Fine structure of the giant aflagellate spermatozoon in pseudostomum quadrioculatum (leuckart) (platyhelminthes,prolecithophora)

The giant aflagellate spermatozoa of P. quadrioculatum are composed of two different parts: a thicker head piece and a more slender tail piece. In the head there exist a large elongated nucleus and an elongated mitochondrial derivative situated in a groove-like cavity of the nucleus. In mature spermatozoa the nuclear material is arranged in many small membrane bounded areas. Both structures, nucleus and mitochondrial derivative, are spirally coiled. The outer part of the membrane in the mitochondrial derivative forms many loop-like foldings. Both organelles continue to the tail in form of two small, helically coiled ribbons; the nucleus is anchored within the mitochondrial derivative by an electron-opaque process. A sheath of spirally-orientated cortical microtubules starting from the tip of the head runs to the tip of the tail under the cell membrane. In addition, a second sheath of tubules occurs in the tail region, these tubules also run parallel to each other, but in the opposite direction to the microtubules of the outer sheath.The possible relations between the structures observed and the motility of the spermatozoa are discussed; in addition, some phylogenetic comments are attempted.Abbreviations c — cerebrum - com — cortical microtubules - cop — copulatory organ - fm — foldings of the mitochondrial membrane - l — lattice - mid — mitochondrial derivative - mt — microtubules - n — nucleus - ne — nuclear envelope - ph — pharynx - pn — protonephidium - rp — ribbon-like nuclear process - te — testis - tt — testis - tt — tip of the tail - vi — vitellarium - vs — vesicula seminalis     

Ultrastructure of spermiogenesis and spermatozoa in Marchalina hellenica (Gennadius) (Hemiptera: Sternorrhyncha,Marchalinidae)

The spermiogenesis, the sperm structure and the sperm motility of Marchalina hellenica (Gennadius) were examined. In the early spermiogenesis a centriolar apparatus was identified, but this structure is not involved in the production of the sperm flagellum. As in other Coccoidea, the flagellar axoneme originates by the activity of the thickened tip of the numerous microtubules surrounding the nuclear anterior region close to the periphery of the cell. This region pushes against a narrow cytoplasmic layer, giving rise to a papilla. In this region a novel structure, consisting of a regular network of thin filaments, arranged orthogonally to the bundle of microtubules, is visible. The sperm flagellum consists of a series of about 260 microtubules, regularly arranged in rings around the axial nucleus. This latter extends in the middle part of the sperm length. As usual in scale insects, sperm form a bundle, which in M. hellenica is composed of 64 sperm cells, surrounded by somatic cyst cells. The sperm bundle has an helicoidal array, with a cap of dense material at its apex, lending the anterior and the posterior region of the sperm bundle with a different structural organization. This difference is responsible of the different speed gradient observed in the helical wave propagating along the sperm bundle.     

Structure and development of sperm bundles in the dragonfly Aeshna juncea L. (Odonata)

A re-examination of the origin and development of sperm bundles in aeshnid dragonflies (Odonata, Anisoptera) was carried out using light and electron microscopy. During their elongation, intracyst spermatids of the testis of the dragonfly Aeshna juncea L. form a slender cytoplasmic protrusion, the acrosomal conicoid, beyond the nucleus and acrosome rodlet. Gathering and parallel alignment of the transforming spermatids into a tight bundle take place inside the cyst. The original, rigid spermatid foreparts eventually associate, initially by becoming adhesive and swelling progressively to intertwine, and thus come to constitute a cap that binds together all sperm heads within a cyst in a spermatodesma. The development of the spermatodesma seems to occur disjunct from somatic cyst cells. Bundled in this form, the sperms are transferred to the intratestis canal and moved down the spermiduct to the seminal vesicle. They are then forwarded to the male copulatory apparatus, from which they are transmitted to the female. Individual, fully formed sperms are seen to be liberated from the bundle when in the female receptaculum seminis. The remnant of the cytoplasmic acrosomal conicoid, which is considered an envelope of the acrosome rodlet, is then dissolved. The spermatodesmata are large sperm aggregates that constitute efficient vehicles for transmission of amounts of filamentous sperm to the female. J. Morphol. 235:239–247, 1998. © 1998 Wiley-Liss, Inc.     

