Temperature induces gonadal maturation and affects electrophysiological sexual maturity indicators in Brachyhypopomus pinnicaudatus from a temperate climate.
In contrast to most of the previous studies in gymnotiform reproduction, which have been conducted in the tropical region, this study examines a gymnotid from the temperate region in both the natural habitat and the laboratory. The gonadal histology of Brachyhypopomus pinnicaudatus is described for the first time. The male had a paired, lobular testis of the unrestricted spermatogonial type, and females a paired saccular cystovary. Analysis of gonads and their annual cycle enabled us to confirm the breeding season and to conclude that this species is a multiple spawner. Water temperature and photoperiod showed the expected annual cycles for the region. High temperature and a 14 h:10 h L:D photoperiod in the natural habitat coincided with (1) mature gonadal stages, (2) electrophysiological sexual dimorphism: males present a lengthened negative phase in their electric organ discharge (EOD) and (3) decreased temperature sensitivity of the EOD: the waveform does not change when temperature increases above 20 degrees C. Acclimation to sustained high temperature (30 days, 28 degrees C, 12 h:12 h L:D, low conductivity) induced gonad maturation along with EOD dimorphism. Our data show that high environmental temperature is enough to trigger sexual maturity in Brachyhypopomus pinnicaudatus from a temperate climate.
Quintana
Laura
L
Depto de Neurofisiología, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de Facultad de Ciencias-Universidad de la República, Avda, Italia 3318, Montevideo, Uruguay. lauraq@iibce.edu.uy
Silva
Ana
A
Berois
Nibia
N
Macadar
Omar
O
D000064:Acclimatization / Q000502:physiology; D000818:Animals; D004557:Electric Organ / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D006066:Gonads / Q000033:anatomy & histology* / Q000254:growth & development; D023702:Gymnotiformes / Q000033:anatomy & histology* / Q000502:physiology; D006652:Histological Techniques; D008297:Male; D017440:Photoperiod; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D012727:Sex Characteristics; D012741:Sexual Maturation / Q000502:physiology*; D013696:Temperature