Three-dimensional motion of avian spermatozoa

Observations have been made on spermatozoa from the domestic fowl, quail and pigeon (non-passerine birds) and also from the starling and zebra finch (passerine birds). In free motion, all these spermatozoa roll (spin) continuously about the progression axis, whether or not they are close to a plane surface. Furthermore, the direction of roll is consistently clockwise (as seen from ahead). The flagellar wave has been shown to be helical and dextral (as predicted) for domestic fowl sperm when they swim rapidly in low viscosity salines. Calculations have shown that their forward velocity is consistent with their induced angular velocity but that the size of the sperm head is suboptimal for progression speed under these conditions. Dextrally helical waves also occur on the distal flagellum of fowl, quail and pigeon sperm in high viscosity solutions. But in other cases, the mechanism of torque-generation is more problematical. The problem is most profound for passerine sperm, in that typically these cells spin rapidly while seeming to remain virtually straight. Because there is no evidence for a helical wave on these flagella, we have considered other possible means whereby rotation about the local flagellar axis (self-spin) might be achieved. Sometimes, passerine sperm, while maintaining their spinning motion, adopt a fixed curvature; this must be an instance of bend-transfer circumferentially around the axonemal cylinder-though the mechanism is obscure. It is suggested that the self-spin phenomenon may be occurring in non-passerine sperm that in some circumstances spin persistently, yet without expressing regular helical waves. More complex waves are apparent in non-passerine sperm swimming in high viscosity solutions: added to the small scale bends is a large scale, sinistrally helical curvature of the flagellum. It is argued that the flagellum follows this sinistrally helical path (i.e. "screws" though the fluid) because of the shape of the sperm head and the angle at which the flagellum is inserted into it. These conclusions concerning avian sperm motility are thought to have relevance to other animal groups. Also reported are relevant aspects of flagellar ultrastructure for pigeon and starling sperm.     

An examination of the method of sizing the spermatozoa of the domestic fowl and duck with an electronic counter

Although many estimations have been made electronically of mammalian sperm volume, detailed investigations have not been reported for avian spermatozoa with an electronic counter. In the present study, sizing of spermatozoa of fowls and Muscovy and Pekin drakes was examined using a Coulter counter (model ZB). In our preliminary work on fowl sperm volumes, we found mono- or di-morphic distribution displays that were modified depending on the combination of amplification (AMP) and aperture current (APC). Therefore, methodology to estimate the fowl and drake sperm volume was examined. Dilution of semen had no effect on the dimorphic distribution pattern of the sperm volume. Density-gradient centrifugation did not separate two kind of particles in the semen in either continuous or discontinuous Percoll gradients; therefore, we varied settings of AMP and APC, and found that the most suitable settings for measuring sperm volumes of these birds are 1 for AMP and 8 for APC. With these settings, mean volumes of spermatozoa were 5.1 μm³ for fowls, 5.7 μm³ for Muscovy drakes, and 5.6 μm³ for Pekin drakes.     

Immunohistochemistry of the cytoskeleton in the excurrent ducts of the testis in birds of the Galloanserae monophyly