Pharynx, esophagus, and associated structures in the booklouse, Liposcelis divinatorius

Abstract. Ultrastructural features of the pharynx, esophagus, and associated intrinsic visceral muscular and nervous structures of the booklouse, Liposcelis divinatorius , were studied to determine whether the anatomical arrangements of these structures differed from the general pattern found in insects. The results are compared with previous light microscope studies of this tiny insect. Variations from the usual arrangement reported for intrinsic visceral muscles associated with the pharynx in insects are described. Intrinsic visceral muscles include a narrow band of circularly disposed fibers and both extra-circular and intra-circular longitudinally disposed fibers. This represents a departure from the slightly developed inner longitudinal and more prominent outer circular fibers seen in most insects. The outer surface of some circular muscle cells has apparently unique pouches packed with mitochondria, which contain many cristae. Numerous bacteroids appear in the esophageal epithelial cells and in the sub-esophageal ganglion. Nerve processes associated with the foregut contain neurotubules, synaptic vesicles, and electron-dense granules.     

Influence of image sampling frequency on the perceived movement characteristics of progressively motile human spermatozoa

Tracks of 30 progressively motile washed human spermatozoa were plotted manually from 200-Hz frame rate video recordings. Tracks at 100, 66.7, 50, 40, 33.3., 25, 20, 10, and 5 Hz were then constructed using every 2nd, 3rd, 4th, 5th, 6th, 8th, 10th, 20th, or 40th point. The 200-Hz tracks were analyzed by traditional manual methods, and all ten sets of tracks analyzed using a computer-assisted method (“Videomot,” developed originally to analyze 30-Hz tracks) to eliminate observer bias. Progression velocity (VSL) remained constant under all analysis conditions. Average path velocity (VAP) also remained essentially constant, although Videomot was less reliable at high frame rates due to problems in determining the average path. Curvilinear velocity (VCL) was very frame rate dependent (the 25-Hz mean value was only 56.5% of that at 200 Hz), and Videomot was more accurate than manual analysis at 200 Hz. Values of the amplitude of lateral head displacement (ALH) were acceptable at most frame rates. At < 66.7 Hz the inclusion of spurious curvilinear track deviations caused lower mean ALH values, and at 5 Hz ALH could not be measured since the track was essentially the average path. Beat/cross frequency (BCF) was also frame rate dependent; at high rates there was the same problem as with ALH measurements, while at ? 25 Hz the maximum BCF was restricted by the frame rate. We conclude that human sperm movement characteristics can be measured at frame rates ca. 30 Hz but only if the constraints affecting VCL and BCF values are understood and accepted. Finally, < 10 Hz can only give values for VSL and, perhaps, VAP.     

An ultrastructural analysis of mature sperm from the crayfish Pacifastacus leniusculus,Dana

Sperm from the crayfish, Pacifastacus leniusculus, resemble other reptantian sperm in that they are composed of an acrosome, subacrosomal region, nucleus, membrane lamellar complex, and spikes which radiate from the nuclear compartment. The acrosome (PAS positive vesicle) can be subdivided into three regions: the apical cap, crystalline inner acrosomal material, and outer acrosomal material which is homogeneous except for a peripheral electron dense band. The nucleus contains uncondensed chromatin and bundles of microtubules which project into the spikes. The orientation of the microtubule bundles relative to the nuclear envelope near the base of the subacrosomal region suggests that the nuclear envelope may function in the organization of the spike microtubules.     

Sperm midpiece length predicts sperm swimming velocity in house mice

Evolutionary biologists have argued that there should be a positive relationship between sperm size and sperm velocity, and that these traits influence a male''s sperm competitiveness. However, comparative analyses investigating the evolutionary associations between sperm competition risk and sperm morphology have reported inconsistent patterns of association, and in vitro sperm competition experiments have further confused the issue; in some species, males with longer sperm achieve more competitive fertilization, while in other species males with shorter sperm have greater sperm competitiveness. Few investigations have attempted to address this problem. Here, we investigated the relationship between sperm morphology and sperm velocity in house mice (Mus domesticus). We conducted in vitro sperm velocity assays on males from established selection lines, and found that sperm midpiece size was the only phenotypic predictor of sperm swimming velocity.     

Transformation: how do nematode sperm become activated and crawl?

Nematode sperm undergo a drastic physiological change during spermiogenesis (sperm activation). Unlike mammalian flagellated sperm, nematode sperm are amoeboid cells and their motility is driven by the dynamics of a cytoskeleton composed of major sperm protein (MSP) rather than actin found in other crawling cells. This review focuses on sperm from Caenorhabditis elegans and Ascaris suum to address the roles of external and internal factors that trigger sperm activation and power sperm motility. Nematode sperm can be activated in vitro by several factors, including Pronase and ionophores, and in vivo through the TRY-5 and SPE-8 pathways. Moreover, protease and protease inhibitors are crucial regulators of sperm maturation. MSP-based sperm motility involves a coupled process of protrusion and retraction, both of which have been reconstituted in vitro. Sperm motility is mediated by phosphorylation signals, as illustrated by identification of several key components (MPOP, MFPs and MPAK) in Ascaris and the characterization of GSP-3/4 in C. elegans.     

