Cuticular Formation Research Articles

CYP303A1 regulates molting and metamorphosis through 20E signaling in Nilaparvata lugens Stål (Hemiptera: Delphacidae)

Cytochrome P450s play a crucial role in the breakdown of external substances and perform important activities in the hormone system of insects. It has been understood that P450s were essential in the metabolism of ecdysteroids. CYP303A1 is a highly conserved CYP in most insects, but its specific physiological functions remain poorly understood in Nilaparvata lugens Stål. In this study, NlCYP303A1 was identified and highly expressed in the pre-molt stages, predominantly in the cuticle-producing tissues. Silencing of NlCYP303A1 caused a lethal phenotype with a molting defect. Moreover, the 20E titers, the expression levels of Halloween genes, and critical genes associated with the 20E signaling pathway in N. lugens nymphs were significantly decreased with the silencing NlCYP303A1. We further performed additional backfilling of 20E to rescue the RNAi effects on NlCYP303A1. The gene expression levels that were previously reduced caused by silencing NlCYP303A1 were significantly elevated. However, the molting defects of nymphs were not effectively improved. The results demonstrated NlCYP303A1 plays a crucial role in the molting and metamorphosis of N. lugens by regulating the 20E signaling pathway and cuticular formation, enhances the understanding of the functional role of CYP 2 clans, and identifies candidate gene for RNAi-based control of N. lugens.

Alternative splicing of POUM2 regulates embryonic cuticular formation and tanning in Bombyx mori.

Insect cuticle is an apical extracellular matrix produced by the epidermis, tracheal, hind- and foregut epithelia during embryogenesis and renewed during molting and metamorphosis. However, the underlying regulatory mechanism for embryonic cuticle formation remains largely unclear. Here, we investigate the function of the transcription factor POUM2 in the embryonic cuticular formation in Bombyx mori, a model lepidopteran insect. Clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein-9-mediated knockout of POUM2 resulted in the defect of cuticular deposition, pigmentation, and sclerotization in the embryos. Differentially expressed transcripts analysis of 7-d-old embryos identified 174 up- or downregulated cuticular protein transcripts, 8 upregulated chitin degradation transcripts, 2 downregulated chitin synthesis transcripts and 48 up- or downregulated transcription factor transcripts in the POUM2-/- embryos. The expression levels of the key factors of the tyrosine metabolic pathway, such as tyrosine hydroxylase (Th), Dopa decarboxylase (DDC), and arylalkylamine N-acetyltransferase (aaNAT), were significantly decreased in the POUM2-/- embryos. POUM2 isoform POUM2-L specifically bound the POU cis-regulatory element (CRE) in the Th promoter and increased the transcription of Th, whereas POUM2-S could not bind the POU CRE, although it also increased the transcription of Th. Heterogeneous nuclear ribonucleoprotein Squid-1 directly bound the POUM2 pre-mRNA (messenger RNA) and inhibited the alternative splicing of POUM2-L to POUM2-S mRNA. These results suggest that POUM2 participates in the cuticular formation by regulating the chitin and cuticular protein synthesis and metabolism, and the cuticular pigmentation and sclerotization by regulating tyrosine metabolism during embryogenesis. This study provides new insights into novel function of POUM2 in embryogenesis.

Micromorphological Characteristics of Fruit Surfaces of Some Usable Species of the Genus Valeriana (Valerianaceae) Among Ukrainian Flora

Abstract The micromorphological features of the fruit surfaces of nine species of Ukrainian flora, namely Valeriana tuberosa L., Valeriana tripteris L., Valeriana rossica P. Smirn., Valeriana stolonifera Czern., Valeriana grossheimii Worosch, Valeriana sambucifolia Mikan fil., Valeriana officinalis L. s. str., Valeriana wolgensis Kazak. [ Valeriana officinalis var. nitida (Kreyer) Rostanski], and Valeriana simplicifolia (Rchb.) Kabath, were examined. Depending on the presence and localization of pubescence on the surface of the fruit, three groups of species were distinguished: those with glabrous fruits, those with fruits pubescent only on the adaxial side, and those with fruits pubescent on both sides. Scanning electron microscopy revealed the additional characteristics of the fruits (microsculpture of the fruit surface, shape of cuticular formations on the surface of the outer periclinal walls of epidermal cells and on the surface of hairs, and structure of the stomatal complex), which were useful for the identification of the species. At the supraspecific level, the revealed features of the fruit surfaces somewhat overlapped and could be used to identify series and sections only as additional features. Based on the studied samples from herbarium material (KW), V. officinalis var. nitida was considered synonymous with V. wolgensis since there were no micromorphological differences between their fruits. The detailed micromorphological characteristics of the fruit surfaces of all the studied species can be used for further comparative morphological investigations of different aerial parts to identify stable features independent of geographic and ecological conditions.