The presence, location and degree of immunoexpression of various microfilament (MF) and intermediate filament (IF) systems (actin, cytokeratins, desmin, vimentin) were studied in the excurrent ducts of the testis in sexually mature and active galliform (Japanese quail, domestic fowl, turkey) and anseriform (duck) birds. These proteins were variably expressed between the epithelia and periductal tissue (periductal smooth muscle cell layer and interductal connective tissue) types and between species. Variable heterogeneous co-expression of filament systems was also found in the various duct epithelia and periductal tissue types: co-expression of filament systems was the rule rather than the exception. In the duck, neither vimentin nor cytokeratin was present in any of the tissues, whereas actin and desmin (absent in the rete testis) were co-expressed in the efferent ducts and epididymal duct unit (comprising the ductus conjugens, ductus epididymidis and ductus deferens). Actin, desmin and vimentin were generally co-expressed in the rete testis, efferent ducts and epididymal duct unit of the quail, domestic fowl and turkey, with vimentin being more strongly immunoreactive than actin and desmin in the epididymal duct unit, but more weakly immunoexpressed in the efferent ducts. Cytokeratin was present and co-expressed with actin, desmin and vimentin in the rete testis, efferent ducts and epididymal duct unit of the domestic fowl and turkey, but not in the quail and duck. The periductal smooth muscle cell layer and interductal tissue co-expressed actin, desmin and vimentin variably in all birds. Luminal spermatozoa of both the turkey and duck were immunonegative for all protein systems, whereas those of the quail and domestic fowl co-expressed actin, desmin and vimentin moderately or strongly. The tissues of the reproductive tract of male birds thus contain cytoskeletal protein systems that are variably but mostly co-expressed and whose contractile ability appears necessary and sufficient for transportation through the various excurrent ducts of the voluminous testicular fluid and its high sperm content, characteristic features of male avian reproduction.     

The structural organization of sperm chromatin

The structure of rabbit, fowl, and Xenopus laevis sperm chromatin was explored by study of the reaction of their decondensed nuclei with DNase 1 and micrococcal nuclease. Those of rabbit and fowl were readily digested by DNase 1, and the polyacrylamide gel electrophoresis profiles of DNAs extracted from the digests were similar, each being polydisperse with a single discrete band of DNA smaller than 72 base pairs. There were differences, however, between the sperm chromatins in the course of their digestion by micrococcal nuclease. A limit digest at about 45% acid solubility was obtained with Xenopus sperm chromatin, while 90% of fowl sperm DNA was rendered acidsoluble by the enzyme. The gel profiles of the limit digests were polydisperse, but only those of rabbit and fowl sperm chromatins possessed a discrete band of DNA smaller than 72 base pairs. Bleomycin did not react with DNA of rabbit, fowl, or Xenopus spermatozoa. Since bleomycin reacts with somatic cell chromatin, and the course of DNase 1 or micrococcal nuclease digestion of sperm chromatin was different from that found for somatic cell chromatin, it would appear that sperm chromatin does not have the repeating nucleosometype structure of somatic cell chromatin. The nuclease digestion studies further suggest that the organization of rabbit and fowl sperm chromatins is similar, and is different from that of Xenopus sperm chromatin. The dependence of the structure of sperm chromatin on the composition of its basic proteins, and a possible structure for a protamine-type sperm chromatin, are discussed.     

A single functional testis and long deferent duct papillae: the peculiar male reproductive tract of the classically polyandrous, sex-role reversed Black Coucal (Centropus grillii)

In many birds, the male reproductive tract is asymmetric with the left testis being larger than the right one. Coucals (Centropodidae) represent an exception as the asymmetry is typically reversed. Here, we describe the functional morphology of the reproductive tract of the African Black Coucal (Centropus grillii), a bird species with reversed sex-roles and a classical polyandrous mating system. In this species, the left testis has been reduced to a tiny, disk-like vestige that in almost all cases examined was not visible macroscopically. The vestigial left testis apparently does not participate in sperm production but has retained a vestigial left excurrent duct system. By contrast, the right deferent duct was engorged with sperm, suggesting a sperm storage function. Both deferent ducts opened on the tip of spectacularly long, erectile deferent duct papillae into the urodaeum of the male cloaca. Behavioural observations suggest that they may function as “pseudophalli”. Testis mass represented 0.49% of body mass, less than half the size of other classical polyandrous bird species. Assuming moderate to high levels of sperm competition this represents a paradox. Heavy demands on the energy budget while caring for altricial young may have prevented males from maintaining two testes and large bilateral sperm storage devices. Reduced testis mass may be compensated for by frequent transfer of small amounts of sperm. Female Black Coucals have not evolved any corresponding cloacal specializations, but like all other birds have sperm storage tubules.     

