Morphological
development of eggs, larvae and juveniles of laboratory-reared Ryukyu-ayu Plecoglossus
altivelis ryukyuensis
K.
Tachihara, K. Kawaguchi-2003
Fisheries
Science, 69(2): 323
Abstract:
The
development of embryos, larvae and juveniles of the Ryukyu-ayu, Plecoglossus
altivelis ryukyuensis are described based on laboratory-reared
specimens.The eggs were spherical, 0.98-1.18 mm (mean 1.06 mm) in
diameter with an adherent membrane. The incubation period after
fertilization was approximately 155 h at a water temperature of
19.7-22.0°C(mean 20.7°C). Newly hatched larvae were 5.0-5.9 mm(mean
5.5 mm) in body length (BL) with 59-62 myotomes.Within 5 days after
hatching, the larvae had attained 6.4-8.2 mm (mean 7.8 mm) BL and
had completely consumed their yolk. Notochord flexion began at 13.7 mm
BL and was completed by 16.3 mm BL. The rudimental dorsal, anal, pelvic
and adipose fins appeared at 14.7, 16.3, 21.8 and 21.8 mm BL,
respectively. All fin rays reached the same fixed number of adult fish at
about 28 mm BL. The comb-like teeth began to form at approximately 30 mm
BL and were fully developed at about 40-50 mm BL.The proportions of P. a. ryukyuensis
specimens, which were consistent with adult fish, occurred at approximately
40 mm BL.
(Laboratory of Fisheries Biology & Coral Reef
Studies, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa
903-0213, Japan, Tel: 81-98-895-8556. Fax: 81-98-895-8576. Email: ktachiha@sci.u-ryukyu.ac.jp)