Early Development of the Digestive System and Digestive Enzyme Activity of Reared Mandarinfish Siniperca chuatsi ( Perciformes : Sinipercidae )

Morphological and histological development of the digestive system and changes in digestive enzyme activity were investigated in larvae and juveniles of mandarinfish Siniperca chuatsi reared in an aquarium. Yolk sac larvae (ca. 5.5 mm TL) just before first feeding have a differentiated, functional larval-type digestive system with a large mouth, jaw teeth, pharyngeal teeth and gastric blind sac and they showed activities of both a trypsin-like enzyme and at a relatively low level of a pepsin-like enzyme. Preflexion larvae (ca. 7-8 mm TL) preyed on fish larvae using the largely expandable blind sac. Later-phase flexion larvae (ca. 10 mm TL) showed higher pepsin-like enzyme activity than trypsin-like enzyme associated with the appearance of gastric glands. Postflexion larvae (ca. 12 mm TL) established the adult-type digestive system having pyloric caeca. Metamorphosed juveniles ( > ca. 20 mm) showed increased gastric glands and pyloric caecal lobules in number, and the mouth and gut in size, and digestive enzyme activities. Early appearance of piscivory of larval mandainfish may be supported by the quantitative development of the oral cavity and gastric blind sac which mainly occurred during the early phase of the larval period (< ca. 10 mm TL), and its acceleration could be done by both the continued quantitative developments and functional development of the adult-type digestive system after the mid phase of the larval period (> ca. 12 mm TL).

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