Genetic divergence in natural populations of bronze featherback, Notopterus notopterus (Osteoglossiformes: Notopteridae) from five Indian rivers, analyzed through mtDNA ATPase6/8 regions

Abbreviations

• ATPase, adenosine tri phosphates;
• DNA, deoxyribonucleic acid;
• dent, deoxyribonucleoside triphosphate;
• mtDNA, mitochondrial DNA;
• FAO, Food and Agriculture Organization;
• IUCN Red List, International Union for Conservation of Nature;
• CAMP, Conservation Assessment and Management Plan

Keywords

• Notopterus;
• ATPase6/8;
• Mitochondrial DNA;
• Polymorphism;
• Population genetic

1. Introduction

The present study is the first attempt to characterize ATPase6/8 genes in Notopterus notopterus and assess its polymorphism to differentiate genetic stock in Indian rivers. The N. notopterus, commonly known as bronze featherback, is a teleostean fish of the order Osteoglossiformes and family Notopteridae. The order Osteoglossiformes is considered primitive ( Taverne, 1975) with 19 fossil genera found in upper Jurassic to lower Cretaceous deposits ( Nelson, 1994 and Otero and Gayet, 2001). The featherback, N. notopterus is widely distributed in South and Southeast Asia ( Talwar and Jhingran, 1991). The fish has been categorized as an important commercial fish by FAO (Casavas et al., 1996) for food as well as for ornamental trade. Populations of bronze featherback in wild are declining and categorized as one of the threatened species of the country (CAMP, 1998). However, the species is listed on the IUCN Red List as Least Concern (LC) due to ambiguity in taxonomy and suggested to be a species complex (Ng, 2010). The N. notopterus is a local migrant and prefers stagnant pools, wetlands than fast moving waters, coupled with its breeding preference ( Rainboth, 1996); the fish may possibly have limited scope of dispersal. Therefore the species is likely to have high genetic heterogeneity. Though, to address the need to maintain wild populations and also for aquaculture, artificial propagation of the N. notopterus is pursued with encouraging results ( Haniffa et al., 2004), however, such interventions without stock structure assessed through molecular markers, may not translate into effective means to conserve natural genetic variation.

There is a need of specific knowledge of intraspecific genetic variations to plan rehabilitation and management strategies for populations of the species which are declining in their natural habitat. The ATPase8 and ATPase6 regions of mitochondrial DNA have been successfully analyzed for both phylogeny as well as phylogeography in many fish species ( Chow and Ushiama, 2004, Dammannagoda et al., 2008, Vergara-Chen et al., 2009, Xin-Hong et al., 2004 and Yan et al., 2009). However, the information on polymorphic molecular markers and their applications is limited to a small part of vast distribution ( Takagi et al., 2006a, Takagi et al., 2006b and Takagi et al., 2010) and genetic relatedness with another notopterid fish, Chitala chitala ( Lal et al., 2006). The present study characterized complete sequences of mitochondrial ATPase8 and ATPase6 regions in N. notopterus collected from 5 distant major rivers namely, Satluj, Ganga, Yamuna, Brahmaputa and Mahanadi, and analyzed the polymorphism and identify evolutionary significant subpopulations.

2. Materials and methods

2.1. Sample collection

Details of sampling sites for N. notopterus across different rivers are given in Table 1. The rivers are distant and represent different river basins (Fig. 1). The specimens of N. notopterus were obtained from commercial riverine catches and tissue (blood and muscle) samples were collected at site. The blood was collected through caudal puncture and fixed in 95% ethanol in 1:5 (blood: ethanol) ratio and dorsal white muscles (50 mg) as an alternate source of DNA, were stored in 95% ethanol at 4 °C until use.