Melatonin and its Effects in Fishes: An Overview

Zachmann, Andreas; Ali, M. A.; Falcón, Jacky

doi:10.1007/978-1-4615-3042-8_12

Cited by 60 publications

(56 citation statements)

References 78 publications

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“…The retina also produces melatonin but it is used and metabolized locally, whereas melatonin from the pineal gland is released into the blood and has a paracrine function (Falcón, 1999). Melatonin regulates daily variations in locomotor activity, sleeping, skin pigmentation (which is absent in cavefish), and seasonal growth and reproduction (Zachmann et al, 1992a). Among these periodic activities, seasonal growth and reproduction are particularly important in the cave environment, where influxes of new food resources may occur only once a year during seasonal flooding (Mitchell et al, 1977).…”

Section: Role Of the Cavefish Pineal Eyementioning

confidence: 99%

“…In mammals, the light sensing function of the pineal gland appears to be absent. Another role of the pineal gland is entrainment of circadian rhythms via secretion of melatonin (Zachmann et al, 1992a). To mediate its light-detecting function, teleost pineal photoreceptor cells express the opsin-related photon-transducing pigments VA opsin, parapinopson and ERrod-like opsin (reviewed in Foster et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Shadow response in the blind cavefishAstyanaxreveals conservation of a functional pineal eye

Yoshizawa

Jeffery

2008

Journal of Experimental Biology

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SUMMARYThe blind cavefish Astyanax mexicanus undergoes bilateral eye degeneration during embryonic development. Despite the absence of light in the cave environment, cavefish have retained a structurally intact pineal eye. We show here that contrary to visual degeneration in the bilateral eyes, the cavefish pineal eye has conserved the ability to detect light. Larvae of two different Astyanax cavefish populations and the con-specific sighted surface-dwelling form (surface fish) respond similarly to light dimming by shading the pineal eye. As a response to shading, cavefish larvae swim upward vertically. This behavior resembles that of amphibian tadpoles rather than other teleost larvae, which react to shadows by swimming downward. The shadow response is highest at 1.5-days post-fertilization (d.p.f.), gradually diminishes, and is virtually undetectable by 7.5·d.p.f. The shadow response was substantially reduced after surgical removal of the pineal gland from surface fish or cavefish larvae, indicating that it is based on pineal function. In contrast, removal of one or both bilateral eye primordia did not affect the shadow response. Consistent with its light detecting capacity, immunocytochemical studies indicate that surface fish and cavefish pineal eyes express a rhodopsin-like antigen, which is undetectable in the degenerating bilateral eyes of cavefish larvae. We conclude that light detection by the pineal eye has been conserved in cavefish despite a million or more years of evolution in complete darkness. Supplementary material available online at

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Section: Role Of the Cavefish Pineal Eyementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shadow response in the blind cavefishAstyanaxreveals conservation of a functional pineal eye

Yoshizawa

Jeffery

2008

Journal of Experimental Biology

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“…In teleosts, research has predominantly focused on temperate, annual breeding species such as salmonids, pike Esox lucius and sea bass Dicentrarchus labrax (Iigo et al 1998;Bayarri et al 2002;Bayarri et al 2003). Results to date in these species have suggested a more decentralized organization in fish compared to that found in other vertebrates, where the pineal gland is light sensitive and independent of the SCN (or similar structure still to be found) or eyes (retina) and may contain, depending on the species, an endogenous oscillator that can sustain in vitro melatonin rhythms (Zachmann et al 1992a;Cahill 1996;Okimoto and Stetson 1999b;Iigo et al 2004). …”

Section: Introductionmentioning

confidence: 99%

Clock‐Controlled Endogenous Melatonin Rhythms in Nile Tilapia (Oreochromis niloticus niloticus) and African Catfish (Clarias gariepinus)

Martinez-Chavez

Al-Khamees

Campos‐Mendoza

et al. 2008

Chronobiology International

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The purpose of this work was to investigate the circadian melatonin system in two tropical teleost species characterised by different behavioural habits, Nile tilapia (diurnal) and African catfish (nocturnal). To do so, fish were subjected to either a control photoperiod (12L:12D), continuous light (LL) or darkness (DD) or a 6L:6D photoperiod. Under 12L:12D, plasma melatonin levels were typically low during the photophase and high during the scotophase in both species. Interestingly, in both species melatonin levels significantly decreased prior to the onset of light, which in catfish, reached similar basal levels to those during the day, demonstrating that melatonin production can anticipate photic changes probably through circadian clocks. Further evidence for the existence of such pacemaker activity was obtained when fish were exposed to DD, as a strong circadian melatonin rhythm was maintained. Such an endogenous rhythm was sustained for at least 18 days in Nile tilapia. A similar rhythm was shown in catfish although DD was only tested for four days. Under LL, the results confirmed the inhibitory effect of light on melatonin synthesis already reported in other species. Finally, when acclimatised to a short photo-cycle (6L:6D), no endogenous melatonin rhythm was observed in tilapia under DD, with melatonin levels remaining high. This could suggest that the circadian clocks cannot entrain to such a short photo-cycle. Additional research is clearly needed to further characterise the circadian axis in teleost species, identify and localize the circadian clocks and better understand the environmental entrainment of fish physiology.3

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“…As with all other vertebrate classes [4], the pineal gland of fishes secretes melatonin dur ing the dark phase [5][6][7], Melatonin release from the pineal gland of fishes occurs in vitro, for up to a week, and in some species, such as northern pike (Esox lucius) and white sucker (Catostomus commersoni), there is an in vitro endogenous circadian rhythmicity that per sists for several days [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

2-[<sup>125</sup>I]Iodomelatonin Binding in the Brains of Four Salmonids

et al. 1994

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[¹²⁵I]-Labelled iodomelatonin binding to brain membrane preparations was examined in adults of 4 species of salmonid fishes; 3 species were of cultured stock (Arctic charr, Atlantic salmon, rainbow trout) and 1 was taken from the wild (coho salmon). The specific binding of 2-[¹²⁵I]iodomelatonin to the brain membrane preparations collected from all 4 species was specific, stable, saturable, reversible and of high affinity. Competitive inhibition studies showed that only melatonin, 2-iodomelatonin, 6-chloromelatonin and N-acetylserotonin showed significant inhibition of radioligand binding. In the 4 species studied, the equilibrium dissociation constant (K_d) ranged from 9.3 ± 0.2 pmol/l in coho salmon to 13.2 ± 0.7 pmol/l in rainbow trout, and those in rainbow trout were significantly higher (p < 0.05) than in the others. The maximum number of binding sites (B_max) of the Atlantic salmon preparations (14.3 ± 0.7 fmol/mg protein) was significantly higher than those of the other 3 species (means rang-ing from 9.9 to 11.6 fmol/mg protein). Hill coefficients of all 4 species were close to unity indicating one class of binding site. The interspecies differences in K_d and B_max could not be correlated with phylogeny or life history of the various species. For the three cultured species, samples were collected at both mid-dark and mid-light to examine for diurnal variations; none were found.

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Melatonin and its Effects in Fishes: An Overview

Cited by 60 publications

References 78 publications

Shadow response in the blind cavefishAstyanaxreveals conservation of a functional pineal eye

Shadow response in the blind cavefishAstyanaxreveals conservation of a functional pineal eye

Clock‐Controlled Endogenous Melatonin Rhythms in Nile Tilapia (Oreochromis niloticus niloticus) and African Catfish (Clarias gariepinus)

2-[<sup>125</sup>I]Iodomelatonin Binding in the Brains of Four Salmonids

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