Delineation of Seven Species of Genus Channa from Upper Assam Region, India Using Sagittal Otolith Morphology
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Journal of Fisheries eISSN 2311-3111 Volume 8 Issue 3 December 2020 Pages 868–872 pISSN 2311-729X Peer Reviewed | Open Access | Online First Original Article Delineation of seven species of genus Channa from upper Assam region, India using sagittal otolith morphology Jyotirmoy Sonowal Moirangthem Kameshwor Singh Shyama Prasad Biswas Department of Life Sciences, Dibrugarh University, Dibrugarh, Assam 786004, India Correspondence Jyotirmoy Sonowal; Department of Life Sciences, Dibrugarh University, Dibrugarh, Assam 786004, India [email protected] Manuscript history Received 18 November 2019 | Revised 5 July 2020 | Accepted 9 July 2020 | Published online 13 October 2020 Citation Sonowal J, Singh MK, Biswas SP (2020) Delineation of seven species of genus Channa from upper Assam region, India using sagittal otolith morphology. Journal of Fisheries 8(3): 868–872. Abstract Morphology of sagittal otoliths of seven species of genus Channa from upper Assam, India was studied to obtain baseline information for their prospective role in taxonomic studies. In the present study, variations were recorded in morphological characteristics of sagittal otolith among the studied species. Of all the studied parameters, otolith shape, sulcus acusticus, ostium, and cauda, in particular, were found to be taxonomically important features for the identification of the species. The pentagonal shape of sagitta in Channa punctata, pseudo-ostiocaudal sulcus acusticus in C. marulius, bent concave ostium in C. stewartii, straight cauda in C. bleheri were found to be species-specific features. Sagitta size was smallest in C. gachua while the largest was recorded in C. striata. The proposed taxonomic keys enumerated through the combination of different otolith characters from the present investigation will be useful in the identification of these species when standard methodologies fail to deliver satisfactory results. Keywords: Identification; sagittal otoliths; snakehead taxonomy; taxonomic keys; variation 1 | INTRODUCTION reported nine channid species from the region and de- Snakeheads belonging to Channidae family are predatory scribed its diagnostic characters. However, samples col- air-breathing fishes well distributed in African and Asian lected from aquarium trade indicated greater diversity of continents (Ruber et al. 2020). Three distinct genera viz. snakehead fishes from the region. Within a decade, ten Parachanna, Channa, and recently discovered Aenigma- new species of Channa have been discovered from East- channa together comprises about 51 valid species (Conte- ern Himalayan region of India that includes C. melanos- Grand et al. 2017; Britz et al. 2019; Kumar et al. 2019; tigma (Geetakumari and Vishwanath 2010), C. andrao Praveenraj et al. 2019a). Among the three genera, genus (Britz 2013), C. pardalis (Knight 2016), C. aurantipectoralis Channa has the highest species diversity with 46 valid (Lalhlimpuia 2016), C. quinquefasciata (Praveenraj et al. species (Praveenraj et al. 2019a). 22 valid species of 2018a), C. bipuli (Praveenraj et al. 2018b), C. pomanensis Channa have been reported from India, out of which 19 (Gurumayum and Tamang 2016), C. stiktos (Lalramliana et are found in the Eastern Himalayan region (Praveenraj et al. 2018), C. lipor (Praveenraj et al. 2019b) and C. brunnea al. 2019a). Vishwanath and Geetakumari (2009) earlier (Praveenraj et al. 2019a). Due to its high diversity and BdFISH Publication | journal.bdfish.org | © Creative Commons BY-NC-SA 4.0 License 868 Species delineation of Channa spp. using otolith morphology J Fish 8(3): 868–872, Dec 2020; Sonowal et al. species complexes, it is observed that their taxonomy is out from otic capsules and then washed in 70% ethanol. often complicated, over lumping, and grouped into phy- Both left and right otoliths were stored in separate plastic lectic groups (Vishwanath and Geetakumari 2009; Conte- vials for further investigations. Sagitta size was measured Grand et al. 2017). Identification based solely on morpho- to the nearest 0.01 mm using a digital vernier caliper. The logical characters and modern molecular techniques are morphological description of otoliths was described fol- sometimes challenging and have their share of limitations lowing Tuset et al. (2008) under microscopic examination. (Adamson et al. 2010; Lalramliana et al. 2018). In such The following anatomical terminologies were used for situations, otolith morphology emerges as a promising variation studies, (i) otolith shape (ii) sulcus acusticus (iii) taxonomic tool in discriminating many extant fishes (Nolf ostium (iv) cauda (v) anterior and posterior otolith regions 1985; Smale et al. 1995). (vi) otolith