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Egg case ultrastructure in the narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 (Decapoda, Astacidae)

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[The egg case is an extracellular structure that surrounds an egg cell and the embryo after fertilization. Its basic function is to protect the embryo from potentially harmful aspects of the external environment. Changes in the structure of the egg case at different stages of embryogenesis in the crayfish Astacus leptodactylus were studied, with observations made at the beginning of egg incubation, during incubation, and at the time of hatching. We studied the changes using images taken with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The egg case is made of three layers that are all close together. The outer layer was 4.59±0.23 μm thick and composed of an electron-dense material; its external structure was rough. The middle layer was the thickest at 8.94±0.29 μm and was slightly folded. It was made of polyhedral grains, interspersed with multiple aeropylar areas and channels. This second (middle) layer consisted of two sublayers of equal thickness but with variable grain size and aeropyle structure. The third and innermost layer was 3.14±0.33 μm thick and made of tightly packed grains, smaller than those in the middle layer. It included a few, small aeropylar channels. La membrane de l'œuf est une structure extra embryonnaire qui entoure l'œuf ou l'embryon après la fécondation. Sa fonction de base est de protéger l'embryon des aspects potentiellement nuisibles de l'environnement externe. Les changements de la structure de la membrane de l'œuf chez l'écrevisse Astacus leptodactylus ont été étudiés, avec des observations faites au début de l'incubation de l'œuf, durant l'incubation et au moment de l'éclosion. Nous avons étudié les changements à partir d'images prises en microscopie électronique à transmission (TEM) et à balayage (SEM). La membrane de l'œuf est faite de trois couches serrées. La couche externe (4,59±0,23 μm d'épaisseur) est composée de matériel dense aux électrons ; sa surface externe est ruguenx. La couche médiane est la plus épaisse (8,94±0,29 μm) et est légèrement pliée. Elle est constituée de grains polyédriques entrecoupés par de multiples zones aéropyles et des canaux. Cette couche médiane consiste en deux sous-couches de même épaisseur mais avec des tailles de grains et des structures aéropyles variables. La troisième couche interne (3.14±0.33 μm d'épaisseur) est faite de grains étroitement serrés, plus petits que ceux de la couche moyenne. Elle comporte quelques petits canaux aéropyles., The egg case is an extracellular structure that surrounds an egg cell and the embryo after fertilization. Its basic function is to protect the embryo from potentially harmful aspects of the external environment. Changes in the structure of the egg case at different stages of embryogenesis in the crayfish Astacus leptodactylus were studied, with observations made at the beginning of egg incubation, during incubation, and at the time of hatching. We studied the changes using images taken with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The egg case is made of three layers that are all close together. The outer layer was 4.59±0.23 μm thick and composed of an electron-dense material; its external structure was rough. The middle layer was the thickest at 8.94±0.29 μm and was slightly folded. It was made of polyhedral grains, interspersed with multiple aeropylar areas and channels. This second (middle) layer consisted of two sublayers of equal thickness but with variable grain size and aeropyle structure. The third and innermost layer was 3.14±0.33 μm thick and made of tightly packed grains, smaller than those in the middle layer. It included a few, small aeropylar channels. La membrane de l'œuf est une structure extra embryonnaire qui entoure l'œuf ou l'embryon après la fécondation. Sa fonction de base est de protéger l'embryon des aspects potentiellement nuisibles de l'environnement externe. Les changements de la structure de la membrane de l'œuf chez l'écrevisse Astacus leptodactylus ont été étudiés, avec des observations faites au début de l'incubation de l'œuf, durant l'incubation et au moment de l'éclosion. Nous avons étudié les changements à partir d'images prises en microscopie électronique à transmission (TEM) et à balayage (SEM). La membrane de l'œuf est faite de trois couches serrées. La couche externe (4,59±0,23 μm d'épaisseur) est composée de matériel dense aux électrons ; sa surface externe est ruguenx. La couche médiane est la plus épaisse (8,94±0,29 μm) et est légèrement pliée. Elle est constituée de grains polyédriques entrecoupés par de multiples zones aéropyles et des canaux. Cette couche médiane consiste en deux sous-couches de même épaisseur mais avec des tailles de grains et des structures aéropyles variables. La troisième couche interne (3.14±0.33 μm d'épaisseur) est faite de grains étroitement serrés, plus petits que ceux de la couche moyenne. Elle comporte quelques petits canaux aéropyles.]

Affiliations: 1: Marshal's Office of the Westpomeranian Region, Department for Agriculture and Environment Protection, Małopolska 12, PL-70-550 Szczecin, Poland; 2: Department of Fish Anatomy, Hydrobiology, and Biotechnology of Reproduction, West Pomeranian University of Technology in Szczecin, K. Królewicza 4 Str., PL-71-550 Szczecin, Poland; 3: Institute of Zoology, Jagiellonian University in Kraków, PL-30-060 Kraków, Poland

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/content/journals/10.1163/001121611x577927
2011-05-01
2017-10-22

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