Mature adults of the clingfish, Aspasma minima (Döderlein), consisting of six males and.42 females, were collected at the coastal waters of Nomo near Nagasaki during the period from May to June 1970.The males, ranging from 47.9 to 71.4 mm in total length, and the females, ranging from 36.6 to 50.2 mm, showed the secondary sex characters in the forms of head and genital papilla.Three males were selected from the mature adults and paired with some females varying in number from one to seventeen in four cases and being replaced each time. They were placed in a glass aquarium provided with an artificial nest of stone or tile. They spawned egg masses four times at the interval of four to seven days.The egg masses, each mass being rather dense in one layer, were deposited on the underside of the nest. The largest male, being 71.4 mm in total length, was clinging upsidedown to the underside of the nest near the egg mass at every spawning. The number of the eggs in one spawning was enumerated from 140 to 619 in four cases, but the number of the ripe.ovarian eggs was counted from 80 to 210 in 23 mature females.
The egg is ellipsoid in shape, and it is provided with an adhesive pedestal at its bottom.and rather wide perivitelline space.The size of the egg varies from 1.25 to 1.35 mm in.long axis and from 0.90 to 0.95mm in short axis.The yolk of the egg is light greenish yellow in color and granular in appearance, and it contains about 20 oil globules.The incubation period of the egg extends from 301 to 350 hours in some eggs at the water temperature of 18.6 to 23.5°C.
The newly hatched larva measures from 3.62 to 3.98mm in total length and has a little or no yolk.The larva is rather stout in appearance and has large eyes, the rudiments of the air bladder, and 35 myomeres. The anus of the larva is open in the posterior part of the body. One of the hatched larvae, kept in a plastic aquarium and fed with rotifers and. copepods, was reared for 18 days and grew up to a 6.70 mm postlarva.During this rearing period, the larva changed its life mode from a planktonic life to a clinging one.Another postlarva in the planktonic life, collected with fish lamp, was reared up to a 7.45mm juvenile in the complete clinging life.
The rudiment of ventral disc appears in a 4.5mm postlarva in the planktonic life..The disc is completed in a 14mm juvenile in the clinging life.
The collections of the clingfish, carried out at the coastal waters of Nomo during May 1969 to January 1971, show that the postlarvae, being from 3.3 to 7.5mm in total length.and in the planktonic life, come around fish lamp at night during the period from May to July. The juveniles, being over 10mm, enter into the clinging life on the sea weeds, Ecklonia cava and Sargassum spp.and feed on copepods, amphipods, zoea larvae, tinny shells, and ostracods there.The males grow up larger than the females.The life span is.one year.
