DOI: 10.5061/dryad.ngf1vhj3j
title: Data from: In the presence of rivals, males allocate less ejaculate per mating in Japanese pygmy squid with female sperm rejection

description: 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
 copulation, so, after copulation, the amount of a given male’s sperm
 remaining with the female may decrease after each subsequent rival
 copulates with the female. Perhaps in this species the presence of rivals
 signals the risk of further sperm rejection, so males choose to conserve
 their resources and move on.
description: # 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, [ryoheii1219@gmail.com](mailto:ryoheii1219@gmail.com) 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 dataset contains behavioural data obtained from all the aquarium experiment videos. Data from 29 trials, excluding seven trials for which the videos were unclear and analysis could not be performed sufficiently, are used in Data_for_analysis.csv. * Behavioral_raw_data_for_analysis.csv: This dataset contains the estimated values calculated from the “Behavioral_raw_data.csv” file after excluding the missing values. It also includes the body size of the sex in each trial. This file was used for statistical analysis. * Sparm_mass_data.csv: This dataset contains sperm mass sizes linked to the 29 trials included in the "Data_for_analysis" file. It was used for statistical analysis. * Data_for_supplemental_figure_S1.csv: This dataset was gained and generated from data obtained from “ 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” (Noriyosi Sato, Masaaki Yoshida and Takashi Kasugai (2017); doi: 10.5061/dryad.d930g). This data set was used for statistical analysis in the supplemental_figure_S1. * Metadata_of_each_files: This file shows the metadata of the dataset. **"image_sperm_mass" folder** This folder contain all of images about sperm mass. these image was used for evaluate sperm mass size. * sp_scale_trial#.jpeg : iImages of scale. The # symbol is replaced with the number of each trial in the names of the conteined files. In trial 31 were taken at different magnifications, so the letter A or B is placed after "Scale" in the name, and this is linked to the name of the "sp_trial#.jpeg" file. * sp_trial#-#.jpeg: Images of a sperm mass. The first # symbol is replaced with the number of each trial in the name of the included file. The second # symbol was added when multiple photos were taken within the same trial. Only in Trial 31 were multiple images taken at different magnifications, so the name was added with “LinkWithScaleA” or “LinkWithScaleB” , and the file name “sp_trial#.jpeg” was linked according to this notation. **"video_copulation" folder** This folder contain videos of the aquarium experiment. these video footaise used for gain behavioural data of "Behavioral_raw_data.csv". As video data has large data size, this folder include only representative videos from 6 trials * trial#.mp4: videos of the aquarium experiment. The # symbol is replaced with the number of each trial in the names of the conteined files. ## Description of the dataset The following shows the abbreviations used in the CSV file. missing values are indicated as “ND”. **"Behavioral_raw_data.csv" and "Data_for_analysis.csv" file** * Trial_ID: Identity of trials of the aquarium experiment. * Rival_number: Number of rival males exposed focal males during the simulated mating as an experimental treatment. No_rival = absence of rival males(no sperm competition); one_rival= one rival was presented to focal male(low sperm competition intensity); three_rivals=three rival was presented to focal male(high sperm competition intensity). * Male_DML: Dorsal mantle length of male (mm). * Female_DML: Dorsal mantle length of female (mm). * Transferrd_sperm_number: Number of transferred spermatophores of focal male. * Reject_sperm_number: Number of rejected spermatangia by female sperm rejection. * Remain_sperm_number: Number of remaining spermatangia on female body after female sperm rejection. * Stock_sperm_number: Number of stoking spermatophore of focal males after ejaculation. * All_stock_sperm_number: Number of stoking spermatophores of focal males before ejaculation was calculated by Stock_sperm_number+Transferrd_sperm_number. * Mean_sparm_mass_area: Mean area of sperm mass in each focal males = mean Sperm mass area 1~10(mm^2). * EjI: Sperm volume index of ejaculation. * EjaRate: Ejaculated sperm volume rate. * RejI: Rejected sperm volume index. * RejRate: Rejected sperm volume rate. * RemI: Remaing sperm volume index. * StcI: Stocked sperm volume index. **"Sparm_mass_data.csv" file** * Trial_ID: Identity of trials of aquarium experiment. - Sperm_mass_area 1~10: Projected area of sperm mass of focal male's spermatophores (mm^2). **"Data_for_supplemental_figure_S1.csv" file** * Year: Year of the experiment was conducted in supplemental figure S1. * FemaleID: Identity of females in supplemental figure S1. The same females copulated with two males sequentially, so the first male copulated with virgin female and second male copulated with non-virgin female. * 1stMaleID: Identity of male which copulated with a female first (mating status of female was virgin) in supplemental figure S1. * 2ndMaleID: Identity of male which copulated with a female second (mating status of female was copulated) in supplemental figure S1. * Virginity: Mating status of female before she copulated with first male in supplemental figure S1. * 1stEjI: First male's sperm volume index of ejaculation in supplemental figure S1. * 2ndEjI: Second male's sperm volume index of ejaculation in supplemental figure S1.