The snapping strength of the egg shells of various orders of birds

A study of the snapping strength (S) of egg shells and its relationship to the square of the thickness (T²) has been made on seven orders of birds and also in respect of a few shells of ratite birds, domestic fowl and guinea fowl.
There are considerable differences in strength between the egg shells of different orders of birds and when shells are snapped outwards the egg shells of Sphenisciformes are almost twice as strong as those of Podicipitiformes for a given thickness. The shells of the guinea fowl are very strong and those of the domestic fowl weak compared with the seven orders when they are snapped inwards.
Comparisons of the strength of shells with and without the outside chalky cover, which occurs on the egg shells of Sphenisciformes, Pelecaniformes and Podicipitiformes, show very variable relationships, while comparisons of inward and outward snapping strength indicate that in some orders the difference is great but that in others it is negligible.
The presence or absence of a cover on the shell could not explain any difference in snapping strength, nevertheless, a few tests on Pelecanus shells using impact strength showed that then the cover adds considerably to the strength. No other shell characteristics could explain the differences in snapping strength.     

Male mounting alone reduces female promiscuity in the fowl

The fertilization success of an insemination is at risk when a female has the possibility to copulate with multiple males, generating sperm competition and sexual conflict over remating. Female propensity to remate is often reduced after copulation, and a staggering diversity of highly derived male traits that discourage female promiscuity have been investigated. However, it is difficult to separate the effect of such specialized traits and insemination products from the more basic effect that the act of mounting per se may have on female remating. Here, we use a novel approach that separates the influence of mounting from that of insemination on female remating in the promiscuous feral fowl. Mounting alone caused a transient but drastic reduction in female propensity to remate, and-crucially-the number of sperm that a female obtained from a new male. Therefore, like other taxa, female fowl show a reduction in promiscuity after copulation, but this is entirely due to mounting alone. This effect of mounting, independent of insemination and fertilization, indicates that even copulations that deliver little or no semen, a puzzling behavior common in many species including the fowl, may play a crucial role in sperm competition.     

Pre- and post-insemination episodes of sexual selection in the fowl, Gallus g. domesticus

Although much attention has been recently directed to sexual selection arising after insemination from sexual promiscuity, little is known about the mechanisms determining reproductive success after insemination, and the way these mechanisms interact with each other and with selective mechanisms occurring before insemination: mate choice and mate acquisition. Here, we briefly review the findings of an on-going study investigating the mechanisms generating variation in reproductive success at both a pre- and a post-insemination stage in the domestic fowl. Female preference consistently favours socially dominant males before and after insemination. However, although social status mediates the number of sperm that a male inseminates into a female, dominant males may inseminate sperm of lower fertilising quality than their subordinates. We argue that mitochondrial genes may contribute to determine sperm quality, and speculate that the maternal control of mitochondrial genes may prevent sexual selection from operating on males, thus explaining both the lack of a positive correlation between social dominance and sperm quality and the maintenance of variation in male quality in the fowl.     

Seasonal variability in the responses of the domestic fowl,Gallus domesticus, to endotoxemia

Summary The domestic fowl is reported to be extremely resistant toE. coli endotoxemia. We reported (Merrill et al., 1978) that in our hands this species displayed a lowlevel sensitivity similar to that seen in mammals. The discrepancy between previous reports and our recent findings could result from 1) seasonal differences in the responses of the domestic fowl to endotoxemia, 2) the age and nutritional status of animals used in these various studies, and/or 3) the toxicity of the different endotoxins used. Since there is a paucity of information regarding seasonal influences on the responses of experimental animals to shock and trauma, we have extended our earlier studies (conducted in October, fall group) to each of the remaining seasons of the year.Overnight, fasted, unanesthetized white Leghorn roosters (N=38) weighing 2.44±0.6 kg were injected intravenously with anE. coli endotoxin suspension (2.5 mg/kg). A separate group of birds (N=8) were injected with 0.9% saline. Plasma glucose, lactate, corticosterone, arterial blood gases and pH and selected hemodynamic variables were monitored for 24h or until death. Only four of eleven endotoxemic fall birds survived 24 h (LD64). All winter birds (N=9) survived the challenge (LDO), while seven of nine spring and summer-challenged animals (N=9 each group) survived for 24 h (LD22 both groups). The preterminal hypoglycemia and progressive lactacidemia seen in similarly-challenged mammals did not occur in any group. Plasma glucose levels in the fall group (least resistant) were significantly lower than in all other groups. The winter group (most resistant) showed the highest glucose levels. Elevation of plasma corticosterone following the endotoxin challenge was greatest in the winter group and least in the fall group. Similar corticosterone increases were seen in the spring and summer groups. We conclude that resistance to endotoxemia in the domestic fowl is influenced by the season of the year and that such seasonal influences are reflected, in part, by circulating levels of glucose and corticosterone.     

