Abalone, Haliotis discus hannai Ino, can synthesize myo-inositol de novo to meet physiological needs

The experiments were conducted to investigate the effects of dietary myo-in ositol on the survival, growth, proximate composition and de novo synthesis of myo-inositol in abalone, Haliotis discus hannai Ino. The possible inosi tol-synthesizing capacity of intestinal microflora was also examined. Seven semipurified diets were formulated to provide graded levels of myo-inosito l (28.7-1020.1 mg/kg diet). A control diet, the basal diet supplemented wit h 4 g/kg tetracycline hydrochloride, was employed to suppress synthesis of myo-inositol by intestinal bacteria. Abalone juveniles of similar size (wei ght, 144.6 +/- 0.8 mg; shell length, 10.92 +/- 0.10 mm) were distributed in a flow-through system using a completely randomized design with eight trea tments and three replicates per treatment. They were fed the appropriate di ets once daily for 16 wk. Survival, growth, crude protein, lipid, moisture of whole soft body and visceral inositol content were independent of myo-in ositol supplementation (P > 0.05). The addition of the antibiotic also did not affect the survival, growth and whole soft body composition. It indicat ed that intestinal microflora contributed little to the myo-inositol nutrit ion in abalone. The present study, for the first time, demonstrated de novo synthesis of myo-inositol in mollusks because the visceral tissue of abalo ne showed high levels of myo-inositol synthetase activities (combined activ ities of myo-inositol-1-phosphate synthetase and inositol-1-phosphatase), r anging from 74.0 to 98.2 mu mol/(h.g protein). The enzyme activity signific antly and negatively correlated with dietary myo-inositol level (r = -0.81) . Hence, dietary myo-inositol is not essential for abalone because tissue s ynthesis of the vitamin appears to be sufficient to support normal growth a nd health of this mollusk.