Morphotaxonomic studies of Bangana (Hamilton, 1822) species from north-east India

Introduction

North East India is a global biodiversity hotspot and has attracted many scientists to work on icthyodiversity of this region (Kar and Sen, 2007, Vishwanath et al., 2007; 2010, [20] Goswami et al. 2012; [2] Sarma et al. 2022) as boasting over 512 fish species (approx. 33% of India's total), heavily dominated by the Cyprinidae family (carp family). The freshwater cyprinids of genus Bangana inhabit mostly tropical and subtropical waters and are distributed across much of Southern and Eastern Asia. Bangana as sub-genus of Cyprinus Linnaeus based on specimens collected from the river Brahmaputra. However, Bangana was later regarded as an invalid taxonomic unit, and its species were assigned to either Labeo Cuvier (Jayaram, 1981) [7] or Sinilabeo Rendahl (Wu et al., 1977) [22] . Kottelat (1985) [10] resurrected Bangana and considered it to be a senior synonym of Tylognathus Heckel. Jayaram and Dhas (2000) [6] have also referred Bangana as a synonym of Labeo and placed both the species of this genus under Dero group based on the snout with depression, crescentric mouth, lips continuous and interrupted post labial fold. Further, Rainboth (1996), [15] Kullander et al. (1999) [11] and Zhang [24] and Chen (2006) revised the genus Bangana and listed twenty-three species under this genus. However, Zhang [24] and Chen (op cit.) opined that the total number of species of Bangana is somewhat problematical as the other species of this genus outside the China is not studied so far. Twenty-five species of genus Bangana have been reported so far but only five species are found in India viz. B. devdevi, B. dero, B. diplostoma, B. ariza and B. almorhae. Two species of this genus i.e., Bangana dero (Hamilton) and Bangana devdevi (Hora) have their distribution in North-East, India (Vishwanath et al., 2007). [20] The presently known B. devdevi was first described by Hora (1936) from Burma as Labeo devdevi and later redescribed by Jayaram and Das (1980). [8] The conventional tools such as morphological traits, morphometric and meristic studies are widely employed to identify and describe the species. Apart from the availability of the physiological, ecological and anatomical data the ichthyologist is primarily dependent on the morphological characters which differentiate the fishes based on shape, size, placement of fins, body coloration and pigmentation etc. An important taxonomic and nomenclatural work on genus Bangana and its 13 species from China has been documented by Zhang and Chen (2006). [24] There is considerable taxonomic ambiguity regarding both the above-mentioned species; therefore, the present study has been undertaken to address the issue.

Material and Methods

During study, samples were collected from there known distributional ranges and taxonomic data and information on morphological, morphometric and meristic characters were taken and analysed following standard protocols. The specimens of B. dero (Hamilton, 1822) were collected from the river Brahmaputra and its tributaries from the North-Eastern states namely Arunachal Pradesh, Assam, Tripura, Manipur and Nagaland and B. devdevi (Hora, 1936) from Imphal River and Thoubal river from Manipur during May 2017 to April 2018. The samples were collected by employing different gears (with varying mesh sizes) such as cast net, gill net, drag net and other traditional gears (such as Bamboo traps, Hook and Lines) (Table 1). After collection, initial data such as Length, Weight has been taken and morphological characters were noted. Following initial observation, samples were preserved in 10% formalin and bought to laboratory. Specimens collected as part of the ongoing COE-FAB Project in College of Fisheries (CAU), Tripura were also studied in this respect. Further, the specimens of B. dero from NZC of ZSI, Kolkata (Table 2) were also studied for comparison A total of 31 morphometric characters were taken using digital Vernier calliper to the nearest 0.01mm scale and 13 meristic measurements were recorded by counting with naked eye and microscope. The various morphometric parameters were recorded by following Jayaram (2010) [5] some of which are diagrammatically represented in Fig. 1. All the morphometric measurements were converted in to ratios in relation to standard length, head length and body depth and expressed as percentage. The taxonomic redescription of these species is prepared by analyzing the differences in morphology, morphometric and meristic characteristics. The statistical analysis was performed using MS Excel 2007 and SPSS version 16.0.

Morphometric and meristic characters of Bangana dero and Bangana devdevi

Meristic counts: The meristic counts of Bangana dero and Bangana devdevi showed variations in pectoral fin ray count, lateral line scale, counts of anal fin rays, pre-pelvic scale, dorsal fin origin to lateral line scale and circumpendicular scale (Table 3). Among all these, counts of lateral line scales showed highest variation. Both the species possess single pair of maxillary barbels. The first dorsal spine is very small and covered with muscles. 4). The various body parameters were statistically analysed and t-test was performed to arrive at the statistical significance amongst various body parameters and assessed at p<0.05 and p<0.001 significant level wherever necessary (Table5, 6). The Analysis of Variance (ANOVA) of the different morphometric characters is performed between two species to know the significant phenotypic difference between both the species.

Relative growth pattern of different body parts in B. dero (Hamilton, 1822)

The various body parameters were analysed and represented in graphic forms (Fig. 3) which indicated that all the parameters exhibit linear relationship in relation with TL, SL and HL. Maximum number of parameters was found to be highly correlated. The maximum value of correlation coefficient 'r' was of FL with respect to TL (0.997) and minimum was for CFBL with respect to TL (0.256). The 'b' value showed per unit increment in total length, standard length and head length with respect to various body parameters. Per unit increment with respect to total length was maximum for HL and minimum for CFBL. Similarly, the SL has higher per unit increment with HL and lower with VFBL, the HL has maximum increment with respect to POL and ED while minimum with HW. The p-value of t-test indicated that all the body parameters are highly significant (p<0.001).

