RESUMO
Males of Proechimys guyannensis, a rodent living in the Amazon rainforest are studied in biomedical research because of their antiepileptogenic mechanism. Females are usually taken from experimental designs, because of limited data of this sex. This study aimed to characterize the estrous cycle to include females together with males in research in a more balanced approach. The estrous cycle of P. guyannensis based through exfoliative cytology, determination of the vaginal occlusion membrane state, and hormonal analysis. In this study, cytological analyses of vaginal smears were performed for three months, three times a day. The observed length of the estrous cycle was 247 ± 81 h (mean ± SD) with a reproductive phase of 27.08 ± 17.39 h (estrus stage). We observed a frequent presence of both the open and closed states of the vaginal membrane in the estrus stage (fertile period) although only the open stage is a prerequisite for successful copulation. High levels of progesterone and estradiol were detected in proestrus. Levels of follicle-stimulating hormone peaked at the estrus stage. These data will establish the parameters and subsidies to set the grounds for future research either for investigating the biology of this species or to use P. guyannensis in research that previously excluded females. Information regarding female Proechimys is relevant to not only describe the species but also explain the interaction between sex hormones and physiological responses. Moreover, the present results will enhance rigor and reproducibility in preclinical studies. In conclusion, P. guyannensis reproductive cycles can occur spontaneously and cyclically independent of mating stimulation and the high levels of FSH in the estrus stage, suggest that ovulation occurs in the late phase of the estrus.
RESUMO
The rodents Proechimys guyannensis have led a great interest because they are considered as hosts to several pathogens causing zoological diseases. Therefore, it is important to know their biological and physiological parameters. The age at first cubs delivery and the average of birth interval per female were evaluated. The estimated age at puberty was 83 days. The number of pups born per delivery did not differ significantly when associated with the female mating age. However, an increase in the average mortality rate correlated with the increase in delivery number per female was detected. There is no statistical difference neither in the litter size in different seasons of the year, nor in the body weight between sexes for all ages. Differences were found in the daily water consumption and in the feed intake in animals with approximately 100 days of age, perhaps owing to the increased need for energy intake due to sexual activity or even because they had not reached adult weight yet. The parameters assessed in the present study are of relevance for maintaining this species in captivity as a laboratory animal.
Roedores da espécie Proechimys guyannensis têm motivado grande interesse por serem frequentementeconsiderados como hospedeiros de diversos agentes patogênicos causadores de doenças. É importanteestabelecer seus parâmetros biológicos e fisiológicos; neste contexto, foram avaliadas a idade ao primeiroparto e a média de intervalo de natalidade por fêmea. A idade à puberdade foi estimada em 83 dias.O número de filhotes nascidos por parto não diferiu significativamente com a idade das fêmeas aoacasalarem. Observou-se aumento da taxa média de mortalidade de acordo com o aumento do númerode partos por fêmea. Não houve diferença estatística no tamanho da ninhada em diferentes estações doano; tampouco houve diferença de peso entre os sexos. Foram detectadas diferenças no consumo diáriode água e no consumo de ração em animais com menos e mais de 100 dias de idade, talvez em funçãode aumento da necessidade de consumo de energia pela atividade sexual ou mesmo por ainda não teremalcançado o peso corporal de adulto. Os parâmetros apresentados são relevantes para a futura manutençãodesta espécie em cativeiro como animal de laboratório.
