Melatonin synthesis and clock gene regulation in the pineal organ of teleost fish compared to mammals: Similarities and differences

speck, first identified in Drosophila melanogaster in 1910, is encoded by the Arylalkalamine N-acetyltransferase (AANAT1) gene

“…AANAT1 might affect sleep by more than inactivating biogenic amines. In vertebrates, AANAT1 orthologs have been termed a "Timezyme" ( (Klein, 2007)) because its rhythmic night-time expression and/or activity are the rate-limiting steps in the synthesis of melatonin at night (reviewed in ( (Saha, Singh, & Gupta, 2018)), (Zhao et al, 2019)). As in vertebrates, melatonin is present in Drosophila (Finocchiaro, Callebert, Launay, & Jallon, 1988) with levels rising at night (Callebert, Jaunay, & Jallon, 1991;Hintermann et al, 1996), and AANAT1 is thought to be the serotonin acetyltransferase used in its synthesis.…”

Development of innovative methods for induction of European eel (Anguilla anguilla) spermatogenesis

“…Molecularly there is some support for the importance of the light environment on eel reproduction, although opposite to what the results indicate. In particular, melatonin which is released during low light regimes (Falcón et al 2010;Saha et al 2018;Zohar et al 2010) have been shown to upregulate TH, and downregulate fshb and Lhb transcription in European eels (Sebert et al 2008). These results were further followed by decreasing steroid levels, thus it appears plausible that high melatonin levels are a strong reinforce of the DA block of European eel puberty (Sebert et al 2008).…”

“…Furthermore, several studies have indicated that low temperatures does have an effect on the PBG axis of European eels, other than simply blocking maturation (Baeza et al 2014;Pérez et al 2011;Mazzeo et al 2014;Ahn et al 2012;Gallego et al 2012;Peñaranda et al 2016a). This effect has also been hypothesized to potentially be a result of melatonin regulation (Burgerhout et al 2018;Saha et al 2018;Sebert et al 2008). E.g.…”

“…and cry3 in zebrafish. Circadian rhythm genes have further been suggested to regulate melatonin synthesis is mammals (Korf et al 2003) and fish (Vatine et al 2011;Saha et al 2018). Reversely, melatonin itself has also been shown to affect the transcription of circadian rhythm genes (Alonso-Vale et al 2008) and to be regulated by temperature in fish (Falcón et al 2010;Saha et al 2018).…”

“…Circadian rhythm genes have further been suggested to regulate melatonin synthesis is mammals (Korf et al 2003) and fish (Vatine et al 2011;Saha et al 2018). Reversely, melatonin itself has also been shown to affect the transcription of circadian rhythm genes (Alonso-Vale et al 2008) and to be regulated by temperature in fish (Falcón et al 2010;Saha et al 2018). Indeed, melatonin has been suggested as a key transmitter of environmental signals in fish (Dufour et al 2010;Burgerhout et al 2018), and changes in the melatonin level has been suggested as crucial for the onset of puberty (Malpaux et al 2001;Burgerhout et al 2018).…”