Received Date: 04.01.2017; Accepted Date: 18.02.2017; Published Date: 22.02.2017
Batasio spilurus Ng 2006 was described from the vicinity of Dibrugarh, Assam (Brahmaputra River) and its distribution to tributaries of Brahmaputra River is unknown. Recent collections from Siang River at Pasighat, Arunachal Pradesh included this species, and hereby reported for the first time. With the record of this species, a total of five species of Batasio are known from the state. A key to the species of Batasio occurring in Arunachal Pradesh has also been provided.
New record; Batasio spilurus; Siang river; Arunachal Pradesh
Fishes of the genus Batasio Blyth, 1860, are small size fresh water bagrid catfishes inhibiting in the hill streams of the upper reaches of large rivers throughout the south and southeast Asia (Ng, 2006). The genus is diagnosed from its confamilials in having numerous large sensory pores on the head, a narrow mental region, anterior part of vomer with a pair of posteriorly-directed processes, entopterygoid bar-like and transversely-elongated, and the metapterygoid free from the hyomandibular but closely contact with the quadrate (Mo, 1991). Additionally, the genus is readily distinguished from other bagrid catfishes (except Chandramara Jayaram) by its short minute maxillary barbel which is restricted within extend of the head, which rarely crossed the posterior rim of the eye.
The Siang River of Arunachal Pradesh, originated from the Angsi glacier on the northern side of the Himalayas in Burang County of Tibet as the Yarlung-Tsangpo River, is the main tributary of Brahmaputra drainage. The ichthyofauna of the Siang River and its tributaries is poorly explored. Collections from Siang River at Pasighat Arunachal Pradesh included Batasio spilurus Ng 2006, a species described from the vicinity of Dibrugarh, Assam (Brahmaputra basin), and hereby reported its first occurrence record in the Siang river drainage in Arunachal Pradesh.
Methods of measurements and fin count followed Ng and Kottelat (2001). Fin rays were counted under transmitted light using a Nikon SMZ 800 stereoscopic microscope. Numbers in parentheses following a count are the number of specimens with that count. The method for clearing and staining of bones follows Hollister (1934). The collected specimens for this study are deposited in the Rajiv Gandhi University Museum of Fishes (RGUMF), Itanagar.
Measurements were made using dial calipers taken to the nearest tenth of a millimeter. Methods for counts and measurements follow Ng and Kottelat (2001). Fin rays were counted under transmitted light using a stereoscopic microscope. The method for clearing and staining of bones follows Hollister (1934). Osteological characters were observed from cleared and stained specimens and nomenclature of bone follows (Mo, 1991). Specimens Collected for this study are deposited Rajiv Gandhi University Museum of Fishes, Doimukh (RGUMF). Abbreviations: SL-Standard Length; HL-Head Length.
Batasio spilurus (Ng, 2006) shown in Figure 1.
RGUMF 317, 54.8 mm SL, RGUMF 318, 54.1 mm SL; India: Arunachal Pradesh, East Siang District, Siang River at Pashighat; Achom Darshan and Party, 21st February 2015.
Batasio spilurus differs from all known congeners by its short adipose-fin base (10.0-12.8% vs. 14.5-33.3% SL) and slender caudal peduncle (5.7-6.6% SL vs. 6.7-11.8% SL). It further differs from the congeners occurring in the Brahmaputra drainage, except B. tengana (Hamilton) in having a slender body 11.9-14.1% SL (vs.15.8-23.9% SL). Batasio spilurus can be easily differentiated from B. tengana in having a wider head (14.7-16.5% vs. 12.5- 14.5% HL), the presence of a distinct greyish triangular spot at the base of the caudal fin (vs. spot very diffuse or absent), and a more taper snout when viewed laterally (rounded and rounded, bulbous).
Morphometric and meristic data are given in Table 1. Body is moderately compressed. Dorsal profile is rising gently from tip of snout to origin of dorsal fin and then gently sloping ventrally towards caudal peduncle. Ventral profiles almost straight to anal fin origin then gently incline towards caudal peduncle. Anus and urogenital openings located at middle of appressed pelvic fin. Lateral line mid laterally and complete. Skin is smooth. Vertebrae 19-20+19=38-39. Brancheostegeal rays 7.
