Early development of the Australian crimson-spotted rainbowfish, Melanotaenia fluviatilis (Pisces: Melanotaeniidae)

Abstract

This paper describes the early ontogeny of the crimson-spotted rainbowfish Melanotaenia fluviatilis. Eggs ranged in size from 0.98 to 1.07 mm and 35-45 oil droplets were present, as were numerous adhesive filaments which originated from one point. Hatching was predominantly 7-9 days after spawning at 25.5ºC. At hatching, larvae (4.2 mm standard length) had a reduced but still present yolk sac and were strong enough swimmers to remain in the upper 1 cm water layer. The swim bladder inflated within 10 h of hatching and the first ingested food was observed after 12 h. At 32 days after hatching, the mean larval length was 13.86 rnm and at 72 days was 21 mm. Knowledge of the critical developmental stages described in the paper is important in understanding the impact of the major biotic modifying factors influencing the impact of chemicals and other pollutants on rainbowfish, especially given that they are used by ecotoxicologists as a surrogate species for Australian freshwater fish in general.