Environmental color affects Nile tilapia reproduction

Abstract

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 ± 0.45 cm) and 3 females (10.78 ± 0.45 cm) each. After assignment to the respective environmental color (similar luminosity = 100 to 120 Lux), the animals were observed until reproduction (identified by eggs in the female's mouth) or up to 10 days after the first nest building. Photoperiod was from 6:00 h to 18:00 h every day. Food was offered in excess once a day and water quality was similar among aquaria. Daily observations were made at 8:00, 11:00, 14:00 and 17:00 h regarding: a) latency to the first nest, b) number of nests, c) gravel weight removed (the male excavates the nest in the bottom of the aquarium), d) nest area, and e) mouthbrooding incubation (indication of reproduction). The proportion of reproducing fish was significantly higher (6 of 13) in the group exposed to the blue color compared the group exposed to the white color (1 of 12; Goodman's test of proportions). Moreover, males under blue light removed significantly larger masses of gravel (blue = 310.70 ± 343.50 g > white = 130.38 ± 102.70 g; P = 0.01) and constructed wider nests (blue = 207.93 ± 207.80 cm 2 > white = 97.68 ± 70.64 cm 2 ; P = 0.03) than the control (white). The other parameters did not differ significantly between light conditions. We concluded that reproduction in the presence of blue light was more frequent and intense than in the presence of white light.

Visual communication stimulates reproduction in Nile tilapia, Oreochromis niloticus (L.)

“…Blue is known to reduce stress (24) and improve reproduction (16) in Nile tilapia. Water temperature was maintained at 27 ± 1°C by individual thermostats and the photoperiod was 12-h light/dark cycles, starting at 7:00 am.…”

“…In the cichlid Nile tilapia, Oreochromis niloticus, the dominant male increases chasing and courtship of females injected with 17,20βP, but in anosmic males these behaviors are not demonstrable (15). However, the background color of a substrate modulates the frequency of spawning in Nile tilapia (16) and the species shows elaborated courtship movements (17), suggesting that visual communication is part of its reproductive behavior.…”

Larvicultura de piabanha-do-pardo em aquários de cores diferentes

“…O efeito das cores dos ambientes sobre a fisiologia e o comportamento dos animais vem se consolidando como área de amplo interesse para pesquisas (Volpato et al, 2004). A maioria dos estudos foca em mostrar os efeitos das cores do ambiente na sobrevivência e no canibalismo das larvas de peixes e organismos aquáticos (Tamazouzt et al, 2000;Yasharian et al, 2005), e a sua correlação com o estresse (Rotllant et al, 2003) e com o crescimento (Strand et al, 2007).…”

“…A cor do ambiente está relacionada à reprodução (Volpato et al, 2004), à visão e a aspectos adaptativos, como mudanças na pigmentação da pele dos peixes (Sugimoto et al, 2000). Muitos animais marinhos adéquam a cor da sua pele à do ambiente em que vivem, como a espécie Pagrus pagrus (pargo-vermelho) (Rotllant et al, 2003;Van Der Salm et al, 2004).…”

Atividade da catalase e da lactato desidrogenase em tilápias submetidas a estresse de confinamento: efeito da cor do ambiente

“…O espectro de luz azul inibe a mobilização de lipídeos hepáticos induzida pelo estresse em O. mykiss (KARAKATSOULI et al, 2008), aumenta a eficiência alimentar em larvas de Melanogrammus aeglefinus (DOWNING & LITVAK, 2001) e favorece o crescimento em Perccottus glenii e Poecilia reticulata, efeito não observado em Carassius carassius (RUCHIN, 2004). Por outro lado, reduz o crescimento em P. flavescens, comparativamente à luz vermelha (HEAD & MALISON, 2000), e estimula a reprodução em O. niloticus (VOLPATO et al, 2004).…”