Effects of sex and size on boldness and aggression in the zebrafish and the guppy
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2020
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Abstract
In this study, we tested the differences in boldness and aggression in relation to sex and
size in three strains of zebrafish (London Wild Type (LWT), Tupfel Long fin (TL) and
Nacre) and a population of guppies. The objective of this study was to determine the
influence of sex and size on boldness and aggressiveness in the zebrafish and the
guppies. The open field test was used to test for boldness while the mirror test was used
to test for aggression. Twenty five males and 25 females of each of the zebrafish strains
(LWT, TL and Nacre) and 25 male and 25 female guppies were used in this study. Our
results showed that boldness and aggression varied between individuals and that these
traits were associated with sex in some populations and not all. The LWT males and the
Nacre males were bolder than the females of the same strain (p = 0.001 and p<0.001
respectively) but there was no significant difference in boldness between the TL males
and females (p = 0.980). There was no significant difference between LWT males and
females and TL males and females (p = 0.999 and p = 0.885) in aggression. However,
Nacre males were significantly more aggressive than Nacre females (p<0.001). In the
guppies, the males were bolder than the females (p <0.001) but there was no significant
difference in aggression between the male guppies and the female guppies (p = 0.062).
Our results showed that boldness and aggression varied between individuals and that
these traits were associated with size in some populations and not all. In the TL females,
smaller females were bolder than larger females (p = 0.012). However, size did not have
any influence on boldness in the Nacre females, the Nacre males, the LWT females, the
LWT males and the TL males (p = 0.381, p = 0.267, p = 0.183, p = 0.249 and p = 0.229
respectively). In the TL females, smaller females were more aggressive than larger
females (p = 0.026) but there was no correlation between length and aggression in the
males and females of any of the other strains of zebrafish (p>0.05). Furthermore, in the
guppies, size did not have any effect on boldness or aggression (p = 0.089 and p = 0.660
respectively). The variation in the effect of sex and size on boldness and aggression
reported here may be due to factors, such as metabolic requirements, hormonal
differences, and differences in the reproductive roles of both sexes of the population
tested.
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Ariyomo, T. O., Jegede, T. & Watt, P. J. (2020). Effects of sex and size on boldness and aggression in the zebrafish and the guppy. Biological and Environmental Sciences for the Tropics, 17(2), 32 – 42