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Eupyrene and apyrene spermatogenesis in Methona themisto (Lepidoptera: Ithomiidae)

Lais Betty F. Corsato-Alvarenga; Antonio N. Cestari; Alberto F. Ribeiro

Departamento de Biologia, Instituto de Biociências, Universidade de São Paulo, Caixa Postal 11.461, 05499 São Paulo, SP, Brasil. Send correspondence to A.N.C.

ABSTRACT

The two types of spermatogenesis occurring in Lepidoptera, eupyrene and apyrene, were studied during the life cycle of Methona themisto using standard fixation, embedding and staining methods for light microscopy. In vivo and ultrastructural analyses were also performed. Cysts of eupyrene spermatocytes II were observed from the third ecdysis, with metaphase II preparations showing considerably eosinophilic spindle fibers which continued to be visible until the end of telophase II and prevented the end of cytokinesis. Young eupyrene spermatids showed well developed nebenkerns which change during flagellum development. Apyrene spermatogenesis started during the 5th larval instar, with spermatocytes II that were smaller than eupyrene spermatocytes and more condensed nuclei. During the second meiotic division, these spermatocytes showed chromosome masses that segregated at random, resulting in small nuclei which were extruded through the flagella together with cytoplasmic portions. The proportion of apyrene cysts increased during animal development in relation to eupyrene cysts, with the latter being detected even in older adults, in which dividing spermatogonia and activity of the four apical cells were still visible.

Keywords: eupyrene; apyrene; spermatogenesis; Methona themisto.

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