Domestic benchmark indices tumbled in early trade today in line with extremely weak trends in global markets amid fears of a slowdown in the US economy and foreign fund outflows. The Sensex at the Bombay Stock Exchange tanked 2,401 points to 78,580 in morning trade. The Nifty at the National Stock Exchange tumbled 490 points to 24,228. The rupee opened on a muted note and fell to an all-time low of 83.80 against the US dollar, registering a fall of 8 paise from its previous close.