Initiation of compatible wheat-Hessian fly interactions triggers the expression of a novel UDP-glycosyltransferase, MdesUGT1, in virulent Hessian fly larvae

Insect UDP-glycosyltransferases (UGTs) play an important role in detoxification of substrates such as plant allelochemicals, and cuticle formation by the process of glucosidation. Hessian fly (Mayetiola destructor), belonging to the order Diptera (Family: Cecidomyiidae), is a destructive pest of host wheat causing significant economic losses. In the current study, using the assembled genome, we identified thirteen genes in M. destructor that belong to the family of UGTs (MdesUGT). Expression profiling revealed differential expression of MdesUGT genes in Hessian fly feeding instars. Further, we report the molecular cloning of MdesUGT1, designated as UGT301F1, from M. destructor. Characterization of the MdesUGT1 amino acid sequence revealed a conserved signature motif and sugar donor-binding domains characteristic of UGT proteins. Further expression analysis revealed dramatic increase in transcript accumulation of MdesUGT1 in the first and second feeding instars during compatible interactions (susceptible wheat, virulent larvae) but lacked significant upregulation during incompatible wheat Hessian fly interactions. Similar increase in MdesUGT1 transcripts was also observed during interactions of Hessian fly with nonhost, Brachypodium distachyon. These findings suggest the possible early involvement of MdesUGT1 in detoxification of plant toxins, and subsequent role in cuticular formation, thus contributing to the growth and development of this dipteran insect pest. Identification and characterization of insect UGTs could provide valuable insights into the detoxification and growth inhibitory mechanisms and facilitate future plant pest management strategies.

Morphological identification of Nematodirus spathiger nematodes (Nematoda, Molineidae) obtained from the small intestine of sheep

Strongyloidiases are caused by nematodes of the suborder Strongylida and are the most widely prevalent group of gastrointestinal helminthiases of sheep in many regions of the world. Among gastrointestinal strongylids, the helminths of the genus Nematodirus are represented by the largest number of species and highest infection rates in sheep. Nematodirosis causes significant economic losses in the sheep industry through decreased sheep productivity, delayed growth and development of young animals, and a reduced resistance to other diseases. Timely and accurate diagnosis of nematodirosis and identification of the pathogen will effectively prevent the disease and help to carry out treatment and prevention measures. Therefore, the aim of the work was to study the definitive morphometric characters of mature males and females of Nematodirus spathiger Railliet, 1896, obtained from the small intestine of domestic sheep. The results of experimental studies showed that nematodes of this species morphologically are characterized by a thin filiform body, a vesicle at the head end and a chitinous tooth in a short oral capsule. The differential morphological features of male nematodes of N. spathiger include specifics of the structure of spicules, their distal end and the shape and location of the rays of the caudal bursa; in females, those are the features of the structure of the vulva and tail end. In identification of male nematodes of N. spathiger, it is proposed to use 40 metric parameters, of which 11 characterize the overall size of the body, esophagus and vesicles, 24 refer to the size of the tail bursa, 5 to the size of the spicules and the enveloping membrane. To help identify the females of N. spathiger, 25 parameters are chosen, of which 14 also characterize the overall size of the body, esophagus and head vesicle, 6 refer to the size of the cuticular formations of the vulva and its location, and 5 to the size of the tail end, the location of the anus and the size of the tail spike.

Endocuticle is involved in caste differentiation of the lower termite.

