The First Finding of the Oriental Shrimp Palaemon macrodactylus Rathbun, 1902 (Crustacea: Decapoda, Palaemonidae) in the Territorial Waters of Russia in the Azov-Black Sea Basin

Oriental shrimp (Palaemon macrodactylus Rathbun, 1902) was recorded for the first time in the waters of the European part of Russia in the Kerch Strait (Sea of Azov, Chushka Spit coast, Krasnodar krai, Russia) in July 2018. The species natural geographic range is located in the northwestern Pacific Ocean, while the invasion range includes the Atlantic coastal waters of Europe, the Pacific and Atlantic coasts of the United States, and the coast of Argentina. An egg-bearing female was caught, and it had some morphological differences in the armature and relative length of rostrum compared to the specimens collected in the marginal population of the natural distribution range (Peter the Great Bay, Sea of Japan). P. macrodactylus was first discovered in the Black Sea at the Romanian coast in 2002; since that time, its occurrence in the region has increased significantly. The invasion with the ballast waters is the most probable vector, although the dispersal of larvae with the sea currents cannot be excluded. In this case, established but still hidden populations are expected to be discovered in the coastal waters of Turkey and Georgia. P. macrodactylus is an active invader, colonizing transitional waters, where it should be monitored in order to forecast consequences for local species and ecosystems.