Kozo Hiramatsu, 60, a Livedoor executive and president of Livedoor's accounting software unit, Yayoi Co, became president as of Tuesday, but the company has not named a replacement for Horie as chief executive, a company spokesman said on Tuesday.
Horie, 33, will stay as a director for now, since Livedoor has not received his resignation from that post, but he will not have the right to represent the company, the spokesman added.
At the same time, the Tokyo Stock Exchange, expecting heavy trading in the internet firm's stock, which had been placed under watch for possible delisting, said it would shorten trading hours in Livedoor shares from Wednesday to ease the burden on its computer systems.
Livedoor, a patchwork of 50 online retail and financial units acquired by Horie in a heated 10-year expansion, has lost about three-quarters of its $6bn market value since prosecutors raided its headquarters and Horie's home on 16 January.
Hiramatsu, the new president, told a news conference that he had yet to map out a business strategy.
Livedoor has seen three-quarters
of its market value wiped out
Fumito Kumagai, director with new rights to represent the company, said Livedoor had no plans to be taken over and that its finances were sound.
In a separate announcement, Livedoor restated its interim earnings results for six months ended on 31 March 2005, slashing cash flow from operations by nearly 90% to 1.15bn yen ($10m) and shifting it to cash flow from investment.
The company said it was now including margin trade on its own account in cash flow from investment, but the spokesman declined to provide further details or explanation.
Trading in Livedoor will be allowed only between 1.30pm and 3pm (0430-0600 GMT) from Wednesday. The measure, which a TSE official said was a first for the bourse, will last for the foreseeable future.
Flood of sell orders
The bourse also said it could suspend trading in the stock, depending on trading volume.
Tokyo Stock Exchange will reduce
trading hours in Livedoor shares
It has been delaying the opening of its afternoon session for all stocks by 30 minutes, starting at 1pm (0400 GMT) since a flood of sell orders threatened to overwhelm its computer systems last Wednesday.
Horie and three other executives were arrested on Monday on suspicion of spreading false information to manipulate share prices.
A raid on Livedoor by authorities a week ago sparked chaos on the Tokyo stock market and sent share prices plunging across the board on a huge volume.
The stock remained untraded on Tuesday with a glut of sell orders at 176 yen, down by its maximum daily limit of 80 yen. The shares were trading at 696 yen just before the prosecutors' raid.