By Iain Rogers
BARCELONA (Reuters) - American teenager Missy Franklin won her fourth gold of the week and compatriot Ryan Lochte claimed the 13th of a glittering career on a thrilling day of action at the world championships on Thursday.
Australia's James Magnussen eased the pain of missing gold at the London Olympics and there were also triumphs for Chinese women Liu Zige and Zhao Jing while Denmark's Rikke Pedersen popped up in the midst of it all to set a world record in qualifying for the 200 breaststroke.
Franklin followed up Wednesday's victory in the 200 freestyle by anchoring the U.S. to gold in the 4x200 relay, leaving her one shy of the women's record of five at a single world championships set by Lisbeth Trickett of Australia in 2007 and American Tracy Caulkins in 1978
The bubbly 18-year-old from Pasadena, also a winner at the hilltop Palau Sant Jordi in the 100 backstroke and 4x100 relay, took her career tally of world titles to seven and has a crack at another three before racing ends on Sunday.
Team mate Katie Ledecky, 16, who swam the first leg of Thursday's relay, has three golds after her victories in the 400 and 1,500 meters freestyle.
Australia were leading in the relay when Franklin leaped into the pool but she powered past Alicia Coutts and touched in a time of seven minutes 45.14 seconds.
Coutts held on for silver in 7:47.08 and France, who led at the halfway stage, bronze in 7:48.43 in a repeat of the medal positions at the London Olympics.
Franklin said that being part of a team was the most important part of swimming and she did not care about the blistering final leg she conjured to win the race.
"Regardless of what the time was I knew I have to leave everything in that pool," she told reporters.
"I knew I had to bring it home with everything I had and I was just thinking about these girls the whole time and just trying to get my hand on the wall.
"When you get out there and you have three people that are not only your team mates but your friends that you know are going to support you no matter what, you just have this whole new energy about you and you just want to go out there and race harder than you've ever raced before."
Lochte, who has come into the championships after a break and a crack at a television career, claimed his first gold of the week when he eased to a third consecutive title in the 200 individual medley.
The 28-year-old touched in a time of one minute 54.98 seconds, almost a second slower than the world record of 1:54.00 he set to win the gold in 2011.
Kosuke Hagino of Japan was second in 1:56.29 and Thiago Pereira of Brazil third in 1:56.30.
Lochte is the second man only after Michael Phelps to win a treble of 200 medley world titles, although he still has some way to go before he matches his decorated compatriot's 26 world championships golds.
Immediately after Lochte's race Denmark's Pedersen stunned the arena with a world record in the 200 breaststroke of 2:19.11 to better the previous mark of 2:19.59 set by American Rebecca Soni at the London Olympics.
The Dane, whose previous best was 2:20.53, finished fourth in the event London and was seventh at the last world championships in Shanghai two years ago.
"It was very fast," Pedersen said in an interview with television broadcaster Eurosport.
"I am really happy with the personal best and I really hope I can improve in the final (on Friday)."
Australian Magnussen has come to Spain seeking redemption after both he and his nation, one of swimming's traditional powerhouses, badly underperformed in London.
A second consecutive gold in the 100 freestyle for the man known as "the missile" will help dull the disappointment of losing out to American Nathan Adrian by one hundredth of a second in the Olympic final.
Magnussen clocked 47.71 seconds, with another American, Jimmy Feigen, taking silver in 47.82 and Adrian bronze in 47.84.
The Australian joins exalted company as the only men to have previously won two straight 100 freestyle world titles are American Matt Biondi, Alexander Popov of Russia and Italian Filippo Magnini.
"It was a really emotional swim for me tonight," Magnussen said in an interview with television broadcaster Eurosport.
"I think it shows I have matured a lot over the last year," added the 22-year-old.
"I think I can put everything behind me now and look forward. I had a really tough year and there's a lot of emotions in my win.
"Now that a little of the pressure is off I can go back to Australia and work even harder and I want to get down around that world record."
(Additional reporting by Emma Pinedo in Madrid and John Mehaffey in London, editing by Alison Wildey)