Close-up observations on the spawning behavior of a captive Japanese flying squid (Todarodes pacificus)

Yamamoto, Jun; Adachi, Kohsuke; Bower, John R.; Matsui, Hajime; Nakaya, Mitsuhiro; Ohtani, Ryusei; Puneeta, Pandey; Suzuki, Satoshi; Tokioka, Shun; Vijai, Dharmamony; Yanagimoto, Takashi; Yoo, Hae-Kyun

doi:10.1038/s41598-019-56071-0

Cited by 4 publications

(1 citation statement)

References 13 publications

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“…TheseSRs are located in the buccal membrane, which (being within the arms, encircling the mouth) is physically isolated from the oviduct, which opens inside the mantle cavity (Drew 1911;Hanlon et al 1999;Marian 2015). Fertilisation occurs externally and is usually achieved following a series of muscular contractions around the female SRs, releasing sperm to the vicinity of the eggs when depositing them with her arms at spawning (Iwata et al 2019;Yamamoto et al 2019). Since sperm transfer takes place without the insertion of male genitalia, the diversi cation of SSOs in cephalopods is clearly due to factors unrelated to the interaction between male and female genitalia (since there is no direct genital interaction in cephalopods).…”

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Multiplicity of sperm receptacles for securing the offspring genetic variability in a pelagic squid

et al. 2023

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Female eumetazoans often develop sperm storage organs (SSOs). Although the processes of sperm storage may in uence sperm competition and cryptic female choice in polyandrous species, the signi cance of developing multiple SSOs is not well understood. In contrast to coastal squids (which develop no more than two SSOs), the female Japanese common squid Todarodes paci cus, a more oceanic pelagic species, develops more than 20 SSOs, which take the form of specialized pockets, called seminal receptacles (SRs), on the buccal membrane. We investigated the sperm storage pattern of SRs by paternity analysis of hatchlings obtained after arti cial insemination using sperm retrieved from 6 arbitrarily selected SRs. The results showed that females were capable of storing sperm contributed by 9 to 23 males, indicating that females are broadly promiscuous. In the pattern of sperm storage, the number of males and proportion of their sperm present in the SRs varied widely among SRs, and sperm storage was biased towards particular males at the individual SR level. However, when calculated as a proportion of all the SRs within a female, the number of sires increased and the paternity bias towards any particular male weakened. These results suggest that one function of having multiple SRs in T. paci cus may be to ensure genetic diversity of the offspring.

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Multiplicity of sperm receptacles for securing the offspring genetic variability in a pelagic squid

et al. 2023

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A review of sperm storage methods and post-copulatory sexual selection in the Cephalopoda

Sato

2021

Biological Journal of the Linnean Society

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In many animal phyla, females have a unique sperm storage organ (SSO). Post-copulatory sexual selection is a powerful driving force of SSO evolution. SSOs are generally considered to have evolved through sexual antagonistic coevolution between male genitalia and the SSO and/or cryptic female choice (CFC). In cephalopods, sperm transfer and fertilization are conducted through complex processes, and sperm storage methods show inter-species variation. In some species, males implant spermatangia superficially under the female skin, and then sperm released from the spermatangia are transferred into a seminal receptacle (SR). Deep-sea cephalopods, which lack a SR, have instead evolved a deep-implanting method by which the spermatangium is embedded deep in the musculature of the mantle wall of the female. In some species, the female stores whole spermatangia within a spermatangium pocket. Because the males of most species do not insert an intromittent organ into the female when transferring sperm, SSO evolution may have been influenced by CFC alone. This review summarizes the sperm storage methods and the mechanisms of post-copulatory sexual selection in cephalopods and it is proposed that these diverse methods evolved as adaptive mechanisms through post-copulatory sexual selection.

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Genetic evidence for multiple mating and mixing of sperm from multiple males in the seminal receptacles of female Japanese flying squid (Todarodes pacificus)

Ohtani

Yamamoto

Yanagimoto

et al. 2022

Journal of Molluscan Studies

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The genetic diversity of sperm and spermatangia stored by mated Japanese flying squid (Todarodes pacificus) was examined to better understand how this ommastrephid squid mates and stores sperm. Analyses were conducted using spermatangia implanted in the lips of immature squid collected in Tsugaru Strait, northern Japan, in July–August 2019, spermatangia implanted in the lips of mature squid collected in the East China Sea in April 2019, and sperm stored in the seminal receptacles of squid collected off Tosashimizu, Kochi Prefecture, Japan, in February 2019. DNA was extracted, microsatellite loci were amplified using five PCR primers, and allele peaks were analysed. Analysis of the spermatangia confirmed that females in the field mate with multiple males, suggesting that males transfer from 1 to at least 14 spermatangia in each mating. Analysis of the seminal receptacles showed that sperm from multiple males are mixed within individual sperm chambers. Spermatangia were also found implanted in the lips of males, providing evidence of same-sex sexual behaviour. To date, studies of cephalopod mating systems have focused on coastal species, and the results of this study add to our growing knowledge of more oceanic species.

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Close-up observations on the spawning behavior of a captive Japanese flying squid (Todarodes pacificus)

Cited by 4 publications

References 13 publications

Multiplicity of sperm receptacles for securing the offspring genetic variability in a pelagic squid

Multiplicity of sperm receptacles for securing the offspring genetic variability in a pelagic squid

A review of sperm storage methods and post-copulatory sexual selection in the Cephalopoda

Genetic evidence for multiple mating and mixing of sperm from multiple males in the seminal receptacles of female Japanese flying squid (Todarodes pacificus)

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