Michael Sohn, Associated Press
South Africa's Cameron van der Burgh swims in his men's 50m breaststroke heat at the Swimming World Championships in Kazan, Russia, Tuesday, Aug. 4, 2015. Van der Burgh lowered his own 50m breaststroke world record to 26.62 seconds.

KAZAN, Russia — Cameron van der Burgh heated up a chilly Tuesday morning at the swimming world championships by improving his own world record in the 50-meter breaststroke.

The South African won his one-lap heat in 26.62 seconds, shaving five hundredths off his previous mark established in a now-banned rubberized suit at the 2009 worlds in Rome.

Van der Burgh celebrated by propping himself up on a lane rope and pointing his arms up, then he bowed to the crowd and flexed his biceps after climbing out of the pool.

It's the first men's world record to fall at this meet after four women's marks were set on the opening two days.

"It's nice to be joining the ladies for a bit of the fun," Van der Burgh said.

Britain's Adam Peaty also swam 26.62 at the European Championships in Berlin last August but that mark was not ratified by governing body FINA because he was not tested at the time for the blood-booster EPO.

It was a simple administrative error because a box was not checked on the drug-testing form, FINA officials said.

Peaty qualified second in 26.68, winning the last of nine heats.

"Just went out there and had fun and didn't take it that seriously," Peaty said. "There's definitely more in there tonight and hopefully more tomorrow."

More records could come in the semifinals later Tuesday and the final Wednesday.

"I think we can definitely get ready for a new time," Van der Burgh said.

Peaty came from behind to edge Van der Burgh for gold in the 100 breast on Monday but now Van der Burgh has shown he intends to hold on to his title in the 50, which is not an Olympic event.

"I had the luck of a good touch (today)," Van der Burgh said. "I knew I had great speed from the first split of the 50 last night."

The session was held in an air temperature of about 15 Celsius (60 Fahrenheit) at the Kazan Arena, where a temporary pool has been placed inside a football stadium. A roof placed over the pool is open on one side, letting the outside air in. The warmup pool has no roof.

American teenager Katie Ledecky kept up her impressive form by leading the 200 freestyle heats in 1:55.82, a day after she improved her world record in the marathon-like 1,500 — also in prelims.

"I was pretty slow around the turns. Hopefully I can clean that up tonight," Ledecky said. "I don't focus on the time here as I do on the other races. It was definitely tough coming off a really great swim. The 200 is a different animal."

Katinka Hosszu, who also set a world record Monday, qualified second in 1:56.32. Defending champion Missy Franklin was third in 1:56.42 and world-record holder Federica Pellegrini advanced sixth in 1:57.34.

Hungarian veteran Laszlo Cseh led the 200 butterfly in 1:53.71, while Olympic and defending champion Chad Le Clos only barely advanced in 14th, more than three seconds behind. Only the top 16 qualifiers made it to the semifinal.

At the 2012 London Games, Le Clos won this event ahead of Michael Phelps, who is not at te worlds after being suspended by USA Swimming for a second DUI arrest.

Cseh took silver behind Phelps at the 2008 Beijing Games but has never won a medal in this event at worlds.

"It was a big surprise for me. I was not thinking of swimming this time in the morning," Cseh said. "I am capable of winning a medal but I need to keep focusing."

In another non-Olympic event, Connor Jaeger of the U.S. led the 800 free in 7:44.77, just ahead of Italy's Gregorio Paltrinieri. Two-time defending champion Sun Yang of China won his heat but only narrowly advanced in sixth with 7:47.87.

Another contender, Ryan Cochrane of Canada, finished right behind Sun in his heat but didn't qualify in 10th — as only the top eight finishers advanced directly to the final.

Andrew Dampf can be followed at www.twitter.com/asdampf