The Ukrainian stickleback (Pungitius platygaster) is a relative of widespread in Belarus nine-spnied stickleback, but could be easily distinguished by the absence of bone plates covering the sides. This species passed into Belarus through the Dnieper river. It was registered in our country first time in 2007 in lower Belarusian part of Dnieper near Nizhniye Zhary village. Recent years we caught a very little number of this fish, but this year the sticklebacks were quite numerous. We suppose the abundsnce of submerged riparian plants made the habitat more suitable for this fish.
Apeltes quadracus (Four-spined Stickleback). Fig.22 Embryo in the egg, showing the asymmetrically disposed vitelline vessels; figs. 23 & 24 Other views of the same stage, showing the lateral position of the heart; Fig.25 Dorsal view of a recently hatched embryo, showing the distribution of the brown pigment blotches on the median line and the symmetry in the distribution of the vascular channels on the dorsal side of the yelk; Fig.26 Side view of the same stage, showing the pigmentation and vascular loops in the dorsal fin-fold