DOI: 10.5061/dryad.h18931zvs
title: Data from: Male medaka continue to mate with females despite sperm depletion

description: In animals where males engage in multiple matings, sperm depletion can
 substantially reduce the reproductive success of both sexes. However,
 little is known about how successive matings affect sperm depletion,
 fertilisation rates, and mating behaviour. Here, we investigated this
 phenomenon under laboratory conditions. Medaka (Oryzias latipes), an
 externally fertilising fish, is an ideal model to test predictions of
 sperm depletion because there are established methods to observe its
 mating and count sperm. Medaka males mated with multiple females (19 per
 day, on average; range, 4–27), experiencing significant sperm depletion,
 with sperm release declining markedly after the first few matings,
 reaching only 0.5–6.3% by the last mating of the day. Fertilisation rates
 decreased, particularly after approximately 10 consecutive matings,
 although there was some recovery in the next-day’s matings. The decline in
 courtship effort and mating duration probably resulted from the males
 becoming increasingly fatigued. Despite the reduced sperm availability,
 females did not adjust their clutch size as a counterstrategy. These
 results suggest substantial reproductive costs for males and the potential
 for sexual conflict owing to limited sperm availability. For species with
 frequent successive mating, these findings highlight the need to
 reconsider reproductive strategies and their impact on sexual selection.
description: # Data from: Male medaka continue to mate with females despite sperm
 depletion
 [https://doi.org/10.5061/dryad.h18931zvs](https://doi.org/10.5061/dryad.h18931zvs) Data on male medaka (*Oryzias latipes*) reproductive limits, examining mating behavior until exhaustion by presenting fertile females. The experiment used medaka (himedaka) maintained at Osaka Metropolitan University, Japan. Contact Yuki Kondo ([youkukondou@gmail.com](mailto:youkukondou@gmail.com)) with any questions. This manuscript has been accepted for publication (11/26/2024). | variables | units | description | | :------------------------------------------ | :-------------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------- | | No | number | Line number. | | Date | number | Experiment day. | | Male ID | categorical | Male experimental ID. | | Female ID | categorical | Female experimental ID. The next day's spawning behaviour is described as ‘Next day’. | | Number of mating | number | The number of times the male has laid eggs. The next day's spawning behaviour is described as ‘Next day’. | | Male mass (g) | g | Body mass of male. | | Standard length of male (mm) | mm | Standard length of male. | | Female mass (g) | g | Body mass of female. | | Standard length of female (mm) | mm | Standard length of female. | | Number of spawned eggs | number | Number of eggs spawned by the female during spawning behaviour. | | Number of fertilised eggs | number | Number of eggs confirmed to have been fertilised under a microscope. | | Number of sperm counted | number | The number of sperm counted under a microscope. | | Number of sperm released | number | The number of sperm released, estimated from the number of sperm counted under a microscope. | | Mating latency (s) | s | Time until the start of spawning behaviour. | | Mating duration (s) | s | Duration of spawning behaviour. | | Total time of following (s) | s | Time when ‘following’, a male courtship behaviour, was observed. | | Number of quick circle | number | Number of times the male courtship behaviour ‘quick circle’ was observed. | | The number of eggs remaining in the ovaries | presence (1) or absence (0) | Whether or not there were any residual eggs in the dissected ovaries. 1 if there were, 0 if there were not, and n/a if they were not dissected. |