The sperm of Matsucoccus feytaudi (Insecta,Coccoidea): Can the microtubular bundle be considered as a true flagellum?

In the present work the spermiogenesis and sperm structure of Matsucoccus feytaudi, a primary pest of the maritime pine in southern eastern Europe, is studied. In addition to the already known characteristics of coccid sperm, such as the absence of the acrosome and mitochondria, and the presence of a bundle of microtubules responsible for sperm motility, a peculiar structure from which the microtubule bundle takes origin is described. Such a structure – a short cylinder provided with a central hub surrounded by several microtubules with a dense wall – is regarded as a Microtubule Organizing Centre (MTOC). During spermiogenesis, quartets of fused spermatids are formed; from each spermatid, a bundle of microtubules, generated by the MTOC, projects from the cell surface. Each cell has two centrioles, suggesting the lack of a meiotic process and the occurrence of parthenogenesis. At the end of the spermiogenesis, when the cysts containing bundles of sperm are formed, part of the nuclear material together with the MTOC structure is eliminated. Based on the origin of the microtubular bundle from the MTOC, the nature of the bundle as a flagellum is discussed.     

The motility of rabbit spermatozoa recovered from the female reproductive tract

The motility of rabbit spermatozoa recovered from the vagina, endocervix, uterus, and four regions of the oviduct was assessed visually by phase-contrast microscopy at intervals from one minute to 16 hours after a single mating. The percentage of motile cells in each sample was dependent on the temperature of recovery, ie, 23° vs 37°C, but was not influenced by the temperature of observation. Spermatozoa in the lower isthmus of the oviduct were the most temperature sensitive population to recovery at 23°C. When all manipulations and observations were performed at 37°C, the percentage of spermatozoa with progressive motility varied according to the region sampled and interval after mating. Populations from the vagina, uterus and upper regions of the oviduct usually had a high proportion of progressively motile cells with vigorous flagellar activity. Fewer spermatozoa showed progressive movement on recovery from the endocervix and lower 2 cm of the tubal isthmus and their flagellar activity was generally depressed. The decrease in flagellar beat frequency noted in the latter regions may be a major factor limiting sperm ascent in the female tract. A unique pattern of “activated” motility was seen exclusively in populations taken from the oviducts at 6 to 16 hours after mating. This motility pattern, consisting of alternating episodes of linear progressive and vigorous nonprogressive movement, may be analogous to the activated motility described for capacitated rodent spermatozoa.     

长吻鮠精子超微结构的观察

用透射电镜和扫描电镜观察了长吻（ＬｅｉｏｃａｓｓｉｓｌｏｎｇｉｒｏｓｔｒｉｓＧｕｎｔｈｅｒ）精子的超微结构。长吻精子具有椭圆的头部和复杂的中片;近侧中心粒和远侧中心粒靠近核的中央;鞭毛呈９＋２轴丝结构,并具有由外膜折迭形成的波浪形的鳍状结构。研究表明,长吻精子具有某些区别于其它鱼类精子的不同结构。     

Ultrastructure of Sperm in <Emphasis Type="Italic">Mercenaria stimpsoni</Emphasis> and <Emphasis Type="Italic">Mactra chinensis</Emphasis> (Mollusca: Bivalvia) from the Sea of Japan

The ultrastructure of the sperm of the common bivalve species Mercenaria stimpsoni and Mactra chinensis from Peter the Great Bay is described. The sperm structure is typical for animals with external insemination. The sperm consists of a head, middle part, and flagellum. The sperm head of M. stimpsoni has a curved crescent form and includes the nucleus and acrosome; the head length is 9.8 μm. The acrosome is subdivided to the acrosome granule and the periacrosomal material. There are 4 mitochondria of about 0.8 μm in size in the middle part of the spermatozoon. The mitochondria surround the centriolar apparatus, which consists of proximal and distal centrioles located at a right angle. The axoneme originates from the distal centriole. The sperm of M. chinensis is barrel-shaped, with a head length of 3.2 μm. The acrosome is relatively larger, and its height is 1–1.2 μm. There are also 4 mitochondria 0.6–0.8 μm in the middle part of the spermatozoon. The sperm structure of the described species is typical of the families to which the mollusks belong, with insignificant variations.     

