Figure 1.

Two types of male mating behaviour and sperm size. (a) Alternative reproductive tactics by males and sperm storage sites in the female body. The externally located seminal receptacle (blue) and the internal oviduct opening (red) are the targets for sperm transfer by smaller sneaker and larger consort males, respectively. Yellow arrows indicate the route for egg passage. (b) Sperm dimorphism in the squid Loligo bleekeri. A representative DIC image of spermatozoa collected from consort (right) and sneaker (left) males (scale bar, 10 μm).