Many arthropods and the majority of insects lay their eggs without parental care. These immobile stages of life must rely on the various eggshell layers deposited upon the developing embryo to survive biotic and abiotic stresses such as desiccation, flooding, predators and pathogens. At the same time, these protective layers must allow sperm entry and gas exchanges. During insect oogenesis most of these layers are deposited by the follicle cells: vitelline membrane, wax layer, innermost chorionic layer, endochorion and exochorion. Follicle cells will also produce some regions with chorionic complexities such as micropyles, aeropyles and the operculum. After fertilization and egg deposition, the developing egg of insects and other arthropods produces a blastodermal or serosal cuticle, which is located below the vitelline membrane and serves as an additional protective extracellular structure. Through a literature survey comprising more than 40 species this chapter is dedicated to the description of the formation, structure and physiology of these multilayered and multiregional composite structures as well as the cellular and molecular mechanisms underlying it.

Composite Eggshell Matrices: Chorionic Layers and Sub-chorionic Cuticular Envelopes

. We described and compared the chorion morphology of 22 species in 12 genera of the subfamily Coliadinae, collected from 80 females in Mexico, Colombia, and Ecuador. Their characterization and ilustration include the main structural features of the eggs: colors, shapes, sizes, and diversity of ornamentation or reticula; possibly from the most widespread in Pieridae (polygon grid) to the derivatives Coliadinae (with the formation of axes and ribs relatively reduced number). We describe for the first time microreticulum associated with the macroreticulum.

Chorionic Morphology in the Coliadinae Subfamily (Lepidoptera: Pieridae)

. We describe and compare the chorion morphology of three species of the genus Ascia and Ganyra. Their characterization and illustration include the main structural features of the egg: number and arrangement of longitudinal axes (short and long), and quantification of ribs or cells, protuberances, projections, and reminiscent ribs; the color and size are also described. We typify three egg models: ellipsoidal with protuberances exhibiting a grid of pores in Ascia, elongated or oblong ellipsoidal with laminar projections unciforms in Ganyra. Comparisons are made between the chorion features of different species and related genera (Glutophrissa and Leptophobia). We discuss their phylogenetic and taxonomic implications.

Chorion Morphology in the Genus Ascia and Ganyra and Its Comparison with other Proximate Genera to Pierinae (Lepidoptera: Pieridae)

Background: Waste product compound of rice bran and lufenuron are considered safe compounds to the human and to the environment. They can be used to control Schistocerca gregaria.Objective: The aim of the present study is to examine the ultrastructural changes and histopathological alteration in the Schistocerca gregaria embryogenesis induced by selected waste product compound of rice bran (Oryza sativa) and a chitin synthesis inhibitor (lufenuron).Materials and Methods: Histological and ultrastructure study of normal and affected eggs of Schistocerca gregaria were conducted to demonstrate the effects of lufenuron and rice bran extract on the embryogenesis. Cleavages started about 5 hrs post oviposition (pop) and continue to divide until formation of cellular blastodrem by 1 day pop. By 2 days pop germ band is formed, differentiated into ectoderm and mesoderm. At 3 days pop segmentation of germ band into mouthpart and three thoracic segments occur. Antenna was observed at 3 days pop. Fore and midgut were detected by 5 days pop. Hindgut was also observed by 5 days pop. By 4 days pop, eyes and brain appeared. Brain appeared as two ganglionic masses separated by oesophagus, which by 5 days pop appears as 2 large interconnect cerebral lobes enwrapped by neurilemma. Histological section of affected eggs showed great effects on brain, alimentary canals and compound eyes.Results: Ultrastructure study of newly deposited eggs showed that, the chorion consists of several easily distinguishable layers and in 30-hour-old eggs, cleavage nuclei of different shapes could be observed. The nuclei of the blastoderm cell have spindle shape and have condensed chromatin, which attaches to nuclear membrane. Electron micrograph of lufenuron-affected eggs revealed abnormal chorion and cleavage nuclei. In rice bran affected eggs, disintegrated blastoderm that failed to arranged and sever malformed nuclei were seen. Vaculation and lysis of cell components leaving cavities within the ooplasm were detected in both treatments.Conclusion: The tested compounds induced serious changes to the embryos of Schistocerca gregaria as revealed by the histological and ultrastructure studies

https://ejh.journals.ekb.eg/article_48005_442b42a0ef82bee7d75bfb225dfcbbea.pdf

Histopathological and Ultrastructure Changes in the Embryonic Development of Schistocerca Gregaria (Forskal) (Orthoptera): Acrididae Induced by Lufenuron (CSI) and Rice Bran Extract (Waste Product)

El estudio de la biodiversidad es imprescindible ante la dinamica de la modificacion ambiental. Para ello es necesario emplear diferentes tecnicas que permitan la obtencion de resultados optimos de la manera mas eficiente y estandarizada. En Lepidoptera, el estudio de la estructura del exocorion ofrece un sistema de informacion util en la discriminacion taxonomica a diferentes niveles jerarquicos. En este estudio se describen y valoran tres tecnicas de rehidratacion abdominal a partir de muestras alojadas en colecciones cientificas y se compara con el material recien recolectado en el campo, con el fin de examinar su efectividad y costos. En el campo a menudo es dificil o imposible obtener hembras para estos estudios, por lo que el uso del material de museos, con el empleo de estas tecnicas, podria ser un gran avance en el conocimiento de este sistema de caracteres morfologicos en mariposas, ya que se podrian estudiar hembras de especies raras, cripticas y/o con muestreo deficiente. Ademas, tambien permitiria el registro de la variacion temporal y geografica de tales caracteres. A pesar que lo mas recomendable es usar material fresco, de acuerdo con los resultados hallados en el presente estudio, las tecnicas de rehidratacion podrian permitir la recuperacion del corion en un grado aceptable para su analisis y comparaciones, aunque se necesita mas tiempo para limpiar la muestra. La tecnica de rehidratacion de proteinasa K obtuvo los huevos mas conservados, incluso con material que se recolecto hace mas de treinta anos.

Una Comparación de Técnicas de Rehidratación Abdominal y Coriónica en Especies de Emesis Fabricius1 y Lasaia H. Bates1

Surface Ultrastructure of the Egg Chorion of Eri Silkworm, Samia ricini (Donovan) (Lepidoptera: Saturniidae)

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Surface Ultrastructure of the Egg Chorion of Eri Silkworm, Samia ricini (Donovan) (Lepidoptera: Saturniidae)