Article available at http://www.parasite-journal.org or http://dx.doi.org/10.1051/parasite/1994012115 U ltrastructure o f spermiogenesis a n d spermatozoa OF POLYLABROIDES AUSTRALIS (PLATYHELMINTHES, MONOGENEA, POLYOPISTHOCOTYLEA, MICROCOTYUDAE) R O H D E K .* and WATSON N.A.* Sum m ary : R é su m é : U ltrastructure de la spermiogenèse et du spermato­ Testis follicles are surrounded by a sheath and conlain several zo ide de P olylabroides australis (P latyhelminthes, M onogenea, stages of spermatogenesis. Primary spermatocytes have large P olyopisthocotylea , M icrocotylidae). nuclei with a loose granular appearance and synaptonemal com­ Les follicules du testicule sont entourés par une gaine et contiennent plexes, and their densely packed cell bodies are small and rich in différents stades de la spermiogenèse. Les spermatocytes I ont de mitochondria. Spermatids are joined to a central cytophore; their grands noyaux clairs et des complexes synaptonémaux, et leurs nuclei are at first spherical and located near the tips of the sperma­ corps cellulaires, très serrés, sont petits et riches en mitochondries. tids, later they elongate and coil. In each of the cytoplasmic protu­ Les spermatides sont attachées à un cytophore central; leurs noyaux berances (the "zones of differentiation") in the periphery of the sont tout d'abord sphériques et localisés près des extrémités des cytophore, two flagella, each with a cross-striated rootlet, grow spermatides, puis ensuite allongés et enroulés. Dans chacune des out from basal bodies separated by an intercentriolar body, and protubérances cytoplasmiques (les “zones de différenciation"), dans later fuse in a proximo-distal direction with the median cytoplasmic la périphérie du cytophore, deux flagelles, chacun avec une racine process which has developed at the tip of the zone of differentia­ striée, grandissent à partir de corps basaux séparés par un corps tion. The zones of differentiation and the median cytoplasmic pro­ intercentriolaire et ensuite fusionnent dans une direction proximo- cesses possess a row of peripheral microtubules. Mature sperm distale avec l’expansion cytoplasmique médiane qui s'est dévelop­ have a single row of peripheral microtubules that is incomplete in pée à l'extrémité de la zone de différenciation. Les zones de diffé­ some parts of the sperm. Number of peripheral microtubules renciation et l'expansion cytoplasmique médiane possèdent une decreases towards both ends from about 55 in the principal rangée de microtubules périphériques. Les spermatozoïdes mûrs ont region. One axoneme terminates before the other in the nuclear une rangée simple de microtubules périphériques qui est incomplète region, and nucleus and mitochondrion overlap only in the middle dans certaines parties du spermatozoïde. Le nombre de microtu­ regions. The proximal end contains the axonemes, and the distal bules périphériques décroît vers les deux extrémités à partir de 5 5 end the nucleus. environ dans la région principale. Un des axonèmes se termine avant l'autre dans la région nucléaire, et le noyau et la mitochondrie se superposent seulement dans les régions moyennes. L'extrémité KEY WORDS : Monogenea. Polyopisthocotylea. Polylabroides australis. ultra- proximale contient les axonèmes, et l'extrémité distale contient le structure. spermatozoa. spermiogenesis. noyau. MO TS CLES : Monogenea. Polyopisthocotylea. Polylabroides australis. ultra- structure. spermatozoïdes, spermiogenèse. INTRODUCTION 1991a, b; Schmahl and Obiekezie 1991). In this paper, we describe the ultrastructure of sperm and spermio­ genesis in the microcotylid Polylabroides australis. he ultrastructure of sperm and spermatogensis of Monogenea has received much recent attention, mainly with the aim of contributing MATERIALS A N D METHODS T to a phylogenetic system of the group (reviews by Justine 1991a, 1993). Ultrastructure of sperm of pecimens of Polylabroides australis were col- Monogenea Polyopisthocotylea has been examined by lected from the gills of bream, Acantbopagrus Rohde (1971, 1975, 1980), Ktari (1971), Tuzet and australis, and fixed for 3 h at 4°C in 3% gluta- Ktari (1971a,b), Bekkouche et al. (1974), MacDonald Sraldehyde in 0.1M phosphate buffer at pH 7.4. They and Caley (1975), Halton and Hardcastle (1976), were washed in the same buffer at 4°C and postfixed Justine and Mattei (1984, 1985a, b, c), Justine (1985, for 1 h at room temperature in 1% OsO4 in buffer, 1991), Justine et al. (1985a, b), and Schmahl and dehydrated in alcohol and embedded in Spurr resin. Obiekezie (1991). Spermiogenesis of Polyopisthoco­ Ultrathin longitudinal sections through a mature indi- tylea has received much less attention (Tuzet and vidual were stained with uranyl acetate and lead Ktari 1971a; Justine and Mattei 