Ultrastructure du tissu apical testiculaire du doryphore<i>Leptinotarsa decemlineata</i>Say (Coléoptère: Chrysomélidé): étude autoradiographique et cytochimique / Ultrastructure of the apical testicular tissue of the doryphore<i>Leptinotarsa decemlineata</i>Say (Coleopterae: Chrysomelidae): an autoradiographic and cytochemical study

The gonads of Lampyris noctiluca are sexually undifferentiated during the first larval instars. They consist of many gonadal follicles that include the germ stem cells enclosed by the somatic cells of the follicle wall. Follicle wall cells are more numerous at the follicle apices than at the distal parts, but different cell types cannot be distinguished. In male larvae, the appearance of apical follicle tissue, derived from follicle wall cells, marks the onset of testis differentiation. When maximally expressed, the apical tissue occupies about the upper half of the testis follicles and can be observed in larvae of the fifth and sixth instar. The apical tissue is characterized by its "light" appearance (due to poor stainability) caused by the small number cellular organelles, especially a paucity of free ribosomes. Maximal expression of the apical tissue must be very brief, since in most examined fifth and sixth instar larvae the apical tissue is partly or mostly translocated into the center of the upper half of the follicles and spermatogonia then occupy the apical follicle tips. During and after translocation apical cells form projections that grow around clusters of spermatogonia (spermatocysts). Thus, the apical cells transform into spermatocyst envelope cells. They retain their "light" appearance but undergo dramatic subcellular differentiation: smooth ER becomes extremely prominent, forming stacks and whorls of parallel cisternae. Golgi complexes are also conspicuous. The cellular organization suggests secretory activity. The possibility of ecdysteroid production and its function is discussed. The spermatocyst envelope cells persist into the pupal stage. When spermiohistogenesis takes place in cysts, cyst envelope cells show signs of regression. At all stages of testis development apical cells and their derivatives, the spermatocyst envelope cells, phagocytize degenerating spermatogonia. Although this is an important task of these cells, the impressive formation of sER in the cyst envelope cells is indicative of an additional, as yet unknown, function.

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Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue

Balles

Maas

Sehn

et al. 2001

Journal of Morphology

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Structural polarity and dynamics of male germline stem cells in the milkweed bug (Oncopeltus fasciatus)

Schmidt

Dorn

2004

Cell Tissue Res

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The male germline stem cells (GSCs) of the milkweed bug present an extraordinary structural polarity that is, to our knowledge, unequalled by any other type of stem cells. They consist of a perikaryon and numerous projections arising from the cell pole directed toward the apical cells, the proposed niche of the GSCs. The projections can traverse a considerable distance until their terminals touch the apical cells. From hatching until death, the GSC projections undergo conspicuous changes, the sequence of which has been deduced from observations of all developmental stages. Projection formation starts from lobular cell protrusions showing trabecular ingrowths of the cell membrane. Finger-like projections result from a process of growth and "carving out". The newly formed projections contain mostly only free ribosomes other than a few mitochondria. A stereotyped degradation process commences in the projection terminals: profiles of circular, often concentric, cisternae of rough endoplasmic reticulum appear and turn into myelin bodies, whereas mitochondria become more numerous. The cytoplasm vesiculates, lysosomal bodies appear, and mitochondria become swollen. At the same time, the projection terminals are segregated by transverse ingrowths of the cell membrane. Finally, autophagic vacuoles and myelin bodies fill the segregated terminals, which then rupture. Simultaneously, new projections seem to sprout from the perikaryon of the GSCs. These dynamics, which are not synchronized among the GSCs, indicate that a novel type of signal exchange and transduction between the stem cells and their niche is involved in the regulation of asymmetric versus symmetric division of GSCs.

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Histological and histochemical studies of the apical cells of the cotton bollworm, Heliothis armigera (Huebner) (Lepidoptera : Noctuidae)

Sonoli¹,

Hooli

1992

International Journal of Insect Morphology and Embryology

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Cited by 5 publications

References 17 publications

Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue

Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue

Structural polarity and dynamics of male germline stem cells in the milkweed bug (Oncopeltus fasciatus)

Histological and histochemical studies of the apical cells of the cotton bollworm, Heliothis armigera (Huebner) (Lepidoptera : Noctuidae)

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