Aspects of the reproductive biology of tetra (Hemigrammus bellottii; Characiformes: Acestrorhampidae) in an area with anthropic activities in Eastern Amazon Amanda Victória Botelho da Silva, Antônio Elivelton Paiva de Oliveira, Juan Pablo Caldas Caldas, Yanne Alves Mendes, Maria Auxiliadora Pantoja Ferreira, et al. Environmental Biology of Fishes, 2026 The Amazon biome intense environmental impacts due to the exploitation of natural resources, with aquatic environments being particularly vulnerable to these threats. Hemigrammus bellottii is a fish that inhabits this environment and whose ecology is little know. This study aimed to describe reproductive aspects of H. bellottii in areas impacted by mining and agriculture in the Amazon hydrographic basin and to evaluate the effects of aluminum (Al) and iron (Fe) on its reproductive activity. Collections were carried out in the Capim River basin, southeastern Pará state, Brazil. A total of 195 specimens of H. bellottii (117 females and 78 males) were captured, and the stages of sexual maturation were determined by histological analysis. We evaluated the sex ratio, gonadosomatic index (GSI), allometric condition factor (K), maturation stages, and length at first maturity (L 50 ) during the study. GSI values peaked in January, March, and May for both sexes. The L 50 occurred at 22.07 mm for females and 23.13 mm for males. Only females showed significant variations in the GSI. The predictive effect of environmental variables and metals indicated that aluminum in water and sediment, total dissolved solids, and temperature negatively influenced the GSI of females, while aluminum in water and sediment, iron in sediment, precipitation, and total dissolved solids negatively influenced the GSI of males. Although Al and Fe concentrations were higher, especially in the dry season, the results indicate that such conditions did not influence the reproductive activity of the species, suggesting reproductive plasticity.
Reproductive biology of the spotfin hatchetfish Thoracocharax stellatus (Characiformes: Gasteropelecidae) in the Western Amazon Marcelle Fernanda de Oliveira Barbosa, Raquel Santos dos Santos, Felipe Fernando Silva Siqueira, Eduardo Silva do Nascimento Albuquerque, Natalia Rodrigues da Silva, et al. Neotropical Ichthyology, 2026 Fish reproduction in Amazonian rivers may be affected by environmental anthropization and changes in the hydrological regime. Thoracocharax stellatus is an ecologically important species, but its reproductive cycle remains poorly understood. Its reproductive patterns were evaluated in the Western Amazon across four hydrological seasons and areas with different environmental impact levels. Two areas were sampled monthly between February 2023 and January 2024, one with low ecological impact (LI) and another with high impact (HI). A total of 232 specimens were collected. Biometric and histological analyses determined the reproductive cycle and gonadal maturation phases (Immature, In Development, Able to Reproduce, Spawning Capable, Regression, Regeneration). Thorachocarax stellatus exhibits parcellated spawning, which is synchronized with the rainy season, peaking during high water. Females in low-impacted area matured at larger sizes with greater reproductive investment, whereas those in high-impacted environment exhibited earlier maturation and lower reproductive activity, suggesting environmental degradation negatively affects reproduction. GSI peaked during high water, and the Redundance analyses highlighted pH, temperature, and seasonality as the main factors influencing reproduction. Environmental integrity is crucial for T. stellatus reproduction, and habitat degradation, exacerbated by global warming, threatens population sustainability. Conservation strategies are needed to mitigate anthropogenic impacts on Amazonian aquatic ecosystems.
Morphological and ecological approaches in reproduction of the endemic catfish of the eastern Amazon Juliana R. Molica, Yanne A. Mendes, Bruno S. Prudente, Renata S. Oliveira, Juliana Caroline D. Pantoja, et al. Journal of Fish Biology, 2025 This study aimed to describe reproductive ecology based on morphological aspects of Peckoltia oligospila in stream rapids, eastern Amazon. A total of 186 fish (75 males and 111 females) were collected. The sex and gonadal maturity stage of these specimens were obtained based on histological characteristics of the gonads. The sex ratio, gonado‐somatic index (GSI), relative frequency of the different maturity stages, size at first sexual maturation, condition factor of the population, and fluviometry were evaluated during the study. There was a significant female frequency during the study. The population exhibited positive allometric growth without differences between sexes. GSI and relative frequency showing a reproductive period synchronized in February, and the species exhibited parcelated spawning. L50 was estimated at 5.85 and 7.39 cm for females and males, respectively. There were significant differences in the condition factor only in females that showed a highest value in August. Thus, based on the results P. oligospila has an intermediate strategy between the opportunistic and equilibrium strategies.
