Acrosome differentiation inMolgula manhattensis (Ascidiacea, Tunicata)

Fukumoto, Manabu

doi:10.1016/0889-1605(85)90043-6

Cited by 15 publications

(6 citation statements)

References 14 publications

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“…However, the vesicles are present in the proper location for an acrosome. Furthermore, the vesicle in ascidian spermatozoa is not an oddity which is only found in one or two species, but a feature of all species examined in Orders of Pleurogonan and Enterogonan ascidians (Fukumoto 1985(Fukumoto , 1986(Fukumoto , 1988(Fukumoto , 1990c. It is reasonable to conclude that the "apical vesicles" of Lambert and Koch are an acrosome.…”

Section: Discussionmentioning

confidence: 99%

“…A single acrosomal vesicle has been found in mature spermatozoa of many ascidian species of both Pleurogona and Enterogona (Fukumoto 1985(Fukumoto , 1986(Fukumoto , 1990c. During acrosome differentiation in Pyura houstor, Styela plicata and Molgula manhattensis, small vesicles, presumably derived from the Golgi apparatus, appear in a blister at the apex of early spermatids.…”

Section: Discussionmentioning

confidence: 99%

“…During acrosome differentiation in Pyura houstor, Styela plicata and Molgula manhattensis, small vesicles, presumably derived from the Golgi apparatus, appear in a blister at the apex of early spermatids. These vesicles subsequently fuse with each other to form a single acrosomal vesicle during a later stage of spermiogenesis (Fukumoto 1983(Fukumoto , 1985. Three or four acrosomal vesicles have been found in mature P. nigra spermatozoa (Figs.…”

Section: Discussionmentioning

confidence: 99%

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Morphological aspects of fertilization in Phallusia (Ascidia) nigra (Ascidiacea, Tunicata)

Fukumoto

1993

Roux's Arch Dev Biol

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The spermatozoa of Phallusia (Ascidia) nigra have an elongated head (approximately 5 μm in length) in which a nucleus and a single mitochondrion are located side by side. There is no midpiece. The apex of the head is wedge-shaped. Acrosomal vesicles (approximately 55-65 nm in diameter) and moderately electron-dense material (MEDM) are present between the plasmalemma and the nuclear membranes in the anterior tip of the head. The MEDM occupies a central position and three or four acrosomal vesicles are seen in a line alongside it. The acrosomal vesicles disappear as the sperm makes contact with the surface of the chorion. Gamete fusion most likely occurs between a small process extending from the peripheral margin of the sperm apex and the egg surface, resulting in incorporation of the sperm into the egg from the anterior region of its head.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Morphological aspects of fertilization in Phallusia (Ascidia) nigra (Ascidiacea, Tunicata)

Fukumoto

1993

Roux's Arch Dev Biol

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“…For aplousobranchs, reports of acrosomes in some didemnids (Tuzet et al 1972(Tuzet et al , 1974 were not convincingly illustrated, and Burighel et al (1985) found none in two species. The only information on sperm of other aplousobranchs is an unillustrated report by Fukumoto (1985) claiming small vesicles in the tip of the sperm of Clavelina huntsmani, Aplidium ealifornicum and Distaplia oecidentalis. However, none is present in spermatids or sperm of C. oblonga (Holland unpublished data).…”

Section: Shaping Of the Pyrosome Sperm Mitochondrion And Nucleusmentioning

confidence: 97%

“…The only difference between solitary and colonial ascidians is that the sperm of the latter have additional modifications. In mature sperm of solitary ascidians, the acrosome is reduced to a minute vesicle(s) of dubious function (Cloney and Abbott 1980, Cotelli et al 1980, Fukumoto 1983, 1985, Villa and Tripepi 1983, Rosati et al 1985, Honneger 1986. It may disappear just before the sperm and egg fuse, but has never clearly been observed to undergo exocytosis; there is certainly no acrosomal tubule produced, and the sperm head appears to fuse directly with the egg plasma membrane after the sperm is in the perivitelline space (Fukumoto 1984a, Honneger 1986.…”

Section: Shaping Of the Pyrosome Sperm Mitochondrion And Nucleusmentioning

confidence: 99%

Spermatogenesis inPyrosoma atlanticum (Tunicata: Thaliacea: Pyrosomatida): Implications for tunicate phylogeny

Holland

1990

Mar. Biol.

