Fisiologia reprodutiva das fêmeas de Potamotrygon wallacei Carvalho, Rosa e Araújo (2016): gonadotrofinas, hormônios esteroides, condição corporal e perfil bioquímico

Abstract

This study investigated during different moments of the reproductive cycle, the profile of gonadotropic (FSH and LH) and steroid (T, E2, P4 and 11-CT) hormones, as well as the biochemical variables (lipids, proteins, glucose, mineral salts and nitrogen compounds) in plasma and uterine fluid of Potamotrygon wallacei females. Seventy P. wallacei females were collected from which 26 were pregnant (8 in early pregnancy and 18 in late pregnancy), 28 postpartum and 16 in reproductive rest. It was noticed that pregnancy occurs during the whole period of ebb, while childbirth during drought and the beginning of the flood in Rio Negro. The cost of reproduction is high in cururu stingrays, demonstrated by the low values of relative condition factor (Kn - 0.93) in postpartum females. Like Kn, IHS tends to decrease gradually from early pregnancy (3.55%) to delivery (2.75%). Pregnancy may stimulate the mobilization of maternal mineral salts to the embryo, as the calcium (Ca2+), chloride (Cl-) and magnesium (Mg2+) plasma ions were in low concentration (2.50 mM, 109.26 mM and 0.94 mM) at this stage. In contrast, urea has an increase (12.36mM) during pregnancy, indicating that this is due to both maternal and embryonic ureogenic activities. Lipids are among the most important substrates involved in reproduction. The positive correlation between IHS and plasma triacylglycerol (TGC) concentration (p<0.005) reinforces the role of the liver as an important energy reserve organ for the pregnancy period. P. wallacei females with high levels of plasma steroids such as 17β-Estradiol (E2) and progesterone (P4) were found to have low plasma lipid content (TGC and total cholesterols). Similarly, both E2 and P4 showed low values during cururu stingray pregnancy, especially in late gestation (2060 pg/mL and 309.70 pg/mL), but increased after delivery (2679.70 pg/mL). 741.36 pg/mL) and is maintained during reproductive rest (2760.95 pg / mL and 458.25 pg / mL). P4 can act to maintain pregnancy, similar to mammals. As for androgens, only T varied between reproductive stages, assuming as precursor of E2. The concentrations of FSH and LH were quantifiable in the plasma of the cururu stingray, however, they did not vary according to the reproductive state. Our studies reveal that the female supplies the fetus by producing and/or transferring various nutritional compounds. However, the cost of reproduction is extremely high, suggesting that cururu stingray populations may be extremely dependent on environmental quality.