Gonadal development in scorpion mud-turtles, Kinosternon scorpioides, in a controlled environment Brenda Braga, Verônica Oliveira‐Bahia, Maria Auxiliadora Ferreira, José Ribamar Felipe Marques, Diva Araújo Guimarães Anatomical Record, 2025 Research on gonadal development including sexual differentiation of gonads in chelonians is essential for understanding the mechanisms that determine offspring sex and, consequently, the sex ratio of egg clutches. This directly impacts population structure, as sex ratios influence reproductive dynamics and species' long‐term viability. The aim of this study was to characterize the gonadal development of scorpion mud‐turtle ( Kinosternon scorpioides ). A total of 85 embryos from stages 12–26 were analyzed, kept under digital temperature control (28.5 ± 0.5°C). The reproductive system was dissected and processed for histological analysis using light and transmission electron microscopy. The average incubation time was 117.35 ± 9.5 days. From stage 12 onwards, gonadal ridges containing primordial germ cells (PGCs) were observed. At stage 14, the undifferentiated gonads consisted of cuboidal coelomic epithelial cells that invaginated to form cord‐like structures containing germ cells. At stage 20, at approximately 50 days of incubation, sexual differentiation of gonads was noted. The ovaries showed a cortical region containing oogonia and oocytes, and a medullary region with a stroma rich in vessels. The testes were characterized by a peripheral band of dense connective tissue beneath the tunica albuginea, and by the presence of seminiferous tubules occupying the central portion of the organ. The results of this study provide important information on the gonadal development of K. scorpioides , as the identification of the moment of gonadal differentiation, stage 20, makes it possible to understand the influence of the environment on sex determination. These findings provide support for the reproductive management of K. scorpioides and can be applied directly to the sexual control of populations in situ and ex situ.
Ovarian structure and oogenesis in King Tiger Pleco, L333, Hypancistrus seideli, (Siluriformes: Loricariidae) from the Amazon region Ivana Kerly da Silva Viana, Iann Leonardo Pinheiro Monteiro, Ryuller Gama Abreu, Maria Auxiliadora Pantoja Ferreira, Leandro Melo de Sousa, et al. Zygote, 2025 Summary In this study, we describe the ovarian structure and oogenesis up to the final maturation of oocytes of Hypancistrus seideli. A total of sixty females were used for gonadal analysis and subsequently submitted to light and scanning electron microscopy analyses. Four maturation stages were defined: immature, maturing, mature, and spawned. The oocytes were classified into four stages (I–IV), and the presence of atretic oocytes and post-ovulatory follicles was demonstrated. During oocyte development, changes were observed in color, size, and shape, as well as in the formation of the follicular complex. These results may support reproductive management in captivity, since the species has great commercial importance in the international ornamental fish market and lacks established reproductive protocols in aquaculture. To our knowledge, this is the first morphological characterization of oogenesis in this species, providing original and detailed data that may contribute to the development of captive breeding protocols and to reducing pressure on natural stocks.
Inhibition of acetylcholinesterase and histopathological changes in Aedes aegypti and Aedes albopictus larvae exposed to ethanolic extract of Acmella oleracea (L.) R.K. Jansen (Asteraceae) C. L. S. Cabeça, M. A. P. Ferreira, A. C. S. Ferreira, D. R. Alves, S. M. Morais, et al. Brazilian Journal of Biology, 2025 Important arboviruses for public health such as Dengue, Zika, and Chikungunya are transmitted by mosquito vectors, primarily Aedes aegypti and Aedes albopictus. The control of populations of these mosquitoes can be carried out by mechanical, chemical, and biological control. In view of the environmental impacts caused by synthetic chemical insecticides, the search for botanical larvicides with larvicidal potential has intensified. The objective of this work is to investigate the occurrence of acetylcholinesterase inhibition and histopathological alterations in Aedes aegypti and Aedes albopictus submitted to treatment with the ethanolic extract of the leaves of Acmella oleracea as possible mechanisms of larvicidal action. Larvae of Aedes aegypti and Aedes albopictus were exposed to treatment with the ethanolic extract of Acmella oleracea for an exposure period of 24 hours. After this time, larval mortality was recorded, and the larvae were separated in order to investigate the mechanisms of action. The ethanolic extract of Acmella oleracea had an LC50 of 29.15 µg.mL−1 and 16.00 µg.mL−1 against Aedes aegypti and Aedes albopictus, respectively. Significant reductions in acetylcholinesterase activity were observed in larvae treated with the ethanolic extract of Acmella oleracea, as well as histopathological changes in the midgut of treated larvae, including loss of integrity of the intestinal epithelium, vacuolation of the cell cytoplasm, and disruption of the peritrophic matrix. These results suggest that that the mechanism of action of the ethanolic extract of Acmella oleracea against Aedes larvae includes the potential to inhibit acetylcholinesterase and cause histopathological alterations in the midgut.
