Embryonic Development of the Chicken External Cloaca and Phallus

The use of the scanning electron microscope has provided new detailed information about the embryonic development of the chicken external cloaca and phallus and has consequently clarified the origin of the differences between the anatomy of the chicken and turkey phallus. At Day 6 (of incubation), the genital (g.) tubercle is formed in the ventral aspect of the embryo between the caudal fold of the amnion and the tail bud. On the ventral surface of the tail bud are paired g. swellings which flank the g. tubercle. Originating at the midline between the g. swellings is the g. crest which is joined cranially to the g. tubercle and later in development forms the ventral floor of the proctodeum (the most caudal cloacal compartment). By Day 8 the base of the g. tubercle has expanded caudolaterally to merge with the craniolateral extensions of the g. swellings. The g. swellings have likewise merged medially thus completing a collar-like structure around the g. tubercle. By Day 16, the dorsal and ventral lips of the cloaca have differentiated from the collar-like structure and the rounded, apical region of the g. tubercle gives rise to the primitive phallus. Further development of the external cloaca and phallus is limited primarily to the rotation of the phallus toward the ventral floor of the proctodeum and the concurrent shortening (longitudinally) of the proctodeum. Additional differentiation of the phallus occurs after hatching

Turkey hen fertility and egg production after artificial insemination and multiple oviduct eversion during the pre-laying period

The onset of egg production (mean 18 · 3 days after the onset of photostimulation) and the rate of egg production (flock averaged 4 · 9 eggs per bird per week for the first 8 weeks of egg production) were not affected by 5 days of twice daily oviduct eversion (\u27venting\u27) in the pre-laying period when compared to unvented controls. After the onset of photostimulation, pre-laying hens were inseminated twice daily on Days 12 to 16 with 3 μl semen containing 15 × 106 spermatozoa, and compared with groups of hens inseminated once daily on Days 15 and 16 with 15 μl semen containing 75 × 106 spermatozoa or 41 μl semen containing 200 × 106 spermatozoa. Fertility remained high for the first 5 weeks ofegg production. However, by Week 6 the fertility of the hens receiving frequent low doses of semen dropped significantly below that of the others, which suggests that multiple inseminations with a low semen volume containing relatively low numbers of spermatozoa does not lead to an increase in the efficacy of sperm transport and storage in the oviduct

Anatomical Basis of Sperm-Storage in the Avian Oviduct

The anatomical basis of oviductal sperm-storage in the avian oviduct is the sperm-storage tubule (SST). In the turkey this is composed of a simple columnar epithelium characterized by a supranuclear vacuole, which possibly contains lipid material, and appears to differentiate from the oviductal surface epithelium prior to full sexual maturation. Turkey SST epithelium was periodic-acid Schiff-negative and failed to bind four of the five lectins examined. Only winged pea agglutinin, which has an affinity for fucose-containing glycosidic residues, bound to some individual SST epithelial cells. Short-term cultures of oviductal mucosae containing SST showed aggregates of sperm associated with the spaces between adjacent folds and in surface openings assumed to be SST

Turkey Sperm Reside in the Tubular Glands in the Urodeum Following Artificial Insemination

A turkey hen in egg production requires 48 h after the last insemination to maximize the number of sperm in the uterovaginal junction sperm-storage tubules. Where the sperm that continue to fill the oviductal spermstorage sites during this 48-h period reside remains unknown. Histological sections of the juncture of the vagina with the urodeum, the central compartment of the cloaca, revealed deep tubular glands containing periodic acid- Schiff-positive secretory material. When examined 36 h after the last artificial insemination, sperm were observed in the lumen of the tubular glands associated with the urodeum. We suggest that sperm reside in the tubular glands within the urodeum and are released in association with the secretory activity of the tubular glands. These sperm then may ascend the vagina to continue to populate the sperm-storage tubules. Alternatively, the sperm in the tubular glands of the urodeum may be evidence of spermatorrhea and have no functional role in the fertilization process

