Comparative Morphology of Digestive Tract Among 11 Different Marine Fish Species

Limited information is available about the digestive tract morphology and function in some marine fish species. Using anatomical methods, this study compared the morphological characteristics of the digestive tract among 11 marine fish species of different taxonomic status, feeding habits and ecological niches. Except for black scraper ( Thamnacomus modestus ), a omnivores fish, the rest of fish species involved in this study, are carnivorous fish. Three replicate fish of each species were used. The relative intestine length (RIL) of black scraper ( T. modestus ) was the highest among all species investigated, while skate ( Raja kenojei ) had the lowest RIL. The hepatosomatic index (HSI) was the highest in tiger puffer ( Takifugu rubripes ) and the lowest in Japanese Spanish mackerel ( Scomberomorus niphonius ). The highest viscerosomatic index (VSI) was found in black scraper and the lowest value was found in Japanese Spanish mackerel. In terms of stomach morphology, black scraper, tiger puffer, turbot ( Scophthalmus maximus ), javelin goby ( Synechogobius hasta ) and skate had ‘I’‐shaped stomach; greenling ( Hexagrammos otakii ), rockfish ( Sebastes schlegelii ) and hybrid grouper ( Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) had ‘V’‐shaped stomach; while Japanese Spanish mackerel, Chinese seabass ( Lateolabrax maculatus ) and conger eel ( Conger myriaster ) had ‘Y’‐shaped stomach. Besides, the pyloric caeca were found in turbot ( S. maximus ), greenling ( H. otakii ), rockfish ( S. schlegelii ), hybrid grouper ( E. fuscoguttatus♀ × E. lanceolatus ♂), Japanese Spanish mackerel ( S. niphonius ) and Chinese seabass ( L. maculatus ). The oropharyngeal morphology of fish provided clues to fish feeding pattern. In conclusion, for the 11 marine fish species, the morphological structure of stomach and oropharyngeal cavity, and the RIL had high correlation with their body shape, oropharyngeal capacity and feeding habit.