This genus Macrotrema distributed from Ganges to Mekong Delta, and may be compose of many spp., from small 5-6 cm to over 20 cm spp. as we seen in last month which eaten by Pond heron. I got spec. from the Mekong delta is ca. 20 cm and completely different from the Bang Sai spec. I heard that Tyson going to revise this.