Morphology and taxonomy of Aulacoseira muzzanensis (Bacillariophyta)

Abstract

Morphological investigation of wild populations of Aulacoseira granulata shows significant variability of its quantitative morphological characteristics: valve diameter and height; number of rows of areolae and number of areolae in 10 μm on the valve mantle; and number of spines and their length on separation valves. Low values of mantle height to valve diameter ratio and large numbers of areolae in 10 μm, typical for A. muzzanensis, are also found in populations of A. granulata. The valve height/diameter ratio decreases as the valve diameter increases, and such relationships also occur in other taxa of this genus (A. baicalensis, A. islandica, and A. subarctica). No correlation is found between valve diameter and number of spines in separation valves. Our investigations confirm the correctness of referring A. muzzanensis to the synonymy of A. granulata, and based on original and published data, we suggest emendation of the diagnosis of A. granulata.