We manipulated the density (and thus, sperm environment) of a broadcast spawning ascidian (Styela plicata) in the field and then determined whether the phenotype of eggs and sperm changed.

• 同样地，当雌性海鞘探测到过多的雄性竞争交配结合卵细胞时（过多的精子将杀死一些生物体的卵细胞），雌性海鞘将生产出更小的卵细胞，很精子很难探测到。