在追求雌乌贼的过程中，小个子的雄乌贼是无法战胜大块头的竞争对手的，因此它们诉诸一种卑鄙的伎俩：在最后关头释放它们的精子。
在一只雌乌贼选择一只大个的雄乌贼之后，后者会将它的精子包放入前者的输卵管中，这些精子会与雌乌贼一直呆在一起直至其产卵，这样一来，其他雄乌贼便没有机会横刀夺爱了。
但是小块头的乌贼会在这对甜蜜的恋人附近闲逛，并在雌乌贼排卵的一刹那抢过去与其交配。
这些矮个子的罗密欧会将它们的精子包放在雌乌贼的体外，靠近其精子储存器官的位置——位于雌乌贼的口腔下方。
随着雌乌贼将它的卵子沉入海底，这些精子也会使其中的一些卵子受精。
尽管这些卑鄙的雄性并不会像它的竞争对手那样让那么多的卵子受精，但这依然是一个有效的手段。
研究人员在8月9日的《BMC进化生物学》杂志上报告了这一研究成果。
实验室研究同时表明，尽管体型较小，但小乌贼的精子却要比大乌贼的大。这并不是因为大一点的精子比小一点的精子更有优势，它们之所以大是因为这些精子必须禁得起雌乌贼体外的严酷环境。(生物谷 Bioon.com)
doi:10.1186/1471-2148-11-236
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Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours
Yoko Iwata, Paul Shaw, Eiji Fujiwara, Kogiku Shiba, Yasutaka Kakiuchi, Noritaka Hirohashi
(provisional)Background Sperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by adaptation to the environmental conditions at the site of fertilization. Strong stabilizing selection limits intra-specific variation, and therefore polymorphism, among fertile sperm (eusperm). Here we analyzed reproductive morphology differences among males employing characteristic alternative mating behaviours, and so potentially different conditions of sperm competition and fertilization environment, in the squid Loligo bleekeri. Results Large consort males transfer smaller (average total length = 73 um) sperm to a female's internal sperm storage location, inside the oviduct; whereas small sneaker males transfer larger (99 um) sperm to an external location around the seminal receptacle near the mouth. No significant difference in swimming speed was observed between consort and sneaker sperm. Furthermore, sperm precedence in the seminal receptacle was not biased toward longer sperm, suggesting no evidence for large sperm being favoured in competition for space in the sperm storage organ among sneaker males. Conclusion sHere we report the first case, in the squid Loligo bleekeri, where distinctly dimorphic eusperm are produced by different sized males that employ alternative mating behaviours. Our results found no evidence that the distinct sperm dimorphism was driven by between- and within-tactic sperm competition. We propose that presence of alternative fertilization environments with distinct characteristics (i.e. internal or external), whether or not in combination with the effects of sperm competition, can drive the disruptive evolution of sperm size.
