Anurans have a high reproductive diversity, which is closely associated with testicular dynamics and sperm production. This variety in reproduction is modulated by the sexual characteristics of reproductive strategies, such as polyandry. Leptodactylus podicipinus has high reproductive plasticity, wide geographical distribution, and polyandric behavior. Although aspects of the testes and sperm of this species are known, knowledge about the relationship between these aspects and reproductive investment is scarce. The present study evaluated the morphological characteristics of the testes and sperm in an urban environment. We used 11 sexually mature males from the city of Campo Grande, Mato Grosso do Sul, Brazil. The specimens were obtained from night excursions between April and September, the months that constitute the postrainy season. The biometric data (snout-vent length, testes, and body mass) were associated with sperm parameters (length of the spermatozoon head and tail). Stereological analyses of sperm morphology and the testes were performed. The results showed correlations between testis mass and spermatozoon length, which were positively related to head length and negatively related to tail length. The locular area and tail length were also negatively correlated. The percentage of normal spermatozoa was 97%; however, some sperm heads and tails exhibited different morphologies from the pattern described for the species. The germinative structure comprised more than 50% of the locular area composed of spermatozoa. The results of this study contribute to the knowledge of aspects related to the reproductive biology of L. podicipinus obtained from an urban environment.

Pygocentrus nattereri is a widely distributed species in the Neotropical region and a potential bio-indicator. Kidneys have functions in fish physiology, allowing them to live in different environments. We aimed to compare the histological characteristics of caudal kidneys between males and females, associating them with the renosomatic index (RSI). For this purpose, 15 males and 14 females were used for biometric and histological analyses. Structural volumetric density (SVD), renal corpuscle histometric measures, and hemosiderin and lipofuscin deposit frequency in macrophages melanogenic (MMs) were assessed. No biometric differences were observed between the sexes, but body weight and standard length were correlated with RSI. The SVD showed difference in hematopoietic tissue between female and males, whereas the density of the other structures was not different. The RSI was positively associated with hematopoietic tissue and proximal tubule density in contrast to distal tubules, blood vessels, collecting ducts and MMs. Females exhibited a higher renal corpuscle area, glomerulus area, distal tubule diameter, collecting tubule area, and collecting tubule lumen area. These differences may be due to metabolic differences between males and females. Sex effect in P. nattereri may define punctual differences in future studies on the metabolism and immunity of this species.