Quantification of Spermatozoa in the Sperm-Storage Tubules of Turkey Hens and the Relation to Sperm Numbers in the Perivitelline Layer of Eggs

This study was conducted to determine the number of spermatozoa residing in the oviduct sperm-storage tubules (SST) and the relationship between these numbers and the number of spermatozoa embedded in the perivitelline layer of oviductal eggs after a single insemination of 200 X 104 spermatozoa. The SST of hens inseminated within one week before the expected onset of egg production were filled faster (4 h vs. 2 days) and possessed more spermatozoa (4.1 vs. 2.0 X 106) than the SST of hens inseminated after the onset of egg production. Furthermore, for hens in egg production, significantly fewer spermatozoa were recovered from the SST if the hen was inseminated within 2 h before or after oviposition than if inseminated more than 2 h before or after the oviposition. There was a strong positive correlation between the number of spermatozoa in the SST and the number of spermatozoa embedded in the perivitelline layer of the oviductal eggs (r = 0.85, p \u3c 0.01). These data show that the population of spermatozoa actually accepted by the SST is quite small relative to the number of spermatozoa inseminated and that maximum sperm-storage is achieved when the hen is inseminated just prior to the onset of egg production. It is suggested that the sperm-storage capacity of the oviduct and the quality of the semen sample can be estimated on the basis of numbers of spermatozoa embedded in the egg penvitelline layer

Quantification of Spermatozoa in the Sperm-Storage Tubules of Turkey Hens and the Relation to Sperm Numbers in the Perivitelline Layer of Eggs

This study was conducted to determine the number of spermatozoa residing in the oviduct sperm-storage tubules (SST) and the relationship between these numbers and the number of spermatozoa embedded in the perivitelline layer of oviductal eggs after a single insemination of 200 X 104 spermatozoa. The SST of hens inseminated within one week before the expected onset of egg production were filled faster (4 h vs. 2 days) and possessed more spermatozoa (4.1 vs. 2.0 X 106) than the SST of hens inseminated after the onset of egg production. Furthermore, for hens in egg production, significantly fewer spermatozoa were recovered from the SST if the hen was inseminated within 2 h before or after oviposition than if inseminated more than 2 h before or after the oviposition. There was a strong positive correlation between the number of spermatozoa in the SST and the number of spermatozoa embedded in the perivitelline layer of the oviductal eggs (r = 0.85, p \u3c 0.01). These data show that the population of spermatozoa actually accepted by the SST is quite small relative to the number of spermatozoa inseminated and that maximum sperm-storage is achieved when the hen is inseminated just prior to the onset of egg production. It is suggested that the sperm-storage capacity of the oviduct and the quality of the semen sample can be estimated on the basis of numbers of spermatozoa embedded in the egg penvitelline layer

Fertilizing capacity and ultrastructure of fowl and turkey spermatozoa before and after freezing

The fertilizing capacity, motility and ultrastructure of fowl and turkey spermatozoa were examined at various stages of the freezing process. For both species, fertility and motility were depressed after equilibration with dimethylsulphoxide at 5 °C. After freezing, motility was maintained at 55% for fowl spermatozoa and 40% for turkey spermatozoa; however, fertility was 55% for the fowl and 0% for the turkey. Qualitatively, the damage to the spermatozoa of both species was nearly identical, as revealed by scanning and transmission electron microscopy. The plasmalemma was the primary site of damage. \u27Bent\u27 spermatozoa, coiled tails and swollen mitochondria were also present. Damage to the acrosome was only observed in spermatozoa which had been frozen to -180 ° or -196 °C. These changes were attributed to adverse osmotic conditions. Binding of cationic ferritin to the plasmalemma of spermatozoa from both species remained unaltered

SHORT COMMUNICATIONS: Localization of Oviductal Sperm-storage Tubules in the American Kestrel (\u3ci\u3eFalco sparverius\u3c/i\u3e)

