In the presence of rivals, males allocate less ejaculate per mating in Japanese pygmy squid with female sperm rejection

When mating is promiscuous, the ejaculate volume allocated to each female is expected (intuitively) to be linked with the presence and number of rival males. Previous theories have indicated that, in the absence of rival males, males will allocate the minimum ejaculate volume sufficient for fertilization of all available oocytes. However, it is unclear if this ejaculation strategy is still effective where females have a mechanism to remove sperm after copulation (‘female sperm rejection’). In the Japanese pygmy squid, Idiosepius paradoxus, female sperm rejection was observed to occur frequently, but males were able to increase the remaining sperm volume available for fertilization, suggesting that there is no significant impact of female sperm rejection on male ejaculation strategy. However, males decreased ejaculate volume in the presence of rival males and increased it in their absence, a pattern counterintuitive to predictions from previous theories. Females reject sperm at every cop..., , , # Data from: In the presence of rivals, males allocate less ejaculate per mating in Japanese pygmy squid with female sperm rejection [https://doi.org/10.5061/dryad.ngf1vhj3j](https://doi.org/10.5061/dryad.ngf1vhj3j) Authors: Ryohei Tanabe, Nobuhiko Akiyama, Noriyosi Sato Contact details: Ryohei Tanabe, Tokai University, [[e-mail]](mailto:[e-mail]) Title of study: In the presence of rivals, males allocate less ejaculate per mating in Japanese pygmy squid with female sperm rejection Summary: Here, we investigate the ejaculation strategy in Japanese pygmy squid. We report unexpected ejaculate patterns of males and discuss how female sperm rejection affects male ejaculation strategy. Responsible for collecting data: Ryohei Tanabe ## File structure We submitted a zip file which includes three folders (\"dataset\", \"image_spem_mass\", and \"video_copulation\"). **\"dataset \" folder** This folder contains all of the CSV files. * Behavioral_raw_data.csv: This data...