title: Daily variation of melatonin content in the optic lobes of the crab Neohelice granulata.
abstract: Melatonin is a biogenic amine, known from almost all phyla of living organisms. In vertebrates melatonin is produced rhythmically in the pinealocytes of the pineal gland, relaying information of the environmental light/dark cycle to the organism. With regard to crustaceans only a handful of studies exist that has attempted to identify the presence and possible daily variation of this substance. We set out to investigate whether in the crab Neohelice granulata melatonin was produced in the optic lobes of these animals and underwent rhythmic fluctuations related to the daily light/dark cycle. Our experimental animals were divided into three groups exposed to different photoperiods: normal photoperiod (12L:12D), constant dark (DD), and constant light (LL). The optic lobes were collected every 4 hours over a 24-h period for melatonin quantification by radioimmunoassay (RIA). N. granulata kept under 12 L:12D and DD conditions, showed daily melatonin variations with two peaks of abundance (p<0.05), one during the day and another, more extensive one, at night. Under LL-conditions no significant daily variations were noticeable (p>0.05). These results demonstrate the presence of a daily biphasic fall and rise of melatonin in the eyestalk of N. granulata and suggest that continuous exposure to light inhibits the production of melatonin synthesis.
authors.affiliation: Programa de Pós-Graduacão em Fisiologia Animal Comparada, Departamento de Ciências Fisiológicas, Fundação Universidade Federal do Rio Grande, Rio Grande-RS, 96201-900 Brazil.
authors.forename: Fábio Everton
authors.initials: FE
authors.lastname: Maciel
authors.forename: Márcio Alberto
authors.initials: MA
authors.lastname: Geihs
authors.forename: Marcelo Alves
authors.initials: MA
authors.lastname: Vargas
authors.forename: Bruno Pinto
authors.initials: BP
authors.lastname: Cruz
authors.forename: Bianca Padovani
authors.initials: BP
authors.lastname: Ramos
authors.forename: Olli
authors.initials: O
authors.lastname: Vakkuri
authors.forename: Victor Benno
authors.initials: VB
authors.lastname: Meyer-Rochow
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Maia Nery
authors.forename: Silvana
authors.initials: S
authors.lastname: Allodi
mesh_terms: D000818:Animals; D003386:Brachyura / Q000502:physiology / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000502:physiology; D008027:Light; D008550:Melatonin / Q000032:analysis / Q000096:biosynthesis*; D009899:Optic Lobe, Nonmammalian / Q000378:metabolism / Q000528:radiation effects*; D010775:Photic Stimulation; D017440:Photoperiod; D010870:Pineal Gland / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D011863:Radioimmunoassay; D013997:Time Factors
chemical_list: D008550:Melatonin