JOURNAL OF ULTRASTRUCTURE AND MOLECULAR STRUCTURE RESEARCH 94, 188-194 (1986) The Ultrastructure of Xenopus Spermatozoon GIOVANNI BERNARDINI, ROBERTO STIPANI, AND GIULIO MELONE Dipartimento di Biologia. Universitri di Milano, 26 Via Celoria, I-20133 Milano, Italy Received July 22, I986 The spermatozoon of Xenopus consists of a coiled head 20 pm long and of a tail 40 Nrn long. The acrosome is a thin vesicle capping the anterior region of the nucleus. A manchette of mito- chondria surrounds the posterior region of the nucleus, the two centrioles, and the beginning of the flagellum. The flagellum shows a conventional 9*2+2 appearance and is devoid ofany accessory StlllctUre. 0 1986 Academic Press, Inc. Xenopus luevis is an anuran of the family gave a general description of mature sper- Pipidae whose eggs are commonly used to matozoa of several amphibians. study fertilization and development (Ma- This paper describes the ultrastructure of lacinski, 1985). However, Xenopus sper- mature spermatozoa of X. laevis. matozoa have not received great attention; we think that to have a better understanding MATERIAL AND METHODS of fertilization we cannot ignore sperm mor- X. Zaevis males were killed by head concussion and decapitated. Since Xenopus do not have seminal ves- phology. Reed and Stanley (1972) published icles for sperm storage (Deuchar, 1975), spermatozoa a study on the spermatogenesis in Xenopus, were obtained from testes. Testes were tom in 1- to and the mature spermatozoa have been 2-ml of Ringer; sperm suspension was diluted to 10 studied in other anurans as in Bufo (Furieri, ml, passed through a nylon mesh (Mundialnyl 8 1 -T), 196 l), Rana (Poirier and Spink, 197 1) and and centrifuged at 500g for 10 to 15 min. The pellet Bombina (Furieri, 1975). Pugin-Rios (1980) was fixed (2.5% glutaraldehyde in 15 mM cacodylate buffer, pH 7.5) for 2 h at room temperature. FIGS. 1 AND 2. SEM pictures of Xenopus spermatozoa. FIG. I. Spermatozoa are visible in their natural three-dimensional shape in a testis that has been cut after fixation. x 7300. FIG. 2. Isolated spermatozoon; arrowhead indicates where the mitochondrial manchette begins. x 7300. FIGS. 3-5. TEM micrographs of thin sections of Xenopus spermatozoa. FIG. 3. Longitudinal section of the head tip. Arrowheads point to the end of the acrosome. x 60 000. FIG. 4. Cross section in the acrosomal region. x 60 000. FIG. 5. Cross section in a region between the acrosome and the mitochondria. x 60 000. FIGS. 6-10. TEM micrographs of thin sections of Xenopus spermatozoa. FIG. 6. Longitudinal section of the nucleus terminal portion and of the flagellum initial one. x 60 000. FIG. 7. Cross section at the level of the terminal portion of the nucleus. x 60 000. FIG. 8. Cross section in the centriolar region. x 60 000. FIG. 9. Longitudinal section showing the beginning of mitochondrial manchette. x 34 000. FIG. 10. Cross section of the initial portion of the flagellum. Y-links connect the nine doublets to the plasma membrane of the flagellum. x 60 000. FIGS. 1 l-14. TEM micrographs of thin sections. FIG. 11. Section through the proximal (PC) and distal (DC) centrioles. Arrowheads point to banded structures. x 60000. FIG. 12. Longitudinal section of the same area of Fig. 11. x 60 000. FIG. 13. Cross section through a basal body. Pericentriolar processes are well visible. x 170 000. FIG. 14. Longitudinal section of the tail. x 60 000. 188 0889-1605/86 $3.00 Copyright 0 1986 by Academic Press,Inc. All rights of reproduction in any form reserved.