The liver is an important metabolic organ in vertebrates. In anurans, the hepatosomatic index (HSI) reflects differences in energy storage and reproductive activities between males and females. The objective of this study was to describe the histological and histometric parameters of the livers of five species of Neotropical anurans, taking sex‐related differences into account. We also tested how the relationship between quantitative histometric variables and HSI varied between males and females in different species. Five males and five females of Elachistocleis matogrosso, Leptodactylus podicipinus, Lysapsus limellum, Pseudis platensis, and Trachycephalus typhonius were captured in central Brazil during the rainy season. HSI did not vary according to sex, but it varied among species. Elachistocleis matogrosso had the highest HSI due to the large hepatocyte size. The percentage of melanomacrophage centers (MMCs) was higher in P. platensis and L. limellum. In T. thyphonius, hepatocyte area was negatively associated with HSI, while the MMC percentages were positively associated with HSI. The liver plays a key role in reproductive activities, especially for species with explosive reproduction. Additionally, histometric patterns and volumetric structural density varied between males and females due to energy utilization for reproduction. Not only are these results important for future studies on hepatic morphophysiology but they also provide tools for evolutionary and phylogenetic studies.

Hematological parameters can provide key information to an animal health status. However, this information is usually hard to obtain. Here, we described hematological parameters of Leptodactylus podicipinus in the Brazilian Pantanal. We measured red blood cell morphometrics, erythrogram, and leukogram. We also tested for phylogenetic signal in erythrogram and leukogram of 48 frog species from 15 families, testing if body size explains their variation. Lymphocytes were the most abundant leukocytes (> 60%) in Leptodactylus podicipinus, followed by neutrophils (∼10%). Given that L. podicipinus is an abundant and widely distributed species in central Brazil, knowing its hematological pattern can help stablish a baseline and improve its use as a bioindicator of environmental degradation. Mean corpuscular hemoglobin and value contributed more to the phylomorphospace of erythrogram, in which Leptodactylus spp. and Hypsiboas raniceps had lower values of these variables, while Bufotes viridis and Hyla arborea had high values. The phylogenetic signal was spread throughout the dimensions of leukogram phylomorphospace. The variables that most contributed to it were total leukocytes counts, lymphocytes and neutrophils. We also found a moderate phylogenetic signal for both the erythrogram and leukogram. Accordingly, body size accounted for a low proportion of variation in both the leukogram (4.7%) and erythrogram (0.57%). By combining phylogenetic comparative methods with hematological parameters, our results add a new perspective on the evolution of blood cell physiology in frogs.

Pygocentrus nattereri is a carnivorous fish widely distributed in the Brazilian wetland and occupies different river strata. Based on the sexual maturity, the standard length (SL) has been used to categorize age and physiological attributes. However, hematological parameters and their relationship with age and growth features are unknow. Here, the aim was to evaluate the hematological profile and leukocyte data of juvenile and adult specimens, associating it with SL. Specimens of both sexes were weighted, and SL were measured for classify as juveniles (SL ≤16.0 cm) and adults (SL ≥16.1 cm). Blood was collected to perform the hemogram, for leukocyte quantification and ultrastructural descriptions. In general, hemogram values and leukocyte, lymphocyte, and monocyte counts were high in juveniles. Hemogram variables were negatively correlated with SL. Thrombocyte and neutrophil counts were higher in adults than in juveniles. SL was correlated with leukogram variables. Ultrastructural analysis showed that granular leukocyte count in P. nattereri was similar another fishes. PAS-positive granular leukocytes are slightly smaller than neutrophils and are characterized by dense elongated and semi-lunar shapes in the cytoplasm. Our results suggest that age-based SL may be useful for the analysis of the relationship between P. nattereri health status and wetland aquatic environments.