FIGURE 6.

Melanization of silkworm feces is inhibited by the PO inhibitor PTU. A, PTU inhibited melanization of HG1 content. HG1 content was removed and dipped into different solutions. Then the contents were placed on new parafilm, and the extra solution was absorbed. HG1 content became black within 20 min after being dipped into EDTA, NaN₃, and Tris solution. PTU inhibited HG1 content melanization. B, PTU solution was spread on mulberry leaves fed to the silkworm larvae. One day later, feces excreted by PTU-fed silkworm larvae were green. C, PTU did not inhibit PPO production or secretion. The arrow and arrowhead indicate PPO and PO, respectively, detected in green feces. D, feeding PTU increased the number of bacterial colonies in green feces. The excreted green feces was suspended for bacterial culture after PTU feeding. Each dot corresponds to the colonies of bacteria suspended from gut content or feces from one silkworm larva. The average for each group is indicated by a horizontal black bar (n = 7). Significant differences were calculated with an unpaired t test program.