Relative growth pattern of different body parts in B. devdevi (Hora, 1936)

The various body parameters were analysed and graphically represented (Fig. 4) which showed that all the parameters exhibit linear relationship in relation with TL, SL and HL. Further, all the parameters were found to be highly correlated with respect to TL, SL and HL. The maximum value of correlation coefficient 'r' was of FL with respect to TL (0.999) and minimum was of PF -VF with respect to SL (0.938). The 'b' value inferred per unit increment in TL, SL and HL with respect to various body parameters. Per unit increment with respect to total length was maximum for FL and minimum for LHCP. Similarly, the SL has higher per unit increment with PAL and lower with VFBL, the HL has maximum increment with respect to PFL while minimum with ED. The p-value for t-test indicated that all the body parameters are highly significant (p<0.001), except SL, PAL and HD with respect to TL, SL and HL are significant (p<0.05). The various body parameters such as FL with respect to TL and PFL with respect to HL are found to be non-significant (p>0.05). Further, the p-value obtained from ANOVA after analysing mean of the different morphometric characters of both the species were found to be significant (p <0.05), except, POL and ED (p>0.05) which revealed that both the species i.e. B. dero and B. devdevi are phenotypically different (Table5). Here: SF-Statistics is significant at 5% level (p<0.05), NSF-Statistics is not significant at 5% level (when p>0.05)

The present observations regarding morphological charaters coincide with the view of Zhang [24] and Chen (2006) [24] and Rainboth (1996). [15] The results revealed that there are mainly four characters which can distinguish B. dero from B. devdevi viz. height of dorsal fin in relation to body depth, gape of mouth reaching the anterior margin of eye, black spot on lateral line scale and anterior tip of hypochordal lobe. Some common characters in both the species are found in accordance with work of earlier authors (Jayaram and Das, 1980; [8] Talwar and Jhingran, 1991; [19] Rainboth, 1996; [15] Jayaram and Dhas, 2000 [6] and Zhang and Chen, 2006). [24] However, Jayaram and Das (1980) [8] reported the presence of faint black blotch above 6th and 7th lateral line scales in juvenile of B. devdevi whereas in present study no such black spot was observed that may develop in preserved specimen later on. Jayaram and Dhas (2000) [6] reported insertion of dorsal fin mid-way between tip of snout and caudal peduncle in B. dero, which does not comply with the present findings. The height of dorsal fin is found to be more than body depth in B. dero and as such follows the view of Talwar and Jhingran (1991). [19] However, in B. devdevi it is less than body depth. The taxonomic description of B. devdevi by Jayaram and Das (1980) [8] reported that eyes are visible from the ventral surface, however this feature was not observed in the present study, which agree with the observations of Talwar and Jhingran (1991) [19] .

The variations in the morphometric and meristic characters have been enormously used by many authors for separating closely related species. Presently, the variations in morphometric and meristic characters are used to detect the amount of phenotypic differences among the two species of genus Bangana. The meristic counts of the two species were almost overlapping except number of branched dorsal fin ray, lateral line scale, dorsal fin to lateral line scale, pelvic fin to lateral line scale and circumpendicular scale. However, all the meristic counts are found to be similar in accordance with Talwar and Jhingran (1991) [19] (except for lateral line to pelvic fin scale) and Jayaram and Dhas (2000). [6] Talwar and Jhingran (1991) [19] Jayaram and Dhas (2000). [6] It was universally accepted that growth of fish increases with the increase in its body length and growth of various body parts are interconnected with each other (Zubia et al., 2015) [25] . However, the 'b' value for all the parameters depicted that per unit increment was very low in B. devdevi as compared to B. dero and as such the growth rate was found to be varying among different body parameters in both the species and coincides with the view of Shabanum et al. (2013) [17] . Amongst the other statistical parameter, the correlation coefficient was found to be strongly correlated (r > 0.7) in B. devdevi and B. dero (except some parameters). The growth of all the body parameters was found to be linear in relation to TL, SL and HL and as such followed the findings of Zafar et al. (2002), [23] Negi and Nautiyal (2002), [13] Krishnan and Tarana (2010) [12] and Negi and Negi (2010). [14] Hence, based on the significant differences (ANOVA, p<0.05) in the mean values for each morphometric character clearly revealed that these species were phenotypically different from each other and confirmed the findings of Zubia et al. (2015) [25] and El-Zaeem (2008). [1] Based on the above finding it is concluded that morphology, morphometric and meristic trait of B. dero and B. devdevi would provide important taxonomic tools in hands of taxonomist to identify and resolve the existing ambiguity amongst the species of genus Labeo and Bangana.

Conclusively based on the present findings, re-description of the two species has been drawn as here under which would help the researchers in identification of these two closely related species. Remarks: Snout with distinct groove and tubercles. Height of dorsal fin less than body depth. Gape of mouth not reaching the anterior margin of eye. Black spot on the 4th or 5th lateral line scale usually absent in fresh specimen. Caudal fin: tip of epichordal and hypochordal lobe pointed.

Re-description of

Acknowledgement

AcknowledgementsThe authors express their sincere gratitude to the Department of Biotechnology, Government of India and COE-FAB project for providing necessary assistance in sample collection. We are also thankful to Late Dr. J.R. Dhanze, Consultant of COE-FAB Project for helping, guiding and his valuable suggestion during the research. Second Author is thankful to Dr. Dhriti Banerjee, Director, Zoological Survey of India for constant encouragement and support. Further first author is also thankful to all his M. F. Sc. advisory committee members (Dr. Pampa Bhattacharjee, Dr. K.V. Radhakrishnan, Dr. Anindya Sundar Barman) for their motivation and encouragement which has made to undertake the present study.

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