Abstract
The discus fishes of the genus Symphysodon are popular ornamental cichlids that occur in floodplain lakes and flooded forests of the lowland Amazon Basin. These habitats are characterized by extreme seasonal fluctuations in the availability of food, shelter and dissolved oxygen, and also the densities of predators and parasites. Most aspects of discus biology are influenced by these fluctuating conditions. This paper reports an autoecological study of the western Amazonian discus S. haraldi (until recently classified as S. aequifasciatus). This species feeds predominantly on algal periphyton, fine organic detritus, plant matter, and small aquatic invertebrates. At high water it forages alone or in small groups in flooded forests. At low water it forms large aggregations in fallen tree crowns along lake margins. Breeding occurs at the beginning of the flood season, ensuring that the progeny are well grown before the next low water period. Symphysodon haraldi is an iteroparous partial spawner, reaches reproductive maturity within a year, and undertakes parental care of its eggs and larvae. The timing of spawning events, and/or the rate of brood survival, may be influenced by fluctuations in the flood level, resulting in a non-unimodal distribution of size classes for the subsequent 1+ cohort.
Highlights
The discus fish genus Symphysodon (Perciformes: Cichlidae) comprises two or three species restricted to floodplain habitats of the lowland Amazon basin (Bleher, 2006; Bleher et al, 2007; Ready et al, 2006)
The aim of this paper is to demonstrate how multiple specializations of life history, behavior, physiology, and anatomy adapt populations of Symphydodon to the constantly changing conditions of the Amazon floodplain
This study focused on two sites in blackwater mouthbay lakes: Uxi Bay, a small embayment of lago Amanã; and the northern margin of nearby lago Urini (Fig. 1)
Summary
The discus fish genus Symphysodon (Perciformes: Cichlidae) comprises two or three species restricted to floodplain habitats of the lowland Amazon basin (Bleher, 2006; Bleher et al, 2007; Ready et al, 2006). Little quantitative data has been published about the ecology and life history of wild discus, despite the importance of Symphysodon in the aquarium trade and an extensive aquarium literature Mayland, 1994, Degen, 1995; Bleher, 2006), and despite recent taxonomic and cytogenetic interest in the genus (Kullander, 1986; 1996; Ready et al, 2006, Bleher et al, 2007; Mesquita et al, 2008). Understanding how fishes are adapted to these constantly changing conditions is central to an understanding of fish diversification in the lowland Amazon basin
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