Hideo Mohri

A dynein light chain of sea urchin sperm flagella is a homolog of mouse Tctex 1, which is encoded by a gene of the t complex sterility locus

The outer-arm dynein of sea urchin sperm flagella contains six light chains with molecular masses of 23.2, 20.8, 12.3, 11.5, 10.4 and 9. 3kDa. We have cloned a cDNA for the 12.3kDa polypeptide (light chain 3) and found that this protein is highly homologous to mouse Tctex1, a protein encoded by a member of the multigene family in the t complex region that is involved in male sterility and the development of the germ cells. Tctex1 has recently been shown to be homologous to a light chain of cytoplasmic dynein. Therefore, the cytoplasmic dynein light chain has been implicated in the mechanism for the transmission ratio distortion (meiotic drive) that is characteristic of t haplotypes in mice. Our present finding, however, indicates that axonemal light chain 3 must be considered equally important.

Ultrastructure and function of long and short sperm in Cicadidae (Hemiptera)

The cicada, Graptopsaltria nigrofuscata, produces two distinct sizes of sperm, as determined by either nuclear volume of early spermatids or nuclear length of mature sperm. Between both sperm, there is no difference in location of the acrosome and flagellum during spermiogenesis. The acrosome is covered by an anteacrosomal bleb, which is inserted in a common mass, spermatodesm, derived from cyst cells. Both kinds of sperm linked to the spermatodesm form sperm bundles, respectively. During copulation, the sperm bundles are transported from the vesicula seminalis of the male to the bursa copulatrix of the female. Morphometric analyses of the nuclear length revealed that the two kinds of sperm reach the bursa copulatrix in the same condition as that found in the vesicula seminalis. Once transferred inside the latter, the sperm bundles disintegrated to individual sperm within a few hours, and the tail components, such as the axoneme and mitochondrial derivatives, become separated from each other over time. The tail completely splits from the sperm nucleus 24 h after copulation. Fertile sperm accumulate in the spermatheca, the final storage organ, where only long sperm survived for any length of time. Fertilized eggs examined by vital staining contain only sperm with long nuclei.

Morphological changes in eupyrene and apyrene spermatozoa in the reproductive tract of the male butterfly Atrophaneura alcinous Klug

Summary Eupyrene and apyrene spermatozoa are contained in separate cysts in the testis of the butterfly Atrophaneura alcinous. Spermatozoa of both types from various parts of the male reproductive tract were examined with particular reference to their morphological characteristics. All spermatozoa collected from the vas deferens and the vesicula seminalis were found to be immotile under a dissecting microscope. No spermatozoa of either type were recognized in any part of the ejaculatory duct. Within the testis, eupyrene spermatozoa are present in bundles and each spermatozoon has a slender nucleus with an acrosome and a long flagellum containing mitochondrial derivatives. Two kinds of appendages, lacinate and reticular, are present on the surface of the sperm membrane. They are replaced with an extracellular sheath during passage through the vas deferens. In contrast, apyrene spermatozoa have neither nucleus nor acrosome, whereas a cup-shaped structure was found at the sperm tip instead of the acrosome. U...

Phylogeny, biogeography, and host-plant association in the subfamily Apaturinae (Insecta: Lepidoptera: Nymphalidae) inferred from eight nuclear and seven mitochondrial genes.

