Melatonin concentrations during larval and postlarval development of gilthead sea bream Sparus auratus: more than a time‐keeping molecule?

Abstract

In this study, melatonin (MEL) and thyroxine (T(4)) concentrations were measured during larval and postlarval development of gilthead sea bream Sparus auratus Hormones were measured in whole bodies of larvae or the head and trunk of postlarvae after 67 days of exposure to constant light, 24L:0D, constant darkness, 0L:24D or 12L:12D and in the plasma of 6 month juveniles kept under the 12L:12D, 0L:24D and 24L:0D regimes. High MEL concentrations in larvae suggested a distinct role of MEL in early organogenesis and development of S. auratus. In larvae, the gastro-intestinal tract seemed to be an important extrapineal and extraretinal source of MEL. No endogenous rhythm of MEL synthesis was demonstrated in 67 day larvae; however, in 6 month juveniles, it was evident. At early ontogenesis of S. auratus, the role of MEL is probably related mostly to the control of development and protection against free radicals, whereas its action as a time-keeping molecule develops later. The increase in T(4) concentration during the S. auratus larva-juvenile transition, i.e. between 50 and 70 days post-hatch, which was observed concurrently with the decrease of MEL concentration, may suggest an inverse relationship between T(4) and MEL.

The Effect of Orally Supplemented Melatonin on Larval Performance and Skeletal Deformities in Farmed Gilthead Seabream (Sparus aurata)

“…Moreover, melatonin has several functions related to vertebral bone growth in Atlantic salmon [19], promotes osteoblastic differentiation in mice, human mesenchymal stem cells (MSC)/peripheral blood mononuclear cells and MC3T3-E1 cells by increased messenger RNA levels of osteogenic markers and improved osseointegration in mice [20][21][22]. In gilthead seabream larvae, melatonin production begins immediately after hatching to reach maximum levels between the 6th and 10th day after hatching [23]. At this time, levels of hormones involved in growth, metabolism and development, i.e., growth hormone and prolactin, are very low [24,25].…”

Sleeping with the fishes: Looking under the bonnet of melatonin synthesis

“…Primarily produced in the pineal gland (Porter et al ., 1996), this hormone is referred to as biological time‐keeping hormone, and its levels peak during the night. Other than sleeping inducing properties, it also interacts with a number of other physiological processes, from reproduction (Dufour et al ., 2010; Migaud et al ., 2010) to development (Kalamarz et al ., 2009). Despite its importance, there is still not a complete understanding of how this hormone is synthesized in response to photoperiod.…”