Feeding frequency affects feed intake and growth in juvenile pirarucu (Arapaima gigas)

Pirarucu is one of the main fish species for the development of aquaculture in the Amazon. In this study, the optimal feeding frequency for juvenile pirarucu was assessed based on growth and feed efficiency. Juvenile pirarucu weighing ca. 80 g were fed once, twice, three or four times daily until apparent satiation for 63 days. Fish fed three or four times per day presented higher growth, feed intake, and fat body content than those fed once or twice per day. There was no significant difference for feed conversion ratio, and protein and energy retention rates among treatments, suggesting that increased feeding frequency did not affect feed utilization efficiency. Mean feed intake per meal was higher when fish were fed once per day, possibly causing hyperphagic behavior. Results suggest that feeding three times per day was sufficient to secure adequate feeding and growth of juvenile pirarucu. (AU)

Morphology and histology of the pirarucu (Arapaima gigas) digestive tract / Morfología e histología del tubo digestivo del paiche (Arapaima gigas)

The present study describes the morphology and histology of the digestive tract of juvenile pirarucu, which is a Neotropical fish species with great potential for aquaculture in the Amazon region. Three size classes of pirarucu juveniles from commercial fish farms were sampled for histological examination of the oesophagus, stomach, pyloric caeca, intestine and liver. The morphological and histological features of the pirarucu digestive tract are similar to other carnivorous teleosts and enable the species to ingest, store and digest large food items. Acidic and neutral mucins are secreted by the mucosa of the oesophagus, stomach, pyloric caeca and intestine to protect the mucosal epithelium and to lubricate and facilitate food passage along the digestive tract. Complex transverse folds are predominant in the intestinal mucosa and most likely contribute to optimization of the digestion and nutrient absorption processes, thereby offsetting the relatively short length of the intestine. The exocrine pancreas appears diffuse in the liver and mesentery around the pyloric region of the stomach, pyloric caeca and initial part of the intestine. The digestive tract morphology and thickness become increasingly developed with the size of pirarucu.

El presente trabajo describe la morfología e histología del tracto digestivo de una especie juvenil de paiche, un pez neotropical con gran potencial acuícola en la region Amazónica. Se tomaron muestras de tres clases de tamaño de juveniles de paiche de granjas acuícolas comerciales para examen histológico del esófago, estómago, ciego pilórico, intestino e hígado. El tracto digestivo del paiche tiene características morfológicas e histológicas comunes a otros teleósteos carnívoros que permiten a la especie la ingestión, el almacenamiento y la digestión de grandes alimentos. Mucinas ácidas y neutras son secretadas por la capa mucosa del esófago, estómago, ciego pilórico e intestino para proteger el epitelio de esta capa, además de lubricar y facilitar el paso de los alimentos a lo largo del tracto. Pliegues complejos y de orientación transversal son predominantes en la mucosa intestinal, contribuyendo, probablemente, a la optimización de los procesos de digestión y absorción de nutrientes, y compensando la longitud relativamente corta del intestino. El páncreas exócrino se encuentra difuso dentro del hígado y en el mesenterio alrededor de la región pilórica del estómago, ciego pilórico y porción inicial del intestino. La morfología y el espesor del tubo digestorio se desarrollan de forma gradual a medida que el paiche crece.

Anatomical Behavior of the Celiacomesenteric Artery of Pirarucu Arapaima gigas Cuvier, 1817 (Osteoglossiforme, Arapaimidae) / Comportamiento Anatómico de la Arteria Celiacomesentérica en Pirarucu Arapaima gigas Cuvier, 1817 (Osteoglosiforme, Arapaimidae)

The pirarucu, Arapaimidae family fish, is one of the most important and emblematic species of Amazon. To investigate their circulatory system anatomies features were used 10 specimens with 74 cm medium total length, from river Araguaia lakes, Sao Miguel do Araguaia, Goias, Brazil. The fishes had their celomatic cavity open with dorsal aorta artery identified and cannulation where was injected synthetic latex. Fixation of those specimens was by injection of 10% formalin. In that specie, the coeliac-mesenteric artery is the only one arterial vessel responsible to digestive tract flow and always ramified from 2nd, 3rd and 4th left efferent branchial arteries. The stomach is flowing by coeliac artery and a gastric branch of the cecal ventral artery; intestine receives coeliac-mesenteric artery branchs and cranial and caudal mesenteries arteries branchs; the dorsal and ventral cecum are supplied by cecal dorsal and ventral arteries respectively.

El pirarucu, pez de la familia Arapaimidae, es una de las especies más importantes y emblemáticas de la ictiofauna amazónica. Para estudiar las características anatómicas de su sistema circulatorio, fueron utilizados 10 ejemplares de Arapaima gigas, con un longitud total media de 74 cm, provenientes de lagos del río Araguaia, Sao Miguel do Araguaia, Goiás, Brasil. A los peces se les abrió la cavidad celomática donde se identificó y canalizó la arteria aorta dorsal, injectándose una solución coloreada de látex sintético. La fijación del material se realizó con inyecciones de formol al 10%. La arteria celiacomesentérica es responsable de la irrigación del tubo digestivo y tiene origen en las 2ª, 3ª y 4ª arterias branquiales eferentes izquierdas. El estómago está irrigado por la arteria celíaca y por una rama gástrica de la arteria cecal ventral. El intestino recibe ramas arteriales procedentes de la arteria celiacomesentérica y de las arterias mesentéricas craneal y caudal; los ciegos dorsal y ventral están irrigados por las arterias cecales dorsal y ventral, respectivamente.