Circadian rhythms of clock gene expression in Nile tilapia (Oreochromis niloticus) central and peripheral tissues: influence of different lighting and feeding conditions

Abstract

The present research aimed to investigate the existence of clock gene expression rhythms in tilapia, their endogenous origin, and how light and feeding cycles synchronize these rhythms. In the first experiment, two groups of fish were kept under an LD cycle and fed at two different time points: in the middle of the light (ML) or in the middle of the dark (MD) phase. In the second experiment, fish fed at ML was fasted and kept under constant lighting (LL) conditions for 1 day. In both experiments, the samples from central (optic tectum and hypothalamus) and peripheral (liver) tissues were collected every 3 h throughout a 24 h cycle. The expression levels of clock genes bmal1a, clock1, per1b, cry2a, and cry5 were analyzed by quantitative PCR. All the clock genes analyzed in brain regions showed daily rhythms: clock1, bmal1a, and cry2a showed the acrophase approximately at the end of the light phase (ZT 8:43-11:22 h), whereas per1b and cry5 did so between the end of the dark phase and the beginning of the light phase, respectively (ZT 21:16-4:00 h). These rhythms persisted under constant conditions. No effect of the feeding time was observed in the brain. In the liver, however, the rhythms of clock1 and cry5 were influenced by feeding, and a shift was observed in the MD fish group (ZT 3:58 h for clock1 and 11:20 h for cry5). This study provides the first insights into the molecular clock of tilapia, a very important fish species for aquaculture. It also reveals the endogenous origin of clock gene rhythms and the ability of feeding time to shift the phase in some clock genes in the peripheral, but not the central, oscillator.

Distribution of endomorphin‐like‐immunoreactive neurones in the brain of the cichlid fish Oreochromis mossambicus

“…Moreover, SCN was not essential for the circadian rhythms in the mutant zebrafish cyclops larvae that lacked a ventral brain, including the region that gives rise to the SCN . However, the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms and the occurrence of daily rhythms that coincided with the expression of clock genes in optic tectum and hypothalamic regions of the brain were reported in the Nile tilapia Oreochromis niloticus . In the present study, sparse EM‐L‐IR perikarya were noted in the SCN, with their fibres directed towards the ventricular margin exhibiting CSF‐C type.…”

Interplay between the endocrine and circadian systems in fishes

“…This classification is presented in a functional way, without involving anatomical structures, as the same tissue could be acting as a clock that is entrained by the LD cycles, the feeding-fasting cycles and perhaps other zeitgebers. The dependence of clock gene expression rhythms in the central and peripheral tissues on LD cycles has been demonstrated in a number of teleost species, including zebrafish , Atlantic salmon (Salmo salar; Huang et al 2010), rainbow trout (Oncorhynchus mykiss; Patiño et al 2011), goldfish , Sánchez-Bretaño et al 2015b, sea bream (Sparus aurata; Vera et al 2013) or Nile tilapia (Oreochromis niloticus; Costa et al 2016).…”

Laboratory and field investigations on the effect of scheduled meal timings on growth performance and nutrient retention in an Indian major carp,Cirrhinus mrigala(Ham) fingerlings: Effect on nitrogen retention and excretion of metabolites

“…According to Sánchez–Vázquez, Madrid, Zamora and Tabata (); Pardini and Kaeffer (); del Pozo, Sánchez‐Férez and Sánchez‐Vázquez (), when rhythms persist and free run during several days under constant environmental conditions, it shows that these rhythms are under endogenous control and are considered as “circadian” rhythms. Since the diurnal feeding rhythm persisted under constant conditions, it also points that C. mrigala may also be possessing an endogenous molecular clock with similar characteristics to those observed in other fish species (see Costa et al., for references).…”

“…Control group was fed every time (at 0.5%) the feed was given to the other six experimental groups. The fish were hand fed and given a single meal only as has been done by many other researchers (Caldini et al,2013;Costa, Serrano, S anchez-V azquez & Olmeda, 2016;L opez-Olmeda, L opez-Garc ıa et al, 2012;Oliveira et al, 2013;Vera et al, 2007) at the fixed time interval and fed at 3 per cent BW on a diet containing 35% protein of plant origin (see Table 2 for ingredients and proximate composition) for the whole duration of 90 days.…”