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Ultrastructure of spermiogenesis and spermatozoa in Marchalina hellenica (Gennadius) (Hemiptera: Sternorrhyncha, Marchalinidae)

Dallai, Romano, Mercati, David, Gounari, Sofia, Paoli, Francesco, Lupetti, Pietro
Arthropod structure & development 2017 v.46 no.4 pp. 601-612
Sternorrhyncha, flagellum, microtubules, scale insects, sperm motility, spermatozoa, spermiogenesis, ultrastructure
The spermiogenesis, the sperm structure and the sperm motility of Marchalina hellenica (Gennadius) were examined. In the early spermiogenesis a centriolar apparatus was identified, but this structure is not involved in the production of the sperm flagellum. As in other Coccoidea, the flagellar axoneme originates by the activity of the thickened tip of the numerous microtubules surrounding the nuclear anterior region close to the periphery of the cell. This region pushes against a narrow cytoplasmic layer, giving rise to a papilla. In this region a novel structure, consisting of a regular network of thin filaments, arranged orthogonally to the bundle of microtubules, is visible. The sperm flagellum consists of a series of about 260 microtubules, regularly arranged in rings around the axial nucleus. This latter extends in the middle part of the sperm length. As usual in scale insects, sperm form a bundle, which in M. hellenica is composed of 64 sperm cells, surrounded by somatic cyst cells. The sperm bundle has an helicoidal array, with a cap of dense material at its apex, lending the anterior and the posterior region of the sperm bundle with a different structural organization. This difference is responsible of the different speed gradient observed in the helical wave propagating along the sperm bundle.