High Morphological Variability of Gerris Argentatus Schummel 1832 (Gerridae) and Probably Europe’S Smallest Gerrids, in the Danube Delta (Romania)

On a field trip to the Busurca Canal, near Sulina, in the Danube Delta, an apterous Gerris argentatus male was captured. It measured only 5.1 mm from the tip of the head to the end of the last abdominal segment, and was the smallest adult pond skater recorded in Europe. This specimen was also the first to be describe as an apterous form of G. argentatus, the species previously being known as either macropterous or micropterous. A large macropterous male, measuring 6.77 mm, was also collected in the same habitat, its size exceeding the known measurement for the species. Five G. argentatus females were taken from two sites on the Busurca Canal, each one measuring under the 7.5 mm length documented as a minimum for females of the species, with the smallest sample being only 6.59 mm in length.