Morphological characterization of blue-and-yellow macaw (Ara ararauna) seasonal testicular variations in captivity

Abstract

The reproduction of monogamous wild birds in captivity it`s diffi cult and the apparent low fertility in males requires more investigations. The objective of the study was to test the hypothesis that wild bird species in captivity would present low reproductive potential, through the analysis of the morphological characteristics of Ara ararauna testicles, maintained in captivity, correlating them with the climate variations in the Cerrado Biome. For that, testicles were captured in April (dry) and October (rainy).The right and left testicles showed mean weight, gonadosomatic index, longer axis, and volume similar between the dry and rainy season. Only the shorter axis demonstrated higher values during the rainy season. The morphometric variables of the seminiferous tubules have also higher values during the rainy season. By these histological and morphometric characteristics of the seminiferous epithelium we can conclude that, during the rainy season, the testicles were in gonadal recrudescence, which precedes the reproduction phase. During the dry season, the testicles were in the rest phase of the seminiferous epithelium. Therefore, we concluded that the species in captivity, under Cerrado environmental conditions, have kept their reproductive potential, presenting a complete spermatogenic cycle during the rainy season, which can guarantee the species perpetuation.

Role of the testicular capsule in seasonal modulation of the testis

“…Though few reports on histomorphological alterations of the testicular capsule during maturation of the testis are available (Aire & Ozegbe, 2007;Maretta & Marettová, 2004;Mohanty et al, 2017;Pandey & Mohanty, 2015); detailed information on the seasonal cyclicity of this distinct component of the testis is unavailable. This study demonstrated the seasonal histomorphological alterations in the testicular capsule in an estrildid bird, Amandava Moreira et al, 2021). It binds with AR and mediates paracrine regulation of intra-testicular functions to induce secondary sexual characters and spermatogenesis as well as the development of muscle mass.…”

“…The AR helps to facilitate intra‐testicular actions of testosterone by autocrine/paracrine signals through the testicular capsule during the breeding cycle. Testosterone plays a crucial role in the maintenance of reproductive homeostasis during the breeding phase (Carvalho et al, 2015; Moreira et al, 2021). It binds with AR and mediates paracrine regulation of intra‐testicular functions to induce secondary sexual characters and spermatogenesis as well as the development of muscle mass.…”

“…It binds with AR and mediates paracrine regulation of intra‐testicular functions to induce secondary sexual characters and spermatogenesis as well as the development of muscle mass. In Anser anser f. domestica , Gallus domesticus , and Anas platyrhynchos , an abundance of AR protein has been found in the peritubular myoid cells and epididymal tissues during the reproductively active phase (Carvalho et al, 2015; Moreira et al, 2021). AR‐ir was localized in the spermatogonial cells and interstitium during the breeding cycle of Amandava amandava (Pandey et al, 2017).…”