Distinction of two featherback species (Osteoglossiformes: Notopteridae) in India based on scale structure

Abstract

The fish species are identified primarily based on their morphological and meristic characters and of late, the molecular markers too have been used for differentiating between different genera and species. Scale morphology and structure has been established as a tool in fish taxonomy. The present investigation shows the utility of scale in distinguishing two featherback species occurring in India, Notopterus notopterus (Pallas) and Chitala chitala (Hamilton). Morphology and ultra structure (using SEM) of the scales of both the species were studied. The scales of N. notopterus are granulated with bead like structures in the focus, extending into the anterior part whereas the focus is smooth in C. chitala. Based on the length/ width ratio, the scales are relatively longer in N. notopterus than C. chitala. The lateral line is relatively short in C. chitala with rounded anterior end and trifurcated posterior end whereas it is longer in N. notopterus with elongated anterior opening and rounded posterior opening. Other distinguishing features which separate these two species include intercirculus distance and width of the radial canal. Therefore, the scale of the featherback species in India may be successfully employed in distinguishing them.