Photoperiodic modulation of reproductive physiology and behaviour in the cichlid fish Cichlasoma dimerus.
Timing of breeding to an optimal season is a requirement for a successful reproductive outcome in seasonally breeding species. Photoperiodic signals are capable of modifying the reproductive behaviour and reproductive systems in several vertebrate species. The cichlid fish Cichlasoma dimerus shows highly organized breeding activities and different social status. The aim of this study is to test whether C. dimerus reproductive behaviour (male aggressive behaviour and female choice) and reproductive physiology (GnRH3 morphometric parameters, pituitary hormones content and organ-somatic indexes) are modulated by photoperiod. Before spawning, dominant pairs were isolated and kept in opposite tanks of 20 l for one week, so they could see each other but not physically interact. Afterwards, a group was exposed for four weeks to a short photoperiod (8h light:16 h dark) (short photoperiod exposed animals: SP) while another group was exposed to a long photoperiod (14 h light:10h dark) (long photoperiod exposed animals: LP). Temperature was maintained constant. Behavioural experiments showed that male aggression related to territory selection and its defence is reduced in SP males. Further, SP females were never chosen. At the brain level we demonstrated that GnRH3 neuronal optical density of staining was reduced. Finally, at the pituitary level we showed that SP males showed low levels of beta-LH, PRL and GH in the pituitary, and that SP females showed no significant differences in the pituitary content of any hormone. Taken all together these results suggest that in C. dimerus the photoperiod is a relevant environmental cue related to reproductive behaviour and physiology.
Fiszbein
Ana
A
Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, (C1428EHA) Buenos Aires, Argentina.
Cánepa
Maximiliano
M
Vázquez
Graciela Rey
GR
Maggese
Cristina
C
Pandolfi
Matías
M
D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology; D002755:Choice Behavior / Q000502:physiology; D023681:Cichlids / Q000502:physiology*; D005260:Female; D029941:Fish Proteins / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D006400:Hematocrit / Q000379:methods; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000378:metabolism; D017440:Photoperiod; D010907:Pituitary Hormones / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000502:physiology; D011388:Prolactin / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D055703:Reproductive Physiological Phenomena; D012726:Sexual Behavior, Animal / Q000502:physiology*
D029941:Fish Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D010907:Pituitary Hormones; C448022:gonadotropin-releasing hormone-III; C064448:somatolactin protein, fish; D007987:Gonadotropin-Releasing Hormone; D011388:Prolactin; D011761:Pyrrolidonecarboxylic Acid