• Casein kinase and rhythmicity

In vertebrates, the pineal gland hormone melatonin plays a crucial role in the inner clock system. Produced at night, it regulates daily rhythms, and also annual rhythms such as seasonal changes in reproduction and energy balance.

Fish melatonin systems

The activity of melatonin is modulated by external photic signals, and in mammals it is driven by the suprachiasmatic nucleus (SCN) in the hypothalamus. In fish, scientists have found no SCN or any structure homologous to it. However, the fish pineal gland seems to have all the elements for the generation of circadian rhythmicity.

The Yoav Gothilf Lab (Tel Aviv University, Israel) has done some very in-depth research on the mechanism behind the light entrainment of the circadian system in zebrafish.

Casein kinase

For example, Sima Smadja Storz and her colleagues at this lab investigated the role of casein kinase 1 (CK1), which are enzymes that function as regulators of circadian rhythmicity (research published in PLoS ONE, 2013). They studied both cell cultures and zebrafish at different developmental stages.

Zebrafish larvae activity

To determine rhythmicity, the researchers looked at the activity patterns of zebrafish larvae in 48-well plates in DanioVision. Before the experiment, larvae were kept under 12h light/12h dim light conditions. The effects of specific CK1 inhibitors were measured by comparing the affected larvae’s total distance moved during a 10 minute dim light experiment to the activity of a control group. 

Diminished rhythmicity

Zebrafish larvae normally develop circadian rhythmicity when exposed to light/dark cycles, after which the animals are able to maintain this rhythmicity even under continuous light conditions. In larvae that were exposed to the CK1δ inhibition, rhythmicity was completely diminished. Specific CK1ε inhibition did not have as significant an effect.

Read more

Read more about this study in this blog post. Read about more studies on circadian rhythmicity in zebrafish in this other case about clock genes.  

Zebrafish research with DanioVision

Larvae activity and movement patterns are basic measurements used in many studies. They can reveal information on stereotypic and epileptic behaviors, circadian rhythmicity, motor control, movement disorders, neural development, and more.

DanioVision is a complete system designed for exactly these types of experiments with zebrafish larvae, and is often used in studies related to drug development, safety pharmacology, behavioral genetics, and circadian rhythmicity.

Free demo


The complete publication is accessible online: Smadja Storz, S.; Tovin, A.; Mracek, P.; Alon, S.; Foulkes, N.S.; Gothilf, Y. (2013). Casein Kinase 1δ Activity: A Key Element in the Zebrafish Circadian Timing SystemPLoS ONE8 (1), e54189.