The first records of Niphargus hrabei and N. potamophilus in Ukraine and Bulgaria significantly enlarge the ranges of these species

Insights on the Existence of Ancient Glacial Refugee in the Northern Black/Azov Sea Lowland, with the Description of the First Stygobiotic Microcrustacean Species of the Genus Niphargus Schiödte, 1849 from the Mouth of the Don River

“…The post-glacial re-colonization also largely explained the presence in the fauna of some elements of the Western European and Caucasian fauna in the Black/Azov Sea Lowlands [119][120][121][122][123]. Two epigean species of the genus Niphargus, N. hrabei S. Karaman, 1932 are N. valachicus Dobreanu and Manolache, 1933, currently found in the coastal swamp area of SW Caucasus [14,63] and also the Pannonian River Basin [60][61][62]. Both species are of the Ponto-Caspian origin, dispersed in the Black/Azov Sea Lowland from the Pannonian region throughout the Danube riverbed possibly during or just after the Last Glacial Maximum .…”

“…observ, in prep.) and freshwater mussel Anodonta anatina (Linnaeus, 1758) [54], as well as the whole Black/Azov Sea Lowland (e.g., N. potamophilus [14,63]) (see Figure 9) or different freshwater mollusks and snails [112] (see Table 2).…”

“…Both species are of the Ponto-Caspian origin, dispersed in the Black/Azov Sea Lowland from the Pannonian region throughout the Danube riverbed possibly during or just after the Last Glacial Maximum . At that time, the area of the Black and Azov Sea including the estuary of the Dnieper, Dniester, Danube and Don Rivers represented a freshwater lake, isolated from the World Ocean [62,63,[124][125][126], and lately (about 7-9 Tya) separated by flooding of the saline waters from the Mediterranean Sea [127][128][129]. At the same time, another epigean species, Niphargus potamophilus Birštein, 1954, is most likely native to the Black/Azov Sea Lowland, while currently its populations are somewhat scattered [14,63] or still undiscovered.…”

“…It is also likely that in the past, similar to the modern times, the Danube riverbed connected the middle of the Black Sea with the Pannonian Lowland (Pannonian Basin), and was a channel for the distribution of many ancestral lines of modern groups of stygobiotic animals, such as the genus Niphargus. Currently, it is proven as a transit waterway for Niphargus hrabei S. Karaman, 1932 and Niphargus valachicus Dobreanu and Manolache, 1933 [14,[60][61][62][63]. Moreover, the Danube Delta is the southernmost part of the studied area, and the influence of glaciation on it was significantly lesser, so that the evolutionary processes could occur there in a slightly different way than in the northern areas of the Northern Black/Azov Sea Lowland [64,65].…”

“…Distribution: The species was originally described from small water reservoirs in the delta of the Don River near Rostov-on-Don [50]. Sub-endemic of the Northern Black/Azov Sea Lowland, currently found in the Azov-Prikubanskaya Lowland (from Rostov-on-Don to the lower delta of Kuban River) [14] and the coastal area of the Northern Black/Azov Sea Lowland from southern Ukraine to Bulgaria [63] (Figure 9). A new discovery in the Crimean Peninsula connected the known eastern area of its distribution in the delta of the Kuban and Don rivers with the western one in the deltas of the Dnieper, Dniester and Danube.…”