Reproductive behaviour and development of the glassperchlet, Ambassis agrammus Gunther (Pisces: Ambassidae), from the Alligator Rivers system, Northern Territory

Abstract

A. agrammus showed sexual dimorphism in body shape during the breeding season. Pairing occurred during daylight with a single release of eggs amongst submerged vegetation at nightfall on the same day. The eggs were demersal, adhesive and spherical (0.50-0.56 mm diameter). A single oil droplet (0.15-0.20 mm diameter) persisted throughout egg and larval development. Hatching occurred 19-23 h after spawning at 27-35ºC. At hatching, prolarvae [l .53-1.57 mm in standard length (SL)] were poorly developed and inactive. Feeding commenced 3 days after hatching (at 2.19-2.27 mm SL) after absorption of the yolk-sac. Fin-ray formation was complete in fry of 7.0 mm SL. Aquarium-reared fish first bred at 30 mm SL when 3 months of age. Features of A. agrammus reproduction as they relate to a specific survival strategy are briefly discussed.