About the sexual dimorphism of the crucian carp Carassius carassius (Cyprinidae)

Abstract

The Crucian carp Carassius carassius (Linnaeus, 1758) is widely distributed in the Northern Eurasia. This is a medium-sized schooling fish, mainly its habitat is shallow water bodies overgrown of aquatic plants and slow flowing rivers. The Crucian carp is resistant to hypoxiaand fluctuations of water temperature. It is euryphage. In recent decades, there has been a widespread reduction in its range and a decline in numbers both in Western Europe and in Russia. In Western Siberia, Crucian carp was previously relatively numerous. Since the end of the 20th century, this species has a decrease reduces the number or complete extinction in some water bodies of the region. This provokes an increased interest to the peculiarities of the biology of this fish species, including the variability of its morphological characteristics in different types of water bodies and the environmental characteristics that determine them. We have revealed sexual dimorphism of C. carassius in 47% of the studied plastic characters: females have a longer head length, anteventral and antepectral distances, and males have ventroanal, ventrocaudal, anal-caudal and dorso-caudal distances. In addition, males have larger fins: the height of the dorsal and anal fins, the length of the pectoral, ventral, and lower lobe of the caudal fins are statistically significantly greater. There are differences in head morphology: males have the height of the head through the middle of the eye and diameter of eye are statistically significantly greater. There are no sexual dimorphism of C. carassius in countable morphological characters. The our data obtained make it necessary to take into account the sex composition of the samples when analyzing the features of the variability of the morphological features of the Crucian carp C. carassius.