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Abstract. Colonies of Pyrosoma atlanticum were collected by submersible in October 1988 in the Caribbean Sea, and testes were studied by electron microscopy. Spermatogonia, spermatocytes and early spermatids have two centrioles. The proximal centriole subsequently disappears, its remains apparently persisting in the spermatozoon as dense material adjacent to the distal centriole, which gives rise to the axoneme. At the tip of early spermatids are several 50 nm proacrosomal vesicles, which disappear leaving no trace in early elongating spermatids. The spermatozoon lacks an acrosome and has a head 35 #m long. The head is differentiated into a bulbous posterior portion 5 #m long x 1 #m wide, a thinner anterior portion 25 #m long tapering from a width of 0.7 #m to a width of 0.4 #m, and a very thin anterior extension 5 #m long x 0.5 #m wide. At the start of elongation, the anterior extension begins to form just lateral to the proacrosomal vesicles as a spiral projection comprising part of the nucleus, covered by a thin sheath of cytoplasm. This sheath of cytoplasm undergoes a complex differentiation. Ultimately, the nucleus in the anterior extension is overlain by two membrane-bound sheaths of cytoplasm connected by a spiral flange of cytoplasm. Between these two sheaths is a spiral space, open to the exterior through a subterminal pore near the sperm tip. In early spermatids the mitochondria fuse into a single mitochondrion, which remains lateral to the nucleus. The cristae become modified late in spermatogenesis. Throughout elongation of the spermatid there are patches of dense material between the nucleus and mitochondrion. A manchette of microtubules transiently encircles the thin anterior portion of the nucleus during the last phase of elongation. A manchette is not present during most of elongation. In the spermatozoon the mitochondrion, which has reticulate cristae, spirals a few times about the nucleus and extends from the junction between the bulbous portion and the thinner anterior portion of the nucleus to the junction between the thinner anterior portion and the nuclear extension. Spermatogenesis in P. atlanticum, compared to that in other tunicates, most closely resembles that in colonial ascidians, and supports the majority view that pyrosomes arose from aplousobranch ascidians that lost their attachment to the substratum. Pyrosome sperm are more highly derived than doliolid sperm, which have an acrosome that is probably capable of exocytosis. When salp and pyrosome sperm are compared, both are highly derived, but neither shares any apomorphies with the other that it does not share with at least one other tunicate order. Thus, sperm morphology does not support the majority view that pyrosomes gave rise to doliolids and neither confirms nor denies the idea that pyrosomes are intermediate between aplousobranch ascidians and salps. Therefore, it is likely that the class Thaliacea is polyphyletic, with doliolids arising very early from the ascidian lineage and with salps and pyrosomes arising somewhat later.

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Multiple acrosomal vesicles and their differentiation during spermiogenesis inAscidia zara andAscidia gemmata (Ascidiacea, Tunicata)

Fujii¹,

Fukumoto²

1999

J. Morphol.

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Acrosome differentiation inMolgula manhattensis (Ascidiacea, Tunicata)

Cited by 15 publications

References 14 publications

Morphological aspects of fertilization in Phallusia (Ascidia) nigra (Ascidiacea, Tunicata)

Morphological aspects of fertilization in Phallusia (Ascidia) nigra (Ascidiacea, Tunicata)

Spermatogenesis inPyrosoma atlanticum (Tunicata: Thaliacea: Pyrosomatida): Implications for tunicate phylogeny

Multiple acrosomal vesicles and their differentiation during spermiogenesis inAscidia zara andAscidia gemmata (Ascidiacea, Tunicata)

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