Melatonin cycle in the fiddler crab Uca pugilator and influence of melatonin on limb regeneration

Abstract

Melatonin was measured over 24 hr in the eyestalks of Uca pugilator by means of radioimmunoassay; crabs were acclimatized either to a LD 12:12 photoperiod or constant darkness. A significant peak occurred at 13.00 hr in the LD 12:12 crabs. A photophase peak in melatonin has only been reported in one other species, also a crustacean. In constant darkness, two melatonin peaks occurred, one at 16.00 hr and the other 12 hr later; these results suggest that the melatonin cycle is a true circadian rhythm. HPLC with ultraviolet-visible detection was used to confirm the identity of melatonin immunoactivity. The influence of melatonin on regeneration of the walking legs was also examined: eyestalks were either removed or left intact, and limb bud length was measured every other day for at least 17 days in control and melatonin-treated crabs (60 microg ml(-1) seawater). Melatonin significantly increased the rate of limb regeneration in both eyestalk-intact and eyestalk-removed groups; this is contrary to results of regeneration studies in other phyla, in which similar melatonin concentrations inhibited regeneration.

Circadian clocks in crustaceans: identified neuronal and cellular systems

“…Even in the haemolymph of N. norvegicus melatonin was recently identified by liquid chromatography combined with mass spectrometry (LCMS) (261). In crabs and Norway lobsters, melatonin contents clearly showed diurnal variations (260,261). In crabs, melatonin even increased the rate of limb regeneration (260).…”

“…In crabs and Norway lobsters, melatonin contents clearly showed diurnal variations (260,261). In crabs, melatonin even increased the rate of limb regeneration (260). The other important marker indicating the presence of melatonin is AA-NAT, which has been detected in P. clarkii by a specific radioactive substrate reaction using 3 H-acetyl-CoA and 5-HT (262).…”

“…However, it cannot be excluded that many 5-HT-ir neurons, in addition, express AA-NAT and HIOMT and produce NAS and finally melatonin, respectively, because they had just been immunostained only for their 5-HT precursor. Therefore, it is certainly decisive to identify melatonin in extracts of crustacean nervous systems as has been done first in brains of crayfish and prawns by use of radioimmunoassay (RIA) combined with thinlayer chromatography (259) or later in eyestalks of crabs U. pugilator by RIA combined with high performance liquid chromatography (260). Even in the haemolymph of N. norvegicus melatonin was recently identified by liquid chromatography combined with mass spectrometry (LCMS) (261).…”

Role of melatonin in the control of depth distribution of Daphnia magna

“…It functions in free radical scavenging, the regulation of body mass and energetic metabolism, and is a key component of the biological clock responsible for modulating physiological rhythms (for reviews see Hardeland & Poeggeler, 2003;Pandi-Perumal et al, 2006). With regard to the effects of melatonin in invertebrates, it has been shown that application of this hormone can alter locomotory activity in the cricket Acheta domesticus (Yamano et al, 2001) and the crayfish Procambarus clarkii (Tilden et al, 2003); it can influence regeneration processes in the planarian Dugesia japonica (Yoshizawa et al, 1991), the nemertean Lineus lacteus (Arnoult & Vernet, 1995) and the crab Uca pugilator (Tilden et al, 1997b); and it can alter life history and reproduction in the aphid Acyrthosiphon pisum (Gao & Hardie, 1997) and the dinoflagellate Gonyaulax polyedra (Balzer & Hardeland, 1991).…”

Melatonin does not affect the black pigment migration in the crab Neohelice granulata

“…In this same species, Tilden et al (2003) reported that injections of melatonin increased the synaptic transmission in the neuromuscular junctions. In the fiddler crab Uca pugilator, melatonin increased the rate of limb regeneration (Tilden et al 1997) and caused a phase delay of the circadian rhythm of glucose and lactate in the haemolymph (Tilden et al 2001).…”