Kazan: Sweden`s Sarah Sjostrom broke the women`s 100m butterfly record on Sunday as Sun Yang and Katie Ledecky retained their 400m freestyle titles at the world championships.
China`s Sun, the reigning 400, 800 and 1500m world champion and record holder over the mile, clocked three minutes 42.58 seconds to win his final by more than a second as Britain`s James Guy took silver.
The Chinese giant is still nearly three seconds from Paul Biedermann`s world record, set by the German in 2009 before neoprene suits were banned, and it remains his goal a year from the Rio de Janeiro Olympics.
"Of course, it was broken in the precious swimsuit period, so now if we want to break this record it will take more effort, but I see it as a goal on the road to Rio," he said.
American teenager Ledecky, a triple world-record holder, built a commanding lead in her final and came within a second of her own world record in the event, but had to make do with a winning time of 3:59.13 mins - a new championship record.
"This gets the momentum going and I couldn`t be happier," beamed the 18-year-old, who has only just graduated from high school.
"It`s a swim I can be really happy with.
"It`s very flattering and a great honour for me that people seem to hope or expect a world record every time I swim, because I guess that is based on what I have done in the past.
"That`s a pretty neat thing for me.
"You guys keep writing what you`re writing and I`ll keep doing what I keep doing," she told reporters.
There was a surprise early in the evening as Sjostrom broke the world record in her semi-final on only the second swim of the night to set herself up for Monday`s 100m butterfly final.
"It was in my plan to set a record in the semi-final, because in the final I am in a different physical state," said the defending world champion.
"I was quite slow in the first 50 metres, but later I sped up. And I had been waiting to set this record for so long."
A gold medal dream came true for sisters Cate and Bronte Campbell as they helped Australia win the women`s 4x100m freestyle title.
The Queensland siblings paired up as Cate, the world 100m freestyle champion, anchored the team to set a new championship record of three minutes 31.48 seconds.
The Netherlands won silver at 2.19 secs back while the United States, including six-time world gold medallist Missy Franklin, won bronze at 3.13 back.
Having stood on the podium together when Australia won silver in Barcelona two years ago, the sisters went one better with gold in Kazan.
"It`s the dream come true," said 21-year-old Bronte Campbell.
"We got a silver together in 2013 and that was amazing, but to stand up on the podium together in front of the world to sing the national anthem with your big sister is something not many people get to do."
After the US team failed to qualify from the morning`s heats for the men`s 4x100m freestyle relay for the first time in world championships history, the French quartet retained their title.
Mehdy Metella, Florent Manaudou, Fabien Gilot and Jeremy Stravius clocked three minutes, 10.74 seconds as Russia finished just 0.45secs behind to claim silver with loud encouragement from the home crowd in Kazan.
Italy took bronze at 1.79secs back.
There will be a battle royal in the men`s 100m breaststroke final on Monday as world-record holder Adam Peaty goes head-to-head with Olympic champion Cameron van der Burgh.
The pair took turns breaking the championship record in the morning heats, then the evening`s semi-finals.
After Peaty broke it in the morning heats, South Africa`s Van der Burgh won his semi-final in a new championships record of 58.49secs, only for the 20-year-old Briton to break it again in his semi by clocking 58.18secs.