Daily activity rhythms and the stress-related response in the wedge sole (Dicologoglossa cuneata Moreau, 1881)

To gain further insights on the wedge sole (Dicologoglossa cuneata Moreau, 1881) physiology and behavior, we evaluated its daily feeding and locomotor activity rhythms and compared three different feeding strategies: self-feeding (SF), diurnal feeding schedule (DS) and nocturnal feeding schedule (NS). 450 fish divided into three groups (three replicates each), were kept during 65days. SF had free access to self-feeders whereas DS and NS were fed four times a day. Physiological stress parameters as plasma cortisol, glucose, lactate, proteins and triglycerides were determined. Under the SF setting, the 91% of feeding demands occurred during the dark phase. Furthermore, locomotor activity was also higher during the scotophase (64% of the total activity). Significantly higher values for specific growth rate (SGR) and feed efficiency rate (FER) were observed in NS (0.49 and 0.48%day^-1, respectively); whereas SF consumed much less food than the rest and presented a high mortality rate (46%). Plasma cortisol levels were dramatically increased in SF and DS compared to NS (21.8±6.1, 65.8±30.3 and 0.3±0.1ngmL^-1, respectively). In summary, the wedge sole appears as a species with nocturnal locomotor and feeding behaviors and NS as the most appropriate feeding strategy. These new findings appear as key information for both the preservation of natural stocks of this species and its rearing.