US junior developers Leah Smith, 17, and Becca Mann, 15, cracked 8:20 in a stroke for stroke 800m free battle on the opening day of finals at the Moscow round of the world cup.
Smith took the touch in 8:19.24, 0.09sec the better of Mann, with Russia's Elizaveta Gorshova third in 8:29.45. Mann clocked 8:28.54 at US Olympic trials this year, while Smith, who did not make the final at trials, on 8:38.94 in heats, clocked 8:28.01 in Japan in August, long-course.
The American teenagers set the pace with 1-minute efforts in the opening 100m. Smith led from the 200m mark, turned in 4:10.03 to Mann's 4:11.66 at 400m and still had a lead of over a second with 150m to go. Mann then started to pile on the pressure, Smith responding. Over the last 50m, Smith clocked 31.61 and was forced to dig deep to hold on as Mann put in a 29.12sec blast to come close to overhauling her teammate. With Katie Ledecky, 15, having won the Olympic 800m crown in London, the US looks set to enjoy a golden time in women's distance freestyle.
Back in fifth in the final on a relative go-slow "better-pace-myself" 8:47.47 was the most winning swimmer of the tour so far, Katinka Hosszu (HUN).
Having kept her powder dry, Hosszu was back on top two races later. In the 200m freestyle, just one men's final after leaving the water in the 800m, clocked 1:55.46 to take the 200m free 0.97sec ahead of Hungarian teammate Zsuzsanna Jakabos. Third place went to 21-year-old Guo Jun Jun(CHN) on a best of 1:56.77.
The Hungarian's repeated their 1-2 finish for the umpteenth time on this tour once again in the 200m medley, Hosszu on 2:08.28, Jakabos on 2:08.76, Britain's Sophie Allen taking third in 2:09.50, a couple of 2:11s encouraging for US juniors Celina Li and Kaitlyn Jones.
Towards the end of the session, Hosszu took her tour earnings beyond $36,000 when she made the podium once more, on 2:07.29 to 2:07.78 for Jakabos in the 200m backstroke, the race won by New Zealand's Melissa Ingram in a stroke for stroke battle with another touring, in-form US junior, Kylie Stewart, 2:05.35 to 2:05.79. Stewart, 16, clocked a best of 2:09.99 long-course in Japan in August, a 2sec improvement on the year.
Tommasso D'Orsogna (AUS) fended got past Darian Townsend (RSA) and Anthony Ervin (USA) on the way to a 47.11 victory in the 100m freestyle. Townsend, first at the 50m mark on 22.57, settled for shared silver with Ervin in 47.43, Evgeny Lagunov locked out at his home round of the cup in 47.76 as the last man inside 48.
Rie Kaneto pipped Japan teammate Mio Motegi by 0.01sec in the 100m breaststroke for a 1:06.18 victory, third place going to Russian Maria Temnikova in 1:07.55. Japan celebrated another win straight off, when Daiya Seto continued to show victorious form in the 400m medley, a 4:01.30 dominating the final, Laszlo Cseh (HUN) on 4:06.20, Gal Nevo (ISR) on 4:09.90. A few finals later, Seto was back to celebrate a Japan 1-2 in the 200m butterfly, his teammate Kazuya Kaneda getting the touch by 0.06sec in 1:52.43 in a close battle with Nikolay Skvoertsov (RUS), on 1:52.63.
Paul Biedermann warmed up for a tilt at victory in front of home crowd and cameras in Berlin at the weekend with a 3:44.00 win in the 400m freestyle. The world record holder from a time of shiny suits (3:32.77) held off Australian Robert Hurley by 0.62sec, third place a few strokes back in the shape of Evgeny Kulikov (RUS), on 3:47.84.
Biedermann's girlfriend, Britta Steffen, gave Germany a second win on the day with a 24.20 effort in the freestyle dash, Jessica Hardy (USA) second in 24.52, Svetlana Knyaginina (RUS) third in 24.76.
Sean Mahoney (USA) led the 200m breaststroke from start to a 2:05.11 finish, chased all the way by the three men who battled for the podium behind him. Viatcheslav Sinkevich (RUS) took second in 2:06.06 ahead of Marco Koch (GER), on 2:06.39, Anton Lobanov (RUS) locked out by 0.19sec. The men's 100m medley also produced a close fight, Kenneth To (AUS) taking the race ahead of George Bovell (TRI) 51.66 to 51.81.
In other action, Ilaria Bianchi (ITA) took the 100m butterfly in 57.18, an Italian record inside the 57.42 she clocked last year. Stanislav Donets put a disappointing long-course season behind him with a 49.74 home-cup win in the 100m backstroke as the only sub-50sec swimmer, on 49.74, Hurley closest to him on 50.70.