The amino acid composition and some properties of histones

Some of the properties and the amino acid compositions of the histones of calf thymus, calf liver, fowl erythrocytes, and of a protamine-like material isolated from rooster sperm were described. The amino acid compositions of the histones were rather similar except that no methionine was found in the fowl erythrocyte histone. In the fowl, histones are found in the somatic chromosomes and protamines are found in the sperm chromosomes. This shows that great variations in chromosome composition can exist in an organism. Histone is digested by pepsin both when isolated and when in the chromosome.     

Group size and perching behaviour in young domestic fowl

To test the hypothesis that young domestic fowl perform less perch-related antipredator behaviour with increasing group size, White Leghorn pullets were reared in four replicate groups of 15, 30, 60 and 120 at a constant density of 5 birds/m(2). Each pen contained perches 20, 40 and 60cm above the ground. Perch space per bird per perch level was the same for all groups. It was predicted that, with increasing group size, domestic fowl would (1) spend less time on perches (i.e. more time down on the floor); (2) be less vigilant while perching; (3) spend relatively more time preening down on the floor. As predicted, the proportion of 3- to 18-week-old birds roosting on perches during scans throughout the photoperiod decreased with increasing group size, from 41+/-1.7% in groups of 15 birds to 33+/-1.6% in groups of 120 birds. This effect was due to reduced use of the lower perches; use of the highest perches was high at all group sizes. The proportion of birds vigilant on the highest perches of those present on that perch level decreased with increasing group size. The proportion of birds engaged in the vulnerable activity of preening down on the floor increased with group size. The frequency of transitions between floor and perches was not affected by group size but birds received more disturbances from other birds when on the top perch level in the larger groups. Thus, the decline in vigilance on the top perch level with increasing group size was not due to reduced disturbance from other birds. In conclusion, despite domestication and protection from non-human predators, changes in the use of perches by young domestic fowl with increasing group size were consistent with the antipredator hypothesis.     

Plasma zinc as an index of vitellogenin production and reproductive status in the domestic fowl.

1. A technique is described for the accurate determination of circulating vitellogenin concentrations by measurement of plasma zinc concentrations before and after selective precipitation of lipoproteins in the domestic fowl. 2. Vitellogenin zinc concentrations exhibit a high degree of correlation with those of another major egg yolk precursor, very low density lipoprotein (VLDL) in immature female birds, during developing and maximum egg production in mature birds and following cessation of egg laying. 3. Mature female patterns of plasma vitellogenin and VLDL were induced by injection of oestradiol 17 beta (5 mg/kg body weight per day for 3 days) into adult cockerels. 4. It is suggested that measurement of plasma zinc provides a simple and accurate technique for the estimation of vitellogenin production and reproductive status in the domestic fowl and that this may be applied to other oviparous vertebrates.     

Interspecific germline transmission of cultured primordial germ cells

In birds, the primordial germ cell (PGC) lineage separates from the soma within 24 h following fertilization. Here we show that the endogenous population of about 200 PGCs from a single chicken embryo can be expanded one million fold in culture. When cultured PGCs are injected into a xenogeneic embryo at an equivalent stage of development, they colonize the testis. At sexual maturity, these donor PGCs undergo spermatogenesis in the xenogeneic host and become functional sperm. Insemination of semen from the xenogeneic host into females from the donor species produces normal offspring from the donor species. In our model system, the donor species is chicken (Gallus domesticus) and the recipient species is guinea fowl (Numida meleagris), a member of a different avian family, suggesting that the mechanisms controlling proliferation of the germline are highly conserved within birds. From a pragmatic perspective, these data are the basis of a novel strategy to produce endangered species of birds using domesticated hosts that are both tractable and fecund.     

