科研之友
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摘要
Longfin batfish Platax teira is one of the most important finfish species in Asian aquaculture. However, knowledge on early ontogeny and reproduction of this species in captivity are scarce and incomplete. In this study, the embryonic, larval and juvenile development of P. teira are described and illustrated for the first time. The effect of temperature (27, 30 and 33 degrees C) on hatching rate, yolk-sac volume and oil globule volume was demonstrated. Cannibalism control via aeration adjustment for the enhancement of larval survival was also examined. Fertilized eggs were spherical, buoyant and had a diameter of 1.29 +/- 0.05 mm (mean +/- SD). Embryonic development lasted 16 h at 26.2 degrees C. Newly hatched larvae were 2.81 +/- 0.24 mm in total length (L-T) with 24 myomeres and had an oil globule in the ventroposterior area of the yolk sac. Early larvae had xanthophores appeared all over the body, except for the tip of the notochord. Larvae completed yolk absorption within 3 days post hatching (dph) at 3.41 +/- 0.11 mm L-T. Larvae were fed initially on rotifers Brachionus ibericus, followed by Anemia nauplii and finally weaned onto an artificial diet. From 8 dph, the larger larvae (over 4 mm L-T) began to exhibit cannibalistic behaviour. Transformation of larvae to the juvenile stage was completed at 23.80 +/- 1.98 mm L-T, all fins had the adult complement of rays and spines. A statistical model: Y = 2.4968e(0.0786x), where Y is mean L-T (mm) and X represents dph, explained 96.45% of variation in growth (P < 0.001, R-2 = 0.9645). The hatching rate, yolk-sac volume and oil globule volume of newly hatched larvae were significantly (P < 0.05) decreased when the incubation temperature increased. Only 2-6% of embryos hatched at 33 degrees C, while the hatching rate was 63 +/- 6% at 27 degrees C. Larvae reared in aeration rate of 300 mL min(-1) attained the highest survival rate at 70.00 +/- 7.20%, but remained significantly (P < 0.05) lower in cannibalism: 24.44 +/- 4.16% compared with 66.67 +/- 5.44% in 20 mL min(-1). These results indicate that the optimal incubation temperature recommended is approximately at 27 degrees C, and aeration at 300 mL min(-1) could enhance larval survival by reducing cannibalism.
