A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

A student from the General Yermolov Cadet School performs with models of swords during celebrations of Maslenitsa, or Pancake Week, a pagan holiday marking the end of winter, in southern city of Stavropol, Russia, March 6, 2019. (Photo by Eduard Korniyenko/Reuters)

Novice DSLR (Digital single-lens reflex camera), 2nd Place. “Smile of a Friend”, American Crocodile (Crocodylus acutus) in Jucaro, Cuba. (Photo by Antonio Pastrana/The Ocean Art 2018 Underwater Photography Competition)

Aleksandra Krunic, of Serbia, drops to the court after defeating Petra Kvitova, of the Czech Republic, during the third round of the 2014 U.S. Open tennis tournament, Saturday, August 30, 2014, in New York. (Photo by Kathy Willens/AP Photo)

The Baby Nager dragon, from DreamWorks’ new “How to Train Your Dragon” Live Spectacular touring musical, shows off it’s colors outside of the New York Public Library. (Photo by Mark Von Holden)

Russia' s Tiffani Zagorski and Russia' s Jonathan Guerreiro compete in the ice dance free dance of the figure skating event during the Pyeongchang 2018 Winter Olympic Games at the Gangneung Ice Arena in Gangneung on February 20, 2018. (Photo by Lucy Nicholson/Reuters)

Senior Buddhist monk Lobsang Tayang sits outside the Amarbayasgalant Monastery in the Baruunburen district, Selenge province, Mongolia, April 26, 2018. (Photo by Thomas Peter/Reuters)

A Flame Skimmer or Firecracker Skimmer dragonfly (Libellula saturata) rests on a small branch in Topanga, California, USA, 18 June 2018. The Flame Skimmer dragonfly is found in the Western United States near ponds and creeks. (Photo by Mike Nelson/EPA/EFE)