On finding of Monocorophium insidiosum Crawford, 1937 (Amphipoda, Corophiidae) in the coastal waters of Crimea (Black Sea), a new species for this region

An illustrated description of morphology of Monocorophium insidiosum Crawford, 1937 from the Crimean coastal waters is given. In this work, 744 specimens from different locations and substrates of the Crimean coastal waters have been analyzed. The main specific parameters of species from the Crimean coastal waters are as follows: rostrum of males is about one half of first article of antenna I length, dactylus of gnathopod II is equipped with 2–4 additional spines along the inner side (both for males and females). Variability is observed in parameters of the following parts: first article of antenna I peduncle, fourth article of antenna II peduncle, inner side of gnathopod II dactylus, and outer sides of the outer and inner rami of uropod II. Morphological parameters of specimens from the Black Sea, the Mediterranean Sea (literature data), and the North America coast (Vancouver area, literature data) have been compared. Specimens from the Black Sea are morphologically similar, but have some differences from the North American ones. In particular, first article of antenna I peduncle of specimens from the North America have conical process (specimens from the Black Sea have rounded process); fifth article of antenna II peduncle is with proximal medial tooth (specimens from the Black Sea are without proximal medial tooth); and outer ramus of uropod II has medial spine (Mediterranean specimens are without such a spine). These differences should be taken into account when carrying out hydrobiological research.