In Vivo Artificial Parthenogenetic Treatments on Live Silkworm Moth, Bombyx mori Can Induce Higher Parthenogenesis

살아있는 누에 나방(Bombyx mori)에 대한 인공적 단위 발생 처리의 단위 발생란 유발 촉진 효과

Abstract

The silkworm performs sexual reproduction for the production of its healthy offsprings from generations to generations. Parthenogenesis in the silkworm, Bombyx mori acquires immense use in the development of outstanding homozygouse lines with higher viability, hybrid vigour, combining ability and less phenotypic variability, and it can serve as a powerful tool in controlling sex of the offsprings as well as a useful tool in selection of breeding schemes. However, naturally occuring parthenogenesis in silkworm could not be found so far. Fortunately, artificial induction of parthenogenesis is possible in silkworm. So, it is very important to find out novel methods for induction of parthenogenesis. We investigated to attempt to get a novel parthenogenetic method. Accordingly, parthenogenetic studies on between unfertilized in vivo ovarian eggs of live silkworm moth(novel) and unfertilized in vitro ovarian eggs(conventional) taken out from live silkworm moth were investigated by hot water ($46^{\circ}C$), hot air ($46^{\circ}C$) and low temperature ($0^{\circ}C$ and $-20^{\circ}C$) treatments. The best ratio of parthenogenetic eggs was obtained with in vivo ovarian eggs of live silkworm moth rather than with in vitro ovarian eggs taken out from live silkworm moth in all the treatments. The optimum exposure time absolutely depended upon the temperatures of treatments and the forms of in vivo or in vitro ovarian eggs. From these results, we expect that in vivo artificial parthenogenetic treatments on live silkworm moth will be useful for the higher induction of parthenogenesis in the silkworm, B. mori.

본 연구는 누에나방에 있어서 몇가지 단위 발생 처리에 의해 미수정란의 단위 발생란 유발 촉진 효과에 대해 실험하였다. 암누에 생체 나방(난소란을 가지고 있는 암나방 생체)과 암나방으로 부터 해부학적으로 채취한 난소란에 대해 각각 온탕 처리($46^{\circ}C$), 건열 처리($46^{\circ}C$) 및 저온 처리($0^{\circ}C$ 및 $-20^{\circ}C$)를 행하여 단위 발생란 유발을 시도한 바, 생체 암나방 처리구가 해부 채취 난소란 처리구보다 모든 처리구에서 우수한 단위 발생 유발을 보였다. 처리별 최고의 단위 발생율을 보인 조건은 처리마다 달랐으며 그 주요인은 처리 시간이었다. 이상의 결과에서 생체누에 나방에 대한 단위 발생 처리가 기존의 표준 방법으로 간주되는 해부 채취 난소란에 하는 것보다 단위 발생유발 효과가 우수함이 입증된 것이다.

Fig. 1. Representive egg colours of unfertilized ovarian eggs (upper pannel a : yellow eggs), and fertilized( lower pannel b : dark eggs) or parthenogenetic eggs( lower pannel b : dark eggs) in the silkworm, B. mori. The length, width and thickness of the eggs in the present photos will be ranged to 1.3 mm-1.4 mm, 1.0 mm-1.2 mm and 0.5mm-0.6mm, respectively.

Fig. 2. The ratios of parthenogenetic eggs on between unfertilized in vivo ovarian eggs of live silkworm moth and unfertilized in vitro ovarian eggs taken out from live silkworm moth , B. mori, according to exposure time in hot water (46℃) treatment. -∘- , unfertilized in vivo ovarian eggs ; -∙-unfertilized in vitro ovarian eggs. Data indicate the mean ± S.D. with three separate experiments.

Fig. 3. The ratios of parthenogenetic eggs on between unfertilized in vivo ovarian eggs of live silkworm moth and unfertilized in vitro ovarian eggs taken out from live silkworm moth , B. mori according to exposure time in hot air (46℃) treatment. See Fig. 2 for further legends.

Fig. 4. The ratios of parthenogenetic eggs on between unfertilized in vivo ovarian eggs of live silkworm moth and unfertilized in vitro ovarian eggs taken out from live silkworm moth, B. mori, according to exposure time in low temperature (0℃) treatment. See Fig. 2 for further legends.

Fig. 5. The ratios of parthenogenetic eggs on between unfertilized in vivo ovarian eggs of live silkworm moth and unfertilized in vitro ovarian eggs taken out from live silkworm moth , B. mori according to exposure time in low temperature (-20℃) treatment. See Fig. 1 and Fig. 2 for further legends.

Fig. 6. Newly hatched larvae (circle) from the parthenogenetic eggs of F1 hybrid, Baeok Jam(Jam 123 x Jam 124) by hydrochloric acid treatment. See Fig. 1 for further legends.