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The penis of ostrich (a-c) and emu (d-f). The ostrich penis protrudes from the cloaca during micturition and defecation (a). Its conical structure bends towards the left; the left fibrolymphatic body (l.f.b.) is larger than the right (r.f.b.) (b). The paralymphatic bodies (p.b.) are paired and located under the urodeum, here shown from the ventral aspect (c). The emu penis has a typical spiral shape (d), and the tip of the penis is eversible, with a single spiral (e). The paralymphatic bodies are located under the urodeum (f). * Dorsal aspect of the cloaca. S.s, Sulcus spermaticus. Scale bar: 2 cm. I, intestine; c.m., cloacal muscles.

The penis of ostrich (a-c) and emu (d-f). The ostrich penis protrudes from the cloaca during micturition and defecation (a). Its conical structure bends towards the left; the left fibrolymphatic body (l.f.b.) is larger than the right (r.f.b.) (b). The paralymphatic bodies (p.b.) are paired and located under the urodeum, here shown from the ventral aspect (c). The emu penis has a typical spiral shape (d), and the tip of the penis is eversible, with a single spiral (e). The paralymphatic bodies are located under the urodeum (f). * Dorsal aspect of the cloaca. S.s, Sulcus spermaticus. Scale bar: 2 cm. I, intestine; c.m., cloacal muscles.

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The erection mechanism of the penis in most vertebrates is blood vascular. A major evolutionary transition occurred in birds, where the erection mechanism changed from blood vascular to lymphatic. Within birds, however, the erection mechanism of the ratite penis has remained unknown. Early work suggested that the erection mechanism in ostrich Strut...

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Context 1
... is a single shaft that bends to the left because of the asymmetry in size of the fibrous bodies. The fibrous bodies have been reported to lack any erectile spaces (Müller, 1836), although King (1981) doubts this conclusion. During copulation and defecation, the penis protrudes from the floor of proctodeum where it usually rests (Gerhardt, 1933; Fig. 1a and b). Movement of the penis is achieved through the action of the muscles that lift and retract the phallus (musculus levator phalli and musculus retractor phalli). The ostrich penis lacks an invaginated portion of the penis, and therefore, it is classified as a type A phallus (lacking a blind tubular cavity; King, ...
Context 2
... penis of the emu (Fig. 1d) was described in some detail by Müller (1836), Boas (1891) and Gerhardt (1933), again without noting the erection mechanism. The emu penis has asymmetric fibrous bodies and an eversible region at the tip (Fig. 1e). The tip is invaginated at rest, and it is therefore classified as a type B phallus (possessing a blind tubular cavity; ...
Context 3
... penis of the emu (Fig. 1d) was described in some detail by Müller (1836), Boas (1891) and Gerhardt (1933), again without noting the erection mechanism. The emu penis has asymmetric fibrous bodies and an eversible region at the tip (Fig. 1e). The tip is invaginated at rest, and it is therefore classified as a type B phallus (possessing a blind tubular cavity; King, ...
Context 4
... both emu and ostrich, we found paralymphatic bodies located on either side of the urodeum, underneath the cloacal muscles ( Fig. 1c and f). In ostrich, they are large ellipsoids of a spongy consistency measuring 8 cm ¥ 4 cm (Fig. 1c), while in emu, they measure 4.0 cm ¥ 2.5 cm (Fig. ...
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... both emu and ostrich, we found paralymphatic bodies located on either side of the urodeum, underneath the cloacal muscles ( Fig. 1c and f). In ostrich, they are large ellipsoids of a spongy consistency measuring 8 cm ¥ 4 cm (Fig. 1c), while in emu, they measure 4.0 cm ¥ 2.5 cm (Fig. ...
Context 6
... both emu and ostrich, we found paralymphatic bodies located on either side of the urodeum, underneath the cloacal muscles ( Fig. 1c and f). In ostrich, they are large ellipsoids of a spongy consistency measuring 8 cm ¥ 4 cm (Fig. 1c), while in emu, they measure 4.0 cm ¥ 2.5 cm (Fig. ...
