The so-called micronekton is an intermediate group between the nekton and the plankton from the view-points of swimming ability as well as of its body size. Most of the micronektonic fishes have been known to undertake diurnal vertical migration and dwell in the meso- and bathypelagic zones of ocean. Fifteen species belonging to four families, Gonostomatidae (A), Sternoptychidae (B), Chauliodontidae (C) and Myctophidae (D), were collected from the surface to about 2000m depths in Sagami and Suruga Bays by ORI-plankton net and Isaacs-Kidd midwater trawl at night.
The lipid contents of the micronektonic fishes on the wet weight basis were 2.1% to 6.0% in A, 1.4% in B, 2.4% in C, and 2.0% to 11.9% in D. The wax esters in their lipids were 13.0% to 69.8% in Gonostomatinae (sub-family of A) and over 50% in most of the genus
Cyclothone, 15.3% and 6.1% in Maurolicinae (sub-family of A), 4.2% in B, 7.2% in C, and 1.7% to 67.1% in D, As the representative example of micronektonic fish,
Cyclothone atraria was chosen and its various tissue lipids were analyzed. The fat-filled swim-bladder contained the highest amounts of lipids (52.1%), in which 78.3% were the wax esters.
The wax esters consist mainly of C
30 to C
44 with even carbon chain-lengths. The major esters are C
34, C
36, C
38, C
40 and C
42, and also a trace amounts of odd numbered esters exist. The acid moiety of wax esters is dominantly monoenoic acids and docosahexaenoic acid, while the alcohol moiety contains mainly C
16 : 0, C
18 : 1, C
20 : 1 and C
22 : 1, as much as 80% in the sum of four components. Comparing the wax ester distribution of micronektonic fish with that of mullet roe, the former ranges rather longer esters because of major moiety of longer chain alcohols in its esters.
Although the relation between the micronektonic fishes and their wax ester contents in the lipids has not been fully understood yet, the bathypelagic nonmigrants, such as the genus
Cyclothone, contain larger quantities of wax esters than the surface and midwater migrants which contain less than 20% and contain a few per cent in most of them.
抄録全体を表示