Evidence of heterosexual and homosexual mating in the Indian squid Uroteuthis duvaucelii (Cephalopoda: Loliginidae) from the tropical Arabian Sea

Sajikumar, K K and Sasikumar, Geetha and Laxmilatha, P and Venkatesan, V and Vidya, R and Jestin Joy, K M and Mohamed, K S (2026) Evidence of heterosexual and homosexual mating in the Indian squid Uroteuthis duvaucelii (Cephalopoda: Loliginidae) from the tropical Arabian Sea. Journal of Natural History, 60. pp. 1211-1222.

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Abstract

The Indian squid Uroteuthis duvaucelii (D’Orbigny) is widely distributed throughout the Indian Ocean, where it is extensively exploited and holds significant importance for the fisheries sector, particularly in Indian waters. Spawning aggregations are known to occur along the west coast of India during the post-monsoon months. However, the mating behaviour of this species remains poorly understood. Spermatangia implantation on the buccal membranes in female U. duvaucelii was examined from the Arabian Sea between January and December 2021. Of the 232 females analysed, 40% carried spermatangia on their buccal membranes, with occurrence recorded year-round and peaks in October. The number of spermatangia ranged from 64 to 385 (mean 178 ± 96), with implantation predominantly on the ventral buccal surface. Statolith analysis revealed ages of mated individuals between 98 and 162 days (110–162 mm, dorsal mantle length, DML), confirming rapid growth and short life spans. Typically, males transfer spermatophores to the female’s buccal region during copulation. However, the presence of spermatangia on the buccal membranes of single male individual provides evidence suggestive of same-sex sexual behaviour in U. duvaucelii. Overall, the widespread and seasonal occurrence of buccal spermatangia, including their presence in males, suggests a complex and previously unrecognised mating system in U. duvaucelii. These findings highlight the need for more detailed studies to fully understand the mating behaviour of loliginid squids in the Arabian Sea.

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