9The color discrimination can confer survival advantages by helping 10 animals to find nutritious food and shelter and to avoid predator.
11Zebrafish as a social species, data on innate color preference in shoals 12 remain controversial and there are limited data for this organism. Here we 13 showed that, when given a choice among two color combinations (R-Y, 14 R-G, Y-G, B-G, B-R, B-Y), shoals of zebrafish exhibited a complex 15 pattern of color preference and the order of RYGB preference was 16 R>Y>G, B>G. By contrast, the individual zebrafish showed marked 17 changes, completely losing their preference for all the tested color 18 combinations. To investigate the role of shoaling behavior in color 19preference, we selected a D1-receptor antagonist (SCH23390), which 20 could disrupt social preference and decrease social interaction in 21 zebrafish. Interestingly, the shoals that were treated by SCH23390 22 showed no color preference for all color combinations. Our findings 23 indicate that social interaction is involved in color-driven behavior in 24 zebrafish, and reveal the possible mechanisms that the dopaminergic 25 system may contribute to innate color preference in shoals of zebrafish. 26 27 28 Recently, Park et al. used zebrafish larvae (5 days post fertilization (dpf)) 60to test the innate color preference in shoals [19]. However, shoaling 61 behavior usually starts to develop after 7 dpf, becoming progressively 62 stronger for the mature [20][21][22]. As far as we know, no research has been 63 published that investigate the innate color preference of mature shoals, 64 although shoaling and social behavior in general has received 65 considerable critical attentions.
66The cohesion of shoals has been found to be associated with the 67 whole brain dopamine level [23]. Dopamine is one of the major 68 neurotransmitters in the central nervous system of the vertebrate brain 69 which plays important roles in a variety of cerebral functions, such as 70 mood, attention, reward and memory [24][25][26]. Abundant evidence shows 71 that dopamine is associated with the neurobehavioral functions in 72 zebrafish [27,28]. Saif et al. [27] found that strong social stimuli will 73 increase the dopamine and its metabolite 3,4-dihydroxyphenylacetic acid 74 (DOPAC) levels in the brain of the adult zebrafish. The short-term 75 isolated zebrafish could reduce the level of DOPAC [28]. The social 76 interaction of shoals in zebrafish can be affected by the dopaminergic 77 system through influence of the dopamine level [29]. D1 dopamine 78 receptor antagonist (SCH23390) is most abundantly expressed dopamine 79 receptor subtypes in the brain of zebrafish [30]. And SCH23390 disrupts 80 social preference of zebrafish by decreasing the level of dopamine in 81 dopaminergic system [31,32].
82In the present study, we used two-color combinations (R-Y, R-G, 83 Y-G, B-G, B-R, B-Y) to test the innate color preference of shoal (10 adult 84 zebrafish) and individual fish, respectively. Moreover, we evaluated the 85 influence of social interac...