|Holotype ZRC 49133||Paratype ZRC 50201||RGUMF 317||RGUMF 318|
|Standard Length in mm||42.0||40.5||54.8||54.12|
|In % SL|
|Length of dorsal-fin base||15.5||15.8||13.8||15.3|
|Length of dorsal spine||15.5||14.3||10.0||10.5|
|Length of anal-fin base||17.4||17.0||14.1||16.8|
|Length of pelvic fin||14.5||17.0||16.2||15.0|
|Length of pectoral fin||20.0||18.8||15.9||damage|
|Length of pectoral spine||16.9||16.3||12.2||damage|
|Length of caudal fin||26.2||26.4||22.1||19.1|
|Length of adipose-fin base||12.6||12.8||10.0||10.0|
|Dorsal to adipose distance||20.2||19.5||22.0||21.8|
|Length of caudal peduncle||16.4||17.8||14.6||15.8|
|Depth of caudal peduncle||6.2||5.7||6.5||6.6|
|Body depth at anus||12.6||13.6||11.9||14.1|
|Head length (LH)||26.9||28.6||23.4||24.2|
|In % HL|
|Length of nasal barbel||42.2||35.9||40.6|
|Length of maxillary barbel||69.0||75.0||82.8||70.7|
|Length of inner mandibular barbel||22.1||25.9||19.5||20.2|
|Length of outer mandibular barbel||48.7||51.7||39.1||41.2|
|Dorsal fin count||II,7||II,7||II,7||II,7|
|Pectoral fin count||I, 8||I, 8||I, 8||damage|
|Pelvic fin count||i,5||i,5||i,5||i,5|
|Anal fin count||v,8,i||v,10,i||v,11||iv,12|
|Caudal fin count||i,7+8,i||i,7+8,i||i,7+8,i||i,8+8,i|
|Gill rakers count||-||-||2+4=6||2+5=7|
Table 1: Morphometric and meristic data of Batasio spilurus. (Holotype and paratype data are from Ng, 2006).
Head is slightly depressed and narrow. Dorsal surface of head covered with thin skin. Median longitudinal groove on head long, originated from slightly ahead of anterior margin of eye and extending to half of occipital spine. Posterior fontanel opening is reaching base of occipital spine. Occipital spine slender, basal half of spine bears a shallow median depression for supporting median longitudinal groove. Occipital spine reaching first nuchal plate of dorsal fin, posterior tip of spine forked to articulate with anteriorly pointed first nuchal plate. Orbit with free margin located on upper half of head, not visible from ventral side. Anterior nostril opening is tubular, well separated from posterior nostril. Sensory pores on head large and prominent. Eye is ovoid, horizontal axis longest; located entirely in dorsal half of head.
Gill openings wide, extending from post temporal to beyond isthmus. Gill membranes free from isthmus. Mouth is inferior. Oral teeth are small and villiform, in irregular rows on all toothbearing surfaces. Gill opening wide, free from isthmus, membranes separated, extending from post-temporal to beyond isthmus. Gill rakers short with 2+4-5=6-7 rakers on first branchial arch. Premaxillary tooth band rounded and equally width throughout. Dentary tooth band narrower than premaxillary and tapering posterolaterally.
Barbel is four pairs. Maxillary barbel is long, distal tip extending to one diameter ahead of posterior rim of opercle. Nasal barbel is slender, extending almost posterior rim of eye. Outer mandibular barbel not reaching end of lateral head and inner mandibular-barbel short, its length extend only half of outer mandibular barbel.
Dorsal fin with a spinelet, a spine and 7 branched rays, fin origin located at anterior two-fifths of body. Dorsal fin spine is short, slender and slightly backward, smooth on both edges. Ad pressed dorsal fin is not reaching origin of adipose fin. Adipose origin at vertical through second or third simple ray of anal fin, its base shorter than dorsal-fin base, fin margin roughly convex. Pectoral fin with a stout spine and 8 branched rays, spine curved backwards, sharply pointed at distal tip, its posterior margin with 10-15 small serrations along entire length. Pelvic fin with i, 5 rays, tip of adpressed fin not reaching anal-fin origin. Anal fin with 4-5 simple and 8-12 branched rays. Caudal fin deeply forked, with i, 7, 8, i or i, 8, 8, i principal rays; upper lobe slightly longer than lower. Procurrent rays extend slightly anterior to fin base with 17 in upper and 15 in lobe. First upper procurrent rays located between the distal tip of 32 and 33 neural spines, similarly origin of lower procurrent rays also located between the distal tip of 32 and 33 haemal spines.
In 70% ethanol: head and body yellowish. Skin over occipital region with dense melanophores, imparting greyish brown colour on posterior portion of head. Mid-dorsal of body posterior to dorsal fin with a distinct greyish brown band, band interrupted at origin and also at posterior end of adipose-fin base. Dorsal half of tympanum (above pectoral fin) having a dark brown semilunate spot. Mid-lateral of body with pale greyish line extending from dorsal margin of tympanum to a greyish triangular spot at caudal fin base, numerous chevron-shaped marks interspersed at regular intervals along mid-lateral line. Anterior half of dorsal fin is dark brown ovoid mark.
The species is known from its type locality Dibrugarh, Assam (Brahmaputra River) (Ng, 2006) and presently recorded from the Siang River in Arunachal Pradesh (Figures 2 and 3).
