Redescription of the Striped Catfish Mystus tengara ( Hamilton , 1822 ) ( Siluriformes : Bagridae ) , India

The Bagrid Catfish Mystus tengara was described from a pond located in India under the genus Pimelodus. The validity of the fish has been confused and has frequently been treated as a synonym of Mystus vittatus. In this study, the species is rediagnosed and redescribed on the basis of fresh material collected from the GangaBrahmaputra drainage. M. tengara is diagnosed from congeners in having a unique combination of the following characters: body with a distinct tympanic spot and four brown stripes which are separated by a pale narrow interspace; origin of adipose-fin not reaching the base of the last dorsal-fin ray, 31–42 gill rakers on first branchial arch, eye rounded with a diameter 19.0–23.8 % HL and dorsal spine length 12.3–17.2 % SL, maxillary barbel length 254.5–360.5 % HL. A key for the identification of Mystus species from Ganga-Bramaputra drainage is also provided.


ISSN
Online 0974-7907 Print 0974-7893 Hamilton (1822) described Pimelodus tengara (now Mystus) from a pond located in India.The identity of the fish is based solely on his description and drawings as he did not preserve any type specimens.The fish has often been treated as a synonym of Mystus vittatus (Bloch) (Venkateswarlu & Menon 1979;Sharma & Dutt 1983;Roberts 1992;Menon 1999).Drashan et al. (2010) redescribed and revalidated Mystus carcio (Hamilton) which had previously been considered as a synonym of either M. tengara or M. vittatus.They also treated the latter two species as Abstract: The Bagrid Catfish Mystus tengara was described from a pond located in India under the genus Pimelodus.The validity of the fish has been confused and has frequently been treated as a synonym of Mystus vittatus.In this study, the species is rediagnosed and redescribed on the basis of fresh material collected from the Ganga-Brahmaputra drainage.M. tengara is diagnosed from congeners in having a unique combination of the following characters: body with a distinct tympanic spot and four brown stripes which are separated by a pale narrow interspace; origin of adipose-fin not reaching the base of the last dorsal-fin ray, 31-42 gill rakers on first branchial arch, eye rounded with a diameter 19.0-23.8% HL and dorsal spine length 12.3-17.2% SL, maxillary barbel length 254.5-360.5 % HL.A key for the identification of Mystus species from Ganga-Bramaputra drainage is also provided.

Mystus tengara
Head depressed.Skin covering dorsal surface of head thin.Anterior cranial fontanel extends from the level of posterior nasal opening to posterior orbital margins, separated from posterior fontanel by a narrow epiphyseal bar.Posterior fontanel extends to base of occipital process in juvenile and upto anterior one-third of supraoccipital bone in adult.Supraoccipital process long, wide at base about one-fifth of its length, reaching basal bone of dorsal fin, tapering distally.Eye rounded, located entirely in dorsal half of head.
Barbels in four pairs, maxillary pair reaching at least posterior end of anal fin base in adult and frequently reaching distal tip of caudal fin or beyond in juvenile specimens, nasal reaching base of occipital process, outer mandibular reaching distal tip of pectoral fin and inner mandibular barbel extend upto base of pectoral fin.Skin smooth.Lateral line complete and midlateral in position.
Dorsal-fin with spinelet, spine and seven branched rays.The spine is serrated anteriorly near the distal tip with 2-4 serrations and posteriorly with 8-10.Adipose fin long, origin not reaching base of last dorsal fin ray and deeply incised at posterior end.Pectoral fin with a backwardly curved stout spine and 7-8 branched rays.Spine with 11-16 large posterior serrations and anteriorly rough.Posterior fin margin almost straight.Pelvic fin short with i,5 rays.Anal fin with ii-iii, 7-10 rays.Caudal fin deeply forked with i,7,7,i or i,7,8,i or i,8,8,i rays, upper lobe longer.
osteological character: Branchiostegal with 9(20) rays.Ribs with 8-9, attached from 6 th to 13 th or 14 th vertebra.Vertebrae with 18+16 = 34(1) or 19+15 = 34(1) or 19+16 = 35(3) or 20+15 = 35(2) or 19+17 = 36(6) or 20+16 = 36(6) or 20+17 = 37(1).Closed haemal canal appears from 11 th (20) vertebra onwards.Caudal fin with five hypural plates (20), three on the upper and two on the lower lobe.Parhypural free from first hypural plate.Hypurapophysis and secondary hypurapophysis fused.Procurrent rays respectively with 12 and 13 on upper Colouration: Specimens preserved in 10% formalin have a body with a distinct oval dark brown tympanic spot and four brown stripes (a mid-dorsal and three lateral stripes), all the stripes are separated by pale longitudinal lines of equal wide.The pale longitudinal lines separating the mid-dorsal and lateral stripes originate from below the middle of the base dorsal fin and extend up to the posterior portion of adipose fin base.Lateral lines appear as thin pale lines in the middle of the midlateral stripe.
distribution: Ganga and Brahmaputra drainage in India, Bangladesh and Nepal.The species is also recorded from Narmada and Mahanadi basins in northern India, Indus River drainage of Pakistan (Talwar & Jhingran 1991;Mirza 2003) and Afghanistan (Coad 1981).