The subfamily Apaturinae consists of 20 genera and shows disjunct distributions and unique host-plant associations. Most genera of this subfamily are distributed in Eurasia South-East Asia and Africa, whereas the genera Doxocopa and Asterocampa are distributed mainly in South America and North America, respectively. Although the Apaturinae larvae mainly feed on the Cannabaceae, those of the genus Apatura are associated with Salix and Populus (Salicaceae), which are distantly related to the Cannabaceae. Here, we infer the phylogeny of Apaturinae and reconstruct the history of host shifting and of colonization in the New World. We analyzed 9761 bp of nuclear and mitochondrial DNA sequence data, including the genes encoding EF1a, Wg, ArgK, CAD, GAPDH, IDH, MDH, RpS5, COI, COII, ATPase8, ATPase6, COIII, ND3, and ND5 for 12 apaturine genera. We also inferred the phylogeny with six additional genera using mitochondrial sequence data alone. Within the Apaturinae, two major clades are recovered in all the datasets. These clades separate the New World genera, Doxocopa and Asterocampa, indicating that dispersal to the New World occurred at least twice. According to our divergence time estimates, these genera originated during the Early Oligocene to the Early Miocene, implying that they migrated across the Bering Land Bridge rather than the Atlantic Land Bridge. The temporal estimates also show that host shifting to Salix or Populus in Apatura occurred more than 15 million years after the divergence of their host plants. Our phylogenetic results are inconsistent with the previously accepted apaturine genus groups and indicate that their higher classification should be reconsidered.

Morphological evidence that spermatogenic cells undergo apoptosis within testis of diapausing swallowtail pupa (Atrophaneura alcinous)

In many lepidopteran species, degeneration of germ cells occurs in the testis of diapausing pupa. We demonstrated that degenerating cells clearly exhibit apoptotic characteristics by supravital staining, TUNEL assay and ultrastructural observations. These characterizations allowed us to identify several steps of spermatocyte degeneration, segregation of nuclear chromatin, nuclear fragmentation, cytoplasmic condensation and phagocytosis by cyst cells. A cluster of TUNEL-positive cells were observed under the light microscope which coincided with a cyst of degenerating spermatocytes revealed under the electron microscope. Secondary spermatocytes in pupal testis undergo apoptotic cell death during diapause. Therefore, neither cysts of spermatids nor sperm bundles exist in testis of diapausing pupa. Our observations also indicate that spermatogenic cells undergo phagocytosis of cyst cells as the diapause period increased. This phenomenon seems to be associated with the seasonal reproductive strategy. J. Exp. Zool. 283:194–201, 1999.

Characterization of outer arm dynein in sea anemone, Anthopleura midori

Outer arm dynein was purified from sperm flagella of a sea anemone, Anthopleura midori, and its biochemical and biophysical properties were characterized. The dynein, obtained at a 20S ATPase peak by sucrose density gradient centrifugation, consisted of two heavy chains, three intermediate chains, and seven light chains. The specific ATPase activity of dynein was 1.3 micromol Pi/mg/min. Four polypeptides (296, 296, 225, and 206 kDa) were formed by UV cleavage at 365 nm of dynein in the presence of vanadate and ATP. In addition, negatively stained images of dynein molecules and the hook-shaped image of the outer arm of the flagella indicated that sea anemone outer arm dynein is two-headed. In contrast to protist dyneins, which are three-headed, outer arm dyneins of flagella and cilia in multicellular animals are two-headed molecules corresponding to the two heavy chains. Phylogenetic considerations were made concerning the diversity of outer arm dyneins.

Spermiogenesis in the stag beetle, Aegus lavicollis Waterhouse (Coleoptera, Lucanidae), with special reference to the centriole adjunct

Summary Ultrastructural changes during spermiogenesis in the stag beetle, Aegus lavicollis, were studied with special attention to the organizing process of the centriole adjunct. In early spermatids the formation of acrosome and flagellum occurs simultaneously in the cytoplasm before nuclear condensation. The centriole adjunct first appears as a sheath surrounding a centriole in a concavity of the nucleus from which the flagellar axoneme is organized. A mass of electron-dense material accumulates progressively in the vicinity of the centriole. As nuclear transformation proceeds, electron-dense material is found at the posterior end of the nucleus and extends beyond the centriolar region to form a partial sheath around mitochondrial derivatives. Electron-dense material seems to contribute to the formation of the centriole adjunct because the former is closely attached to the latter until the latter is completely formed. In mature spermatozoa the centriole adjunct is characterized by its peculiar disposition, extending across about half the length of the flagellum and partly covering the outside of two mitochondrial derivatives.