A novel test of the phenotype-linked fertility hypothesis reveals independent components of fertility

The phenotype-linked fertility hypothesis predicts that male sexual ornaments signal fertilizing efficiency and that the coevolution of male ornaments and female preference for such ornaments is driven by female pursuit of fertility benefits. In addition, directional testicular asymmetry frequently observed in birds has been suggested to reflect fertilizing efficiency and to covary with ornament expression. However, the idea of a phenotypic relationship between male ornaments and fertilizing efficiency is often tested in populations where environmental effects mask the underlying genetic associations between ornaments and fertilizing efficiency implied by this idea. Here, we adopt a novel design, which increases genetic diversity through the crossing of two divergent populations while controlling for environmental effects, to test: (i) the phenotypic relationship between male ornaments and both, gonadal (testicular mass) and gametic (sperm quality) components of fertilizing efficiency; and (ii) the extent to which these components are phenotypically integrated in the fowl, Gallus gallus. We show that consistent with theory, the testosterone-dependent expression of a male ornament, the comb, predicted testicular mass. However, despite their functional inter-dependence, testicular mass and sperm quality were not phenotypically integrated. Consistent with this result, males of one parental population invested more in testicular and comb mass, whereas males of the other parental population had higher sperm quality. We found no evidence that directional testicular asymmetry covaried with ornament expression. These results shed new light on the evolutionary relationship between male fertilizing efficiency and ornaments. Although testosterone-dependent ornaments may covary with testicular mass and thus reflect sperm production rate, the lack of phenotypic integration between gonadal and gametic traits reveals that the expression of an ornament is unlikely to reflect the overall fertilizing efficiency of a male.     

Sperm mobility: A primary determinant of fertility in the domestic fowl (Gallus domesticus).

Previous research demonstrated that sperm mobility is a quantitative trait of the domestic fowl. The trait is quantified by measuring the absorbance of an Accudenz solution after overlay with a sperm suspension and brief incubation at body temperature. In the present work, average and high sperm mobility phenotypes (n = 30 males per phenotype) were selected from a base population. Differences were found between sperm oxygen consumption (p < 0.0001), acylcarnitine content (p < 0.05), linear velocity (p < 0.001), and straightness (p < 0.001), a trajectory variable measured with the Hobson SpermTracker. Oxygen consumption and stearoylcarnitine content of sperm from the high-mobility phenotype were twice those observed with sperm from average males, implying a pivotal role for mitochondria. On the basis of these results, a graded relationship was predicted between fertility and sperm mobility. Males (n = 48) were chosen at random from another base population, sperm mobility was measured per male, and each ejaculate was used to inseminate 8-12 hens (8 x 10(7) viable sperm per hen). When fertility was plotted as a function of sperm mobility, data points approximated a skewed logistic function. The hypothesis that vaginal immunoglobulins constitute an immunological barrier to sperm transport was tested and rejected. Therefore, we concluded that sperm mobility is a primary determinant of fertility in the fowl.     

Sperm size and sperm competition in birds.

In a sample of 20 species of North American passerine birds we found no relation between sperm size and mating system like that previously reported in mammals (Gomendio & Roldan (Proc. R. Soc. Lond. B 243, 181 (1991)). Instead, we found a positive correlation between sperm length and the length of female sperm storage tubules (SSTS) and a negative correlation between sperm length and the number of SSTS. Both of these correlations suggest that the more than fivefold variation in sperm size we found among species can be explained by sperm competition for access to storage sites (SSTS) in females. As longer sperm appear to be able to swim faster, selection should favour long sperm when SSTS are in short supply; sperm long enough to fill an SST might also prevent access to SSTS by the sperm of other males. Conversely, selection should favour shorter sperm when there is an advantage to sperm layering within an SST promoting a last-male mating advantage. Although we conclude that sperm competition influences sperm size in birds, little is known about the interactions between sperm and SSTS. It seems clear, however, that detailed study of this interaction will provide a new dimension to the study of avian mating systems.     

