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

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

doi:10.1038/s41598-019-56071-0

Abstract

The spawning behavior of a Japanese flying squid (Todarodes pacificus) is described based on up-close observation of a captive female. The squid was first transferred from a 10-ton tank to a polystyrene plastic box containing 45 liters of seawater. About one hour later, the mantle-contraction rate increased rapidly, followed by a brief convulsion of the mantle and arms and a whitening of the body. The mantle contractions become shallow and rapid, and several seconds later, semitransparent jelly presumably from the nidamental glands emerged from the funnel and passed between the ventral pair of arms. Approximately 90 seconds after the egg mass first emerged, the female began ejecting oocytes through the funnel into the egg mass using rapid, powerful mantle contractions. Soon after the oocytes were ejected, translucent strands (presumably sperm) emanated from the buccal membrane. The female continued to eject oocytes for approximately two minutes, after which the mantle convulsed, and the mantle-contraction rate decreased slowly for about one minute until the contractions stopped. The squid died soon afterwards.

Highlights

Cephalopod behavior is complex and has intrigued humans for centuries
In the ommastrephid Humboldt squid (Dosidicus gigas), sperm released from the spermatangia actively migrate across the buccal membrane to the seminal receptacles, where they are stored alive until the female spawns[13]
The oocytes pass through the funnel and into a gradually ballooning egg mass surrounded by a layer of jelly from the nidamental glands[14]

Summary

Introduction

Cephalopod behavior is complex and has intrigued humans for centuries. Some of the most diverse behaviors are related to reproduction[1]. The Japanese flying squid (Todarodes pacificus) is a nerito-oceanic, ommastrephid species that occurs widely in continental shelf and slope waters in the northwest Pacific Ocean[4]. It is the target of the largest squid fishery in Japan and is usually one of the three largest cephalopod fisheries in the world[5,6]. Sperm move from the embedded spermatangium to seminal receptacles located on the buccal membrane. In the ommastrephid Humboldt squid (Dosidicus gigas), sperm released from the spermatangia actively migrate across the buccal membrane to the seminal receptacles, where they are stored alive until the female spawns[13]. What triggers the release of sperm from the seminal receptacles is not known

Methods

Results

Conclusion