Adaptive strategies in reproduction to be a simultaneous hermaphrodite

在本研究的初期，我们预测到雌雄同体的双性交配行为，即雄鱼和雌鱼的交配行为，只能在变性期的几天内进行，之后它们只会在变性期内表现出行为。与第一个预测相反，我们在2001年的研究过程中发现，Margaritaceus的两性交配行为超过了一周。但2001年繁殖季节过后，由于土壤侵蚀，水体清晰度严重降低，无法在田间观察到交配行为。因此，我们将研究主题扩大到雄性劳作鱼类的生殖行为的灵活性。结果发现，2003年有一头三斑潜蝇的初生期雄虫在田间转性为雌。这表明变性鱼的性别比例高得令人惊讶。此外，我们还发现，三斑鱼的初始阶段雄鱼使用三种类型的繁殖…更多的策略是根据情况采取偷偷、裸奔和群体产卵。另一研究对象--疣状Onchidium的种群因冲绳海岸相继发生的超高潮汐而大幅减少。结果，我们在2001年找不到足够数量的个体进行观测。2003年，虽然总体数量恢复到正常水平，但成熟个体不足以进行有效观察。因此，我们决定将研究动物改为裸鳃动物。虽然裸枝同时是两性的，但在每次交配中，它们同时扮演着雄性和雌性的角色。另一方面，Onchidium在每次交配场合都扮演着雄性或雌性的角色。我们发现，在已经交配的斑潜蝇个体中，对交配有一种典型的排斥。这与内部受精的两性动物更喜欢在繁殖中扮演雌性角色的预测相反，因为它们不仅可以将接收到的精子用于受精，还可以用作营养。较少

At the beginning of this research, we predicted that protogynous labrid fishes could perform bi-sexual mating behavior, that is court as a male and also as a female, only for a few days in the period of sex change, and afterward they would behave only as the sex they changed to. Contrary to the first prediction, we found that Halichoeres margaritaceus performed bi-sexual mating behavior longer than a week in the course of research in 2001. But we could not observe mating behavior in the field after2001 reproductive season, because the water clearance badly diminished owing to the erosion of the soil. So we enlarged our research theme to the flexibility of the reproductive behavior in the males of labrid fishes. As a result, we found an initial phase male of H. trimaculatus changed its sex into female in the field in 2003. This shows the sex allocation of sex changing fishes are surprisingly high. Further, we found that initial phase males of H. trimaculatus used three types of reproduc … More tive strategies, sneaking, streaking, and group spawning according to their circumstances.The population of Onchidium verruculatum, another research object, diminished on a large scale because of extraordinarily high tide occurred at Okinawan coast successively. As a result, we could not found enough number of individuals for observation in 2001. In 2003, although the overall number recovered to usual level, mature individuals were not enough for effective observation. So we decided to change study animals to nudibranchs. Although nudibranchs are simultaneous hermaphrodite as well as Onchidium, they take both male and female role simultaneously in each copulation. On the other hand, Onchidium acts as a male or a female in each mating occasion. We found a characteristic rejection to copulation in individuals of Chromodoris tinctoria that have already copulated. This is contrary to the prediction that hermaphroditic animals with internal fertilization prefer to take female role in reproduction, because they can use received sperm not only for fertilization but also as a nutrient. Less