Ontogenetic development of digestive enzymes and in vitro digestibility of spotted Babylon (Babylonia areolata) veligers

The ontogenetic development of the main digestive enzymes and in vitro digestibility were investigated in spotted Babylon (Babylonia areolata) veligers. The collected specimens included fertilized eggs, trochophores, veligers, and settlement stage larvae. The activity of each studied enzyme showed strongly positive pairwise correlations with the activity of every other enzyme studied (r = 0.498-0.847, n = 60, p < 0.01). Pepsin showed the highest specific activity during the development of the veligers (p < 0.05). Pepsin and chymotrypsin specific activity followed broadly similar trends, except in late trochophore and early veliger stages. Trypsin specific activity was highest in early-stage veligers. Amylase specific activity progressively increased in middle-stage veligers, and decreased in older veligers. Cellulase activity started to increase before hatching, exhibiting its highest activity during the first seven days of veliger development. Lipase specific activity increased progressively in early-stage veligers and then decreased and remained constant until the end of observation. The in vitro digestibility assay showed that three mixed rations (75:25, 25:75, and 0:100 w/w) of Chaetoceros sp. and Isochrysis sp., and single components of Spirulina meal, and clam feed were suitable for early-stage veligers, while all mixed rations of Chaetoceros sp. and Tetraselmis sp., and single components of Spirulina meal and herbivorous fish feed were suitable for late-stage veligers. Our findings can be used as a feed management reference for spotted Babylon veligers.