中文摘要：

昆虫表皮层的黑色素参与了体色及多种斑纹颜色的形成。为了研究家蚕斑纹黑色素的形成机制,以受控基因同属于p等位基因群（2-3.0）的黑缟（pS）、C108（p）、大造（＋p）3种斑纹家蚕品种为材料,解剖4龄眠期幼虫体壁,对表皮的斑纹黑色素形成过程进行观察。结果发现每一体节3/4部分为黑色的黑缟（pS）在4眠12 h左右形成新表皮,而具有家蚕普通斑纹（＋p）的大造和全身无黑色斑纹的姬蚕（p）C108在4眠16 h才形成新表皮,新生表皮呈透明状;4眠24 h左右,黑缟和大造幼虫新生表皮呈现标志性斑纹的部位有黑色素开始形成。进一步对5龄3 d幼虫体壁半月纹处与非斑纹处的真皮层和外表皮层进行扫描电子显微镜观察,发现3种斑纹品种幼虫的真皮层都有大量颗粒物,以C108最多,而且对应外表皮层含黑色素区域的颗粒物明显少于不含黑色素的区域;在呈现黑色斑纹部位的外表皮中都有三角锥形颗粒物,黑缟与大造的颗粒物数量较多,C108较少,并且黑缟非斑纹黑色部位的外表皮也有大量三角锥形颗粒物,而大造和C108则基本没有。推测真皮层存在的颗粒物主要是尿酸盐,外表皮层存在的颗粒物极有可能就是黑色素。根据家蚕幼虫体壁中的尿酸盐颗粒分布与黑色素颗粒分布呈相反模式,推测黑色斑纹性状基因对真皮层尿酸盐颗粒的形成有抑制作用。

英文摘要：

Melanin in the epidermal layer is involved in formation of various body colors and markings of insects. To study the mechanism of melanin formation in the markings of silkworm （ Bombyx mori）, integuments of the 4th instar molting lar- vae from three silkworm varieties named Striped （pS）, C108 （p） and Dazao （ ＋P）, all of which belong to the same p al- lelic group （2-3. 0）, were dissected for observation of melanin formation process in markings of the epidermis. It was found that Striped （pS）, of which 3/4 of each segment has black strips, generated the new integuments at around 12 h of the 4th molting stage, but Dazao （＋P）, which has normal marking, and C108 （p）, of which whole body has no blackmarking, produced the new integuments at around 16 h of the 4th molting stage and the newly generated integuments were transparent. At around 24 h of the 4th molting stage, melanin formation began at markings in the newly generated integuments of Striped and Dazao larvae. Further observation to dermis and exocuticle of crescent and non-marking parts of the integument from day 3 larvae of the 5th instar by scanning electron micros- copy displayed that the dermis of larvae from all threesilkworm varieties had many particles, among which C108 contained the highest number of particles. However, these particles in black markings of the correspondent integument were much less than those in the melanin-absent integument. Triangular-pyramidal particles were also observed in black markings of exoculticle, among which Striped and Dazao had distinctly more triangular-pyramidal particles than C108. Moreover, at the non-markings, there were still many triangular- pyramidal particles in exoculticle of Striped pS, but none in Dazao and C108. Therefore, we speculated that the particle existing in dermis was mainly of urate and that existing in exocuticle was very possibly of melanin. As the distribution of urate particles and melanin particles was in a reverse pattern, it is suggested that the genes cont