Immunocytochemical localization of tubulins in spermatids and spermatozoa of Euptoieta hegesia (Lepidoptera: Nymphalidae)

Testis Morphology and Dichotomic Spermatogenesis in the Sugarcane Borer Diatraea saccharalis (F.) (Lepidoptera: Crambidae)

In the present study, we describe the testis morphology and spermatogenesis of the sugarcane borer, one of the most destructive pests of sugarcane, using light, transmission, and scanning electron microscopies. Diatraea saccharalis (F.) larvae have paired, kidney-shaped testes that are limited externally and divided into four follicles by tunica cells. The adults have two fused whitish and spherical testes that are divided into eight follicles and are composed of spermatogonia, spermatocyte, spermatid, and sperm bundles. The spermatogonia and spermatocyte cysts are located at the apical extremity of the follicle, while the spermatid cysts and sperm bundles are located at the basal extremity of the follicle. Inside of the cysts, which are formed by the somatic cells, the germ line cells develop synchronously and are interconnected by cytoplasmic bridges. Each cyst contains only apyrene or eupyrene, and none of the cysts contain both of the cells. The inner part of the apyrene cyst consists of an electron-dense cap as opposed to a nucleus. The eupyrene sperm contains a nucleus, acrosome, and reticular and lacinate appendages. Both of the sperm types have a "9 + 9 + 2" axoneme and two mitochondrial derivatives at the tail region. The spermatogenesis process and spermatozoa morphology are similar to that of other Lepidoptera.

New insights into the cell biology of insect axonemes

Insects do not possess ciliated epithelia, and cilia/flagella are present in the sperm tail and--as modified cilia--in mechano- and chemosensory neurons. The core cytoskeletal component of these organelles, the axoneme, is a microtubule-based structure that has been conserved throughout evolution. However, in insects the sperm axoneme exhibits distinctive structural features; moreover, several insect groups are characterized by an unusual sperm axoneme variability. Besides the abundance of morphological data on insect sperm flagella, most of the available molecular information on the insect axoneme comes from genetic studies on Drosophila spermatogenesis, and only recently other insect species have been proposed as useful models. Here, we review the current knowledge on the cell biology of insect axoneme, including contributions from both Drosophila and other model insects.