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Event: 1524

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Increase, Premature molting

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. More help
Increase, Premature molting
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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help
Level of Biological Organization

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Process Object Action
ecdysis, chitin-based cuticle decreased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
SAM depletion leading to population decline (2) KeyEvent You Song (send email) Under development: Not open for comment. Do not cite
SAM depletion leading to population decline (1) KeyEvent You Song (send email) Under development: Not open for comment. Do not cite
Chitinase inhibition leading to mortality KeyEvent Simon Schmid (send email) Under development: Not open for comment. Do not cite Under Development
Chitobiase inhibition leading to mortality KeyEvent Simon Schmid (send email) Under development: Not open for comment. Do not cite Under Development
CHS-1 inhibition leading to mortality KeyEvent Simon Schmid (send email) Open for citation & comment WPHA/WNT Endorsed
SUR binding leading to mortality KeyEvent Simon Schmid (send email) Under development: Not open for comment. Do not cite Under Development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
Pieris brassicae Pieris brassicae High NCBI
Lucilia cuprina Lucilia cuprina High NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help
Life stage Evidence
Larvae High
Juvenile High
Adult Moderate

Sex Applicability

An indication of the the relevant sex for this KE. More help
Term Evidence
Unspecific Moderate

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

This key event is measured on the level of the individual. In order to grow and develop, arthropods need to shed their exoskeleton periodically (molting) (Heming 2018). During molting, the newly secreted cuticle is subject to mechanical stress associated and therefore needs to possess enough structural and functional integrity. The ecdysis motor program, which constitutes the behavioral part of the cuticle shedding requires the newly secreted cuticle to possess a certain strength to support for muscular force in order to shed the old cuticle (Ewer 2005). Cuticular integrity is also important after ecdysis, as insects and crustaceans expand their new cuticle by increasing internal pressure by swallowing air and water, respectively. This happens in order to expand and provide stability to the new cuticle until it is hardened (tanned) (Clarke 1957; Lee 1961; Dall et al. 1978; deFur et al. 1985). If arthropods are not able to molt properly, the organism will eventually die. Premature molting describes the unsuccessful molting where the organism is not able to shed the old cuticle, but also other effects related to molting in an immature stage where the new cuticle is not mature enough for the molt, such as rupture of the new cuticle and associated desiccation, deformities, higher susceptibility to pathogens or impaired locomotion. Specific effects observed are animals stuck in their exuviae (Wang et al., 2019), and if molting can be completed despite an immature cuticle, animals might be smaller and die at subsequent molts (Arakawa et al., 2008; Chen et al., 2008; Mohammed et al., 2017).

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

Premature molting can be determined by observation. No standardized tests for the endpoint of molting exist to date. However, during an OECD 202 Daphnia sp. Acute immobilization test (OECD 2004), the cumulative number of molts can be assessed as an additional endpoint. Molting can also be assessed during a OECD 211 Daphnia sp. Reproduction test (OECD 2012), as proposed previously (OECD 2003). One could even prolong the test to 96h to get a clearer result of this endpoint. Additionally, one could apply histopathological methods to monitor the maturity of the newly synthesized cuticle (e.g. thickness of procuticle).

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

Taxonomic: Effect data for the occurrence of this KE exist from Pieris brassicae and Lucilia cuprina. However, all arthropods undergo molting, so it is highly likely that this KE is applicable to the whole phylum of arthropods.

Life stage: This KE is applicable for organisms that undergo molting in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.

Sex: This KE is applicable to all sexes.

Chemical: Substances known to induce premature molting are of the family of pyrimidine nucleosides (e.g. polyoxin D and nikkomycin Z) (Gijswijt et al. 1979; Tellam et al. 2000; Arakawa et al. 2008).


List of the literature that was cited for this KE description. More help

Arakawa T, Yukuhiro F, Noda H. 2008. Insecticidal effect of a fungicide containing polyoxin B on the larvae of Bombyx mori (Lepidoptera: Bombycidae), Mamestra brassicae, Mythimna separata, and Spodoptera litura (Lepidoptera: Noctuidae). Appl Entomol Zool. 43(2):173–181. doi:10.1303/aez.2008.173.

Chen, X.; Tian, H.; Zou, L.; Tang, B.; Hu, J.; Zhang, W. Disruption of Spodoptera Exigua Larval Development by Silencing Chitin Synthase Gene A with RNA Interference. Bull. Entomol. Res. 2008, 98 (6), 613–619.

Clarke KU. 1957. On the Increase in Linear Size During Growth in Locusta Migratoria L. Proc R Entomol Soc London Ser A, Gen Entomol. 32(1– 3):35–39. doi:10.1111/j.1365-3032.1957.tb00361.x.

Dall W, Smith DM, Press B. 1978. Water uptake at ecdysis in the western rock lobster. J Exp Mar Bio Ecol. 35(1960). doi:10.1016/0022- 0981(78)90074-6.

deFur PL, Mangum CP, McMahon BR. 1985. Cardiovascular and Ventilatory Changes During Ecdysis in the Blue Crab Callinectes Sapidus Rathbun. J Crustac Biol. 5(2):207–215. doi:10.2307/1547867.

Ewer J. 2005. How the ecdysozoan changed its coat. PLoS Biol. 3(10):1696–1699. doi:10.1371/journal.pbio.0030349.

Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in Pieris brassicae (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.

Heming BS. 2018. Insect development and evolution. Ithaca: Cornell University Press.

Mohammed, A. M. A.; DIab, M. R.; Abdelsattar, M.; Khalil, S. M. S. Characterization and RNAi-Mediated Knockdown of Chitin Synthase A in the Potato Tuber Moth, Phthorimaea Operculella. Sci. Rep. 2017, 7 (1), 1–12.

Lee RM. 1961. The variation of blood volume with age in the desert locust (Schistocerca gregaria Forsk.). J Insect Physiol. 6(1):36–51. doi:10.1016/0022-1910(61)90090-7.

OECD (2003), Proposal for an Enhanced Test Guideline. Daphnia magna Reproduction Test. Draft OECD Guidel. Test. Chem. Enhanc. Tech. Guid. Doc. 211 21.

OECD (2004), Test No. 202: Daphnia sp. Acute Immobilisation Test, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris,

OECD (2012), Test No. 211: Daphnia magna Reproduction Test, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris,

Tellam RL, Vuocolo T, Johnson SE, Jarmey J, Pearson RD. 2000. Insect chitin synthase. cDNA sequence, gene organization and expression. Eur J Biochem. 267(19):6025–6043. doi:10.1046/j.1432-1327.2000.01679.x.

Wang, Z.; Yang, H.; Zhou, C.; Yang, W. J.; Jin, D. C.; Long, G. Y. Molecular Cloning, Expression, and Functional Analysis of the Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants in the White-Backed Planthopper, Sogatella Furcifera (Hemiptera: Delphacidae). Sci. Rep. 2019, 9 (1), 1–14.