Acta Hydrobiologica Sinica (水生生物学报) 2012/36:6 PP.1071-1080
Artificial rearing technique for Inimicus japonicus was conducted at Xishan experimental ground of Zhejiang Marine Fisheries Research Institute from May to June 2011. After obtaining fertilized eggs by artificial insemination, we observed the embryonic and larval development of devil stinger using microscope and described the development time and morphological characteristics of each development stage, which provide basic information for the artificial breeding and early development. The results showed that fertilized eggs had perfectly spherical shape and were transparent, and average egg diameter was (1.42±0.04) mm and without oil globule. Furthermore, the eggs showed buoyancy in seawater at salinity 31. Embryos were incubated in seawater (salinity 31) at (22±0.5)℃. The time-table of major embryonic de-velopment stages of devil stinger were as follows: blastodisc forming stage at 15min post fertilization (pf); 2-cell stage at 25min pf; multicellular stage at 4h and 10min pf; bastula stage at 7h and 20min pf; gastrula stage at 13h and 20min pf; neurula stage at 25h 40min pf; organogenesis stage at 26h 10min pf; tail bud stage at 38h 10min pf; heart beat stage at 40h 30min pf; muscular contraction stage at 46h 20min pf; pro-hatching stage at 52h 10min pf; hatching stage at 52h 10min pf. Newly hatched larvae usually lied on the water surface and had 3.0 mm in average in total length (TH) with yolk sac length of 2.2 mm and height 1.7 mm. The larvae relied on their yolk for nourishment before the 3rd day post hatching at (21±0.5)℃. 4 days later, the yolk sac was consumed completely and started ingesting rotifers. About 13 days after hatching, the whole body length was (7.1±0.35) mm and fin ray appeared on the dorsal fin, indicating the larvae began turned into juvenile. On day 15 post hatching, the whole body length was (7.92±0.61) mm, and golden yellow maculation occurred on each fin. On day 25, whole body length was (13.66±0.55) mm, metamorphosis was completed with yellow brown of total body and the fish turned into young fish, while accompanied by a change from planktonic habits to demersal habits. The morphological development and changes of pigment pattern from embryonic to juvenile stage were observed. Pectoral fin bud was developed early after the later stage of embryo together with the fan-shaped membrane. Three days later, 3—5 melanin pigments appeared in the neighbor of pectoral fin border of larvae, and yel-low pigments were clearly seen in the border with arc distribution. Six days later, a small amount of melanin pigment was developed in the distal end of pectoral fin and yellow pigments showed more intensity. Twenty days later, vivid golden yellow maculation occurred on the outsized? fan-shaped pectoral fin. Two fin rays at the below of pectoral fin of adult fish were connected without membrane, presenting the dissociation state. In the juvenile stage, these fin rays, like the other fin rays, was connected by membrane, subsequently became the free fin ray. From the morphological observa-tion, it is thought that two dissociated fin rays on the pectoral fin were differentiated from the pectoral fin rays.