ドジョウ科の1属Acanthopsoides Fowler, 1934の再検討を行った.Neacanthopsis Smith, 1945は, Acanthopsis属のシノニムとした.Acanthopsoidesの2種 (A. gracilisとA. gracilentus) にくわえて4新種 (A. delphax, A. hapalias, A. molobrion, A. robertsi) の記載を行い, 同属魚類の分布域について検討した.同属魚類は東南アジアに広く分布するが, A. glacilis, A. glacilentus, A. delphax, A.hapaliasは同所的に分布し, またカプアス河のA. molobrionとA.robertsi, メコン河のA. glacilentus, A. delphax, A. hapaliasも同所的であると判断された.本研究で明らかにされたAcanthopsoides属魚類の多様性は以下のことを示していると考えられる.すなわち, 東南アジアの淡水魚類相は現在知られている以上のレベルの多様性を有している可能性がある.
Pelagic fish eggs are usually fixed by formalin solution just after collection in the field. Most of these eggs are difficult to be identified to species, because only limited characters are available for identification and considerable changes in structures take place with fixation . In this study, species names of formalin fixed eggs were estimated by comparing their egg diameters and the diameter and number of oil globules with those of the fresh ones identified by the rearing method . Materials were collected in Wakasa Bay in May, August, and October, 1979-1982. Fresh eggs were classified into 40 species or types by the rearing method, but fixed eggs were divided into only 24 types. Comparison of fresh and fixed eggs revealed that 7 out of 24 types of fixed eggs were referable to species, and 13 types were composed of species groups.The rearing method is surely a useful step in indentifying species names and/or species types of fixed eggs.
In order to examine the distribution, abundance, and food habits of the snailfish, Liparis tanakai, in the Suo Sea, western Seto Inland Sea of Japan, experimental fishing surveys were made using trawl nets on the night (1930-0340h) of 26 May and 2 and 3 June, 1986. The study area was subdivided into 18 areas, each sampled by one trawl tow of 35min duration. A total of 190 fish was collected during the surveys, and most fish (78.9%) were obtained from muddy substrata ranging in depth from 30 to 40m at the middle area of the Suo Sea. The total length of the fish in the samples ranged from 72 to 273mm. The overall length-frequency distribution formed a unimodal curve, the mode occurring at the class of 100-130mm in total length. Of 151 fish examined, 146 (96.7%) had stomachs full of food, including a variety of small crustaceans and fish. Shrimps, especially Crangon affinis, ranked highest in importance in the diet of L. tanakai. These biological data are compared with those of conspecifics from Sendai Bay, northern Honshu of Japan.
Ovarian maturation of the puffer Takifugu exascurus (Jordan et Snyder) was induced, and embry-onic, larval and juvenile development was observed. The brood fish were collected in Tassha Bay, Sado Island (38°05'N, 138°15'E), during the spawning season in 1986 which seemed to extend from late June to mid-July. To each female 3mg acetone-dried pituitary of Hypophthalmichthys molitrix was injected to induce ovarian maturation, which took place in about 77 hours at a water temperature of 19.5-21.0°. The eggs obtained by hormone injection were artificially fertilized with the milt from a collected male. The hatched larvae were fed successively on rotifers Brachionus plicatilis, Artemia nauplii and minced fish meat, and reared for a period of about one year. The eggs were spherical, 1.24±0.04mm in diameter, demersal and adhesive. The egg-membrane Was transparent and yolk was orange in color, containing a cluster of small oil-globules. The incubation period was about 160 hours at a water temperature of 18.5-21.0°. The newly-hatched larvae, measuring 2.9-3.1mm TL, had 8+15=23 myomeres. Absorption of the yolk was completed 3 days after hatching, by which time the larvae had attained 3.5-3.6mm TL. Larval finfolds disappeared and rudimentary dorsal, anal and caudal fins formed at 4.1-4.4mm TL, in 6 days after hatching. In 9-day old larva (5.4mm TL), fin ray rudiments appeared on the dosal, anal and caudal fins and spine-like scale formed on the belly. In 16-day old specimens, 9.1-10.2mm TL, the full complements of fin rays were completed on all the fins and the fish reached the juvenile stage. The growth of larvae and juveniles reared in 1986-1987 is expressed by the following equations, where y is total length (mm) and x is days after hatching. y1=2.9420·1.0639x0≤x≤19 (r=0.998) y2=4.0286·1.0464x19≤x≤33 (r=0.998) y3=9.8854·1.0180x33≤x≤72 (r=0.996) y4=20.1555·1.0080x72≤x≤115 (r=0.998) y5=28.0610·1.0049x115≤x≤202 (r=0.995)
Cyprinid fishes generally replace their teeth alternately and cephalad. The larvae of Carassius auratus grandoculis also replace their teeth alternately and cephalad, in a pattern of 4-2-3-1-. However, adults of Carassius species replace their teeth from anterior to posterior, in a pattern of 1-2-3-4-1-. So I analyzed the appearance pattern of tooth germs in larvae and juveniles in Carassius auratus grandoculis. At stage 5 of the post-larval period, developmental difference is made between both sides. In the pharyngeal dentition on one side developing poorly, the anterior tooth on the fifth replacement wave, tooth 4 [An2] appeared later than the central teeth on following replacement wave, tooth 5 [Po1]. Moreover, the anterior tooth on the seventh replacement wave, tooth 6 [An2], appeared later than the central teeth on the following replacement wave, tooth 7 [Po1], on both sides. The reverse of tooth germ appearance between anterior teeth and central teeth makes a change of replacement pattern from 4-2-3-1-4- to 1-2-3-4-1-. The change of replacement pattern is caused by the confusion of tooth germs of anterior teeth on both sides. Mylopharyngodon piceus and Cyprinus carpio make a change of replacement patterns in the early juvenile period, too. This change of replacement pattern may be a specialized character among the subfamily Cyprininae.