スルメイカOmmastrephes sloani pacificus STEENSTRUPの繁殖生態に関する実験的研究 : V.リンコトイチス幼生の第IV腕形成と触腕変態の追跡

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In the previous studies the author could observe the development of the 3rd arm of the squid, Ommastrephes sloani pacificus STEENSTRUP, using the larvae cultured in the laboratory (HAMABE, 1961 a, b, c and d), but it was difficult to study the formation of the fourth arm. Because the rhynchoteuthis larvae remain at this stage for relatively long time and to observe completely the formation of the fourth arm the larvae must be kept for long time in the laboratory. This makes unable to follow the developmental changes of the larvae. To avoid this attempts were made to collect the rhynchoteuthis larvae at their various developmental stages in nature. Attention was also paid to identify the species of the rhynchoteuthis larvae collected from sea. Morphological continuity from younger larvae to the lantern type rhynchoteuthis larvae was varified by similarity of (1) the forth arm and the fused tentacle, and (2) chromatophoric patterns between them (Fig.2 and 3). Continuity from the lantern type larvae to older forms was established by examining difference in the tooth process of the tentacle suckers (Fig.4). Of three groups of the materials used for these purposes, the first one consisted of the rhynchoteuthis larvae occuring off the Oki Islands. They are lantern shaped with mantle length ranging from 3mm to 15mm (Fig.1). NAEF (1923) has suggested that this from belongs to Ommastrephidae, but the species has not been identified yet. The second group consisted of the larvae of O.sloani pacificus fatched and reared in the laboratory. They were at earier stages than the first group (A and B in Figs.2 and 3). The third group included juvenile larvae and adult of O.sloani pacificus collected from the waters around the Oki Islands. The larvae in this group were greater in mantle length than the other two groups (Fig.4, A to E). Following conclusions were drawn from the observations on the rhynchoteuthis larvae collected. The fourth arm developed later than any other arms (Fig.1.), and the tentacle extended first as a fused rostrum, and then separated into two by the time when they became the larvae with about 15mm in mantle length. It was estimated from the laboratory observations that at least two weeks are needed for the larvae to complete the life of rhynchoteuthis stage from hatching (Fig.1.). Prerhynchoteuthis stage carhacterized by HAYASHI AND IIZUKA (1953) was not identified in both larvae hatched in the laboratory and those found in nature.
社団法人日本動物学会の論文
1962-03-15

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日本海区水産研究所浦郷支所

スルメイカOmmastrephes sloani pacificus STEENSTRUPの繁殖生態に関する実験的研究 : V.リンコトイチス幼生の第IV腕形成と触腕変態の追跡

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