Peristaltic squeezing of sperm bundles at the late stage of spermatogenesis in the silkworm,Bombyx mori

Kawamura, Naoko; Yamashiki, Naoko; Shinmoto, Hiroshi; Sahara, Ken

doi:10.1002/1097-4687(200011)246:2<53::aid-jmor1>3.0.co;2-p

Cited by 23 publications

(16 citation statements)

References 15 publications

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“…We confirm that the apyrene sperm are indispensable in fertilisation of the silkworm and polyploid apyrene sperm function as a substitute for the diploid (Table 1). The irregular meiosis and loss of the nuclei by peristaltic squeezing are common in apyrene spermatogenesis of any ploidy (Wolf & Bastmeyer, 1991;Kawamura et al, 2000Kawamura et al, , 2001. In B. mori, however, there are phenomena which do not always coincide with the proposed function of the apyrene sperm in Lepidoptera (see Introduction): (1) the presence of apyrene sperm in the bursa copulatrix does not delay female remating, (2) the spermatophore is not a requisite structure for dissociation of eupyrene sperm bundles but motility of apyrene sperm may promote the dissociation of eupyrene sperm bundles without the spermatophore in the bursa copulatrix, (3) eupyrene sperm bundles crossed the basement membrane of a testis without apyrene sperm, (4) if apyrene sperm only provided nutrients for the eupyrene sperm, then a single copulation by DH males would fertilise eggs.…”

Section: Discussionmentioning

confidence: 99%

Double copulation of a female with sterile diploid and polyploid males recovers fertility in Bombyx mori

Sahara

Kawamura

2002

Zygote

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Silkworm males produce dimorphic sperm, nucleate eupyrene sperm and anucleate apyrene sperm. Apyrene sperm have been speculated to have an assisting role in fertilisation. However, the coexistence of eupyrene and apyrene sperm in the testis and female reproductive organs has made it difficult to define the role of apyrene sperm. Polyploid males are highly sterile. Microscopic observation revealed that the elimination of eupyrene nuclei by peristaltic squeezing caused the sterility of polyploids. Heatshock applied to pupae of Daizo males (DH) also induced high sterility due to the lack of normal apyrene sperm. When eupyrene sperm of sterile DH males and apyrene sperm of sterile polyploid males were mixed by double copulation, a remarkable increase in fertility of the double-mated females was observed. This finding strongly suggests that the apyrene sperm are indispensable in fertilisation of the silkworm and that polyploid apyrene sperm function as a substitute for diploid sperm. We established an experimental system in which we can separate the two types of sperm for further studies on their functions without chemical and/or mechanical treatments

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Section: Discussionmentioning

confidence: 99%

Double copulation of a female with sterile diploid and polyploid males recovers fertility in Bombyx mori

Sahara

Kawamura

2002

Zygote

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“…Kawamura et al (2000) observed the developmental process of parasperm by using cultured sperm bundles enclosing 256 sperm cells. They termed this process "peristaltic squeezing," which starts from the anterior end of the sperm bundle at the fi nal stage of spermiogenesis of both types of sperm ( Fig.…”

Section: Parasperm Of Invertebratesmentioning

confidence: 99%

“…However, the nuclei of the apyrene sperm are squeezed out together with the cytoplasmic debris. This peristaltic squeezing of sperm bundles in the silkworm is thought to be the fi nal control mechanism forming eupyrene sperm and apyrene parasperm (Kawamura et al, 2000(Kawamura et al, , 2001.…”

Section: Parasperm Of Invertebratesmentioning

confidence: 99%

“…In the course of spermatogenesis in cottoid fi sh, no feature indicating the initiation of divergence to the parasperm line from the normal line is observed in germ cells before meiosis. However, aberrant spermatids, which differ from normal euspermatids morphologically, appear after Yamashiki and Kawamura (1997) and Kawamura et al (2000)] the second meiotic division in every cyst (Hayakawa et al, 2002b). Generally, cleavage furrows occur at telophase after karyokinesis in animal cells (Rhodin, 1974).…”

Section: Parasperm Of Vertebratesmentioning

confidence: 99%

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Parasperm: morphological and functional studies on nonfertile sperm

