Kudo Hiromi, Karino Kenji
Department of Biology, Tokyo Gakugei University, 4-1-1, Nukui-kita, Koganei, Tokyo 184-8501, Japan.
Zoolog Sci. 2012 May;29(5):319-26. doi: 10.2108/zsj.29.319.
It has been demonstrated that the exaggeration of male sexual ornaments and the intensity of female mate preferences of a wild guppy population change over a period of several months. However, the factors that determine the short-term changes in male ornaments and female preferences remained unclear. In this study, we examined the effect of season on these short-term changes by measuring these traits in the same seasons of different years for a wild guppy population in Okinawa, Japan. We also compared the characteristics of the offspring in each collection term, as female guppies are known to have the ability to control offspring characteristics, such as brood size and sex ratios, depending on their mates' attractiveness. Results showed that the total lengths of the males changed seasonally; males in the summer were larger than those in the spring. In contrast, the size of orange spots in males and the intensity of female mating preferences differed in the same seasons of different years. Brood size and offspring body size in each term showed seasonal changes. However, offspring sex ratios exhibited different patterns in the same seasons of different years. Females produced female-biased broods when attractive males with large orange spots were rare. These results suggest that short-term changes in some traits of adult male and female guppies as well as offspring sex ratios may be not determined by seasonal factors, and that these traits may be interrelated.
已有研究表明，野生孔雀鱼种群中雄性性征的夸张程度以及雌性配偶偏好的强度在几个月的时间里会发生变化。然而，决定雄性性征和雌性偏好短期变化的因素仍不明确。在本研究中，我们通过测量日本冲绳一个野生孔雀鱼种群在不同年份相同季节的这些特征，研究了季节对这些短期变化的影响。我们还比较了每个采集期后代的特征，因为已知雌性孔雀鱼有能力根据配偶的吸引力来控制后代特征，如产仔数和性别比例。结果表明，雄性的体长有季节性变化；夏季的雄性比春季的更大。相比之下，不同年份相同季节中雄性橙色斑点的大小和雌性交配偏好的强度有所不同。各时期的产仔数和后代体型呈现季节性变化。然而，不同年份相同季节的后代性别比例呈现出不同的模式。当带有大橙色斑点的有吸引力的雄性较少时，雌性会产出偏雌性的后代。这些结果表明，成年雄性和雌性孔雀鱼的一些特征以及后代性别比例的短期变化可能不是由季节因素决定的，而且这些特征可能相互关联。