Context 7
... 2c). Few blood vessels are seen within the fibrous bodies or the elastic vascular body. The collagenous connective tissue in the elastic body is irregular, and fibers run in all directions (Fig. 2c). In all three emu specimens observed, the eversible portion of the penis was small, with a single full turn of the sulcus spermaticus at the tip (Fig. 1e). In cross-section, the collagen matrix in the emu penis is dense and disorganized just as in ostrich, but the separation between the fibrous bodies and the elastic vascular body is well demarcated. In addition, the emu has a tubular cavity lined with secretory cells (the blind tubular cavity of a type B penis), surrounded by dense ...
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... the male lowers his cloaca to meet the female's cloaca, release of the sphincter muscles allows the lymph to flow freely into the large lumen of the penis causing explosive eversion (Brennan, Clark & Prum, 2010). Because ejaculation happens at the moment of maximum eversion, the lymph is also pushing the seminal fluid from the base of the ejaculatory groove, along the length of the sulcus spermaticus to the tip of the penis (Brennan et al., 2010). Immediately after ejaculation, the penis is flaccid, and it is slowly returned to the cloaca (Brennan et al., 2010). ...
Context 9
... body of the ostrich penis occupies most of the procto- deum, and it must be extruded from the vent to allow defeca- tion and urination ( Fig. 1a; Fowler, 1991). This penis extrusion is carried out by muscular action of a pair of muscles, the m. levator phalli. It is likely that in both ostrich and emu, the penis is similarly protracted by muscular action when copulation takes place, and that lymph then flows in to aid in engorgement and ejaculation. Reports that the ostrich ...

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Citations

... However, larger birds such as duck, ostrich and emu have penis. Ostrich has a conical-shaped penis that is wider at the base as given by Brennan and Prum [8]. Even if birds reproduce through internal fertilization, 97% of the males absolutely lack a functional intromittent organ. ...
Chapter
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There are about 10,400 living avian species belonging to the class Aves, characterized by feathers which no other animal classes possess and are warm-blooded vertebrates with four-chamber heart. They have excellent vision, and their forelimbs are modified into wings for flight or swimming, though not all can fly or swim. They lay hard-shelled eggs which are a secretory product of the reproductive system that vary greatly in colour, shape and size, and the bigger the bird, the bigger the egg. Since domestication, avian species have been basically reared for eggs, meat, pleasure and research. They reproduce sexually with the spermatozoa being homogametic and carry Z-bearing chromosomes, and the blastodisk carries either Z-bearing or W-bearing chromosomes, hence, the female is heterogametic, and thus, determines the sex of the offspring. The paired testes produce spermatozoa, sex hormones and the single ovary (with a few exceptions) produces yolk bearing the blastodisk and sex hormones. Both testis and ovary are the primary sex organs involved in sexual characteristics development in avian. In avian reproduction, there must be mating for fertile egg that must be incubated to produce the young ones. At hatch, hatchling sex is identified and reared to meet the aim of the farmer.
... The present study revealed that, the phallus of the goose was an intromittent type, it was a spiral coiled structure invested within a double peritoneal membrane (Phallic pouch), similar to King (1981), Kevin (2000), Brennan et al. (2009) andEl Gindy et al. (2016) in duck and King and McLelland (1984), Brennan and Prum (2012) in Ostrish and kiwis and Rajendranath et al. (2013) in emu, while, the phallus of the turkey was an non intromittent type and lied on the crest of the ventral lip of the vent, these results similar to the results in the domestic fowl that were confirmed by Bull et al. (2007). ...
... While in the turkey, the phallus was composed of a median phallic groove flanked on either side by lateral phallic bodies. Regarding the total length of the phallus, it was ranged from 8-10cm during fully erection in goose, while, reached 22cm in Argentine duck (Kevin 2000), 20cm in ostrich (Elias et al. 2007;Brennan and Prum 2012), 25-30cm in ostrich (Yong and Zhanjun 2011) who stated that this penis was very strong, while the penis of the turkey as in chickens was not strong, 3 cm in rhea (Góes et al. 2010), 8.5 cm in Laysan ducks and 5.3cm in Mandarin ducks (Herrera et al. 2014) and ranged from 13-15cm in Balady duck (El Gindy et al. 2016). The phallus had some black coloration on its outer surface in Mandarin ducks and also lacked this coloration in the Laysan ducks that was recorded by Herrera et al. (2014), this coloration was not recorded in the goose in this study and also was not recorded by El Gindy et al. (2016) in Balady duck. ...