margin. Otoliths are aragonitic mineralisation found in teleosts fishes. They are composed of calcium carbonate and 0.2 to 10% organic matter and serves as an organ of balanc- ing and hearing in fishes (Platt and Popper 1981; Gauldie 1988; Campana 1999). The otoliths are categorised into three distinct classes: lapillus, asteriscus, and sagitta, of which the sagitta is the largest (Zorica et al. 2010). Among the three types, sagitta otoliths show the highest degree of morphological variation and often are found to be spe- cies-specific (Battaglia et al. 2010; Kumar et al. 2012; Jaramillo et al. 2014). Due to such variations in morpho- logical features, they are widely employed in different aspects of fish systematics (Lombarte et al. 1991; Smale et al. 1995; Volpedo and Echeverria 2000). Application of FIGURE 1 Geographical location of different sampling sites in sagitta in extrapolating fish sizes and identity have often Dibrugarh and Tinsukia districts of upper Assam, India. proved to be a reliable taxonomic tool, especially in situa- 3 | RESULTS AND DISCUSSION tions where other methods fail to deliver conclusive in- ferences (Lombarte et al. 2006; Tuset et al. 2011). Fur- The sagittal otoliths find wide application in taxonomical ther, it has been observed that information on sagittal studies of fishes due to their distinct form, weight, otolith morphology is available only for commercially im- growth, consistency, chemical composition, and easy ac- portant marine fishes (Battaglia et al. 2010). There is a cessibility (Nolf 1985). In fishes, when accepted method- paucity of knowledge and data on the sagitta morphology ologies through morphological studies do not provide of freshwater fishes (Sonowal et al. 2018). With this con- satisfactory results, the otoliths act as an added taxonom- cern, the current investigation was undertaken to study ic tool to delineate fishes. The current investigation on the sagittal otolith morphology of seven species of Chan- sagittal characters of seven species of genus Channa from na from upper Assam which may aid as a taxonomical upper Assam, revealed variation in its morphological fea- tool for their identification. tures (Table 1). During the study, the smallest sagitta was observed in C. gachua while the largest was found in C. 2 | METHODOLOGY striata among the studied species. Earlier, all the studied Total 164 specimens belonging to seven species of genus species had been grouped into two phylectic groups by Channa including C. aurantimaculata Musikasinthorn, Vishwanath and Geetakumari (2009) based on their ex- 2000 (n = 18); C. bleheri Vierke, 1991 (n = 15); C. gachua ternal morphological features to aid in their identifica- (Hamilton 1822) (n = 26); C. punctata (Bloch, 1793) (n = tion. Species with prominent V-shaped sharp isthmus, 30); C. marulius (Hamilton, 1822) (n = 17); C. stewartii grouped sensory pores, as well as the absence of big cy- (Playfair, 1867) (n = 26) and C. striata (Bloch, 1793) (n = cloid scales on lower jaw were designated as ‘marulius’ 32) were examined during the current study. Fish speci- group while species with U-shaped isthmus, single senso- mens were collected from eight different sampling sta- ry pore and presence of one or two big cycloid scales on tions of Dibrugarh (Bogibeel, Dibrugarh University pond, lower jaw were grouped into ‘gachua’ group. It was ob- Lezai, Madhupur, Maijaan and Merbeel) and Tinsukia dis- served that four members of ‘gachua’ group (C. bleheri, C. tricts (Guijan and Maguri beel) of upper Assam, India, gachua, C. stewartii and C. aurantimaculata) showed el- during March 2018 to May 2019 (Figure 1). The collected liptical-shaped sagitta with varying size and shape differ- specimens were first preserved in 10% formalin and anal- ences (Table 1). The other three species i.e. C. punctata, yses were carried out at the Freshwater Biology Research C. striata and C. marulius had pentagonal, oval, and spin- Laboratory, Department of Life Sciences, Dibrugarh Uni- dle-shaped shape respectively (Figure 2). Even though C. versity. Sagittal otoliths of the fish were then dissected punctata belonged to ‘gachua’ group (Vishwanath and BdFISH Publication | journal.bdfish.org | © Creative Commons BY-NC-SA 4.0 License 869 Species delineation of Channa spp. using otolith morphology J Fish 8(3): 868–872, Dec 2020; Sonowal et al. Geetakumari 2009), sagitta shape was different from oth- ‘marulius’ group i.e. C. striata and C. marulius had unique er members of the same group. The members of oval shaped and spindle-shaped sagitta respectively. FIGURE 2 Images of sagittal otoliths of seven studied spe- cies of genus Channa. A, Chan- na aurantimaculata; B, C. ble- heri; C, C. gachua; D, C. punc- tata; E, C. marulius; F, C. stew- artii; G, C. striata). TABLE 1 Morphological characteristics of sagitta of seven Channa species from