Scale structure of a cyprinid fish, Garra Rossica (Nikol’skii, 1900) using scanning electron microscope (SEM)

Abstract

The normal and lateral line cycloid scales of the native species Garra rossica (Nikol'skii, 1900), one of the most common and poorly known cyprinid fish in south-eastern Iran have been subjected to the scanning electron microscopy technique in order to study their detailed structure. Normal scale below the dorsal fin showed a clearcut demonstration between the anterior and posterior region with the focus lying towards the anterior region that is covered by reticulate or honeycomb form structures with few mucous pores. There is a wedge shaped circuli only in the anterior and lateral fields which are partitioned by deep and narrow grooves called radii and run radially towards the focus. On the dorsal side, the anterior circuli bear numerous pointed lepidonts. In the posterior section, the scale has several rows of pigmented granules (tubercles) with different shapes from round to oval, semi oval and even oblong structure. The lateral line scale has a canal which characteristically lies along the anteriorposterior axis, with a wider anterior opening than the posterior opening which is hidden by an eyelike extension cantilevered over it. Although the scale of G. rossica shows the general structure of a cycloid cyprinid scale, the shape and size of lepidonts on the circuli crest, shape and size of tubercles on the posterior region and the pattern of reticulate or honeycomb that form structures in the focus region may provide more reliable taxonomic tools. The present analysis of scale morphology in G. rossica may be used in combination with other morphological and molecular data in a synergic approach to the phylogenetic and systematic study of the genus.