... The penis of goose had the inner glandular part lined with secretory cells surrounded by outer cutaneous layer of collagen fibers; the latter layer was composed of two distinct parts: an inner layer of lose circumferential and an outer dense disorganized layer in between the two layers was large lymphatic lumen. These results agreed with Brennan et al. (2009) in mallard duck, Prum (2012) in emus, El Gindy et al. (2016) in Balady duck, while Brennan and Prum (2012) in ostrich recorded that, the penis lacked a blind tubular cavity and formed of fibrous bodies composed of dense, largely disorganized collagen matrix except in the areas surrounded the narrow lymphatic spaces. ...
Research
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AB S T RA C T The work applied on the phallus of the adult goose and turkey to give knowledge for the phallus functional morphology and the mechanism of copulation of these domestic birds. It helped the surgical interfering of the wild geese and the artificial insemination in the turkey for commercial production. The phallus of the goose and the phallic bodies of the turkey were demonstrated by anatomical, histological, histochemical and scanning electron microscopy to compare the micromorphological features. The goose has an intromittent type phallus. It consisted of inner glandular part and outer cutaneous one. The former lined by mucous secretory cells, while the later cover externally by stratified squamous non-keratinized epithelium. The turkey phallus was a non-intromittent type. It composed of a median phallic furrow on the crest at the ventral vent lip and flanked on either side by lateral phallic bodies. The later lined by stratified squamous non-keratinized and supported by longitudinal oriented skeletal muscle which circular in the furrow between two phallic bodies. Additionally, lymphatic aggregation was observed in phallus of two birds. This study helped in comparative studies and surgical operations.
... Male turtles and crocodilians each have a single phallus with an open phallic sulcus (Gadow 1887;Reese 1915Reese , 1924Zug 1966;Ferguson 1985;Raynaud and Pieau 1985;Kelly 2004;Ziegler and Olbort 2007;Moore et al. 2012). Similar to crocodilians, basal birds have an intromittent phallus with an open phallic sulcus; however, most extant bird species have either a reduced, non-intromittent phallus or lack a phallus altogether (Liebe 1914;King 1979b;Oliveira and Mahecha 2000;Rao and Vijayaragavan 2000;Brennan et al. 2010;Brennan and Prum 2012;Rajendranath et al. 2014). Tuataras are sister to squamates (Townsend et al. 2004;Crawford et al. 2012;Pyron et al. 2013) and have no phallus (Günther 1867;Gadow 1887). ...
... Squamate hemipenes (King 1979b;Arnold 1986;Capel et al. 2011;Porto et al. 2013) and some avian intromittent phalluses (Gadow 1887;King 1979b;Oliveira and Mahecha 2000;Brennan et al. 2010;Brennan and Prum 2012) are stored in an inverted state when at rest; during copulation the phallus is everted upon increased hydrostatic pressure generated by elevated fluid volume in endothelial spaces that are supported by connective tissue meshes. Interestingly, different fluids produce hydrostatic pressure in reptilian penile endothelia. ...
... Interestingly, different fluids produce hydrostatic pressure in reptilian penile endothelia. Lymphatic vasculature supplies hydrostatic pressure to the avian phallus (King 1979b;Oliveira and Mahecha 2000;Rao and Vijayaragavan 2000;Brennan et al. 2008;Brennan and Prum 2012;Rajendranath et al. 2014) and squamate hemipenes were historically believed to be inflated by a combination of both blood and lymph (Dowling and Savage 1960;Arnold 1986); however, more recent evidence suggests that only blood is active in hemipenial eversion (Capel et al. 2011;Porto et al. 2013). Similar to the mammalian baculum, calcified hemibacula have been described in two families of squamates, Gekkonidae and Varanidae (Shea and Reddacliff 1986;Böhme 1995;Rösler and Böhme 2006). ...
