Ecology and life history of an Amazon floodplain cichlid: the discus fish Symphysodon (Perciformes: Cichlidae)

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.Os acarás-disco do gênero Symphysodon são peixes ornamentais comumente encontrados em lagos e florestas alagadas das planícies inundadas da Amazônia. Estes habitats são caracterizados por uma variação sazonal extrema na disponibilidade de alimento, abrigo e oxigênio dissolvido, e também pela densidade de predadores e parasitas. A maioria dos aspectos da biologia do acará-disco são influenciados por esta variabilidade de condições sazonais. Este artigo apresenta um estudo autoecológico de S. haraldi (até recentemente classificado como S. aequifasciatus) da Amazônia Ocidental. Os acarás-disco alimentam-se predominantemente de perifiton, detritos orgânico, material vegetal, e invertebratos aquáticos pequenos. Durante a estação da 'cheia' eles forrageiam sozinhos ou em pequenos grupos dentro das florestas alagadas. Porém, na estação da 'seca' eles formam grandes cardumes nas coroas de árvores caídas ao longo das margens de lagos. A reprodução ocorre no início do período das enchentes, assegurando que a prole esteja bem crescida antes da próxima seca. Os acarás-disco são iteróparos, executam desova parcial, alcançam a maturidade reprodutiva em um ano, e executam cuidado parental dos ovos e alevinos. O início da desova, e a taxa de sobrevivência da prole podem ser influenciados pelas flutuações do nível da água, resultando em distribuições não-unimodais das classes de tamanho do subsequente '1+ cohort'.

A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae), with descriptions of 15 new species

“…Adaptations to hypoxia: The influence of dissolved oxygen on the distributions of Brachyhypopomus is discussed by Crampton (1998b;2008) and Crampton & Albert (2006). Species that occur in seasonally or perennially dysoxic habitats such as whitewater floodplains and terra firme swamps are adapted to survive protracted periods of hypoxia (< 1mgl -1 ) or complete anoxia, while those that occur in permanently normoxic habitats, such as terra firme streams, are not (Crampton, 1998a,b).…”

“…It is known from floating macrophytes in whitewater floodplains at the confluence of rio Solimões and Japurá (see description of B. belindae for water quality parameters in this area), and from the large low-conductivity (usually <30 μScm -1 ) blackwater floodplain ria lake, lago Amanã; see Crampton (2008) for notes on the water chemistry of lago Amanã. Specimens in reproductive condition were found during the rising and high water period, which is consistent with the reproductive seasonality of sympatric congeners.…”

New cases of pathogens imported with ornamental fish

“…and Symphysodon discus, Heckel, 1840 (Cichlidae: Perciformes) (Froese & Pauly 2010) (discus fish) are ornamental cichlid fish that occur in floodplain lakes and flooded forests of the lowland Amazon Basin (CramPton 2008). Their aquaculture in several Asian countries is well developed (sands 1988).…”

A new species of Dadayius Fukui, 1929 (Digenea: Cladorchiidae), parasite of Symphysodon aequifasciatus Pellegrin, 1904 (Perciformes: Cichlidae) from the Purus River, Amazon, Brazil

“…It is a small fish that does not present sexual dimorphism (Kullander, 2003), with a maximum total length of 17 cm. Although being an economically important fish, there are few studies related to its endoparasitic fauna (Crampton, 2008). Dadayius Fukui, 1929 belongs to the family Cladorchiidae and is found parasitizing fish, reptiles, amphibians and mammals (Jones, 2001).…”