Spermatozoan Morphology Of Brachidontes Darwinianus And Brachidontes Solisianus (bivalvia, Mytilidae) From The Southern Brazilian Coast

Abstract

Numerous investigations have demonstrated the usefulness of sperm morphology in evaluating molluscan phylogeny. In this work we used transmission and scanning electron microscopy to study the structure of mature spermatozoa from two bivalves, Brachidontes darwinianus and Brachidontes solisianus, and compared them with those of other bivalves, particularly other mytilids. These two species have a wide geographic distribution and are particularly abundant in the intertidal zone of many rocky shores along the Brazilian coast, often in areas with strong water currents. B. darwinianus occurs from the state of Rio de Janeiro, Brazil, to Patagonia, in Argentina, whereas B. solisianus is distributed from Mexico to Uruguay. The spermatozoa of both species were of the primitive or ect-aquasperm form. In both species the spermatozoan head contained an spheroidal nucleus capped by a conical acrosome with an anterior extension. No actin was detected in the subacrosomal region. However, immunocytochemical staining identified actin throughout the nucleus of the sperm of both species. The chromatin was strongly electron-dense, homogenous and compact. The nuclei contained randomly distributed, electron-lucent regions formed by invaginations of the nuclear envelope. These invaginations were detected by E-PTA staining for glycoproteins at low pH. The mid-piece region consisted of five spherical mitochondria grouped in a ring around a pair of short cylindrical centrioles. The flagellum exhibited the typical 9+2 microtubule structure (9 double outer tubules + 2 single central tubules). These findings, together with conchological characteristics, can be used to distinguish between B. darwinianus and B. solisianus. The only marked difference in the morphology of spermatozoa from these two species was the longer anterior extension of the acrosomal vesicle in B. solisianus. This elongated acrosome may facilitate penetration of the jelly coat and cytoplasm of large oocytes and could increase the efficiency of fertilization. The resulting enhanced reproductive success could account for the wider geographic distribution of B. solisianus. © 2004 Balaban.462-3149158Berger, E.M., Population genetics of marine gastropods and bivalves (1983) The Mollusca, 6, pp. 563-596. , W.D. Russel-Hunter (ed.), Academic Press, LondonBernard, R.T.F., Hodgson, A.N., The fine structure of the sperm and spermatid differentiation in the brown mussel Perna perna (1985) South Afr. J. Zool., 20, pp. 5-9Bernard, R.T.F., Davies, B.R., Hodgson, A.N., Reproduction in a brackish-water mytilid: Gametogenesis and embryonic development (1988) The Veliger, 30, pp. 278-290Chichvarkhin, A.Y., Letter to the editor (2002) Mol. Phylogen. Evol., 22, pp. 330-332Distel, D.L., Phylogenetic relationships among Mytilidae (Bivalvia): 18S rRNA data suggest convergence in Mytilid body plans (2000) Mol. Phylogen. Evol., 15, pp. 25-33Eckelbarger, K.J., Bieler, R., Mikkelsen, P.M., Ultrastructure of sperm development and mature sperm morphology in three species of commensal bivalves (Mollusca: Galeommatoidea) (1990) J. Morphol., 205, pp. 63-75Ferreira, A.A., (2003) Estrutura, Ultra-estrutura e Citoquímica Da Espermatogênese, Dos Ductos e Ovidutos Do Lagarto Tropidurus itambere Durante O Ciclo Reprodutivo, , Doctoral Thesis, Unicamp, BrazilFoighil, D.O., Fine structure of Lasaea subviridis and Mysella tumida sperm (Bivalvia, Galeommatacea) (1985) Zoomorphology, 105, pp. 125-132Franzén, A., Sperm structure with regard to fertilization biology and phylogenetics (1977) Verh. Dtsch. Zool. Ges., pp. 123-138Franzén, A., Ultrastructural studies of spermatozoa in three bivalve species with notes on evolution of elongated sperm nucleus in primitive spermatozoa (1983) Gamete Res., 7, pp. 199-214Fricker, M., Hollinshead, M., White, N., Vaux, D., Interphase