. Our findings are discussed in relation to the spatial and temporal patterns of neurogenesis in insects.

Memoirs: On the Development of the Male Genitalia and the Efferent Genital Ducts in Lepidoptera

1933 ◽  
Vol s2-76 (301) ◽  
pp. 35-61
Author(s):  
DEV RAJ MEHTA
Keyword(s):  
Male Genitalia ◽  
Abdominal Segment ◽  
Larval Instar ◽  
Ejaculatory Duct ◽  
External Genitalia ◽  
Reproductive Organs ◽  
Proximal Portion ◽  
Genital System ◽  
Larval Life ◽  
Accessory Glands

A general account of the internal reproductive organs and the external genitalia and their development is given. The ‘penis lobes’ develop earlier than the ‘valvae lobes’, and independently of them. The tegumen is the modified ninth tergite. The tenth segment is visibly distinguished into a tergal and sternal part in the pupal stages, and the anal tube passes between the two sclerites. The uncus and the gnathos are dorsal and ventral processes respectively of the tenth segment. The anellus lobes develop as lateral processes of the ninth sternite on either side of the penis. The vasa deferentia during larval life do not extend beyond the eighth abdominal segment and lie in a latero-ventral position. They meet the extensions from the ectodermal ‘ductus ejaculatorius duplex’ during the last larval stadium. From the earliest caterpillar stage there exists a pair of ectodermal ducts formed by the differentiation of the epidermis on the ninth sternite. Towards the end of larval life they divide by constriction to form the accessory glands and the ‘ductus ejaculatory duplex’. At this stage they extend on either side to meet the vasa deferentia. The vesiculae seminales develop by distension from the region of junction between the vasa deferentia and the proximal portion of the ejaculatory duct. The ‘ductus ejaculatorius simplex’ arises as an ectodermal invagination between the pair of ‘penis lobes’ during the final larval instar. It is established that, with the exception of the vasa deferentia, all the remaining elements in the efferent genital system are derived from the ectoderm.

scholarly journals Breaking the rule: Five larval instars in the podonomine midge Trichotanypus alaskensis Brundin from Barrow, Alaska

2018 ◽  
Author(s):  
Alec R. Lackmann ◽  
Malcolm G. Butler
Keyword(s):  
Life Cycle ◽  
Larval Instar ◽  
Adult Emergence ◽  
Head Capsule ◽  
The Arctic ◽  
Larval Instars ◽  
Daily Monitoring ◽  
Field Samples ◽  
Standard Life ◽  
Capsule Size

Except for one unconfirmed case, chironomid larvae have been reported to pass through four larval instars between egg and pupal stages. We have observed a fifth larval instar to be a standard life-cycle feature of the podonomine Trichotanypus alaskensis Brundin 1966 in tundra ponds on the Arctic Coastal Plain near Barrow, Alaska. T. alaskensis has a one-year life cycle in these arctic ponds. Adults emerge in June ~2-3 weeks after pond thaw, then mate and oviposit; most newly-hatched larvae reach instar IV by October when pond sediments freeze. Overwintering larvae complete instar IV within a few days of thaw, then molt again to a fifth larval instar. Imaginal discs, normally seen only during instar IV in Chironomidae, develop across both instars IV & V prior to pupation and adult emergence. While monitoring larval development post-thaw in 2014, we noticed freshly-molted T. alaskensis larval exuviae a week or more prior to any pupation by that species. In 2015-16 we reared overwintering instar IV larvae from single pond sources, individually with daily monitoring, through molts to instar V, pupa, and adult. Some overwintering instar II and III larvae were reared as well, but were few in number. During 2016 we also reared T. alaskensis progeny (from eggs) through instar II, thus documenting head capsule size ranges for all five instars in a single pond’s population. Without individual rearings, the fifth larval instar was not readily apparent for two reasons: 1) The molt itself occurs immediately after thaw and is so synchronous it is difficult to discern in daily field samples. 2) The head capsule size increment between instars IV-V is much lower than the ratio predicted by the Brooks-Dyar Rule. Up through instar IV, the Brooks-Dyar ratio for T. alaskensis ranged 1.30-1.61, but during the IV-V molt head capsule dimensions (sexes pooled) increased by a ratio of 1.09 – comparable to the magnitude of sexual dimorphism in head capsule size within each of the final two larval instars. Individual rearings coupled with 2014-2016 field surveys in nine other ponds suggest that five larval instars is an obligatory trait of this species at this location. As this is the first confirmed case of five larval instars in a chironomid, the phylogenetic uniqueness of this trait needs further investigation.