1983; Justine 1985, citrate and examined under a JEOL 1200EX electron * Department of Zoology, University of New England, Armidale microscope at 60kV. N.S.W. 2351, Australia Parasite, 1994, 1, 115-122 Mémoire 115 ROHDE K. a n d WATSON N.A. Figs. 1-4. - Spermiogenesis of Polylabroides. Fig. 1. Testis follicle containing spermatids and spermatocytes (double arrow- head). Note sheath (large arrowheads) around follicle and nucleus (arrow) in wall of follicle. Fig. 2. Part of testis follicle with spermatids connected to a central cytophore, and primary spermatocytes. Fig. 3 . Probably primary spermatocyte with pair of centrioles (arrowheads). Fig. 4. Primary spennatocytes containing large nuclei surrounded by little cytoplasm. Note synaptonemal complexes and cell membranes between spermatocytes. Scale bars 2 pm. Abbreviations : a, attachment zone; ax, axoneme; b, basai body; c, cell membrane; cy, cytophore; e, extension (?) of nucleus; i, intercentriolar body; m, mitochondrion; me, median cytoplasmic process; mi, microtubule; mu, muscle fibre; n, nucleus; p, primary spermatocyte; s, synapto­ nemal complex; sp, spermatid. 1 1 6 Mémoire Parasite, 1994, 1, 115-122 SPERMIOGENESIS OF P olylabroides (MONOGENEA) Figs 5-11. Spermiogenesis of Polylabroides. Fig 5. Cross-sections through outgrowing spermatids at different levels: bottom right below level of flagella, note large nucleus and mitochondrion; others at level of median cytoplasmic process, note free flagella, mitochondrion in some sections through process, and incomplete row of peripheral microtubules. Fig. 6. Cross-section through median cytoplasmic process with nucleus and mitochondrion, incomplete row of peripheral microtubules and zones of attachment, and pair of free flagella. Fig. 7. Cross-section through median cytoplasmic process with mito­ chondrion and incomplete row of peripheral microtubules, and pair of free flagella. Fig. 8. Cross-section through median cytoplasmic process at level of ciliary rootlets, note peripheral microtubules, microtubules in periphery of rootlets possibly extensions of the basai bodies, and some microtubules in the interior of the median cytoplasmic process. Fig. 9. Cross-section through median cytoplasmic process at level of intercentriolar body and basai bodies, note nucleus on one and mitochondrion on the other side, and incomplete row of peripheral microtubules. Figs. 10. 11. Longitudinal sections through out­ growing spermatid. Note intercentriolar body between basai bodies of flagella, cross-striated rootlets, and median cytoplasmic process with nucleus and mitochondrion. Scale bars 0.5µm. Parasite, 1994, 1, 115-122 Mémoire --------------------------------------------------- 117 ROHDE K. a n d WATSON N.A. RESULTS nemes (Figs. 14, 16-20). Nucléus and mitochondrion, in those parts of the sperm where both are present, are either close to each other or separated by the S permiogenesis axonemes (Figs. 17-20). A small elongate body, pro­ estis follicles are surrounded by a sheath bably an extension of the nucléus, was observed only (Fig. 1) and nuclei, possibly belonging to die in those parts of the sperm lacking the nucléus pro- sheath, are located in their periphery (Fig. 1). per (Figs. 19, 20). Aggregations of electron-dense T The follicles examined contained several stagesmaterial, of probably glycogen, are present usually close spermatogenesis. Primary spermatocytes are small, to the nucléus and the elongate body (Fig. 19). Once, densely packed and contain many mitochondria (Figs. a lamellate body was observed in addition to nucléus 2, 4), and their nuclei have an electron-lucent, loosely and mitochondrion (Fig. 17), and occasionally, sec­ granular appearance (Figs. 2, 4) and contain synapto- tions through two mitochondria (?) or a single coiled nemal complexes (Fig. 4). Fig. 4 probably illustrâtes a mitochondrion were seen. In part of the middle spermatocyte with a pair of centrioles at the begin- région, only one axoneme is present in addition to ning of cell division and Fig. 13 illustrâtes two sper­ the nucléus and mitochondrion (Figs. 12, 18, 19). matocytes containing two nucleoli each. Clusters of Some sections contained only two axonemes surroun­ cells, also densely packed but with denser cytoplasm ded by an incomplète or complété row of peripheral and chromatin in distinct, dense patches are probably microtubules (Fig. 18), some contained an axoneme, either secondary spermatocytes or primary spermato­ nucléus and mitochondrion surrounded by the peri­ cytes with condensed chromatin (Fig. 1). Early sper- pheral microtubules (Fig. 17), some contained only matids are joined by a central cytophore (Fig. 2). peripheral and some internai microtubules (Fig. 17). Their nuclei are at first spherical and located near the Basai