title: Melatonin in octopus (Octopus vulgaris): tissue distribution, daily changes and relation with serotonin and its acid metabolite.
abstract: Information regarding melatonin production in molluscs is very limited. In this study the presence and daily fluctuations of melatonin levels were investigated in hemolymph, retina and nervous system-related structures in the cephalopod Octopus vulgaris. Adult animals were maintained in captivity under natural photoperiod and killed at different times in a regular daily cycle. Levels of melatonin, serotonin (5-HT) and its acid metabolite (5-hydroxyindole acetic acid, 5-HIAA) in the hemolymph, retina, optic lobe, and cerebral ganglion were assayed by HPLC. Melatonin content fluctuated rhythmically in the retina and hemolymph, peaking at night. In the retina, but not in the other neural tissues, the rhythm was opposite to that of 5-HT, which displayed basal levels at night. Also, 5-HIAA levels in the retina were higher during the night, supporting that rhythmic melatonin production could be linked to diurnal changes in 5-HT degradation. The high levels of melatonin found in the retina point to it as the major source of melatonin in octopus; in addition, a large variation of melatonin content was found in the optic lobe with maximal values at night. All these data suggest that melatonin might play a role in the transduction of the light-dark cycle information for adjustment of rhythmic physiological events in cephalopods.
authors.affiliation: Lab. Fisioloxia Animal, Facultade de Bioloxía, Universidade de Vigo, Campus Universitario sn, 36310, Vigo, Spain.
authors.forename: José L P
authors.initials: JL
authors.lastname: Muñoz
authors.forename: Marcos A
authors.initials: MA
authors.lastname: López Patiño
authors.forename: Consuelo
authors.initials: C
authors.lastname: Hermosilla
authors.forename: Marta
authors.initials: M
authors.lastname: Conde-Sieira
authors.forename: José L
authors.initials: JL
authors.lastname: Soengas
authors.forename: Francisco
authors.initials: F
authors.lastname: Rocha
authors.forename: Jesús M
authors.initials: JM
authors.lastname: Míguez
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002940:Circadian Rhythm / Q000502:physiology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism*; D049831:Octopodiformes / Q000033:anatomy & histology / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D008550:Melatonin