Sexual dimorphism and perineal structure in Coendou prehensilis (Prehensile-tailed porcupine)

ABSTRACT:

Coendou prehensilis is a mammal that belongs to the Rodentia order, which consists of five suborders: Sciuromorfos, to which the squirrels belongs; Castorimorfos where we have the beavers; Myomorfos, which include the mice; Anomaluromorfos, Hare jumper, and Hystricomorfos, where we have the capybara. We used the porcupine clerk in the research (Coendou prehensilis), one male and one female, both adults. These animals were transferred to the Laboratory of Anatomy, Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of São Paulo (FZEA/USP), originating from roadaccidents in Pirassununga, SP (Registration n. 43274-1 SISBIO). The animals were fixed with 10% formaldehyde and dissected in the perineum region. The results showed that the only feature which allows us to differentiate males from females is the space between anus and the genitals of the animals; the male has a larger space than the female. The perineum is an extra cavity region with lozenge definition, and this definition is formed by interpubic bones, the pubic and processes of the pubic and ischium. The male Coendou prehensilis perineum consists of five major muscles, three arranged on the urogenital diaphragm surface (ischiocavernosus muscles, M. bulbocavernosus and Mm. bulboesponjosos) and two in the pelvic diaphragm (M. levator ani and M. penis retractor). The female’s perineum is composed by ischiocavernosus, bulbospongiosus, levator ani and external anal sphincter muscles. We conclude that both sexes have the ischiocavernosus muscles, Mm. bulboesponjosos, M. levator ani and external anal sphincter, and it is very important to study the perineal region of the animals, because understanding the function and location of each muscle we can contribute to future research on reproduction and animal behavior during copulation, helping to a better knowledge about reproductive potential of Erethizontidae rodents, and to contribute in the applied biotechnology development of reproduction, what can be helpful even in captivity reproduction of these animals besides the ones in free environment.

INDEX TERMS:
Sexual dimorphism; perineum; Coendou prehensilis; prehensile-tailed porcupine; Rodent; hystricomorpha; perineal muscles.