nuclei of many mammalian cell types contain deep, dynamic, tubular membrane-bound invaginations of the nuclear envelope (1997) J. Cell Biol., 136, pp. 531-544Garrido, O., Gallardo, C.S., Ultrastructure of sperms in bivalve molluscs of the Mytilidae family (1996) Invert. Reprod. Develop., 29, pp. 95-102Guerra, R., Campos, B., Esponda, P., Analysis of the spermatozoa of four bivalves with particular reference to the acrosome and plasma membrane glycoproteins (1994) J. Submicrosc. Cytol. Pathol., 26, pp. 489-495Gwo, J.C., Chang, H.H., Jong, K.J., Ultrastructure of the spermatozoa of the small abalone, Sulculus diversicolor supertexa (Mollusca, Gastropoda, Haliotidae) (1997) J. Submicrosc. Cytol. Pathol., 29, pp. 239-244Gwo, J.C., Yang, W.T., Sheu, Y.T., Cheng, H.Y., Spermatozoan morphology of four species of bivalve (Heterodonta, Veneridae) from Taiwan (2002) Tissue Cell, 34, pp. 39-43Healy, J.M., Spermiogenesis and spermatozoa in the relict bivalve genus Neotrigonia: Relevance to trigonioid relationships, particularly Unionoidea (1989) Mar. Biol., 103, pp. 75-85Healy, J.M., Sperm ultrastructure in the marine bivalve families Carditidae and Crassatellidae and its bearing on unification of the Crassatelloidea with the Carditoidea (1995) Zool. Scripta, 24, pp. 21-28Healy, J.M., Buckland-Nicks, J.A., Jamieson, B.G.M., Spermatozoal ultrastructure of spiny oysters (Spondylidae, Bivalvia) including a comparison with other bivalves (2001) Invert. Reprod. Develop., 40, pp. 27-37Ishikawa, M., Numamiya, T., (1988) Experiments on Development of Marine Invertebrates: Mollusca (Bivalvia), pp. 87-96. , Baiffuukan, TokyoJamieson, B.G.M., A biological classification of sperm types, with special reference to annelids and mollusks, and an example of spermiocladistics (1987) New Horizons in Sperm Cell Research, pp. 311-332. , H. Mohri (ed.), Japan Scientific Societies Press, Gordon and Breach Science, New YorkJohnson, N., Krebs, M., Boudreau, R., Giorgi, G., Legros, M., Larabell, C., Actin-filled nuclear invaginations indicate degree of cell de-differentiation (2003) Differentiation, 71, pp. 414-424Kafanov, A.I., Drozdov, A.L., Comparative sperm morphology and phylogenetic classification of recent Mytiloidea (Bivalvia) (1998) Malacologia, 39, pp. 129-139Komaru, A., Konishi, K., Ultrastructure of biflagellate spermatozoa in the freshwater clam, Corbicula leana (Prime) (1996) Invert. Reprod. Develop., 29, pp. 193-197Nalesso, R.C., Duarte, F.L., Mendes, E.G., Phenotypic plasticity in Brachidontes darwinianus (Bivalvia, Mytilidae) (1992) Rev. Brasil. Biol., 52, pp. 245-249Popham, J.D., Comparative morphometrics of the acrosomes of the sperms of "externally" and "internally" fertilizing sperms of the shipworms (Teredinidae, Bivalvia, Mollusca) (1974) Cell Tissue Res, 150, pp. 291-297Popham, J.D., Comparative spermatozoon morphology and bivalve phylogeny (1979) Malac. Rev., 12, pp. 1-20Reunov, A.A., Hodgson, A.N., Ultrastructure of the spermatozoa of five species of South African bivalves (Mollusca), and an examination of early spermatogenesis (1994) J. Morph., 219, pp. 275-283Rios, E.C., (1995) Seashells of Brazil, 2nd Ed., , Museu Oceanográfico da FURG, Rio Grande do SulRouse, G.W., Jamieson, B.G.M., An ultrastructural study of the spermatozoa of the polychaetes Eurythoe complanata (Amphinomidae), Clymenella laseroni and Micromaldane laseroni (Maldanidae) with definition of sperm types in relation to reproductive biology (1987) J. Submicrosc. Cytol., 19, pp. 573-584Seed, R., Factors influencing shell shape in the mussel Mytilus edulis (1968) J. Mar. Biol. Ass. UK, 48, pp. 561-584Souza, M., Oliveira, E., An ultrastructural study of Crassostrea angulata (Mollusca, Bivalvia) spermatogenesis (1994) Mar. Biol., 120, pp. 545-551Tanaka, M.O., Magalhães, C.A., Morphometric species recognition in Brachidontes darwinianus (Orbigny, 1846) e Brachidontes solisianus (Orbigny, 1846) (Bivalvia: Mytilidae) (1999) The Veliger, 42, pp. 267-27