PECULIARITIES OF EGG STRUCTURE AND EMBRYONIC DEVELOPMENT OF GARFISH (BELONE BELONE (L.))

Peculiarities in egg morphometry and in the course of embryogenesis of the Baltic garfish (Belone belone (L.)) were studied. The eggs, measuring 3.27 ±0.15 mm in diameter and 18.34 ±2.6 mm3 are equipped in viscous filamentous processes. The eggs lack the so- called structural lipids in the form of lipid vesicles, for which reason the embryonic disc is never located in the upper part of the egg and moves sideways during embryonic development. The perivitelline space, small (about 5% of the egg's volume) at first (after activation), expands gradually as the embryo grows to occupy up to 45% of the egg's volume when the embryo is fully formed. The embryonic development takes 340 Dº (at 16ºC). The Baltic garfish embryonic mortality is high and exceeds 90%. The larvae carry a residual yolk sac and are fully prepared to live independently in water and to feed efficiently. The structural and embryological peculiarities observed in the garfish development evidence an exceptional plasticity and adaptive potential of the species with respect to changing environmental conditions, which enables it to expand its natural range.