Data for Body size matters for mate choice of the paradise fish

In nature, animals of varying body sizes exhibit differences in genetics, growth rates, and resource-holding capacities. Numerous species display size-assortative mating patterns, which, according to matching theory, stem from mutual preferences for larger partners among both sexes. Although mate choice has been extensively studied in various animals (e.g., mammals and reptiles), some knowledge gaps remain regarding the role of morphological traits such as body size and the underlying behavioral mechanisms in fish. Here, our study investigates mate choice and same-sex behavior in the paradise fish (Macropodus opercularis). we have employed a male-male behavioural preference testing as a control measure to verify whether the outcome of this binary choice is associated with social preference Our findings indicate that female paradise fish consistently prefer larger individuals in both same-sex and opposite-sex encounters, regardless of their own body size. In contrast, male paradise fish exhibit a preference for smaller individuals in both types of encounters. Furthermore, the general activity levels of paradise fish, including swimming speed and percentage time spent on moving, do not appear to influence mate choice outcomes. These results provide evidence that larger body size may confer an advantage in mate choice for female paradise fish.自然界中，不同体型的动物在遗传特性、生长速率与资源占有能力方面均存在差异。诸多物种呈现出体型选型交配模式，依据匹配理论，该模式源于两性对体型更大配偶的共同偏好。尽管学界已针对哺乳类、爬行类等多种动物的配偶选择展开了广泛研究，但针对鱼类体型等形态性状的作用及其背后的行为机制，仍存在诸多认知空白。本研究以中国斗鱼（Macropodus opercularis）为对象，探究其配偶选择与同性行为。我们采用雄性间行为偏好测试作为对照手段，以验证该二元选择结果是否与社会偏好存在关联。研究结果显示，无论自身体型大小，雌性中国斗鱼在同性与异性互动场景中均始终偏好体型更大的个体。与之相反，雄性中国斗鱼在两类互动场景中均偏好体型更小的个体。此外，中国斗鱼的整体活动水平（包括游泳速度与移动时长占比）似乎并未对配偶选择结果产生影响。上述结果表明，体型更大或许能为雌性中国斗鱼的配偶选择带来竞争优势。