PDFDOI: https://doi.org/10.2478/vzoo-2014-0014
Traditionally, shells of Dreissena polymorpha Pallas, 1771 mussels are studied as a whole by the investigation of population variability of coloration. However, shell surface is divided into zones by the lines of growth delay called annual rings, and mussel shell coloration is an array of patterns in the consequent age zones. In the present paper traditional term “pattern type” is expanded by its relation to definite shell zone; pattern types change along with annual ring formation. Th e pattern is considered not as a holistic feature but rather a sequence of states realized during the mussel’s growth. Frequencies of some pattern types showed to be age dependent. Geographic variability of patt ern sequences was found. High diversity of pattern sequences’ arrays observed in populations may reflect wide adaptation potential of zebra mussels.