Abstract
This study was conducted to record the histological features of the gastrointestinal tract of wild Indonesian shortfin eel, Anguilla bicolor bicolor (McClelland, 1844), captured in Peninsular Malaysia. The gastrointestinal tract was segmented into the oesophagus, stomach, and intestine. Then, the oesophagus was divided into five (first to fifth), the stomach into two (cardiac and pyloric), and the intestine into four segments (anterior, intermediate, posterior, and rectum) for histological examinations. The stomach had significantly taller villi and thicker inner circular muscles compared to the intestine and oesophagus. The lamina propria was thickest in stomach, significantly when compared with oesophagus, but not with the intestine. However, the intestine showed significantly thicker outer longitudinal muscle while gastric glands were observed only in the stomach. The histological features were closely associated with the functions of the different segments of the gastrointestinal tract. In conclusion, the histological features of the gastrointestinal tract of A. b. bicolor are consistent with the feeding habit of a carnivorous fish.
Highlights
The Indonesian shortfin eel, Anguilla bicolor bicolor (McClelland, 1844), is native to Malaysia
Samples were placed in a solution containing tricaine methanesulfonate (MS 222) at 50 mg/L to achieve stage three of anesthesia, before they were sacrificed by cervical dislocation according to method approved by the Animal Utilization Protocol, Universiti Putra Malaysia
Organs were sampled in triplicate, labeled, and fixed in 10% buffered formalin for 12 hours before they were embedded in paraffin, sectioned at 5 μm thick, and stained routinely with Harris haematoxylin and eosin (HE) and periodic acidSchiff (PAS)
Summary
The Indonesian shortfin eel, Anguilla bicolor bicolor (McClelland, 1844), is native to Malaysia. Bicolor are found in estuarine areas and they occasionally migrate around 60 km from the ocean into freshwater rivers [3] This is due to the migration behavior of the eels as well as a strategy to avoid competition for space and food [4, 5]. For A. bicolor, a study showed that the fish change their feeding habits markedly as they grow They feed mainly on invertebrates when small and become more piscivorous as they grow, while no seasonal variation in the feeding habits was observed [8]. Their main feeding habits consisted of macrophytes, algae, crustaceans, mollusks, insects, annelids, insect larvae, and bony fishes [8,9,10]
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