Effects of body size on the diet of Rivulus haraldsiolii (Aplocheiloidei: Rivulidae) in a coastal Atlantic Rainforest island stream, southern Brazil

The effect of body size on the feeding habits of the little-known killifi sh Rivulus haraldsiolii, collected in a coastal Atlantic Rainforest island stream, was investigated. Samples were collected during a study trip on 13 July 2009 in a brackish stream located in the northern part of Ilha do Mel Island, one of the most important southern Atlantic Forest areas in southern Brazil. The diet included aquatic immature insects (Diptera pupae and Chironomidae), aquatic insects (Hemiptera – Vellidae), microcrustaceans (Cladocera), aquatic ticks (Acarina), gastropods (Pomacea sp.), terrestrial insects (Coleoptera, Formicidae and Isoptera), insect fragments, and plant fragments. The species presented an omnivorous feeding habit, and differences in diet could be related to variations in body sizes. Adults (large individuals) feed mainly on Formicidae, plant fragments and aquatic ticks, whereas juveniles (small individuals) feed basically on aquatic immature insects (Chironomidae) and aquatic ticks