Natural diet and feeding habits of a freshwater prawn (Macrobrachium carcinus: Crustacea, Decapoda) in the estuary of the Amazon River

Abstract

Macrobrachium carcinus is a Brazilian native prawn with recognized potential for use in aquaculture activities. However, there is little information about the natural diet and feeding habits of this species. The aim of this study was the identification of the diet items of M. carcinus based on the analysis of the stomach contents. Specimens were collected in the Amazon River estuary between January 2009 and January 2010. The stomach analysis was carried out by using the frequency of occurrence (FO), methods of points (MP) and feeding index (FI). It was observed that prawns fed on detritus, animals and plant fragments as the most important food items. Sediment accounted for the main stomach content, accounting for 43.2% by the MP, 44.9% by FI and 100% by the FO. Sexual differences in feeding preferences were not found in this study, and seasonal differences in the frequency of items ingested by M. carcinus were not observed. The results indicated that M. carcinus can be considered omnivorous species, but with an important carnivorous component, similar to that found in other Macrobrachium species. KEYWORDS: food, stomach morphology, pitu, sand ingestion, palaemonid Dieta natural e hábito alimentar de um camarão de água doce (Macrobrachium carcinus: Crustacea, Decapoda) no estuário do rio Amazonas RESUMO Macrobrachium carcinus é uma espécie nativa com reconhecido potencial para ser utilizada na aquicultura, devido seu grande porte e seus bons índices de fecundidade e fertilidade. Apesar de seu evidente potencial para cultivo, poucas informações sobre dieta natural e habito alimentar desta espécie são conhecidos na literatura. O objetivo principal deste estudo foi identificar os itens da dieta natural de M. carcinus, com base na análise de conteúdo estomacal de espécimes coletados no estuário do rio Amazonas entre janeiro de 2009 e janeiro de 2010. A análise do conteúdo estomacal foi feita usando frequência de ocorrência (FO), método de pontos (MP) e índice alimentar (FI). Os dados revelaram que os componentes alimentares mais importantes desta espécie foram detrito, fragmentos animais e vegetais. O item sedimento constituiu o maior componente do estômago com 43,2% pelo MP, 44,9% pelo FI e 100% pela frequência de ocorrência, respectivamente. Diferenças sexuais entre as preferências alimentares sobre os alimentos não foram encontrados no presente estudo. Diferenças sazonais na frequência de itens ingeridos por M. carcinus não foram observados. Os resultados indicaram que M. carcinus pode ser considerado como um onívoro, mas com um componente importante carnívoro, semelhante ao encontrado em outras espécies de Macrobrachium. Outros aspectos sobre o hábito alimentar e morfologia do estômago são brevemente discutidos. PALAVRAS-CHAVE: alimento, morfologia do estômago, pitu, ingestão de areia, palaemonideo.

Foregut morphology of Macrobrachium carcinus (Crustacea, Decapoda, Palaemonidae)

“…The general morphology of the foregut of M. carcinus and other palaemonid prawns indicates that the food trituration and digestion occurs normally at the level of the stomach and not only by the mechanical action of the mandibles as suggested by Meiss and Norman (1977). However, the grinding surfaces of the lateral teeth, typical of penaeid shrimps, is absent in M. carcinus and the food trituration is feasible only because of the large amount of sand in the diet, along with gastric juices and the motion of the cardiac chamber (Lima et al 2014). …”

“…These pieces are elongated and form a shallow trough that often supports sand grains and little pebbles that through the constant peristaltic movements of the stomach are mixed with food, helping the digestion. As observed by Lima et al (2014), food maceration in M. carcinus is facilitated by the large amount of sand in the diet which, along with the motion of the cardiac stomach, functions similarly to a gastric mill; such a mechanism is capable of breaking down large fleshy pieces (see also Coombs and Allen 1978;Suthers 1984 and references therein). We thus suggest that culturing M. carcinus in eathern ponds would possibly enhance digestion efficiency.…”

“…The occurrence of animal components indicates that Macrobrachium species and penaeids have similar predation behavior; however, the absence of gastric mill in Macrobrachium (lateral and dorsal teeth) suggests a different mechanism of digestion in the genus (Lima et al 2014). …”

“…There is much information about the decapod digestive tract, particularly concerning to economically important species, such as palinurids, scyllarids and penaeids (Cox and Bruce 2003;Suthers and Anderson 2006;Abrunhosa and Melo 2008). Little information on the mouthparts or alimentary tract of the genus Macrobrachium Bate 1868 and other caridean prawns has been reported in the literature, as an example larvae of M. rosenbergii De Man, 1879 (Abrunhosa and Melo 2002) and M. amazonicum (Heller, 1862) (Queiroz et al 2011) and adults of M. malcolmsonii (Milne Edwards, 1844) (Patwardhan 1935a), M. acanthurus (Wiegmann, 1836) (Felgenhauer and Abele 1989) and M. carcinus (Lima et al 2014).…”

“…The study of the stomach contents of Macrobrachium species has revealed numerous food items as algae, detritus, plant parts, small aquatic insects, juvenile prawns, small fish, and other animals, showing a clear omnivorous diet with an important carnivorous component (Jimoh et al 2011;Melo and Nakagaki 2013;Lima et al 2014). The occurrence of animal components indicates that Macrobrachium species and penaeids have similar predation behavior; however, the absence of gastric mill in Macrobrachium (lateral and dorsal teeth) suggests a different mechanism of digestion in the genus (Lima et al 2014).…”