VERTICAL DISTRIBUTION OF MUSSEL MYTILUS GALLOPROVINCIALIS (LAMARCK, 1819) OF DIFFERENT PHENOTYPIC GROUPS FOULING THE DEPTH OF ODESA COAST

Abstract

Mussel Mytilus galloprovincialis (Lamarck, 1819) is widespread in the north-western part of the Black Sea, it is the active filter feeders sea water, is an important component of various zoocenoses. Mollusk is the object of fisheries and mariculture. Three phenotypes of mussel are separated on features of distribution of a violet pigment in outer prismatic shell layer: Fa – in a prismatic layer of purple pigment absent; Fb – pigment paints the whole of prismatic layer; Fc – pigment is localized in the form of radial strips alternating with unpigmented zones. The first two forms are interpreted homozygotes, last – heterozygotes.The purpose of the work is to study the distribution of mussels different phenotypic groups on the depths of the Odessa coast.The material for the work were the mussels collected in may 2012 at two stations – on the beach Langeron (depth 3,5 m) and in the area of hydrobiological station of Odessa National Mechnikov University (at a depth of 1 m breakwater; 6 m – fouling stones). Samples were collected with the frame area of 0,01 m2. Total collected and analyzed 459 exemplars of mussels, which were divided into the size groups with an interval of 10 mm.Index deficiency of heterozygotes (D) was calculated according to the equation:D = (Hо– Hс)/Нс ,Hо – the number of heterozygotes observed in the population; Hс – the number of heterozygotes expected by Hardy-Weinberg equation. A positive value means a deficit of heterozygotes D and negative – of their surplus.At a depth of 3,5 m represented only mussels of three size groups. About 52% of the total numbers of mollusks are size class of 20-29 mm, for other two classes remaining accounted to 24%.Among the small mollusks provided only at a depth of 6 m, the dominant were mussels of phenotype Fb (60%); half mussel of phenotype Fa (30%) and 10% – mussels of phenotype Fc. In large size class at a depth of 1 m dominated mussels of phenotype Fb – up to 100%.Mussels of phenotype Fa represent a smaller part of mollusks in almost all researched depths (1, 3,5, and 6 m), respectively, 23, 18 and 25% of the total number.At a depth of 1 m the number of mussels of phenotypes Fb and Fc is almost the same – 40 and 37%. At a depth of 3,5 m the number of these mussels of phenotypes differ slightly – 35 and 47%. Mussels of phenotype Fb, on the contrary, is dominated at a depth of 6 m, they accounted for more than half of the total number of animals – 55%. Analysis of the conformity of actual frequencies of phenotypes with theoretical data calculated by the relation of the Hardy-Weinberg equilibrium using the criterion c2 showed that at depths of 1 and 3,5 m obtained facts were not statistically significant.At a depth of 1,0 and 3,5 m observed a deficit of heterozygotes, and at the 6-meter depth – their surplus.