| Summary: | 碩士 === 國立東華大學 === 海洋生物多樣性及演化研究所 === 99 === Early ontogeny of silver moony, Monodactylus argenteus, was described and illustrated by using optical microscope, stereomicroscope and scanning electron
microscopy (SEM). The 96 h acute toxicity of ammonia in juvenile M. argenteus for the water quality management were also discussed and evaluated. Fertilized eggs were limpid and floa表, with a mean diameter of 0.94 ± 0.03 mm, narrow perivitelline space, and a single oil globule. As the egg developed, appeared on th surface of egg, oil globule and embryo. Embryonic development lasted 30 hours at 25.85℃. Newly hatched larvae were 2.11± 0.03 mm in total length (TL) with 24-26 (10-11+14-16) myomeres and an oil globule in the ventroposterior area of the yolk sac. First feeding of larvae began at two days post hatch (DPH) (2.79 ± 0.13 mm in TL and 311± 33 μm in gape height). During this stage, with melanophores covered on the abdominal region, the pectoral fins were developed and the yolk sac was absorbed. Five DPH, the pelvic fins were developed. Twelve DPH, 2-3 caudal fin rays had begun to develop and the larvae started the flexion stage. Eighteen DPH, the dorsal and anal fins were developed. Thirty-five DPH (12.30 ± 1.53 mm TL), all fins had this species complement of rays and spines (D.Ⅶ-Ⅷ, 29-30; A.Ⅲ, 31; P1. 18; P2.Ⅰ, 5; C. 17), and the juvenile stage begun. Under the scanning electron microscopy, fertilized egg was spherical and smooth. The pores on the egg surface were uniform in size and were protrudent, with a density about 19/100 μm2. The pores that were in the micropyle region were larger than in the other regions, and surrounded the micropyle in an orderly manner. The micropyle was cylinder shape, about 10.4 μm in diameter with 4 pieces ring-like ridge structure and a long and narrow gap in the middle.In larvae, a few neuromasts were observed on the surface of the larvae, and increase as the fish growing. Scales began to develope in 12 DPH, and fully developed in 28 DPH. Primary teeth were appeared in 10 DPH on maxilla, the teeth in side the mouth began to grow in 18 DPH, and fully developed in 21 DPH. 2 opercular spines appeared in 10 DPH, an increase as larvae growing, posttemporal spines and serrate supraocular spines appeared in 18 DPH, and spine began to wither after 28 DPH. To evaluate the 96 h acute toxicity of ammonia, the juveniles were treated in 0, 0.47, 0.80, 0.90, 0.98 and 1.02 mg/L unionized ammonia-N (UIAN) respectively. The experiment was conducted as a completely randomized design with three replicates. The LC50-96 h of M. argenteus for UIAN was 0.89 mg/L, and the suggested concentration for rearing was 0.089 mg/L UIAN.
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