Reproduction and development of the asian bronze featherback Notopterus notopterus (Pallas, 1769) (Osteoglossiformes, Notopteridae) in captivity

摘要

Experimental data demonstrate that the environmental factors decreasing conductivity, slight variation of temperature, and water level have no influence on gonad development or courtship behavior in Notopterus notopterus. Spawning occurs during day time at a temperature of 25–28 °C. Newly spawned 3.8–4 mm adhesive eggs are guarded by the male until hatching. The egg envelope has external spiraling ridges, which are centered round the micropyle. Hatching occurs within 168–204 hours depending on temperature and even with some variability at 27°C constant incubation temperature. Exogenous feeding then starts on day 17 with a total length of 16.2 mm and yolk-sac remnants still present. The larval period lasts until day 36. Dark brown stripes appear on the body as one of the characteristic pigment patterns of juvenile N. notopterus at day 70 with a total length of around 34 mm, replacing the dotted pigment pattern of larvae and early juveniles. Later again a spectacular color change to uniformly gold-bronze coloration occurs. The genital papilla can macroscopically be recognized at day 80. Sexual maturity of N. notopterus in captivity as indicated by courtship behavior is first observed in 30-month old specimens of both sexes of the F1 generation with a total length of around 275 mm in males and 230 mm in females, whereas this might occur at smaller size in the P generation and in natural environment. Generally, in N. notopterus the embryonic period lasts longer and the onset of the larval period starts much delayed as compared to a typical indirect or saltatory development. The larval period before onset of the juvenile period with its spectacular color changes, shows few discernible stages of morphological development. It is immediately a pterygiolarva with the jaws, branchial arches, most fins differentiated, a distinct pigmentation pattern and the mouth opened during the embryonic and free embryonic phases.