Quantitative comparison of the passage of homologous and heterologous spermatozoa through the uterotubal junction of the golden hamster

A quantitative method was used to determine whether the spermatozoa of foreign species could pass through the uterotubal junction (UTJ) of the hamster as efficiently as homologous (hamster) spermatozoa. Estrous female hamsters were artificially inseminated with epididymal spermatozoa of homologous and heterologous (foreign) species. The number and distribution of spermatozoa in the oviduct were determined several hours after insemination (shortly before ovulation). The passage of immotile (dead) hamster spermatozoa through the UTJ was also examined. It was found that the spermatozoa of all foreign species tested (rat, mouse, guinea pig, and rabbit), as well as immotile hamster spermatozoa, could pass through the UTJ but did so in much smaller numbers compared to live hamster spermatozoa. This was not specifically due to poor survival of foreign spermatozoa in the hamster uterus, as the viability of all inseminated spermatozoa (including hamster spermatozoa) was considerably reduced by 1 h after insemination. While a large number of live hamster spermatozoa were distributed throughout the caudal isthmus at the time of examination, none or only a very few foreign spermatozoa had advanced this far. The few foreign and immotile spermatozoa that reached the caudal isthmus were confined to the first ascending loop of this segment. Some possible causes for the small number and retarded advance of foreign spermatozoa in the hamster oviduct were discussed.     

Initiation,prolongation, and reactivation of the motility of salmonid spermatozoa

The motility of salmonid spermatozoa initiated by dilution of the milt with ovarian fluid or isotonic saline is brief duration; it was believed that it can be activated only once in the life of the spermatozoon. Dilution of the milt with an equal volume of isotonic saline (0.12 M-NaCl) containing 5 mM-3-isobutyl-1-methylxanthine (MIX) prolonged and intensified sperm motiliy. When motility had stopped after initial mobilization with saline or ovarian fluid, it could be reactivated by addition of MIX; reactivated spermatozoa fertilized eggs. Dilution with saline containing K⁺ (24 mEq/liter) did not initiate sperm motility even in the presence of MIX. The spermatozoa were mobilized by subsequent with 0.12 M-NaCl. The concentration of adenosine triphosphate (ATP) in sperm suspensions dropped on dilution with saline and rose as motility ceased, but declined without subsequent recovery following dilution with MIX-saline. The concentration of cyclic adenosine monophosphate (cAMP) rose and fell sharply on initiation of motility and rose again after motility had declined. While salmonid spermatozoa can be mobilized by dilition with saline alone, the effectiveness of MIX in reactivating “spent” spermatozoa supports the assumption that cAMP plays a role in the initiation of sperm motility.     

Cholesterol and phospholipid levels of washed and percoll gradient centrifuged mouse sperm: Presence of lipids possessing inhibitory effects on sperm motility

Levels of DNA, cholesterol, and phospholipids of mouse caudal epididymal and vas deferens sperm that were processed through simple washing and Percoll gradient centrifugation were measured. The DNA and cholesterol contents of washed sperm and Percoll gradient centrifuged (PGC) sperm (DNA = 3.6 ± 0.3 pg/sperm and 3.4 ± 0.3 pg/sperm, respectively; cholesterol = 0.219 ± 0.057 nmole/μg DNA and 0.224 ± 0.030 nmole/μg DNA, respectively, for washed and PGC sperm) were not significantly different from each other; however, the phospholipid level of PGC sperm was only one half of that of washed sperm (0.315 ± 0.071 nmole/μg DNA versus 0.720 ± 0.075 nmole/μg DNA, respectively). The presence of 0.3% bovine serum albumin (BSA) in the culture medium used in sperm washing did not change the cholesterol and phospholipid contents of washed sperm. Similarly, the cholesterol and phospholipid levels of washed sperm and PGC sperm that were further incubated in BSA-containing medium for 30 min remained the same. Interestingly, substantial amounts of lipids, as determined by the cholesterol and phospholipid levels, were released into the supernatants of the sperm washes, and sperm needed to be washed at least twice to ensure their stable levels of cholesterol and phospholipids. The lipid mixture in the first sperm wash supernatant was shown to have inhibitory effects on PGC sperm motility. © 1996 Wiley-Liss, Inc.     

The proventriculus of the carpenter bee, Xylocopa virginica virginica (L.), with special reference to bacteria-containing luminal tunnels

Abstract. Four tunnels off the lumen of the proventriculus of the carpenter bee, Xylocopa virginica virginica , have been discovered. Light and electron micrographs revealed the presence in the tunnels of gram-positive, rod-shaped bacteria, some of which showed division stages. The occurrence of the bacteria exclusively in the tunnels—not in the lumen of the proventriculus—makes speculation as to their function difficult. The function of the tunnels is also obscure, as no glands were seen emptying into them. The bacteria may be symbionts that release enzymes into the tunnels, which are subsequently transported to the midgut to aid digestion. They could also be parasites. This is the first report of such bacterial-containing tunnels in insects.