Abstract
We carried out ultramorphological characterization of spermatogenesis in A. yamamai, A. pernyi, and their reciprocal hybrids (F1) as part of basic studies on the reproduction of wild silkworms. A spermatogonium derived from a primordial germ cell was differentiated by somatic cell division into a primary spermatogonium and a cyst-wall cell. The former proliferated by division until 64 (26) cells were produced. These 64 cells were linked by cell-bridges. This structure was retained until the stage of chondriosome-body formation in the spermatid. The 64 spermatogonia were enclosed by a gonocyst differentiated from a cyst-wall cell. The synaptonemal complex formed in the spermatocyte nucleus was detected in both parents and reciprocal hybrids, indicating that synapsis of homologous chromosomes occurs both in parents and interspecific hybrids. Maturation divisions in A. yamamai (Y) and A. pernyi (P) were found to involve prereduction. Karyogamy was observed during the chondriosome-body formation only in the spermatid of Y×P and P×Y hybrids. Sperms with plural axial filaments in the flagellum were found in both hybrids. These abnormal sperms comprised 40-50% of the sperms in one sperm packet. The motile function of sperms in fertilization is probably harmed by these abnormal sperms.
