Data from: Impact of cryptic female choice on insemination success: larger sized and longer copulating male squid ejaculate more, but females influence insemination success by removing spermatangia

In polyandrous mating systems, sperm competition and cryptic female choice
(CFC) are well recognized as postcopulatory evolutionary forces. However,
it remains challenging to separate CFC from sperm competition and to
estimate how much CFC influences insemination success because those
processes usually occur inside the female's body. The Japanese pygmy
squid, Idiosepius paradoxus, is an ideal species in which to separate CFC
from sperm competition because sperm transfer by the male and sperm
displacement by the female can be observed directly at an external
location on the female's body. Here, we counted the number of
spermatangia transferred to, removed from, and remaining on the female
body during single copulation episodes. We measured behavioral and
morphological characteristics of the male, such as duration of copulation
and body size. Although males with larger body size and longer copulation
time were capable of transferring larger amounts of sperm, females
preferentially eliminated sperm from males with larger body size and
shorter copulation time by spermatangia removal; thus, CFC could attenuate
sperm precedence by larger males, whereas it reinforces sperm precedence
by males with longer copulation time. Genetic paternity analysis revealed
that fertilisation success for each male was correlated with remaining
sperm volume that is adjusted by females after copulation.