Spermatogenesis in the testes of diapause and non-diapause pupae of the sweet potato hornworm, Agnus convolvuli (L.) (Lepidoptera: Sphingidae)

Masami Shimoda, Miyoko Kubo-Irie, Kazumasa Ohta, Masaru Irie, Hideo Mohri

    Research output: Contribution to journalArticlepeer-review

    13 Citations (Scopus)

    Abstract

    Dichotomous spermatogenesis was examined in relation to diapause in the sweet potato hornworm, Agrius convolvuli. In non-diapause individuals, eupyrene metaphase began during the fifth larval instar and eupyrene spermatids appeared in wandering larvae. Bundles of mature sperm were found after pupation. Apyrene spermatocytes also appeared during the fifth larval instar, but meiotic divisions occurred irregularly and their nuclei were discarded from the cells during spermiogenesis. Morphometric analyses of flagellar axonemes showed a variable sperm number in apyrene bundles. The variation ranging from 125 to 256 sperm per bundle indicated abnormal divisions or the elimination of apyrene spermatocytes. In diapause-induced hornworms, spermatogenesis progressed similarly during the larval stages. The cessation of spermatogenesis during diapause is characterized by 1) secondary spermatocytes and sperm bundles degenerating gradually as the diapause period lengthens, and 2) spermatogonia or primary spermatocytes appearing throughout diapause. A TUNEL (TdT-mediated dUTP-biotin nick end-labeling) assay revealed that DNA fragmentation occurred in the nuclei of secondary spermatocytes and early spermatids. Aggregates of heterochromatin along the nuclear membrane indicated the onset of apoptosis, and condensed chromatin was confirmed by electron microscopy to be the apoptotic body. These results show that the degenerative changes in spermatogenic cells during pupal diapause were controlled by apoptosis.

    Original languageEnglish
    Pages (from-to)1036-1044
    Number of pages9
    JournalZoological Science
    Volume24
    Issue number10
    DOIs
    Publication statusPublished - 2007 Oct

    Keywords

    • Agrius convolvuli
    • Apoptosis
    • Diapause
    • Hornworm
    • Reproduction
    • Spermatogenesis

    ASJC Scopus subject areas

    • Animal Science and Zoology

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