Morphology Of Male Reproductive System And Spermiogenesis Of Chinese White Pine Beetle (Dendroctonus Armandi) (Coleoptera: Scolytinae)

The Chinese white pine beetle, Dendroctonus armandi Tsai et Li (Coleoptera: Scolytidae), is concentratedly distributed in Qinling and Bashan Mountains of China, it is a key pest and the pioneer community of Chinese white pine, more than 30 years old, in Qinling Mountains. They are attacked into the lower half or the lower trunk, and their mating, laying eggs, larvae hatching, and pupating within the phloem and xylem. Eventually lead to pine weakness and even death. Although, biology and ecology of Dendroctonus armandi have been widely studied, no reports about the reproductive system, sperm ultrastructure and spermatogenesis of Dendroctonus armandi, which are the influence on the reveal the reproduction and population dynamics of Chinese white pine beetle in Qinling forest Ecosystem.In this paper, we use scanning electron microscopy and transmission electron microscopy methods to study systematically the male reproductive system, sperm structure and spermatogenesis of the Chinese white pine beetle. The major conclusions:1. The reproductive tract of D. armandi is composed of the testes comprising a pair of testis, deferent ducts, seminal vesicles, accessory glands and an ejaculatory duct. Testis is sperm producing organ and deferent ducts is sperm-storage organ. Just immature bark beetles glands appear to be transparent in the emergence period, until the time of fully mature for the mating, the gland was milky white.2. Early spermatid phase the nucleus resembles that of somatic cells, sperm nucleus with scattered chromosomes and some electron-dense region. During this period, the nuclear membrane electron-dense than any other phases, a large number of mitochondria transform mitochondrial derivatives or nebenkern. The structure of 9+2 axoneme begins to form the structure of nine pairs of accessory microtubules around a pair of central microtubule. During intermediary stages of spermatic maturity, there was a gradual condensation of nuclear chromatin and electron-dense increased. The process of concentration begins from periphery to the center, while the nucleus is elongated gradually. Proacrosomal vesicle transform in acrosome complex, located in front of the nucleus. Microtubules are around nucleus and other organelles. The last phase is fully differentiated spermatozoa.3. The sperm is 80-90μm length. The fully differentiated spermatozoa are elongated cells. Nucleus electron-dense turn into from the point-like to fibrous, finally turned into a dense uniform electron-dense. Proacrosomal vesicles turn into acrosomal complex, located in front of the nucleus. Axonemes show the 9+9+2 microtubules structure in cells.Mitochondrial complex turns into two different sizes mitochondrial derivatives, closed to the axoneme. Centriolar adjunct links nuclear and flagellar, parallels with the large mitochondrial derivatives. Cross-section of centriolar adjunct is roughly triangular and electron-dense. Mitochondrial derivatives are different size and length, the minor derivatives close to centriolar adjunct. Accessory bodies are between the axoneme and mitochondrial derivatives. The minor mitochondrial derivative disappears in the end of the sperm tail, but the major mitochondrial derivative extends to the tip of the axoneme, while the axoneme gradually becomes disordered.