Caste differentiation in termites is one of the most conspicuous examples of facultative polyphenism in animals. It is clear that specific cuticular formation occurs in hard exocuticles during caste differentiation. However, the developmental pattern of the soft endocuticle in the differentiation pathways of castes is unknown. To reveal whether the endocuticle is involved in caste differentiation, we compared the exocuticle and endocuticle thickness of individuals in 2 pathways (nymph line and worker line) of caste differentiation in the termite Reticulitermes aculabialis. The endocuticle protein genes were identified by transcriptome analysis and the expression patterns of these genes were confirmed in caste differentiation. We found that the endocuticle structure showed dynamic changes in 2 pathways, and the first difference in endocuticle structure occurred after larvae differentiation bifurcated into workers and nymphs. The thinning of the endocuticle was a significant event from nymphs developing into alates with the thickest exocuticle and thinnest endocuticle. The thickest endocuticle layers were found in the heads of the workers and the ultrastructure of the endocuticle in the heads was more complex than that in the thorax–abdomens. Six endocuticle protein genes were identified and annotated as endocuticle structural glycoproteins SgAbd-2, SgAbd-9, and Abd-5. The expression levels of endocuticle protein genes changed dramatically during caste development and the expression levels in neotenic reproductives (secondary reproductives) were significantly higher than those in alates (primary reproductives). These results reveal the roles of endocuticles in caste differentiation and adaptation to the environment.

Morphological peculiarities of flowers, pollen grains and fruits of Valeriana tuberosa (Valerianaceae)

The results of the study of flowers, pollen grains and fruits of Valeriana tuberosa (sect. Tuberosae, Valerianaceae) are presented. Materials of the National Herbarium of the M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine (KW) were studied. The morphological structures of flowers, pollen grains and fruits were examined using both light microscopy and scanning electron microscopy; detailed descriptions of the elements of the flower, pollen grains and fruits were made and their specific features were established. The morphological features of the inflorescence, bracteoles, and the elements of the hermaphrodite flowers have been clarified. The pollen grains of V. tuberosa are 3-colpate, suboblate to subprolate (P/E = 0.85–1.33), medium- or large-sized. Their outline in equatorial view is elliptic, rarely circular, in polar view slightly trilobate or trilobate. Exine sculpture is echinate-microechinate with verrucae. The known and new carpological features are specified. In particular, papillate growth of periclinal walls of exocarp with stroke-shaped, jet and warty cuticular formations of the surface were noted the first time; details of exocarp stomatal system were revealed; features of trichomes and their cuticular structure on fruit wall are described. The obtained data are important additional characters for identification of the species and for the issues of taxonomy and phylogeny.

Involvement of the transcription factor E75 in adult cuticular formation in the red flour beetle Tribolium castaneum

Insect adult metamorphosis generally proceeds with undetectable levels of juvenile hormone (JH). In adult development of the red flour beetle Tribolium castaneum, biosynthesis of adult cuticle followed by its pigmentation and sclerotization occurs, and dark coloration of the cuticle becomes visible in pharate adults. Here, we examined the molecular mechanism of adult cuticular formation in more detail. We noticed that an exogenous JH mimic (JHM) treatment of Day 0 pupae did not inhibit pigmentation or sclerotization, but instead, induced precocious pigmentation of adult cuticle two days in advance. Quantitative RT-PCR analyses revealed that ecdysone-induced protein 75B (E75) is downregulated in JHM-treated pupae. Meanwhile, tyrosine hydroxylase (Th), an enzyme involved in cuticular pigmentation and sclerotization, was precociously induced, whereas a structural cuticular protein CPR27 was downregulated, by exogenous JHM treatment. RNA interference-mediated knockdown of E75 resulted in precocious adult cuticular pigmentation, which resembled the phenotype caused by JHM treatment. Notably, upregulation of Th as well as suppression of CPR27 were observed with E75 knockdown. Meanwhile, JHM treatment suppressed the expression of genes involved in melanin synthesis, such as Yellow-y and Laccase 2, but E75 knockdown did not result in marked reduction in their expression. Taken together, these results provided insights into the regulatory mechanisms of adult cuticular formation; the transcription of genes involved in adult cuticular formation proceeds in a proper timing with undetectable JH, and exogenous JHM treatment disturbs their transcription. For some of these genes such as Th and CPR27, E75 is involved in transcriptional regulation. This study shed light on the molecular mode of action of JHM as insecticides; exogenous JHM treatment disturbed the expression of genes involved in the adult cuticular formation, which resulted in lethality as pharate adults.