scholarly journals Effect of Leaves and Fruits Ethanolic Extract of Duranta repens on Mosquito Culex pipens pipens

2011 ◽  
Vol 8 (4) ◽  
pp. 870-876 ◽  
Author(s):  
Baghdad Science Journal
Keyword(s):  
Life Cycle ◽  
Mortality Rate ◽  
High Mortality ◽  
Culex Pipiens ◽  
Ethanolic Extract ◽  
Pupal Stage ◽  
Fourth Generation ◽  
Larval Instars ◽  
Larval Stages ◽  
Biological Performance

The study aimes to investigate the effects of leaves & fruits ethanolic extract of Duranta repens L. on biological performance for all stages of life cycle of the mosquito Culex pipiens piepiens L., For this purpose the mosquitoes were reared in the laboratory till the fourth generation .Different concentrations of leaves (800,1000,1200,1400ppm) and fruits (800,1000,1200ppm) were tested on (eggs,larval stages,pupal stages and the adult stages). The results revealed that the extracts gave highest mortality rate for the eggs at(100%) compared with control,fruits extract shown highest mortality rate of the four larval instars (100%)at 1200ppm compared with leave extract at(80,50,33.33,20%).Also the extract caused a high mortality rate for pupal stage compared with fruits extract at(76.66,53.33%)respectively.Also ethanolic extract caused a 83.33,76.66% for male &femail. Developmental deformation was observed.. In conclusion, the findings of the present study indicate that the leaves &fruits extracts of Duranta repens L., , can be widely and effectively used in the control of mosquito.

scholarly journals The efficiency of Paecilomyce farinosus as biocontrol to larve stage on second ad sixith instar larve of Trogoderma granarium (Everts)

2013 ◽  
Vol 10 (4) ◽  
pp. 1096-1101
Author(s):  
Baghdad Science Journal
Keyword(s):  
Larval Instar ◽  
The Other ◽  
Biocontrol Agents ◽  
Larval Instars ◽  
Paecilomyces Farinosus ◽  
Trogoderma Granarium ◽  
Laboratory Conditions ◽  
Other Hand ◽  
Laboratory Results ◽  
Treatment Concentration

The present study was conducted to determine the pathogenicity of Paecilomyces farinosus as biocontrol agents against Tragoderma granarium (khapra) under laboratory conditions with three concentrations ( 2.8 x 108 , 2.8 x 106 ,2.8 x104 spores/ ml). The laboratory results revealed that fungi showed it's higher pathogencity to larve stage on 2nd instar and 6th instar , although their capability differs according to the fungi concentrations this fungi caused higher mortality of 2nd larval instar 70% and 60% ,55% when it was used at concentrations 2 .8 x 106 ,2.8 x104 spores/ ml respectively. On the other hand on 6th larval instars 55% , 35% , 30% at concentrations ( 2.8 x 108 , 2.8 x 106 ,2.8 x104 spores/ ml) respectively, and the highest rate of distortions in the adult insects from the 2nd instar treatment than the adult insects from the 6th instar treatment concentration of this fungi.

scholarly journals Formation of Pattern and Diagnostic Instar Features of the Head in Caterpillars from Genus Peridea (Lepidoptera, Notodontidae)

2009 ◽  
Vol 43 (1) ◽  
pp. e-15-e-24
Author(s):  
I. Dolinskaya
Keyword(s):  
Pattern Formation ◽  
Larval Instar ◽  
Head Capsule ◽  
Diagnostic Character ◽  
Key To Species ◽  
Larval Instars ◽  
Diagnostic Characters ◽  
Ontogenetic Stages ◽  
First Time ◽  
Taxonomic Relations

Formation of Pattern and Diagnostic Instar Features of the Head in Caterpillars from Genus Peridea (Lepidoptera, Notodontidae) Pattern and colouration of caterpillar head of all larval instar of 7 species from genus Peridea Stephens, 1828 are studied. Formation of caterpillar head pattern in ontogenesis is discussed. Diagnostic characters, both specific and larval instars, are recorded for the first time. Key to species according to larval instars is given. Evidently, only larvae of the 1st instar demonstrate different directions in the pattern formation. This characteristic can be used for clearing of taxonomic relations in the genera and on the earliest ontogenetic stages (1st larval instar) only. In the following (2nd-5th) instars, the pattern became more or less of the same type. It depends on stripes shape or colouration only and can serve as good specific diagnostic character. To determine larval instar, both width of the head capsule and head pattern should be taken into account.