Ng (2006) re-described and clarified the identity of Batasio tengana based on the specimens collected from the Tista River and original drawing of Hamilton (1822), and he also pointed out that those specimens assigned to B. tengana by earlier workers viz. Hora and Law (1941), Jayaram (1977), and Ng and Kottelat (2001) are misidentifications of Batasio fasciolatus Ng. Hithertho, four species of Batasio are recorded from Arunachal Pradesh viz. B. fasciolatus form the Panye River (Subansiri basin) (Bagra et al., 2009), Batasio merianiensis (Chaudhuri, 1913) from Sille River, a tributary of Siang River in East Siang district (Tamang and Sinha, 2014), Batasio tengana (Hamilton, 1822) from Noadhing River (Nath and Dey, 2000) and Batasio batasio (Hamilton, 1822) by Sen (2000) without mentioning the place of its occurrence. Present investigators also encountered B. batasio from the Siang, Subanshri, and Dibang Rivers of the state. Further, the present study recorded Batasio spirulus, a fifth species, from the Siang River of Arunachal Pradesh. It is observed that the specimens of B. spilurus slightly differ from the original description in the length of predorsal 36.1-38.1% SL (vs. 40.5-42.0% SL), dorsal-fin base 13.8-15.3 (vs. 15.5-15.8), adipose fin base 10.0% SL (vs. 12.6- 12.8), post adipose distance 19.5- 20.3 (vs. 18.3-19.0), depth of caudal peduncle 6.5-6.6 (vs. 5.7-6.2), and head length 23.4-24.2% SL (26.9-28.6); and also lesser anal fin count iv-v, 11-12 (vs. V, 8-19, i). These differences may be due to accessing small sample size (only two specimens) and immature stage fishes (40.5-42.0 mm SL), resulting in failure to accommodate the actual range of morphometric and meristic parameters of the species in the original description. We observed that the species get mature at about 54.1 mm SL (confirmed by observing egg during dissection).
Artificial key for identification of Batasio species occurring in Arunachal Pradesh, Brahmaputra basin:
1a. Body with four to six vertical dark brown bars on light brown ground colour.........2.
1b. Body lacking vertical dark brown bars...................3.
2a. Adipose fin short with length 16.9-22.2% SL, distal tip of adpressed dorsal fin not reaching the origin of adipose fin......Batasio merianiensis.
2b. Adipose fin long with length 24.5-25.3% SL, addressed dorsal fin overlap on the anterior portion of adipose fin.......................................................Batasio merianiensis.
3a. Body with a distinct dark brown elliptical spot on the greyish mid-lateral stripe below dorsal fin, adipose-fin base long with length 24.5-25.3% SL...............Batasio batasio.
3b. Spot below dorsal fin absent, adipose fin short with length 10.0-17.5% SL.............4.
4a. Slender caudal peduncle with depth 5.7-6.6% SL, short adipose base with 10.0-12.8% SL, sharper snout in lateral view.......................................................Batasio spilurus.
4b. Deeper caudal peduncle with 6.7-8.2% SL, short adipose base with 14.5-17.5% SL, snout rounded and bulbous in lateral vi ew..........................................Batasio tengana.
Batasio batasio: RGUMF 319 (1), 57.4 mm SL, Siang River at Pasighat, Arunachal Pradesh, India.
Batasio fasciolatus: RGUMF 0102 (7), 43-83 mm SL, Panye River, Arunachal Pradesh, India. RGUMF uncat., (5), 65.1–78.5 mm SL, Dikrong River, Arunachal Pradesh, India.
Batasio merianiensis: ZSI F 7781/1 (1), holotype, 65.7 mm SL; India: Meriani junction, Assam, India. Additional data from Ng (2009).
Batasio tengana: MUMF uncat., (18), 3.6-4.5 mm SL, Ujjan Bazar, Guwahati, Assam, India.
Batasio travancoria: ZSI F 13449/1 (1), holotype, 74.0 mm SL; India: Travancore. ZSI F 13451/1-13452/1 (2), 58.1-66.1 mm SL, paratype, Travancore, India.
Batasio affinis: MUMF 9028, 79.1 mm SL, India: Khujailok stream, Chandel district, Manipur. MUMF 9033 (5), 78.7-93.1 mm SL, same as above. Addditional from data from Ng and Kottelat (2007).
Batasio dayi: Data from Vinciguerra (1890) and Ng (2008).
Batasio elongatus: Data from Ng (2004).
Batasio feruminatus: Data from Ng and Kottelat (2007).
Batasio fluviatilis: Data from Day (1888) and Ng and Kottelat (2007).
Batasio macronotus: Data from Ng and Edds (2004).
Batasio pakistanicus: Data from Mirza and Jan (1989).
Batasio pocerus: Data from Ng (2008).
Batasio sharavatiensis: Data from Bhatt and Jayaram (2004) and Arunachalam and Muralidharan (2007).
Batasio tigrinus: Data from Ng and Kottelat (2001).
The authors are grateful to the University Grants Commission (UGC), New Delhi, for providing fellowship and research facility to AD (first author) and RD (second author) through the ‘Centre with Potential for Excellence in Biodiversity (CPEB-II), RGU, Doimukh. SA and DND (third and fourth author respectively) also acknowledged to the Department of Biotechnology, New Delhi (Project No. F.No. BT/382/NE/TBP/2012, dated 27/01/2014) for financial assistance.
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