Sperm-storage tubules (SST) are discrete tubular invaginations of the bird\u27s oviduct epithelium located in the anterior end of the vaginal folds, a region generally referred to as the uterovaginal junction (UVJ). [We prefer to refer to the UVJ sperm-storage sites collectively as the SST (originally used by Mero and Ogasawara 1970) because SST accurately describes their function and structure.] Of the 27 recognized orders of birds, SST have been identified histologically only in selected species of Charadriiformes and Procellariformes (Hatch 1983), Galliformes (Fujii and Tamura 1963), Anseriformes (Pal 1977), and Passeriformes (Bray et al. 1975). Whether SST are structures common to all birds, as suggested by Gilbert (1979) and Hatch (1983), remains to be investigated. The presence of SST has not been demonstrated histologically in the Falconiformes. The high frequency of copulations in the course of laying one clutch of eggs prompted Corten (1973) to suggest that SST do not exist in the Northern Goshawk (Accipiter gentilis). Bird and Buckland (1976) observed the mean duration of fertility following artificial insemination of the American Kestrel (Falco sparverius) to be 8.1 days (range = 4-12 days). They suggested that SST were present in the oviduct. We present evidence that SST exist at the UVJ of the American Kestrel. In addition, a technique for the precise localization and isolation of oviductal mucosa containing SST is described

Cryptic female choice favours sperm from major histocompatibility complex-dissimilar males

Cryptic female choice may enable polyandrous females to avoid inbreeding or bias offspring variability at key loci after mating. However, the role of these genetic benefits in cryptic female choice remains poorly understood. Female red junglefowl, Gallus gallus, bias sperm use in favour of unrelated males. Here, we experimentally investigate whether this bias is driven by relatedness per se, or by similarity at the major histocompatibility complex (MHC), genes central to vertebrate acquired immunity, where polymorphism is critical to an individual's ability to combat pathogens. Through experimentally controlled natural matings, we confirm that selection against related males' sperm occurs within the female reproductive tract but demonstrate that this is more accurately predicted by MHC similarity: controlling for relatedness per se, more sperm reached the eggs when partners were MHC-dissimilar. Importantly, this effect appeared largely owing to similarity at a single MHC locus (class I minor). Further, the effect of MHC similarity was lost following artificial insemination, suggesting that male phenotypic cues might be required for females to select sperm differentially. These results indicate that postmating mechanisms that reduce inbreeding may do so as a consequence of more specific strategies of cryptic female choice promoting MHC diversity in offspring

Segregation of spermatozoa within sperm storage tubules of fowl and turkey hens

In avian species, spermatozoa reside in the oviduct for prolonged periods in specialized structures known as sperm storage tubules, but little is known about the relative distribution of spermatozoa in these tubules after successive inseminations by different males. The staining efficacies of various fluorescent dyes for fowl and turkey spermatozoa were evaluated to investigate one proposed mechanism of sperm competition. Hens were then inseminated at different intervals with stained and unstained spermatozoa to observe the spatial distribution of spermatozoa within the storage tubules. Several novel fluorescent lipophilic tracers that successfully stain mammalian spermatozoa either did not stain fowl or turkey spermatozoa, or greatly impaired sperm motility. In contrast, Hoechst 33342 readily stained sperm nuclei (fowl: 25 nmol l–1; turkey: 77 nmol l–1) within 4 h without inhibiting sperm motility, or affecting fertility or the hatching ability of the eggs. Hens were tandemly inseminated with equal numbers of stained or unstained spermatozoa at 24 h intervals and were killed 24 h after the final insemination to study sperm entry and storage within the tubules. Oviductal mucosa containing sperm storage tubules was removed, and individual tubules were classified as containing stained spermatozoa, unstained spermatozoa, a mixture of stained and unstained spermatozoa, or as not containing spermatozoa. Results from the present study indicate that spermatozoa from two different inseminations generally segregate into different storage tubules in both fowl and turkey hens. Storage tubules containing mixed populations of spermatozoa were found in only 4% of fowl and 12% of turkey storage tubules examined. Thus, the mechanism of last-male precedence does not appear to be due to the stratification of spermatozoa within the tubules