scholarly journals THE POTENTIAL OF THREE LARVAL PREDATORS AGAINST FALL ARMYWORM SPODOPTERA FRUGIPERDA (LEPIDPTERA: NOCTUIDAE) UNDER THE LABORATORY CONDITION

2020 ◽  
Vol 5 (1) ◽  
pp. 41-42
Author(s):  
Moses Otuba ◽  
Jumrae Cho
Keyword(s):  
Spodoptera Frugiperda ◽  
Larval Instar ◽  
Fall Armyworm ◽  
Economic Loss ◽  
Cereal Crops ◽  
Podisus Maculiventris ◽  
Larval Instars ◽  
Significant Difference ◽  
Orius Strigicollis ◽  
Set Up

Most cereal crops are often damaged by lepidopterous insects. Of recent, fall armyworm, S. frugiperda (J.E. Smith) has resulted into yield and economic loss in many African and Asian countries. This reduces farmers’ income drastically and to overcome this damage, pesticides have been used which are not also environmentally friendly. Experiments were set up to collect data on the potential of three larval predators Orius strigicollis, Micromus angulatus, and Podisus maculiventris against S. frugiperda. The consumption of S. frugiperda larvae by three predators had highly significant effects (P≤0.05) on first, fourth, and sixth instars. No significant difference was reported between M. angulatus and O. strigicollis on second, third and fifth larval instars of S. frugiperda. O. strigicollis consumed more first larval instar (6.2±0.71) of S. frugiperda than M. angulatus (4.9±1.07) and P. maculiventris (4.2±0.74). However, P. maculiventris consumed more second to sixth larval instars of S. frugiperda than other two predators (O. strigicollis and M. angulatus). The predator P. maculiventris is recommended for controlling S. frugiperda in their second to sixth larval instars while O. strigicollis in the first larval instar. It can be also concluded that fourth larval instars of S. frugiperda is more suitable for its control using predator P. maculiventris as compared to other larval instars. This study therefore recommends predator Podisus maculiventris to be used in control of S. frugiperda under laboratory conditions.

scholarly journals Efficacy of Bacillus thuringiensis (Berliner) isolates on fig moth, Ephestia cautella (Walker) Larvae

2014 ◽  
Vol 11 (2) ◽  
pp. 943-951
Author(s):  
Baghdad Science Journal
Keyword(s):  
Bacillus Thuringiensis ◽  
Larval Stage ◽  
Filter Paper ◽  
Larval Instar ◽  
Ephestia Cautella ◽  
Larval Stages ◽  
The Third ◽  
Total Percentage ◽  
First Instar ◽  
Paper Method

The following dilution 5×10-1, 10-1, 10?2 , 10-3 gm/L for the indigenous isolate of Bacillus thuringiensis bacteria and the commercially isalate were used for experiments against the different stages of fig moth of E.cautella which exposed by filter paper method. The results showed that mortality of larval stages was increased with the increasing concentration of the biocide, in addition to increase in the mortality of the larval stages reached to the highest percentage in the third days of treatment of the larval stage in comparison with the first and second days of exposure. The results also showed that the sensitivity of larval stages was increased in first and second instars while reduced in the last instars .The high percentage of first instar mortality for the indigenous isolate in the concentration of 5×10-1 was 72.8% , while the low percentage of mortality showed in the concentration of 5×10-1 for the fifth instar larvae which was 13.3% in third days of treatment while a high percentage of mortality was showed for the first instar larvae for the commercially isulate in the concentration of 5×10-1 was 59.4% Furthermore, low percentage of mortality was shown in the concentration of 5×10-1 in fifth instar larval which was 8.3% in the third days of treatment. The results also showed that the indigenous isolated was more effective than the commercially produced bacteria for killing larval instars of fig moth E.cautella .The total percentage of larval instar mortality reached to 44.5 % after the third days of treatment in concentration 5×10-1 in the indigenous isolate , and it was 33.8 % in the commercially produced bacteria .

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