Rec. zool. Surv. India: Vol. 120(3)/241–246, 2020 ISSN (Online) : 2581-8686 DOI: 10.26515/rzsi/v120/i3/2020/152790 ISSN (Print) : 0375-1511 Distinction of two featherback species (Osteoglossiformes: Notopteridae) in India based on scale structure Yogesh Kumar Rawal1, Oshin Dhillon2 and Inderpal Singh Sidhu3* 1Department of Zoology, Fish and Fisheries Laboratory, Panjab University, Chandigarh – 160014, India 2Department of Zoology, Akal University, Talwandi Sabo, District Bathinda, Punjab – 151302, India 3Department of Zoology, SGGS College, Sector 26, Chandigarh – 160019, India Email: [email protected] 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 differentiatingNotopterus between notopterus different genera Chitala and species. chitala Scale morphology and structure has been established as a tool in fish taxonomy. The present investigation shows theN. notopterusutility of scale in distinguishing two featherback species occurring in India, (Pallas) and (Hamilton).C. chitala Morphology and ultra structure (using SEM) of the scales of both theN. species notopterus were studied.C. chitala The scales of are granulated withC. chitala bead like structures in the focus, extending into the anterior part whereas the focus is smoothN. notopterus in . Based on the length/ width ratio, the scales are relatively longer in than . The lateral line is relatively short in with rounded anterior end and trifurcated posterior end whereas it is longer in with elongated anterior opening and rounded posterior opening. Other distinguishing features which separate these two species include inter- circulus distance and width of the radial canal. Therefore, the scale of the featherback species in India may be successfully employed in distinguishing them. Keywords: Chitala, Notopterus, Lepidology, Morphometry, SEM, Taxonomy Introduction Due to the numerous and extensive ichthyological studies and taxonomic revisions conducted recently, India constitutes about 11.72% of the global fish diversity, many major changes have been made at generic level most of which is harboured by the hotspots such as in fresh water fishes during the last two decades. For Himalayas, northern plains, Eastern and Western instance, the long known genus Puntius has been divided Ghats (Lakra et al., 2010). Out of the 3396 fish species into to four genera (Dawkinsia, Haludaria, Systomus and known in India, 1027 are freshwater forms (858 primary Pethia), that further led to creation of one more genus freshwater fishes, 32 introduced freshwater fishes and Sahyadria (Pethiyagoda et al., 2012, Pethiyagoda, 2013; 137 secondary freshwater fishes) (Chandra et al., 2017; Raghavan et al., 2013). Molecular markers too have been Chandra & Sheela, 2019). Because of high diversity and used for studying the genetic divergence in generic level closely similar color patterns, the freshwater fishes pose (Lal et al., 2006). more challenges in their identification both at the species The use of scale morphology became important in and generic levels. While most fish species are identified fish taxonomy following the introduction of scanning on the basis their morphological and meristic characters, electron microscopy (Hughes, 1981; Roberts, 1993; for the identification of higher levels of taxa the use of Jawad, 2005a,b). Lepidology was often used to identify various osteological and anatomical characters are in certain groups of fish for taxonomic purpose, but in vogue, for which the fish has to be sacrificed, and in doing a very restricted extent. Apart from the counts, scale so, vouchers may be lost. Therefore, alternate authentic morphology now has become an important component taxonomic tool needs to be explored for this purpose, of fish systematics and features of the scale can contribute without sacrificing the fish. * Author for correspondence Article Received on: 27.05.2020 Accepted on: 24.06.2020 Distinction of two featherback species (Osteoglossiformes: Notopteridae)... towards discrimination amongst different species of a N. notopterus where the growth stops restricting them to genus (Kaur & Dua, 2004; Jawad, 2005b). the posterior border of the eyes. Further these two species Notopteru notopterus (Pallas, 1769) and Chitala chitala also show variation at molecular level apparent upon the (Hamilton, 1822) commonly known as Bronze Featherback application of RAPD profile, thereby suggesting that they and Humped Featherback respectively belong to a are quite different from one another at genetic level (Lal primitive Order Osteoglossiformes (Nelson et al., 2016). et al., 2006). Fishes belonging to this order are considered important However, it has been observed that there is a very to explore phylogenetic changes, phylogeographic thin line of difference between these two species information and genetic evolution in the Class Pisces morphologically, whether it is the insertion of the dorsal (Hilton & Lavoué, 2018; Capobianco & Friedman, 2019). fin or the extension of the jaw with respect to the position