title: 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.
authors.affiliation: Biology Department, Macalester College, St. Paul, Minnesota 55105, USA. tilden@macalester.edu
authors.forename: A R
authors.initials: AR
authors.lastname: Tilden
authors.forename: P
authors.initials: P
authors.lastname: Rasmussen
authors.forename: R M
authors.initials: RM
authors.lastname: Awantang
authors.forename: S
authors.initials: S
authors.lastname: Furlan
authors.forename: J
authors.initials: J
authors.lastname: Goldstein
authors.forename: M
authors.initials: M
authors.lastname: Palsgrove
authors.forename: A
authors.initials: A
authors.lastname: Sauer
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis / Q000378:metabolism*; D003386:Brachyura / Q000737:chemistry / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm / Q000502:physiology*; D005121:Extremities / Q000502:physiology; D016166:Free Radical Scavengers / Q000032:analysis / Q000378:metabolism*; D006458:Hemolymph / Q000737:chemistry; D008297:Male; D008550:Melatonin / Q000032:analysis / Q000502:physiology*; D017440:Photoperiod; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry / Q000502:physiology; D011863:Radioimmunoassay; D012038:Regeneration / Q000502:physiology*
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D008550:Melatonin