The present study gives the first detailed results on the partner-finding behaviour of tardigrades. We investigated whether the finding of mating partners by Isohypsibius dastychi followed certain criteria that are expected if pheromone signals are involved. For this purpose, tardigrade pairs were positioned in an arena, at a range of distances from each other. Only those females that were ready for mating attracted the male. The smaller the initial distance between them, the more directly the male headed for the female. The route travelled and time taken increased exponentially with increasing initial distance between partners, which means that the male lost orientation with respect to the female the larger the distance between the pair became. The findings indirectly suggest a yet undetermined female pheromone, which produces a concentration gradient in the water and loses strength quickly in terms of distance. Our assumption is supported by rare observations of sperm release without direct contact between partners that nevertheless resulted in fertile offspring. The observation that the female partners in this no-contact mating behaviour then deposited their eggs (a behaviour that was never seen when males were absent) suggests that they, likewise, can sense a fresh ejaculate of spermatozoa in their direct vicinity.

中文翻译：

---

达菲异蝇（Isohypsibius dastychi）（Isohypsibiidae：Tardigrada）的伴侣发现行为的实验研究

本研究给出了关于缓步动物伙伴发现行为的第一个详细结果。我们调查了Isohypsibius dastychi是否发现了交配伙伴如果涉及信息素信号，则遵循某些标准。为此，将缓坡对放置在舞台上，彼此之间保持一定距离。只有那些准备交配的雌性才吸引雄性。它们之间的初始距离越小，雄鱼就越直接朝向雌鱼。随着伴侣之间的初始距离增加，行进的路线和花费的时间呈指数增加，这意味着当两对之间的距离变大时，雄性相对于雌性的迷失方向。这些发现间接暗示了一种尚未确定的雌性信息素，该信息素会在水中产生浓度梯度，并且在距离方面会迅速丧失强度。我们的假设得到了精子释放的罕见观察结果的支持，而伴侣之间没有直接接触却导致了可育后代。观察到雌性伙伴在这种非接触式交配行为中会沉积卵子（这种行为在雄性雄性动物不存在时是从未见过的），这表明它们同样可以在其附近感觉到新鲜的精子射精。