Morphological characteristic of Skrjabinema ovis (Nematoda, Oxyuridae) obtained from domestic sheep

Skrjabinemosis is a widely prevalent helminthiasis of sheep, goats and wild ruminants. It is caused by Skrjabinema ovis Skrjabin, 1915. Parasitization by S. ovis induces inflammatory processes of the large intestine, in skin around the anus and tail base, resulting in reduced productivity and weight loss. The measures of prevention and control of skrjabinemosis on sheep farms depend on the timely and accurate diagnosis, based on the reliable identification of nematodes. We studied the identification morphometric characters of this species The nematodes were obtained from the large intestine of 710 pasture-kept sheep (Ovis aries) on farms of Kyiv, Poltava and Zaporizhzhia regions ( Central and South-Eastern Ukraine). In total, 5723 adult S. ovis nematodes were collected, 1981 of which were males and 3742 were females. Sexual dimorphism was found in S. ovis both in metric and morphological parameters. The size dimorphism is characterized by values larger by 43.9–64.6% of 11 parameters in females compared to males. The differential characters of mature S. ovis males and females are morphological specifics of the mouth organ complex and the distribution of cuticular formations on the head end of the parasite. The lips of the female nematodes are anchor-shaped and adorned with tooth-like lamellae, and the lips of the males are oval and lack the tooth-like lamellae. Cuticular nodes on the head ends of the females are considerably longer and wider than in the males. The species-specific morphological characters of the males are the features of morphology and sizes of the pseudobursa, the shape and length of the spicule and gubernaculum, and their width parameters in different areas. In the identification of females, the morphology of the vulva and tail end, and the metric parameters of the location of the vulva, anus, and sizes of eggs in the uterus should be considered. Additional metric and morphological parameters are presented for use in the differentiation of males and females for better identification.

Proteomic Analysis of Larval Integument in a Dominant Obese Translucent (Obs) Silkworm Mutant.

The dominant obese translucent (Obs) mutant of the silkworm (Bombyx mori) results in a short and stout larval body, translucent phenotype, and abnormal pigmentation in the integument. The Obs mutant also displays deficiency in ecdysis and metamorphosis. In the present study, to gain an understanding of multiple Obs phenotypes, we investigated the phenotypes of Obs and performed a comparative analysis of the larval integument proteomes of Obs and normal silkworms. The phenotypic analysis revealed that the Obs larvae were indeed short and fat, and that chitin and uric acid content were lower but melanin content was higher in the Obs mutant. Proteomic analysis revealed that 244 proteins were significantly differentially expressed between Obs and normal silkworms, some of which were involved in uric acid metabolism and melanin pigmentation. Twenty-six proteins were annotated as cuticular proteins, including RR motif-rich cuticular proteins (CPR), glycine-rich cuticular protein (CPG), hypothetical cuticular protein (CPH), cuticular protein analogous to peritrophins (CPAPs), and the chitin_bind_3 motif proteins, and accounted for over 84% of the abundance of the total significantly differentially expressed proteins. Moreover, 22 of the 26 cuticular proteins were downregulated in the Obs mutant. Comparative proteomic analysis suggested that the multiple phenotypes of the Obs mutant might be related to changes in the expression of proteins that participate in cuticular formation, uric acid metabolism, and melanin pigmentation. These results could lay a basis for further identification of the gene responsible for the Obs mutant. The data have been deposited to ProteomeXchange with identifier PXD010998.

The chemical NJ15 affects hypocotyl elongation and shoot gravitropism via cutin polymerization.

Caf: cafenstrole; DEG: differentially expressed gene; FDR: false discovery rate; FOX: full length cDNA-overexpressor; VLCFA: very-long-chain fatty acid.

An RNAi Screen for Genes Involved in Nanoscale Protrusion Formation on Corneal Lens in Drosophila melanogaster

