The overlapping reproductive traits of the two male mating types of the oval squid Sepioteuthis lessoniana

  • Chun-Yen Lin
  • Chih-Shin Chen
  • Chuan-Chin ChiaoEmail author
Original Article Biology


The oval squid Sepioteuthis lessoniana is polyandrous, and a female mates with several males during a spawning season. This has resulted in two alternative male mating tactics in this species. The larger consort males usually use the male-parallel (MP) mating posture to put spermatophores at the opening of the oviduct; the smaller sneaker males predominantly use the male-upturned (MU) mating posture to place spermatophores around the female’s buccal membrane. Since squid eggs are released from the oviduct, MP mating is expected to have a higher fertilization rate than MU mating. Given the fact that these two male mating tactics are largely dependent on the body size of the male relative to the female, it is unclear how the smaller males are able to reproductively compete with the larger males. On analyzing spermatophore and sperm morphology from populations of adult male squids, spermatophore size was found to be positively correlated with mantle length of these squids, but sperm length was negatively correlated with squid mantle length. More importantly, no distinct size dimorphism exists in relation to either spermatophore morphology or sperm morphology. The overlap in size distributions of the spermatophores and sperms of the male squid thus implies that medium-sized males may have flexible reproductive strategies, switching between MP and MU mating tactics depending on the context of the mating event and/or female choice. This presumed behavioral plasticity might increase the reproductive success of these males and maintain the dynamic stability of two alternative mating types in this polyandrous species.


Polyandry Sperm competition Alternative mating tactics Consort males Sneaker males 



We thank the fishermen of Ho-ping Island for their assistance with the collection of squid specimens. We also thank Ms. Jing-Yu Chen and Chiao-Wen Lin at the National Taiwan Ocean University for assistance in sample preparation and data processing. We are grateful for the invaluable comments from two anonymous reviewers. This study was supported by the Ministry of Science and Technology of Taiwan NSC-101-2313-B-019-001 (to CSC), and MOST 106-2311-B-007-010-MY3 (to CCC).

Supplementary material

12562_2018_1283_MOESM1_ESM.jpg (66 kb)
Figure S1. The age and mantle length in both cohorts are not correlated. (a) The selected samples from the 2012 Fall cohort. The correlation between age and mantle length was low. (b) The selected samples from 2013 Spring cohort. Similarly, the correlation between age and mantle length was low. Squid age was determined based on the statolith microstructure analysis (jpeg 65 kb)
12562_2018_1283_MOESM2_ESM.jpg (58 kb)
Figure S2. The fresh and fixed spermatophores and sperms are highly correlated. (a) The length of spermatophores was decreased slightly after fixation, but the correlation between fresh and fixed samples was high. (b) Similarly, the length of sperms was decreased slightly after fixation and sonication, but the correlation between fresh and fixed samples was high (jpeg 57 kb)


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Copyright information

© Japanese Society of Fisheries Science 2018

Authors and Affiliations

  1. 1.Institute of Molecular MedicineNational Tsing Hua UniversityHsinchuTaiwan
  2. 2.Institute of Marine Affairs and Resource ManagementNational Taiwan Ocean UniversityKeelungTaiwan
  3. 3.Institute of Systems NeuroscienceNational Tsing Hua UniversityHsinchuTaiwan
  4. 4.Department of Life ScienceNational Tsing Hua UniversityHsinchuTaiwan

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