India's index options turnover fell 27% Monday due to the Jane Street embargo, low volatility, and U.S. market factors.

• Jefferies says Jane Street's embargo and market factors equally caused Monday's index options turnover drop.
• India's Jane Street ban, citing derivative index manipulation, likely reduces derivatives volumes, analysts say.
• Low volatility, the U.S. long weekend, and the tariff announcement reduced trader activity, leaving indices flat.