Do the tropical freshwater fishes feed on aquatic fungi?

Abstract

Consumption and processing of allochthonous plant litter by fishes is more common in tropical than temperate streams and rivers. Therefore, aquatic hyphomycetes in water (filtration), leaf litter (bubble chamber incubation), and fecal pellets (direct observation and inoculation to sterile leaf litter) of three dominant fishes belonging to the family Cyprinidae (Aplocheilus lineatus, Puntius filamentosus, and Rasbora daniconius) in two locations of the River Kali of the Western Ghats, India, were evaluated during postmonsoon season. Spores of 14 and 9 species of aquatic hyphomycetes were recovered on filtering water samples of Kaiga stream and Kadra dam with equal number of spores (32 spores$100 mL -1 ) and high Shannon diversity in Kaiga stream. In a bubble chamber incubation of leaf litter, 16 and 9 species were recovered from Kaiga stream and Kadra dam with high spore output (1122 versus 324 spores per mg dry mass) and high Shannon diversity in Kaiga stream. Both direct and indirect methods of examination of fecal pellets of fishes revealed more species in Kaiga stream than Kadra dam (4-7 versus 1-4 species). The spore release in leaf litter incubated with fecal pellets ranged from 2.3 to 98 spores$mg -1 $d -1 with the highest Aplocheilus lineatus in Kaiga stream; while in Kadra dam, it was from 0.02 to 22.9 spores$mg -1 $d -1 with the highest in Puntius filamentosus. The Shannon diversity of aquatic hyphomycetes was high in fecal pellets of Aplocheilus lineatus of Kaiga stream and Rasbora daniconius of Kadra dam. The top-ranked five species of aquatic hyphomycetes differed in water, leaf litter, and fish fecal pellets; however, Triscelophorus konajensis was common for all. All five top-ranked species of aquatic hyphomycetes in feces produced multicelled spores; thus, they were likely to have a better chance of viability through gut passage than single-celled spores. Preferential feeding, fungi in gut and feces, and survival and dissemination of spores by invertebrates and fishes with reference to aquatic hyphomycetes were discussed.

Aquatic Fungi

“…The foregut content of 109 different aquatic insects collected on submerged wood showed that in 66% of all studied insect species fungi were part of their diet (Pereira et al, 1982) and many conidia of aquatic fungi were found in faeces of fish (Sridhar & Sudheep, 2011). Furthermore, it has been shown that food web manipulations greatly alter the fungal biomass in lakes (Mancinelli et al, 2002).…”