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Cryptic bachelor sex change in haremic colonial groups of the coral-dwelling damselfish Dascyllus reticulatus


Protogynous sex change has been widely reported as a life-history strategy in polygynous reef fish. Dascyllus reticulatus is known to form haremic colonial groups on branching corals and is thought to undergo protogynous sex change based on gonad histology. We conducted a 2-year underwater survey on 13 haremic groups to examine the sex-change patterns of D. reticulatus on reefs of southern Japan. We observed 11 instances of protogynous sex change. One involved a take-over sex change by the largest female following the disappearance of the dominant male. In other contexts, females undergo sex changes in the presence of males or larger females. These sex-change individuals commonly had limited mating opportunities as females. Of the ten sex changers, five subordinate females became bachelor males showing no sexual behavior despite their ability to release sperm. Owing to behavioral crypticity, these bachelor males remained within their groups without suffering attacks from territorial males. Furthermore, sex changers showed higher growth rates than females. Two bachelor sex changers subsequently obtained mating status, of which one became a female again after inter-group migration. It is suggested that female D. reticulatus often overcomes reproductively isolated situations via the growth advantages of protogynous sex change and sexual plasticity.

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We thank the people of Kuchierabu-jima Island for enabling us to conduct the field survey. We are grateful to Dr. H. Hashimoto, Dr. T. Tomiyama, Dr. Y. Kimura, and colleagues at the Laboratory of Biology of Aquatic Resources, Hiroshima University, for their kind support. We also thank Dr. T. Fujii (Kagoshima University) and Mr. T. Shimada (Japanese Society for Coral Taxonomy) for their assistance with the taxonomic identification of coral species. We would like to thank Editage ( for English language editing. This study was supported by grants from JSPS KAKENHI (Grant Numbers 24570027, 15K07222, and 18K06419) to YS and the Sasakawa Scientific Research Grant from The Japan Science Society to RS.

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Correspondence to Rei Sakanoue.

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The authors declare no conflicts of interest.

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All procedures performed in this study followed the Guidelines for the Proper Conduct of Animal Experiments and related activities laid down by the Hiroshima University Animal Research Committee (No. 020A170410 certified on April 10th, 2017), the ASAB/ABS Guidelines for the Use of Animals in Research (Guidelines for the Treatment of Animals in Behavioral Research and Teaching;, the Guidelines for the Use of Fishes in Research by the Ichthyological Society of Japan (, and the Guideline for Ethological Studies by the Japan Ethological Society (

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Sakanoue, R., Sakai, Y. Cryptic bachelor sex change in haremic colonial groups of the coral-dwelling damselfish Dascyllus reticulatus. J Ethol 40, 181–192 (2022).

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  • Pomacentridae
  • Haremic colonial group
  • Protogyny
  • Bachelor sex change
  • Reversed sex change