Hayakawa

2007

Ichthyol Res

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Sperm polymorphism, a phenomenon in which more than one type of sperm is produced within a species, occurs widely in animals from invertebrates to vertebrates. Sperm in this phenomenon can be categorized into fertile sperm and nonfertile sperm on the basis of fertilization ability. Nonfertile sperm can be further classifi ed into parasperm and aberrant deformed sperm. Parasperm are sperm produced through a constant developmental process along with normal fertile eusperm, and they are readily distinguished from deformed sperm, which are irregularly crippled by unpredictable errors at certain stages during spermatogenesis. Sperm identifi ed as parasperm occur widely in invertebrates but are presently quite limited in vertebrates. This may be the result of the defi ciency both of studies on parasperm and of clear criteria to identify parasperm in vertebrates. Some vertebrates show unique spermatogenesis, such as symplastic spermatid and semicystic spermatogenesis. Thus, parasperm must be identifi ed by comparing cells in each cyst and in semen, because irregularly shaped cells in the seminal duct could be either parasperm or normal spermatids. Although parasperm are identifi ed by clear criteria in vertebrates, only in cottoid fi shes to date, it is possible for parasperm to be discovered in other vertebrates. Recently, roles related to sperm competition have been reported in several species (e.g., the marine cottoid fi sh Hemilepidotus gilberti), and, with some of them, parasperm production is infl uenced by an intraspecifi c factor such as a sex ratio or the density of a population. Sperm competition is one of the important candidates for infl uencing evolution of parasperm functions, but not all parasperm seem to have a relation to sperm competition. Parasperm function may relate to the ecological conditions of each species that produces parasperm. Studies on parasperm function will be advanced by an ecological approach concerning male fertilization success as well as cytological investigation for parasperm.

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“…As described in detail previously (Yamashiki & Kawamura, 1997;Kawamura et al, 2000), spermatocysts and sperm bundles from excised testes of fifth-instar larvae and pupae were smeared on a coverslip coated with 3-aminopropyl-triethoxy-silane (Sigma Chemical, St. Louis, MO) and fixed in 4% paraformaldehyde in phosphate-buffered saline (PBS, pH 7.0) for 1 h. Mouse monoclonal antibody against chicken alpha-tubulin (Cederlane Laboratory, Hornby, Ontario, Canada), which is cross-hybridised with Bombyx alpha-tubulin, and fluorescein isocyanate-conjugated goat antimouse IgG (MBL, Tokyo, Japan) with propidium iodide (Sigma) was applied on the coverslip. The coverslip was mounted on a glass slide with 90% glycerin-DABCO (Sigma) mountant.…”

Section: Indirect Immunofluorescence Staining For Tubulinmentioning

confidence: 99%

Significance of peristaltic squeezing of sperm bundles in the silkworm, Bombyx mori: elimination of irregular eupyrene sperm nuclei of the triploid

Kawamura

Yamashiki

Shinmoto

et al. 2001

Zygote

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Silkworm (Lepidoptera) males produce dimorphic sperm: nucleate eupyrene sperm and anucleate apyrene sperm. The eupyrene sperm are ordinary sperm to fertilise the eggs, while the function of apyrene sperm remains uncertain. After meiosis, 256 sperm cells are enclosed by a layer of cyst cells, forming a sperm bundle. We have previously documented that the nucleus of eupyrene sperm anchors to the head cyst cell, which locates at the anterior apex of the bundle, by an acrosome tubule-basal body assembly. Neither the basal body attachment to the nucleus nor the acrosome is seen in apyrene sperm, and the nuclei remain in the middle region of the bundle. Peristaltic squeezing starts from the anterior of the bundles in both types of sperm, and cytoplasmic debris of the eupyrene sperm, and both the nuclei and debris of apyrene sperm, are eliminated at the final stage of spermatogenesis. Since the irregularity of meiotic division in apyrene sperm is known, we used triploid silkworm males that show irregular meiotic division even in eupyrene spermatocytes and are highly sterile. The irregular nuclei of the triploid are discarded by the peristaltic squeezing just as those of the apyrene sperm. Transmission electron microscopic observations disclose the abnormality in the acrosome tubule and in the connection to the basal body. The peristaltic squeezing of sperm bundles in the silkworm appears to be the final control mechanism to eliminate irregular nuclei before they enter female reproductive organs

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Peristaltic squeezing of sperm bundles at the late stage of spermatogenesis in the silkworm,Bombyx mori

Cited by 23 publications

References 15 publications

Double copulation of a female with sterile diploid and polyploid males recovers fertility in Bombyx mori

Double copulation of a female with sterile diploid and polyploid males recovers fertility in Bombyx mori

Parasperm: morphological and functional studies on nonfertile sperm

Significance of peristaltic squeezing of sperm bundles in the silkworm, Bombyx mori: elimination of irregular eupyrene sperm nuclei of the triploid

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