Anti-mullerian hormone (AMH) in pregnant buffaloes: maternal and fetal plasma concentrations and immunolocalization in the fetal gonads Nathalia Nogueira da Costa, Maria Auxiliadora Pantoja Ferreira, Priscilla do Carmo Azevedo Ramos, Alessandra Ximenes Santos, Marcela da Silva Cordeiro, et al. Animal Reproduction, 2025 Anti-Müllerian Hormone (AMH), a member of the TGF-β superfamily, plays a critical role in mammalian fertility. This study aimed to investigate AMH concentrations in pregnant buffalo cows and their fetuses, and to characterize the cellular distribution and immunolocalization of AMH within fetal gonads. Gonads were collected from 12 male and 14 female buffalo fetuses, fixed in 10% buffered formalin, and processed for routine histological analysis and immunohistochemical localization of AMH. Blood samples were collected from 26 pregnant buffalo cows and their corresponding fetuses into EDTA-coated tubes. AMH levels in both maternal and fetal blood were quantified using a commercially available bovine AMH ELISA kit. Significant (p < 0.05) inter-individual variations in maternal and fetal AMH concentrations were observed. In males, fetal AMH concentrations increased significantly with gestational age, with levels substantially higher compared to females at all gestational ages (52-1222 times higher). Immunohistochemistry revealed intense AMH immunoreactivity in the cytoplasm of pre-Sertoli cells in male fetuses. In females, no significant correlation was found between fetal AMH concentrations and follicular populations, although intense AMH immunostaining was observed in the cytoplasm of oocytes within primordial follicles. These findings suggest that fetal AMH concentrations in buffaloes are influenced by gestational age and sex, and that fetal AMH likely does not readily cross the placental barrier. Further investigations are warranted to elucidate the intricate role of AMH in gonadal development and function in buffaloes.
Influence of abiotic factors on the fecundity and ecological plasticity of a freshwater prawn in estuary and river environments Breno R. M. Silva, Gicelle M. F. Silva, Yanne A. Mendes, Juliana C. D. Pantoja, Ivana K. S. Viana, et al. Marine and Freshwater Research, 2024 Context Macrobrachium amazonicum is a freshwater prawn of socioeconomic importance in the Amazon region, whose growth, reproduction and fecundity vary according to the environment. Aims To determine which abiotic factors influence the size and fecundity of populations of M. amazonicum in estuary and river environments. Methods To do so, we captured a total of 255 ovigerous females, 181 from the estuary and 74 from the river, and measured temperature, total dissolved solids, turbidity, salinity, pH, dissolved oxygen and precipitation. Key results We found that turbidity, precipitation and dissolved oxygen explained the variation in M. amazonicum size, and that the estuarine females were larger and had more and smaller eggs than riverine females. Conclusions Precipitation, turbidity and dissolved oxygen were found to bedetermining factors for the ecological plasticity of M. amazonicum females in different environments. Implications Freshwater prawn species display different reproductive strategies for distinct environments, and understanding their fecundity is important to establish efficient management policies. In addition, this information should be useful to improve the cost–benefit ratio of freshwater prawn farming in the Amazon region.
Epididymal morphophysiology of adult collared peccaries (Pecari tajacu) Anna Patrycia Martins de Oliveira, Deise De Lima Cardoso, Ana Cássia Sarmento Ferreira, Maria Auxiliadora Pantoja Ferreira, Natália Inagaki de Albuquerque, et al. Brazilian Journal of Veterinary Research and Animal Science, 2016
Particle breakage behaviour at simulated pneumatic conveying impact conditions using a bench scale tester Chops 2015 8th International Conference for Conveying and Handling of Particulate Solids, 2015
