Ectodermally derived gut and epidermal cells in crustaceans are covered by cuticle, a chitinous apical extracellular matrix, and at the opposite side they are underlined by a basal lamina. Thus, the same cell performs synthesis and spatiotemporal control of elaboration of two extracellular matrices that differ in ultrastructure, composition and functions. Differentiation of the extracellular matrix in epithelial tissues is an integrative part of the establishment and maintenance of the characteristic apicobasal polarized cell architecture. We present here the ultrastructural description of the hindgut cells’ apical matrix differentiation during embryonic and larval development of crustacean Porcellio scaber. In addition, in the same developmental stages the ultrastructure of basal lamina was described.

The ultrastructural hallmarks of the hindgut cells and their extracellular matrices (ECM) in adults are: (i) apical ECM is a chitinous cuticle, consisting of distinct horizontal layers – electron dense epicuticle and electron lucent procuticle (Fig. 1), (ii) extensive apical and basal plasma membrane infoldings, forming prominent membrane labyrinths, (iii) basal lamina that is forming an extensive interface surface to hemolymph space (Fig. 2). The ultrastructure of cuticle differs in the two anatomic regions of the hindgut, namely the anterior chamber and the papillate region. In the anterior chamber the epicuticle is much thinner than procuticle and lamellae are discernible in the procuticle due to helicoidally arranged chitin protein fibers (Fig. 1). In papillate region epicuticle and procuticle are of approximately equal thicknesses and no lamellae could be discerned in the procuticle.

Differentiation of the hindgut cuticular matrix during embryonic and larval development involves a sequential formation and shedding of several apical matrices, which gradually display ultrastructural features characteristic for adults. The outline of the pre-cuticluar apical matrix in embryos is ruffled and consists of homogenous lucent material and a distal electron dense lamina. In late embryos of stage 18 the first deposition of the apical cuticle was evidenced. In marsupial larvae the cuticle follows the outline of apical hindgut surface and is already differentiated into thin electron dense epicuticle and thicker electron lucent procuticle. In the epicuticle a trilayered surface lamina and electron dense material beneath are discernible (Fig. 3). The procuticle is homogenous along the whole length of the hindgut and non-lamellate as is characteristic in anterior chamber of adults. The basal side of the hindgut epithelium of marsupial larvae is in contact with basal lamina (Fig. 4) exhibiting fibrillary structure in certain section profiles.

Figures:

Figure 1: Ultrastructure of the apical part of hindgut epithelial cell in adult. CU – cuticle, EP – epicuticle, PRO – procuticle with discernible lamellae due to helicoidally arranged chitin-protein fibers, ML – membrane labyrinth, HEC – cytoplasm of hindgut epithelial cell, L – lumen.

Figure 2: Ultrastructure of the basal part of hindgut epithelial cell in adult. BL – basal lamina, HEC – cytoplasm of hindgut epithelial cell, ML – membrane labyrinth, white arrows - mitochondria.

Figure 3: Ultrastructure of the apical part of hindgut epithelial cell in marsupial larva. CU – cuticle, HEC – cytoplasm of hindgut epithelial cell, black arrow – trilayered surface lamina, white arrow – electron dense material of epicuticle.

Figure 4: Ultrastructure of the basal part of hindgut epithelial cell in marsupial larva. (A) Oblique section through basal lamina. (B) Transverse section through basal lamina. BL – basal lamina, HEC – cytoplasm of hindgut epithelial cell, white arrow – basal plasma membrane infoldings.

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EMC Abstracts - https://emc-proceedings.com/abstract/apical-chitinous-matrix-and-basal-lamina-the-ultrastructure-and-formation-of-two-distinct-extracellular-matrices-of-crustacean-hindgut-cells/