Summary
The spermatozoon of Ascidia callosa has a head with a wedge-shaped tip. Between the nuclear envelope and the plasmalemma, at the tip of the head, there are one or two previously undescribed vesicles, 45 to 55 nm in diameter. These vesicles have the characteristics of an acrosome. Their role in the process of fertilization has not been determined. Ultrastructural studies of sperm activation are needed, but claims that the spermatozoa of ascidians do not have an acrosome should be reconsidered.
Behind the tip of the sperm there are pores in the nuclear envelope. This part of the envelope also contains a dense band of amorphous material that may have a supportive function. A nearly identical structure, associated with pores has been found in the spermatozoon of Boltenia villosa. An analysis of the nuclear envelope of Ascidia callosa indicates that the same structure has previously been misinterpreted as an acrosome in the spermatozoon of Ascidia nigra.
Similar content being viewed by others
References
Baccetti B, Afzelius BA (1976) The biology of the sperm cell. Monographs in developmental biology. Wolsky A (ed) S. Karger, Basel, vol 10
Colwin AL, Colwin LH (1963) Role of the gamete membrane in fertilization in Saccoglossus kowalevskii (Enteropneusta) I. The acrosomal region and its changes in early stages of fertilization. J Cell Biol 19:477–500
Dale B, Denis-Donini S, De Santis R, Monroy A, Rosati F, Taglietti V (1978) Sperm-egg interaction in the ascidians. Biol Cellulaire 32, 129–133
Ezell SD (1963) The lateral body of Ciona intestinalis spermatozoa. Exp Cell Res. 30:615–617
Franzén A (1970) Phylogenetic aspects of the morphology of spermatozoa and spermatogenesis. In: Baccetti BC (ed) Comparative spermatology. Academic Press, New York
Franzén A (1976) The fine structure of spermatid differentiation in a tunicate Corella parallelogramma (Müller) Zoon 4:115–120
Georges D (1969) Spermatogénèse et spermiogénèse de Ciona intestinalis L. observées au microscope électonique. J Microscopie 8:391–400
Kubo M, Ishikawa M, Numakunai T (1978) Differentiation of apical structures during spermiogenesis and fine structures of the spermatozoon in the ascidian Halocynthia roretzi. Acta Embryol Exp 3:283–295
Rosati F, De Santis R (1978) Studies on fertilization in the ascidians I. self-sterility and specific recognition between gametes of Ciona intestinalis. Exp Cell Res 112:111–119
Schabtach E, Ursprung H (1965) The fine structure of the sperm of a tunicate Ascidia nigra. J Exp Zool 159:357–366
Summers RG, Hylander BL (1974) An ultrastructural analysis of early fertilization in the sand dollar, Echinarachnius parma. Cell Tissue Res 150:343–368
Tuzet O, Bogoraze D, Lafargue F (1972) Recherches ultrastructurales sur la spermiogénèse de Diplosoma listerianum (Milne-Edwards, 1841) et Lissoclinum pseudoleptoclinum (von Drasche, 1883), (Ascidies composées, Aplousobranches). Ann Sci Nat Zool 14:13–190
Tuzet O, Bogoraze D, Lafargue F (1974) La spermatogénèse de Polysyncraton lacazel, 1872 et Trididemnum cereum Giard, 1872 (Ascidies composées, Aplousobranches). Bull Biologique 108:151–167
Villa L (1975) An ultrastructural investigation of normal and irradiated spermatozoa of a tunicate, Ascidia malaca. Boll Zool 42:95–98
Villa L (1977) An ultrastructural investigation on preliminaries in fertilization of Ascidia malaca (Urochordata). Acta Embryol Exp 2:179–193
Woollacott RM (1977) Spermatozoa of Ciona intestinalis and analysis of ascidian fertilization. J Morphol 152:77–88
Woollacott RM, Porter ME (1975) Biochemical and ultrastructural investigations of the sperm of Ciona intestinalis (Urochordata). J Cell Biol 67:463
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Cloney, R.A., Abbott, L.C. The spermatozoa of ascidians: Acrosome and nuclear envelope. Cell Tissue Res. 206, 261–270 (1980). https://doi.org/10.1007/BF00232770
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00232770