Discussion
Roberts (1998) reported that Francis Hamilton made all his drawings from fresh specimens and discarded them after completing the drawing and did not preserve any type specimen.He also reported that the description of the fishes were written later (sometimes much later) from the drawings.Robert's (1998) assumption might be partly correct.But Francis Hamilton must have certainly noted some important points about the fishes, without which he would not have been able to write detailed descriptions of all the 271 species in his book on Gangetic fishes.Mukherji (1931) It can be assumed that the type locality of Mystus tengara is in the Ganga-Brahmaputra basin on the basis of Mukerji's (1931) report of its collection and also the fact that Hamilton's (1822) work on Gangetic fishes was confined to this basin.Thus, striped catfishes of the genus Mystus from the Ganga-Brahmaputra basin have been made in order to redescribe M. tengara and to clarify its type locality.Hamilton (1822) shows two figures (plate 3, fig.61) of Mystus tengara along with the description of the fish.One of his figures shows the lateral view, showing the striped pattern of the fish (see fig. 1) and another the dorsal view showing the extent of the cranial fontanel invading the supraoccipital region.A cleared and stained mature specimen of M. tengara clearly shows that half of the posterior fontanel is located at the posterior portion of frontal and the remaining portion at the supraoccipital bone.In the case of M. vittatus, posterior fontanel tapers posteriorly to a point at the anterior border of the supraoccipital bone, not invading the supraoccipital region.The same structure can also be observed in the formalin preserved specimens after drying for some time (Image 2).Moreover, Mystus tengara differs from M. vittatus (Image 3) in having a longer maxillary barbel length ) and dorsal spine length 2); body colour pattern consisting of a dark brown oval tympanic spot with distinct margin (vs.diffuse tympanic spot); four brown stripes (for details see description) separated by the three pale interspace lines (vs.three brown stripes separated by two pale interspace lines of equal width, one above and another below the mid-lateral stripe).Moreover, M. vittatus has a diffused dark spot at the base of caudal fin, sometimes indistinct in some specimens (vs.no such spot in M. tengara).Day (1877) also observed this black spot in M. vittatus collected from Madras (southern India), though Bloch (1794) did not mention it.
Our extensive surveys of the Ganga and Brahmaputra River drainage have not encountered any species of Mystus with a short posterior fontanel (not invading the supraoccipital region) as in Mystus vittatus.Several records of M. vittatus from northeastern India and Gangetic basin were found to be misidentifications of either M. tengara or M. carcio (Darshan et al. 2010; above list of synonymy).For easy identification the species has also been incorporated in the given artificial key.
, on the basis of the manuscript of Hamilton's Gangetic fishes, reported that Mystus tengara was collected from Brahmaputra River at Goalpara, on 29 July 1808.Goalpara was the place where Francis Hamilton stayed as the rainy season station in 1808 during his Bengal survey.The name 'tengara' is in fact a Bengali or Assamese local name of Pimelodus tengara (now Mystus).Hamilton (1822) usually used local names in naming a fish.Hamilton (1822) mentioned that 'tengara' was very common in the ponds of India.Subsequent workers felt the type locality mentioned in the original description may not be correct and modified it without giving any reason (examples: lower Bengal: Sharma & Dutt 1983; India: Roberts 1992; northern parts of Bengal: Talwar & Jhingran 1991; Jayaram 2006, Jayaram & Sanyal 2003).