The spawning behaviour of the endangered Eastern Cape rocky, Sandelia bainsii (Anabantidae), in South Africa

Abstract

Sandelia bainsii is an endangered freshwater fish species which only occurs in short sections of several Eastern Cape river systems in South Africa. The spawning behaviour of S. bainsii is described for the first time. Female S. bainsii remained a light grey colour. Males exhibited distinctive nuptial coloration consisting of an intense black with a white bar on their caudal fin and white windows on the posterior areas of their dorsal and anal fins. There was a darkened post orbital contact organ of ctenoid scales on the reproductively active males. The spawning behaviour was recorded on a video recorder and analyzed during frame by frame replay. Sandelia bainsii are uniparental substrate breeders. The male prepared a spawning area by clearing the substrate with rapid body movements (sweeps). There were a number of preliminary courtship movements, several trial embraces by the male before the actual final embrace. The male underwent a U bend around the female, anchored himself with the contact organ, squeezed the abdominal area of the female with a quick head movement. Courtship and spawning all took place near the substratum. Twenty one separate mating bouts were filmed and analyzed. The duration varied from 1.44 to 5.11 seconds with an average embrace of 3.39 seconds. During the mating clench the female was not normally turned over, as in some anabantoids, but remained upright. The male then guarded the spawning area. Eggs were light yellow, adhesive, demersal and 1.28 mm in diameter with 0.61 mm oil globules. The breeding behaviour of S. bainsii has some similarities with both breeding behaviourial groups, the bubble nesters and the free spawners, within the other African anabantid genus, Ctenopoma. Sandelia bainsii have acquired some temperate specializations with regard to their reproductive style. Free spawning and the release of buoyant eggs is the plesiomorphic anabantid reproductive style. The demersal eggs and male substratum nest sites of S. bainsii are considered apomorphic.