S. lalandi and G. chilensis are native species that present the greatest expectations for Chilean aquaculture diversification. However, the success of its production depends on efficient reproductive management, where minimally invasive methods of estimating the gonadal maturity are required to contributed to the fish welfare. To evaluate the use of epidermal mucus as an easily accessible matrix for the analysis related to ovarian maturation, in this work we show the pattern of different types of biomarkers in the epidermal mucus of S. lalandi and G. chilensis.
To achieve this objective, we compared mucus and plasma samples from adult females in different states of gonadal maturation of S. lalandi (5 to 10 years-15 to 25kg) acclimated to captivity and from wild adult females of G. chilensis (1.8 to 3 kg). Markers such as vitellogenin and estradiol were measured in both matrices. In general terms, it was only possible to detect estradiol in the plasma of some individuals with concentrations that did not exceed 2 ng/mL. However, vitellogenin could be detected in mucus (0.1 to 4 ng/mL), but with values tenfold less plasma level (1 to 40 ng/mL).
Testosterone was detected in plasma and mucus. In juveniles and mature individuals Testosterone was higher in plasma compared to mucus. A positive correlation (Pearson Coef. 0.85) could be observed between mucus and plasma.
In addition, considering the available knowledge related to the impacts of oxidative stress on the reproduction in different fish species, we evaluated the oxidative status in the mucus of both species by analyzing the antioxidant capacity using ORAC and DPPH. The results show that it is possible to measure antioxidant capacity in mucus and shows the antioxidant capacity of S.lalandi is higher than the antioxidant capacity of G. chilensis, (2800 μmol ET/mL and 140 μmol ET/mL, respectively) via ORAC and DPPH (1500 and 400 μmol ET/mL, respectively).
Our results indicate that the mucus of S. lalandi and G. chilensis adults is a matrix that can be used for the evaluation of gonadal development and the oxidative status of native species, and emerging species of Chilean aquaculture.