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An intromittent phallus is used for sperm transfer in most amniote taxa; however, there is extensive variation in external genital morphology within and among the major amniote clades. Amniote phalluses vary in number (paired, single, or rudimentary), spermatic canal morphology (closed tube or open sulcus), and mode of transition between resting and tumescent states (inflation, rotation, eversion, or muscle relaxation). In a phylogenetic context, these varying adult anatomies preclude a clear interpretation for the evolutionary history of amniote external genitalia; as such, multiple hypotheses have been presented for the origin(s) of the amniote phallus. In combination with historic embryological studies, recent comparative developmental analyses have uncovered evidence that, despite extensive morphological variation in adult anatomy, embryonic patterning of the external genitalia is similar among amniotes and begins with emergence of paired swellings adjacent to the cloaca. External genital development in mammals, squamates (lizards, snakes, and amphisbaenians), Rhyncocephalians (tuataras), turtles, crocodilians (alligators, crocodiles, and gharials), and birds proceeds by iterative sequences of budding and fusion events, initiated by emergence of paired swellings adjacent to the embryonic cloaca. Conservation of the embryonic origins, morphogenetic processes, and molecular genetic mechanisms involved in external genital development across Amniota supports derivation from the common ancestor of amniotes, and suggests that lineage-specific divergence of later patterning events underlies the variation observed in extant adult amniote phallus morphology.
... Intromittent organ made of fibroelastic connective tissue without smooth muscle is found in ratites and Galloanseridae birds [10], crocodiles [2], turtles [3], [11], the lizard Lacerta agilis [12] and the hemipenes of the following snakes: Vipera berus [13], [29], Natrix natrix [13], [29], Bittis arietans arietans [14]; this condition was cited to snakes in general by Dowling and Savage [15]. All those reports were based on poor histological material and were not definitive. ...
... In birds, the penis tumescence is a lymphatic phenomenon without participation of blood [2], [10]. In this case, a gland resting in the floor of the cloaca supports the phallus with the necessary volume of lymph. ...
... The relaxation and contraction of the smooth muscle controls the erection and detumescence, respectively, of the mammal penis. In birds [2], [10], crocodiles [2], turtles [3], [11], Lacerta agilis [12] and some snakes [13]–[15], the corpora cavernosa is formed by fibrous elastic connective tissue. Bundles of muscle are generally absent in penis of this group, but was noted in rattlesnake Crotalus durissus cascavella [16], in Crotalus durissus terrificus [17], in amphisbaenid [18] and Uroastix hardwickii lizard [19]. ...
Article
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Most amniotes vertebrates have an intromittent organ to deliver semen. The reptile Sphenodon and most birds lost the ancestral penis and developed a cloaca-cloaca mating. Known as hemipenises, the copulatory organ of Squamata shows unique features between the amniotes intromittent organ. They are the only paired intromittent organs across amniotes and are fully inverted and encapsulated in the tail when not in use. The histology and ultrastructure of the hemipenes of Crotalus durissus rattlesnake is described as the evolutionary implications of the main features discussed. The organization of hemipenis of Crotalus durissus terrificus in two concentric corpora cavernosa is similar to other Squamata but differ markedly from the organization of the penis found in crocodilians, testudinata, birds and mammals. Based on the available data, the penis of the ancestral amniotes was made of connective tissue and the incorporation of smooth muscle in the framework of the sinusoids occurred independently in mammals and Crotalus durissus. The propulsor action of the muscle retractor penis basalis was confirmed and therefore the named should be changed to musculus hemipenis propulsor.The retractor penis magnus found in Squamata has no homology to the retractor penis of mammals, although both are responsible for the retraction of the copulatory organ.
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We studied the morphology of the copulatory organ of Ortalis canicollis and its evolution in birds. The phallus of O. canicollis is intromittent, with a blind tubular cavity and two distinct regions when erect: the base of the phallus, which shows the mucosa smooth and lined by a pseudostratified columnar epithelium, and the tubular portion, which shows the mucosa lined by a keratinized stratified squamous epithelium with little knobs. The phallus includes two vascular bodies at the cranial portion in the urodeum. A fibrocartilaginous body anchors the tubular portion therefrom up to the eversible portion. A branched elastic ligament inserts on different regions of the tubular portion. The phallus is plesiomorphic in birds and it has disappeared in Megapodius, Leipoa and Neoaves. The asymmetric phallus evolved early and it was retained in the basal branches of birds. The intromittent phallus is plesiomorphic in birds (found in Archosauria’s ancestor), but Crypturellus, Numididae, Odontophoridae and Phasianidae have developed a non- intromittent phallus a posteriori. The blind tubular cavity and the fibrocartilaginous body evolved as an adaptive convergence many times in birds. Therefore, this study shed some light on morphological aspects of the phallus and contributed to understand its evolution in birds.
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