Summary
The present study examines spermiogenesis, and in particular the formation of the acrosome, in ten species of chitons belonging to four families. This study emphasizes the formation of the acrosome but brings to light several other structures that have received little or no mention in previous studies. The process of spermiogenesis is essentially similar in each species, although Chaetopleura exhibits some significant differences. In early spermiogenesis the Golgi body secretes numerous small pro-acrosomal vesicles that gradually migrate into the apical cytoplasm. The chromatin condenses from granules into fibres which become twisted within the nucleus. A small bundle of chromatin fibres projects from the main nuclear mass into the anterior filament; this coincides with the appearance of a developing manchette of microtubules around the nucleus that originates from the two centrioles. Radiating from the distal centriole is the centriolar satellite complex, which is attached to the plasma membrane by the annulus. The distal centriole produces the flagellum posteriorly and it exits eccentrically through a ring of folded membrane that houses the annulus. Extending from the annulus on one side of the flagellum, in all but one species, is a dense fibrous body that has not been previously reported. The proximal centriole lies perpendicular to the end of the distal centriole and is attached to it by fibro-granular material. Pro-acrosomal vesicles migrate anteriorly through the cytoplasm and move into the anterior filament to one side of the expanding nucleus. Eventually these vesicles migrate all the way to the tip of the sperm, where they fuse to form one of two granules in the acrosome. In mature sperm the nucleus is bullet-shaped with a long anterior filament and contains dense chromatin with occasional lacunae. The mitochondria vary in both number and position in the mature sperm of different species. Both centrioles are housed eccentrically in a posterior indentation of the nucleus, where the membranes are modified. The elongate flagellum tapers to a long filamentous end-piece that roughly corresponds to the anterior filament and may be important in sperm locomotion for hydrodynamic reasons. An acrosome is present in all ten species and stained positively for acid phosphatase in three species that were tested.
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References
Al-Hajj HA (1987) Ultrastructural study of spermiogenesis in the chiton Acanthopleura haddoni from the Gulf of Aqaba (Red Sea). Int J Invert Reprod Dev 12:295–308
Baccetti B, Afzelius BA (1976) The biology of the sperm cell. Monogr Dev Biol 10:1–254
Buckland-Nicks JA, Chia FS (1976) Spermatogenesis in a marine snail, Littorina. Cell Tissue Res 170:455–475
Buckland-Nicks JA, Chia FS (1981) Locomotion of the filiform sperm of Littorina (Gastropoda, Prosobranchia). Cell Tissue Res 219:27–39
Buckland-Nicks JA, Williams D, Chia FS, Fontaine A (1983) Studies of the polymorphic spermatozoa of a marine snail. 2. Genesis of the eupyrene sperm. Gamete Res 7:19–37
Buckland-Nicks JA, Chia FS (1986) Spermiogenesis in the marine snail Nerita picea with special reference to acrosome formation. Gamete Res 15:13–23
Buckland-Nicks J, Koss R, Chia FS (1988a) The elusive acrosome of chiton sperm. Int J Invert Reprod Dev 13:193–198
Buckland-Nicks J, Koss R, Chia FS (1988b) Fertilization in a chiton: acrosome-mediated sperm-egg fusion. Gamete Res 21:199–212
Buckland-Nicks JA, Chia FS (1989) Spermiogenesis in Chaetoderma sp. (Aplacophora). J Exp Zool (In Press)
Eckelbarger KJ (1984) Ultrastructure of spermatogenesis in the reef-building polychaete Phragmatopoma lapidosa (Sabellariidae) with special reference to acrosomal morphogenesis. J Ultrastruct Res 89:146–164
Franzén Å (1955) Comparative morphological investigations into the spermiogenesis among Mollusca. Zool Bidr Uppsala 30:399–456
Giusti F, Selmi MG (1982) The morphological peculiarities of the typical spermatozoa of Theodoxus fluviatilis (L.) (Neritoidea) and their implications for motility. J Ultrastruct Res 7:166–177
Hayden JH, Allen RD, Goldman RD (1983) Cytoplasmic transport in keratocytes: direct visualization of particle translocation along microtubules. Cell Motility 3:1–19
Herman B, Albertini DF (1983) Ligand-induced rapid redistribution of lysosomes is temporally distinct from endosome translocation. Nature 304:738–740
Hodgson AN, Baxter JM, Sturrock MG, Bernard RTF (1988) Comparative spermatology of 11 species of Polyplacophora (Mollusca) from the suborders Lepidopleurina, Chitonina and Acanthochitonina. Proc R Soc London Ser B 235:161–177
Maxwell WL (1983) Mollusca. In: Adiyodi KG, Adiyodi RG (eds) Reproductive biology of invertebrates, vol II (spermatogenesis and sperm function). Wiley, Chichester, pp 275–319
Pearse JS (1979) Polyplacophora. In: Giese AC, Pearse JS (eds) Reproduction of marine invertebrates, vol V. Academic Press, New York, pp 27–85
Pearse JS, Woollacott RM (1979) Chiton sperm: no acrosome? Am Zool 19:956
Posalaki Z, Szabo D, Bacsi E, Okros I (1968) Hydrolytic enzymes during spermatogenesis in the rat: an electron microscopic and histochemical study. J Histochem Cytochem 16:249–262
Richardson KC, Jarett L, Finke EH (1960) Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain Technol 35:313–323
Rothschild Lord, Tyler A (1955) Acrosomal filaments in spermatozoa. Exp Cell Res 35:304–311
Russell-Pinto F, Azevedo C, Barandela T (1983) Fine structure of the spermatozoa of Chiton marginatus (Mollusca: Amphineura), with special reference to nucleus maturation. Gamete Res 8:345–355
Russell-Pinto F, Azevedo C, Oliveira E (1984) Comparative ultrastructural studies of spermiogenesis and spermatozoa in some species of Polyplacophora (Mollusca). Int J Invert Reprod Dev 7:267–277
Sakker ER (1984) Sperm morphology, spermatogenesis and spermiogenesis of three species of chitons (Mollusca, Polyplacophora). Zoomorphology 104:111–121
Summers RG (1972) A new model for the centriolar satellite complex in spermatozoa. J Morphol 137:229–242
Thompson TE (1973) Euthyneuran and other molluscan spermatozoa. Malacologia 14:167–206
Walker M (1969) Coiling of the flagellar shaft in the head region of the mature sperm of Nucella (Purpura) lapillus (L.). J Cell Sci 5:211–225
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Buckland-Nicks, J., Chia, FS. & Koss, R. Spermiogenesis in Polyplacophora, with special reference to acrosome formation (Mollusca). Zoomorphology 109, 179–188 (1990). https://doi.org/10.1007/BF00312469
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DOI: https://doi.org/10.1007/BF00312469