The "moth-eye" structure, which is observed on the surface of corneal lens in several insects, supports anti-reflective and self-cleaning functions due to nanoscale protrusions known as corneal nipples. Although the morphology and function of the "moth-eye" structure, are relatively well studied, the mechanism of protrusion formation from cell-secreted substances is unknown. In Drosophila melanogaster, a compound eye consists of approximately 800 facets, the surface of which is formed by the corneal lens with nanoscale protrusions. In the present study, we sought to identify genes involved in "moth-eye" structure, formation in order to elucidate the developmental mechanism of the protrusions in Drosophila. We re-examined the aberrant patterns in classical glossy-eye mutants by scanning electron microscope and classified the aberrant patterns into groups. Next, we screened genes encoding putative structural cuticular proteins and genes involved in cuticular formation using eye specific RNAi silencing methods combined with the Gal4/UAS expression system. We identified 12 of 100 candidate genes, such as cuticular proteins family genes (Cuticular protein 23B and Cuticular protein 49Ah), cuticle secretion-related genes (Syntaxin 1A and Sec61 ββ subunit), ecdysone signaling and biosynthesis-related genes (Ecdysone receptor, Blimp-1, and shroud), and genes involved in cell polarity/cell architecture (Actin 5C, shotgun, armadillo, discs large1, and coracle). Although some of the genes we identified may affect corneal protrusion formation indirectly through general patterning defects in eye formation, these initial findings have encouraged us to more systematically explore the precise mechanisms underlying the formation of nanoscale protrusions in Drosophila.

Comparative study of the morphology of stridulatory organs of the Iberian lycaenid butterfly pupae (Lepidoptera)

We compared the pupal stridulatory organs of 35 species and one subspecies of Iberian Lycaenidae using scanning electron microscopy. The studied species belong to the tribes Theclini, Eumaeini, Lycaenini, and Polyommatini. Nine species do not show stridulatory organs on the pupae but all other species possess them. Stridulatory organs are formed by a stridulatory plate (pars stridens) placed on the fifth abdominal segment and a file (plectron) in the sixth abdominal segment. The plate has tubercles in the Theclini and Lycaenini, tubercles, ridges, or undulations in the Eumaenini, and tubercles, teeth, or unspecialized structures in the Polyommatini. Morphological differences can be found in the files of the different tribes, regarding the number of teeth, their form and size. Cuticular formations of the organs were studied on a surface of 2,500 µm(2) and the average of ridges, tubercles, and teeth was measured searching for relevant taxonomic information. Stridulatory organs were thought to be an adaptation to myrmecophily but we show that they are present both in myrmecophilous and nonmyrmecophilous species; therefore, we suggest that this trait probably did not evolve in relation with myrmecophily, but may be used to enhance relationships with ants.

High Laccase2 expression is likely involved in the formation of specific cuticular structures during soldier differentiation of the termite Reticulitermes speratus

Termite soldiers are morphologically specialized for colony defense. Analysis of the mechanisms of soldier differentiation is important for understanding the establishment of termite societies. Soldiers differentiate from workers through a presoldier stage and have well-sclerotized and pigmented cuticles. These characteristics are important for nest defense and are likely to be caused by soldier-specific mechanisms of cuticular tanning. The molecular mechanisms leading to cuticular tanning have not been elucidated. Laccase2 (Lac2) plays important roles in this process in insects, and we hypothesized that Lac2 expression may be involved in soldier-specific cuticular tanning. We observed inner and outer head cuticle changes and compared the Lac2 expression patterns among three molts (worker–worker, worker–presoldier and presoldier–soldier) in the termite Reticulitermes speratus. Quantitative analyses of head cuticle colors showed that the color properties changed more conspicuously in presoldier–soldier molts than in the other two molts. Histological observations showed that the exocuticles of soldier heads were substantially thicker than those of worker and presoldier heads, underwent tanning before or just after ecdysis, and were pigmented at earlier time points than other molts. Finally, markedly higher Lac2 expression levels were observed just before and after ecdysis only in the presoldier–soldier molt. These results suggest that specific cuticular formation occurs in the exocuticles during soldier differentiation, and that the high level of Lac2 expression during the presoldier–soldier molt is related to soldier-specific cuticular tanning. We speculate that evolution of the regulatory mechanisms of Lac2 expression were important for the acquisition of soldier-specific cuticles.

Pterygodermatites (Mesopectines) niameyensisn. sp. (Nematoda: Rictulariidae), a Parasite ofMastomys natalensis(Smith, 1834) (Rodentia: Muridae) from Niger

Pterygodermatites (Mesopectines) niameyensis n. sp. is described from Mastomys natalensis in Niamey/Niger (West Africa). It differs from other species of same subgenus by the morphology of the head, which presents 4 simple cephalic papillae and nearly axial oral opening, a number of caudal papillae, precloacal cuticular formations, and the spicule length/body length ratio. Scanning electron microscopy shows the presence of 2 pairs of lateral sensory structures for male worms.

