title: The Evolutionary Implications of Hemipenial Morphology of Rattlesnake Crotalus durissus terrificus (Laurent, 1768) (Serpentes: Viperidae: Crotalinae).
abstract: 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.
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, São Paulo, Brazil.
authors.forename: Marcovan
authors.initials: M
authors.lastname: Porto
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: de Oliveira
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pissinatti
authors.forename: Renata Lopes
authors.initials: RL
authors.lastname: Rodrigues
authors.forename: Julio Alejandro
authors.initials: JA
authors.lastname: Rojas-Moscoso
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Cogo
authors.forename: Konradin
authors.initials: K
authors.lastname: Metze
authors.forename: Edson
authors.initials: E
authors.lastname: Antunes
authors.forename: César
authors.initials: C
authors.lastname: Nahoum
authors.forename: Fabíola Z
authors.initials: FZ
authors.lastname: Mónica
authors.forename: Gilberto
authors.initials: G
authors.lastname: De Nucci
mesh_terms: D000818:Animals; D017839:Crotalus / Q000033:anatomy & histology*; D019143:Evolution, Molecular; D008297:Male