Oki Marine Biological Station, Education and Research Center for Biological Resources, Shimane University, 194 Kamo, Okinoshima-cho, Oki, Shimane 685-0024, Japan.
Curr Biol. 2013 May 6;23(9):775-81. doi: 10.1016/j.cub.2013.03.040. Epub 2013 Apr 11.
Behavioral traits of sperm are adapted to the reproductive strategy that each species employs. In polyandrous species, spermatozoa often form motile clusters, which might be advantageous for competing with sperm from other males. Despite this presumed advantage for reproductive success, little is known about how sperm form such functional assemblies. Previously, we reported that males of the coastal squid Loligo bleekeri produce two morphologically different euspermatozoa that are linked to distinctly different mating behaviors. Consort and sneaker males use two distinct insemination sites, one inside and one outside the female's body, respectively. Here, we show that sperm release a self-attracting molecule that causes only sneaker sperm to swarm. We identified CO2 as the sperm chemoattractant and membrane-bound flagellar carbonic anhydrase as its sensor. Downstream signaling results from the generation of extracellular H(+), intracellular acidosis, and recovery from acidosis. These signaling events elicit Ca(2+)-dependent turning behavior, resulting in chemotactic swarming. These results illuminate the bifurcating evolution of sperm underlying the distinct fertilization strategies of this species.
精子的行为特征适应于每种物种所采用的繁殖策略。在一妻多夫的物种中，精子通常形成游动的集群，这可能有利于与来自其他雄性的精子竞争。尽管这种繁殖成功的假定优势，但是对于精子如何形成这种功能组装的了解甚少。以前，我们报道了沿海鱿鱼 Loligo bleekeri 的雄性产生两种形态不同的真精子，这与明显不同的交配行为有关。伴侣雄性和偷偷摸摸的雄性分别使用两个不同的授精部位，一个在雌性体内，一个在雌性体外。在这里，我们表明精子释放一种自我吸引的分子，仅导致偷偷摸摸的精子聚集。我们将 CO2 鉴定为精子趋化剂，而膜结合的鞭毛碳酸酐酶作为其传感器。下游信号来自于细胞外 H(+)的产生、细胞内酸中毒和酸中毒的恢复。这些信号事件引发 Ca(2+)-依赖性转向行为，导致趋化性聚集。这些结果阐明了这种物种独特的受精策略背后的精子分叉进化。
