Autotrophic energy sources for Paracheirodon axelrodi (Osteichthyes, Characidae) in the middle Negro River, Central Amazon, Brazil

Abstract

The cardinal tetra (Paracheirodon axelrodi) is the most abundant species of the Brazilian ornamental fish trade, constituting more than 80% of the ornamental fish collected in the middle Negro River basin. Stable isotope analyses were used to identify the autotrophic carbon sources and trophic position for the cardinal in relation to the plant groups at the base of its foodchain. Filamentous algae, tree and plant leaves and cardinals were collected in stream habitats, flooded forest and interfluvial swamps (campos) during peak flood, falling water and low water periods. d 15 N values of the cardinal in relation to the plants at the base of the food chain indicated a trophic position of omnivore. Values of d 13 C for the plants ranged from À43.1 to À26.4%, with averages of À37.6, À30.4, and À29.4% for filamentous algae, flooded forest leaves, and campo leaves, respectively. The d 13 C values for the cardinal ranged from À35.0 to À27.9%, with an average of À31.4%. Relative contributions of plants to fish carbon were estimated in a two end-member mixing model which determined that the leaves (flooded forest and campo leaves combined) and filamentous algae had average relative contributions to cardinal carbon of 71% and 29%, respectively. However, seasonal variation in the relative contributions was encountered throughout the hydrological cycle. The cardinals least enriched in 13 C were encountered in November during the falling water period, indicating that they had perhaps recently migrated down from interfluvial campos where filamentous algae production is significant. Considering that algal production has been reported to be less than 1% of total primary production in the Negro River, these results could suggest some evidence of selective herbivory in the cardinal's food chain.

Potential influence of water level changes on energy flows in a lake food web

“…These isotopic shifts in consumers were also suggested by the IsoSource model estimation results, which indicated that in the wet season consumers shift to consuming 13 C-enriched endpoints like aquatic macrophytes and terrestrial plants, not seston. These results were consistent with the findings of several authors from different geographical regions which also reported that fish assemblages collected during low and high water level periods showed shifts in their stable carbon isotope compositions in response to a change in the isotope composition of their food [8][9][10][49][50][51].…”

“…Moreover, a variety of aquatic invertebrates developing in the land-lake transfer zone become accessible for fish during this period [8,48]. Terrestrial inputs to the lake food web may be either through microbial decomposition or involve a detrital food chain bringing carbon from microbes relying on vascular plants to invertebrates through intermediary consumers [6,8,10,13,49,50]. The feeding behavior shifts of lower trophic level consumers could also influence the stable isotope composition of top-predators [10,13,15,18].…”

Biologia reprodutiva e hábitos alimentares do rodóstomo (Hemigrammus bleheri) um peixe ornamental da Bacia do Médio Rio Negro, Estado do Amazonas, Brasil.

“…Nos bancos de folhiços podem ser encontrados de 12 a 40 mil indivíduos m -2 nas folhas submersas (WALKER, 1990). Estes microrganismos servem de alimento para animais maiores, macro invertebrados como insetos, camarões e anelídeos, que podem apresentar densidades de 62 a 328 indivíduos m -2 (WALKER, 1990;1994), e que, por sua vez, servem de alimento para pequenos peixes (KNÖPPEL, 1970;GOULDING et al, 1988;HENDERSON e WALKER, 1986;WALKER, 2004;MARSHALL et al, 2008). Como muitos outros peixes, H. bleheri depende dos recursos das florestas sazonalmente inundadas para se alimentar.…”

“…Para algumas espécies de peixes ornamentais do rio Negro, como o cardinal tetra (P. axelrodi); os estudos estão relacionados aos aspectos reprodutivos (GEISLER e ANNIBAL, 1984), abundância e distribuição (CHAO e PRADA-PEDREROS, 1995), estratégias alimentares (WALKER, 2004) e fontes autotróficas de energia (MARSHALL et al, 2008 (TAPHORN, 1992;CAREY, 1993;BOANE, 1995).…”

Color pattern variation in Cichla temensis (Perciformes: Cichlidae): resolution based on morphological, molecular, and reproductive data

“…In Amazon flood pulse rivers, high water inundates the surrounding igapó and interfluvial marshes during the rainy season (Goulding, 1988;Junk, 1997). Small forage fishes are able to feed in the igapó (Forsberg, 2001) while finding shelter from predation (Marshall, 2007). A large predator such as C. temensis entering the dense concentration of flooded trunks, stems and leaves to pursue prey species may not be able to rely solely on the speed and stamina that enable it to hunt in open, low water conditions.…”