Location: Southern Insect Management ResearchTitle: Effects of photoperiod and aging on the adult spermatogenesis of Polygonia c-aureum (Lepidoptera: Nymphalidae), in relation to adult diapause
|HIROYOSHI, SATOSHI - Tokyo University Of Agriculture & Technology|
|Reddy, Gadi V.P.|
|MITSUNAGA, TAKAYUKI - National Agriculture And Food Research Organization (NARO), Agricultrual Research Center|
Submitted to: Journal of Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2020
Publication Date: 3/14/2020
Citation: Hiroyoshi, S., Reddy, G.V., Mitsunaga, T. 2020. Effects of photoperiod and aging on the adult spermatogenesis of Polygonia c-aureum (Lepidoptera: Nymphalidae), in relation to adult diapause. Journal of Comparative Physiology. 206:467-475. https://doi.org/10.1007/s00359-020-01413-x.
Interpretive Summary: While most research on adult diapause has concentrated on the females, the traits of spermatogenesis in adult diapausing males differ considerably among species. Spermiogenesis in lepidopterans is promoted during the late larval and/or pupal stages but is suppressed in these stages if they enter diapause and is resumed after diapause ends. However, the relationship between adult diapause and spermatogenesis in adult Lepidoptera remains unknown. The previous and present results indicate that spermatogenesis of a nymphalid butterfly peaks at the pupal stage and then decreases throughout the late pupal and adult stage. The summer form male butterflies use sperm for mating in summer produced in the larval, pupal, and early adult stages, whereas autumnal form use sperm in spring mainly produced before overwintering. Why adult spermatogenesis decreases with age is still unclear but appears to relate to the developmental restriction in which the spermiogenesis of any lepidopterans is actively performed in the larval and/or pupal stages.
Technical Abstract: Adult spermatogenesis of a nymphalid butterfly Polygonia c-aureum was compared between non-diapausing and diapausing butterflies before overwintering. This butterfly has seasonal polyphenism i.e. summer and autumnal forms. Summer form butterflies that emerged in summer reproduce shortly after emergence, while autumnal forms that emerged in autumn mate in spring. Immatures were reared under either a long photoperiod, which produced the summer form without diapause or under a short photoperiod, which produced the autumnal form with diapause. We found almost no differences in adult spermatogenesis between the two seasonal forms, indicating that adult spermatogenesis is not related to adult diapause. Although adult diapause in the autumnal form is maintained under short photoperiods and terminated under long photoperiods, such a photoperiod did not affect the spermatogenesis of the autumnal form. Our earlier studies indicate that relatively few eupyrene and apyrene sperm are produced after overwintering. Although apyrene spermatogenesis occurred in young adults, eupyrene spermatogenesis did in a small scale before overwintering. These results suggest strongly that male autumnal form butterflies prepare the sperm until overwintering, which had been formed during the larval, pupal and young adult stages.