Effect of Carotenoid Depletion on the Hatching Rhythm of the Silkworm, Bombyx mori

Abstract

To investigate the functional involvement of carotenoid in the insect circadian rhythm, we observed the effect of carotenoid depletion on the hatching patterns of the silkworm under several light conditions. When eggs were transferred from continuous light (LL) to continuous darkness (DD), an overt hatching rhythm was initiated. The first hatching peak, which was observed at 13.2 h after the transfer in the carotenoid-depleted silkworm, was reduced remarkably in both control groups (carotenoid-rich and carotenoid-depleted but with lutein supplementation), though subsequent peaks occurred with similar timing. Under LD 4 : 20, LD 12 : 12 and LD 20 : 4, hatching patterns depended on the dietary carotenoid and the light intensity of the photophase. At a low light intensity, carotenoid depletion suppressed hatching as a masking effect just after light-on. Under LD 4 : 20 at a low light illumination, hatchings in the carotenoid-depleted silkworm were observed during scotophase, but few larvae hatched during scotophase in the control groups. Our findings suggest that carotenoid is not indispensable for the photoreception, formation and entrainment of the circadian hatching rhythm, but that a carotenoid-dependent process that is induced by light-off and damps out in an hour-glass mode, suppresses the hatching during darkness without affecting the circadian oscillation. The possibility that this carotenoid-dependent process is involved in the photoperiodic induction in the silkworm was discussed.

Involvement of the Clock Gene period in the Circadian Rhythm of the Silkmoth Bombyx mori

“…The wild-type strain used in the present study showed circadian rhythms in hatching and eclosion, as reported in other strains (Tanaka, 1966a; 1966b; 1966c; Oshiki and Watanabe, 1978a, 1978b; Sakamoto and Shimizu, 1994; Sakamoto et al, 2003; Shimizu and Matsui, 1983). In developed embryos of this strain, temporal changes in the expression of per and tim were observed during the day.…”

“…In the hatching rhythm of B. mori , Sakamoto et al (2003) hypothesized that a carotenoid-dependent hourglass mechanism suppresses hatching after lights-off. This mechanism suppresses hatching on the first day under DD conditions and in the scotophase under LD conditions.…”

“…In B. mori , clear circadian rhythms are observed in adult eclosion and hatching (Oshiki and Watanabe, 1978a; 1978b; Sakamoto and Shimizu, 1994; Sakamoto et al, 2003; Shimizu and Matsui, 1983; Tanaka 1966a; 1966b; 1966c). Because highly efficient genome editing techniques have been established in B. mori (Daimon et al, 2014), in the present study, we investigated the effect of per knockout on eclosion and hatching rhythms in B. mori .…”

“…In Lepidoptera as well, circadian rhythms have been reported both in behavioral activities and developmental events, such as hatching and adult eclosion (Broadhead et al, 2017;Kamimura and Tatsuki, 1994;Sakamoto et al, 2003;Sakamoto and Shimizu, 1994;Shimizu and Matsui, 1983;Suszczynska et al, 2017). However, the molecular Involvement of the Clock Gene period in the Circadian Rhythm of the Silkmoth Bombyx mori Kento Ikeda, * Takaaki Daimon, † Hideki Sezutsu, ‡ Hiroko Udaka, * and Hideharu Numata *,1 clock producing these rhythms has not been clarified yet.…”

Effects of different wavelengths of light on the life attributes of two aphidophagous ladybirds (Coleoptera: Coccinellidae)

“…Unlike the effect of light intensity on the hatching of eggs of Bombyx mori (L.) (Sakamoto et al, 2003) and Bemisia argentifolii Bellows & Perring (Blackmer et al, 2002), that of coloured light on life processes is, less well explored and, a unique aspect of this study.…”