Invasive Species Palaemon Elegans Rathke, 1836, (Caridea: Palaemonidae) as the Only Species of Palemon Shrimps in Water Bodies of the Kaliningrad Region

Abstract

AbstractGlobalization of the problem of the introduction of aquatic organisms apparently necessitates monitoring of the state of their fauna and primarily in open water bodies. For the first time, this study has assessed the species diversity of shrimp from the genus Palaemon in water bodies of the Kaliningrad region, which is relevant due to the ecological plasticity known for a number of species that promotes their successful dispersal and acclimatization. Palaemon elegans is known to have lived in this region since about 2000; Palaemon adspersus, Palaemon macrodactylus, and Palaemon varians, recorded in waters of Germany and Poland, are potential invaders into water bodies of the region, and their invasion has not been previously estimated. Species identification of 2498 individuals collected in the study water bodies in 2006–2018 revealed only one species—Palaemon elegans Rathke, 1836; the structure of the mandibles was an unambiguous distinguishing character for its identification; a number of other characters varied. The identified sporadic individuals (0.3%) with a two-segmented mandibular palp, which exhibited unusual combinations of other characters, were referred to as atypical representatives of P. elegans. Invasive P. elegans was currently the only palemon species in waters of the Kaliningrad region. An additional analysis of taxonomically important plastic and meristic characters of the structure of the rostrum, pereopods 2, and mandibles performed for 300 individuals of the species specified the diagnosis of Palaemon elegans Rathke, 1836, from water bodies of the Kaliningrad region. Now, it takes into account the morphological variation in shrimp from the southeastern Baltic Sea and the Kaliningrad Bay.KeywordsInvaders southeastBalticKaliningrad bayShrimp