スルメイカOmmastrephes sloani pacificus STEENSTRUPの繁殖生態に関する実験的研究 : II.産卵
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In order to throw light on spawning behavior of the squid, Ommastrephes sloani pacificus Steenstrup, some experiments were carried out in Urago Bay of the Oki Islands during the period from April 1958 to June 1959. In every experiment, several mature females which were caught alive for that purpose from the areasadjacent to the Islands were separetely kept in wooden barrels (50cm. in lengthand 33cm. in inner diameter) installed on the bottom of the inshore waters whose depth raged from 5 to 20 meters (Figs.1 and 2). During the experiments, bottomwater temperatures were in the range from 12°to 20℃, and chlorinity from 18.82‰ to 19.08‰. At the spawning time the temperatures ranged from 15° to 20℃, and chlorinity from 19.04‰ to 19.08‰. Out of about two hundred specimens used throughout the experiments, fifteen individuals could be made to deposite the egg mass in the barrels. Incidentally a continuous observation was made for one ofthe specimens which were spawning in a water tub during the transportation fromthe fishing ground (Table1 1 and 2, Fig.3). The following are the important features of the egg mass. Essentially they consist of three components: ova, the oviductal and the nidamental secretions. In every egg mass about 300 to 4,000 ovaare buried in the oviductal secretion which is viscous and a little buoyant like human saliva. This secretion is again enveloped in a thick capsule made of thenidamental secretion which is also viscous but albuminous and heavier then sea water. The demersal eggs are elliptical or nearly spherical, each measuring about 0.7 to 8.0mm. in the greatest diameter. The egg mass was found sticking by means of a particularly thick layer of the nidamental secretion al over the inner surface of the barrel except the upper part and a net covering the mouth of the barrel. Therefore, the egg mass filled nearly one to two-thirds of the barrel's room and formed rather an eliptical mass according to the shape of the barrel (Fig.6 6-D and E). From those findings it is highly probable that the spawning squidin nature makes use of rocks, gravels or any other solid substance on the sea bed in order to deposit their egg mass into a cavity of the bottom material and fill up the cavity with the eggs. Thus, the egg mass would form an indefinite shape. In the hope of elucidating the spawning process, the results from anatomicalexamination of the squids having finished spawning were combined with the knowledge obtained from the egg mass in the barrels and contnuous observations of thespawning behavior. It has been inferred that spawning takes place in the following sequence. In the first place the squid discharges a mass of the nidamental secretion alongside the arms. Then, the eggs having been fertilized in the buccalmembrane, are transferred to the tips of the first and the fourth arms. (Fig.6). From there they are dispersedly pushed into the oviductal secretion which is discharged from the ovarian funnel and comes floating along the ventral side of the body. Finally, the mixture of the eggs and the oviductal gelatin is envelopedin the nidamental secretion, settled and fastened on a solid material (Fig.6). Thus, the spawning process under experimental conditions is assumed to have beencompleted after about 2 hours.
- 社団法人日本動物学会の論文
- 1961-11-15
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