Specific features of in vivo and in vitro sperm storage in birds

This review focuses on some of the main features of sperm selection and storage in birds mainly on the basis of studies performed in poultry species, with emphasis on the initial selection of sperm at the female vagina level prior to migration towards the sperm storage tubules. Sperm originating from low-quality males or subjected to inappropriate in vitro storage conditions are rapidly discarded, resulting in impaired fertility in corresponding flocks. In the absence of accessible and appropriate technology for matching the 'storing' potential of sperm in the oviduct, conditions for prolonged sperm storage under a liquid (through the use of semen extenders) or a solid state (cryopreservation) have received only limited attention, despite their potential interest to facilitate male and female management in poultry flocks. Despite this, technology for short-term liquid storage is currently used in turkeys, guinea fowl and muscovy ducks and also in progress in chickens. In addition, technology for cryopreservation of avian semen has become available for some species (chicken, goose) to facilitate the management of genetic resources, including the preservation of rare and economically important breeds.     

Organic phosphate probes of the avian renal phosphate secretory mechanism

Parathyroid hormone (PTH) stimulates net renal inorganic phosphate (Pi) secretion in domestic fowl (Gallus domesticus). Recent evidence indicates that secreted Pi is derived from a highly sequestered, presumably organic, phosphate pool. A modified Sperber technique was used to survey the response of domestic fowl to unilateral renal portal infusions of organic phosphate compounds that had been implicated in previous studies of Pi secretion. None of the organic phosphate compounds produced a significant unilateral Pi secretory effect. It is concluded that these compounds neither directly stimulate Pi secretion in normal or parathyroidectomized birds, nor are they rate-limiting for the Pi secretory mechanism in birds infused with PTH.     

Chewing lice (Mallophaga: Insecta) of birds in the Central Ciscaucasia

Collections of 8805 individuals of chewing lice from wild and domestic fowl in the Central Ciscaucasia were processed. According to original and literary data, 102 species of Mallophaga are known from this territory; 15 of them were recorded for the first time. Most of all the chewing lice species known in the territory are parasites of passerine birds; the number of species associated with each of the 12 remaining bird orders of birds is several times smaller. An exchange of chewing lice between some species of hosts, including domestic and wild fowl, is possible.     

Structure of the Testes,Spermatozoa and Spermatozeugmata of Mimagoniates barberiRegan, 1907 (Teleostei: Characidae), an Internally Fertilizing,Oviparous Fish

Abstract The testis of Mimagoniates barberiis bipartite. Spermatogenic tissue is restricted to the anterior part. The posterior part of the testis is devoid of spermatogenic tissue and contains numerous efferent ducts filled with mature sperm. Cells in germinal cysts develop synchronously, sperm nuclei and flagella become oriented parallel in the late stages of spermiogenesis. In the caudal portion of the aspermatogenic part all sperms are arranged into unencapsulated sperm bundles — spermatozeugmata. Two types of spermatozeugmata are found both in the caudal portion of the testis and in milt. In the larger, spindle–shaped type, sperm flagella form the spindle tips. In the smaller ones, which have approximately a length of spermatozoon, the sperm are parallel and approximately in register. In both types sperm heads are arranged parallel. A mature spermatozoon is flail–shaped. The sperm head is highly elongated and situated alongside the flagellum, the tip of the head is directed backwards. Large mitochondria are situated on one side of the elongated nucleus only and form the tip of the head. Live spermatozoa move with the centriolar part ahead. Both testis and spermatozoon structure as well as formation of spermatozeugmata in M. barberiare highly derived features which perhaps evolved as adaptations to internal fertilization.