Pterygodermatites(Mesopectines)quentini(Nematoda, Rictulariidae), a parasite ofPraomys rostratus(Rodentia, Muridae) in Mali: scanning electron and light microscopy

Pterygodermatites (Mesopectines) quentini n. sp. (Nematoda, Rictulariidae) is described from the murine host Praomys rostratus in the south of the Republic of Mali. It differs from other species of the subgenus by the morphology of the head, which bears four simple cephalic papillae and a nearly axial oral opening, the number of caudal papillae, the number of precloacal cuticular formations, unequal spicules and the ratio of spicule lengths/body length. The use of scanning electron microscopy in combination with conventional light microscopy enabled us to give a detailed description of the morphological characters of this new species.

Comparative electron microscopic observations of larval and pupal cuticular formation of Bombyx mori

Comparative electron microscopic observations of larval and pupal cuticular formation of Bombyx mori

Cuticular encystment of Autographa nigrisigna eggs by epidermal cell migration

It was previously established that Autographa nigrisigna loopers form cuticular cysts at the dorsal site of the 9th (penultimate) abdominal segment after parasitization by the solitary endoparasitoid Campoletis chlorideae and get rid of the parasitoid egg with the old cuticle at ecdysis. The cuticular cyst consists of a space between the old cuticle and new cuticle formed by the epidermis to enclose the parasitoid egg. The fact that A. nigrisigna loopers exclude the oviposited egg from the hemocoel using a cuticular cyst raises the question how the parasitoid egg passes through the epidermis. To exclude the endoparasitoid eggs from the hemocoel, the epidermis is required to move the location of the parasitoid egg. In the current study, we investigated the morphological process of cuticular cyst formation. First, the oviposited egg drifted to the 9th abdominal segment located at the open end of the dorsal vessel as a result of force generated by the hemolymph current from the oviposition site, and formed contacts with the integument containing the fat body (FB). The epidermis, in contact with the egg, then began to move along with the basement membrane formed on the surface of the FB, and settled under the egg, thus altering its location. This inversion was duplicated in vitro using integument from the 9th abdominal segment when parasitoid eggs were inserted between the epidermis and FB. When the integument, without the FB, was incubated on an agar plate, the epidermal cells migrated on the plate. Integument without eggs showed no signs of migration from their original sites. When the actin polymerization inhibitor latrunculin B was added to the cultures, the epidermal cells remained in their original location.

Gain of affinity point mutation in the serotonin receptor gene 5‐HT2Dro accelerates germband extension movements during Drosophila gastrulation

Serotonin (5-HT) not only works as a neurotransmitter in the nervous system, but also as a morphogenetic factor during early embryogenesis. In Drosophila, a previous report showed that embryos that lack the 5-HT(2Dro) receptor locus, display abnormal gastrulation movements. In this work, we screened for point mutations in the 5-HT(2Dro) receptor gene. We identified one point mutation that generates a gain of serotonin affinity for the receptor and affects germband extension: 5-HT(2Dro) (C1644). Embryos homozygous for this point mutation display a fourfold increase in the maximal speed of ectodermal cell movements during the rapid phase of germband extension. Homozygous 5-HT(2Dro) (C1644) embryos present a cuticular phenotype, including a total lack of denticle belt. Identification of this gain of function mutation shows the participation of serotonin in the regulation of the cell speed movements during the germband extension and suggests a role of serotonin in the regulation of cuticular formation during early embryogenesis.

Role of Egg Buster in Hatching of Aedes aegypti: Scanning Electron Microscopy Study

Egg hatching has been studied in Aedes aegypti (L.) through scanning electron microscopy. The first sign of egg hatching is a small protrusion on the eggshell in the anterior pole. The larval movement provokes a crack in the eggshell with the egg buster located in the dorsal head. The egg buster provokes a small transverse fissure in the eggshell that gradually increases in the chorion. Then, the rupture is completed around the eggshell. The separation of the anterior pole occurs, showing the dorsal region of the larva head with the egg buster and the cap. After sequential movements, the larva looses the cap. Finally, the first instar is ready to be free showing details of its body with the egg buster over its head. This structure is a cuticular formation, similar to a cone structure that ends in a very fine tip and emerges from a pear-like depression with high rounded borders. Our results describe the anatomy of the egg hatching process in Ae. aegypti, showing details of the participation of the egg buster.