Sodsuk & Sodsuk (2000) studied genetic diversity of of the mouth. In order to further distinguish these featherbacks using allozymes electrophoresis technique two Indian featherback species, the present work was and reported genetic similarities in three Chitala species undertaken with a study of their scales. and separated them from N. notopterus, which they placed in a separate clade. N. notopterus is a species complex, Material and Methods placed in Least Concern category by International Union for Conservation of Nature, but the species stands at high The specimens of C. chitala and N. notopterus were risk owing to overfishing and pollution through factory collected using gill-net from the area around Harike and agricultural effluents (Ng, 2010). wetland (Ramsar site), District Amritsar, Punjab (31.17°N Both the species have certain morphological features 75.20°E) (Figures 1a, b). The specimens were preserved in which distinguish them from one another. Talwar & 10% formaldehyde solution in the field and brought to the Jhingran (1991) observed that in case of C. chitala, the laboratory for further analysis. A total of 69 specimens maxilla extends considerably beyond the posterior edge of C. chitala and 73 specimens of N. notopterus were of the eye, and only up to the middle of the eye in N. investigated. A total of five scales per fish were examined notopterus. They further observed that the dorsal fin is for calculating length/width ratio as well as the percent inserted near the base of caudal fin in case of C. chitala distance of focus from the anterior side. and more towards snout tip in case of N. notopterus. The scales were removed from the body of the fishes Jayaram (2012) separated these two genera on the under study using tweezers having blunt edges from below basis of the craniodorsal profile of the fish, which is the dorsal fin from 3rd row; washed in tap water and then strongly concave in C. chitala while almost straight in N. rubbed between finger tips to remove the mucous and the notopterus. Besides, these species are differentiated with extraneous matter. The scales were further sonicated for incessantly growing jaws across the life span extending 5-7 minutes and then dried in desiccators overnight to beyond the posterior border of the eyes in C. chitala unlike remove even the last trace of moisture. The dried scales Figure 1. a. Chitala chitala (Hamilton); b. Notopterus notopterus (Pallas). 242 Vol 120(3) | 2020 | www.recordsofzsi.com Zoological Survey of India Yogesh Kumar Rawal, Oshin Dhillon and Inderpal Singh Sidhu were mounted between two slides in such a way that the margin of the scale was found to be 69.88% and 67.53% ventral part or shining of the scale is on the lower side and for N. notopterus and C. chitala respectively, indicating studied under ordinary microscope. For SEM studies, the a posterior positioning of the focus in both the species. scales were mounted on the aluminium stub with the help There was an insignificant variation in the percent distance of double stick tape in such a way that the ventral part or of focus from the anterior region. The scale morphometry the shining part touched the stub surface and these were resulted in a higher average percentage length/width ratio kept in desiccators overnight for drying. The dried scales in N. notopterus (189.75%) than C. chitala (149.08 %), were studied in the vacuum chamber of SEM at an electric thereby suggesting that the scales are relatively longer in current of 10kv and 25kv. For comparison, the images of N. notopterus as compared to C. chitala (Figures 2a, b). the scales of these two fish species were taken at the same The ultrastructural details of scale ofC. chitala and magnifications. N. notopterus show very well defined and distinct circuli in all the regions of the scale (Figures 3a-d, f-i). The Results inter-circular distance was more in the anterior region, followed by lateral and posterior regions. The structure The featherbacks have typical cycloid type scale. However, of lateral line scales from the middle region of both the N. notopterus can be differentiated from C. chitala with fish species show variations of taxonomic interest. While bead-like structures present in the focus region of the C. chitala has a relatively short lateral line, broadening scale, which extend up to middle part of the anterior towards the middle, N. notopterus has an elongated lateral region (Figure 2a). Distinct annual marks were observed line with a narrow width throughout. Also, the posterior on the scales of both the species (Figure 2a, b), indicating side of the canal is tri-furcated and the anterior opening their suitability for age and growth studies. The radii is almost rounded in C. chitala unlike N. notopterus with originate at a distance from the focus rather than from an elongated anterior opening and a rounded posterior its centre. Percentage distance of focus from the anterior opening (Figures 3e, j). Length of the lateral line canal Figure 2.