Glyptothorax telchitta (Hamilton, 1822)

Heok Hee Ng, 2005, Glyptothorax botius (Hamilton, 1822), a valid species of catfish (Teleostei: Sisoridae) from northeast India, with notes on the identity of G. telchitta (Hamilton, 1822)., Zootaxa 930, pp. 1-19 : 8-16

Glyptothorax telchitta (Hamilton, 1822)

(Figs. 5-7)

Pimelodus telchitta Hamilton, 1822 : 185 (type locality: Jungipur, Nathpur) .

Glyptosternum botia (non Hamilton) Day, 1877: 497, Pl. CXIII Figs. 4 & 4a.

Glyptosternum botium (non Hamilton) Day, 1889: 198.

Glyptothorax botia (non Hamilton) Hora, 1923: 27.

Glyptothorax sp. Hora, 1923: 26, Pl. IV Fig. 2.

Glyptothorax telchitta Hora & Menon, 1949: 57, Pl. II Figs. 1-3 (in part); Menon, 1954: 42 (in part); Misra, 1976: 281, Pl. XII Figs. 2-4; Jayaram & Singh, 1977: 267; Jayaram, 1979: 47.

Material examined. UMMZ 244946, neotype (herein designated), 69.2 mm SL ; UMMZ 244944 (13), 36.5-63.8 mm SL ; ZRC 49130 (2), 35.4-44.3 mm SL; India: West Bengal, Hooghly River at Kalna, 23°13'30.0"N 88°22'39.0"E . UMMZ 244951 (2), 58.7-79.0 mm SL; India: West Bengal, Hooghly River at Ranaghat . ZRC 49128 (7), 43.5-56.5 mm SL; India: West Bengal, Simurali .

Diagnosis. Glyptothorax botius and G. telchitta can be distinguished from congeners in northeast India in having a combination of large, prominent tubercles on the head and body, a thoracic adhesive apparatus without a median depression, and a very slender body and caudal peduncle (sometimes described as “spindle shaped”). Glyptothorax botius differs from G. telchitta in having a more triangular snout when viewed laterally (Fig. 2), the absence (vs. presence) of dark saddles on the body, a thoracic adhesive apparatus with narrower folds of skin (Fig. 3), a shorter adipose-fin base (9.5-11.5% SL vs. 12.0-16.4) and a deeper caudal peduncle (4.7-5.9% SL vs. 3.1-4.2).

Description. Morphometric data in Table 2. Head depressed, body moderately compressed. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from there to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally from there to end of caudal peduncle. Caudal peduncle long and moderately slender. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin prominently tuberculate, with ovoid tubercles particularly visible on sides of body. Lateral line complete and midlateral, delineated by series of closely spaced, conical tubercles. Vertebrae 13+21 (1), 14+20 (2), 15+19 (1), 13+22 (1), 14+21 (13), 14+22 (6) or 15+20 (1)

Head depressed and narrow, with triangular snout margin when viewed laterally (Fig. 2b). Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill openings broad, extending from immediately ventral to posttemporal to isthmus. Bony elements of dorsal surface of head covered with thick, tuberculate skin. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head. Orbit with free margin.

Barbels in four pairs. Maxillary barbel long and slender, extending almost to base of pectoral spine. Nasal barbel slender, extending to one-third of distance between its base and anterior orbital margin. Inner mandibular-barbel origin close to midline, extending to midway between its base and that of pectoral spine. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to two-thirds of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band almost wholly exposed when mouth is closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth in single broad semilunate band. Dentary teeth in two narrow crescentic bands separated at midline.

Dorsal fin located above anterior two fifths of body, with I,5,i (21) or I,6 (4) rays; posterior fin margin straight or slightly concave; spine moderately long, slender and gently curved, without serrations on anterior or posterior edges. Adipose fin with anterior margin slightly concave and posterior margin angular. Caudal fin strongly forked, with i,7,7,i (1), i,7,8,i (17) or i,8,7,i (7) principal rays, and subequal upper and lower lobes; lower lobe slightly longer and broader than upper lobe. Procurrent rays symmetrical and extending only slightly anterior to fin base. Anal-fin base slightly anterior to adipose-fin origin. Anal fin with straight anterior margin and slightly concave posterior margin; with iv,8 (1), iv,9 (11), iv,9,i (3), iv,10 (9) or iv,11,i (1) rays. Pelvic-fin origin immediately posterior to vertical through posterior end of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (25) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,7,i (5), I,8 (6) or I,8,i (14) rays; posterior fin margin slightly concave; anterior spine margin smooth, posterior margin with 8-10 serrations. Thoracic adhesive apparatus present, located on belly and consisting of narrow longitudinal pleats of skin in elliptical field. Adhesive apparatus without median depression and extending from just behind gill opening to immediately posterior to base of last pectoral-fin ray.

Coloration. In 70% ethanol: Dorsal and lateral surfaces of head, and dorsal surface of body brown to brownish gray, fading to a lighter color ventrally. A paler but distinct stripe running laterally along dorsal second quarter of body (immediately above lateral line). Body with small dark brown spots randomly and sparsely scattered throughout body in some individuals. Ventral surface of head and belly yellowish. Dorsal-fin base brown to brownish gray; dorsal-fin rays with evenly-distributed brown chromatophores along middle third of fin rays, imparting appearance of irregular band across fin; all other parts of dorsal fin hyaline. Pectoral, pelvic and anal fins hyaline. Pectoral spine with slightly darker coloration on dorsal surface throughout most of its length. Adipose fin brown to brownish gray, with hyaline distal margin. Caudal fin hyaline, with dark brown chromatophores on median fin rays of each caudal lobe, imparting appearance of a broad dark brown band along each lobe. Brown bands coalescent with dark brown spot at base of caudal peduncle. Other parts of caudal fin hyaline. Barbels brown to brownish gray dorsally, yellowish ventrally.

Distribution. Known from the Ganges River drainage. Only material from the Hooghly River was examined for this study (Fig. 4).

Discussion

Hamilton (1822) described Glyptothorax botius from “Pargong, fluviis Kamrupa borealis” (=Patgaon in Assam) and G. telchitta from Jungipur (in West Bengal) and Nathpur (in Uttar Pradesh). Subsequent workers (e.g. Day, 1877) had considered the two species distinct, until Hora & Menon (1949) synonymized them (retaining G. telchitta as the valid name). Since then, this convention has been followed and G. telchitta is generally acknowledged as the name for the slender-bodied Glyptothorax species from northeast India (e.g. Talwar & Jhingran, 1991); G. telchitta is considered distinct enough that it is never confused with any other Indian Glyptothorax . During recent ichthyological surveys of northeast India, I encountered two clearly distinct species of slender-bodied Glyptothorax that were found syntopically in the Ganges River drainage in West Bengal. One species had a deeper caudal peduncle, shorter adipose-fin base, a more triangular snout, and more uniform coloration without any distinct saddles; this was referable to G. telchitta as currently understood. The second species had a more slender caudal peduncle, longer adipose-fin base, a more rounded snout, and a series of dark saddles on the dorsal surfaces of the body. The identity of this species was not immediately obvious. It then became necessary to reinvestigate the validity of G. botius (as the only nominal species considered a synonym of G. telchitta ).

The original descriptions of G. telchitta and G. botius are not very informative. A comparison of the descriptions reveals that no significant difference could be found in morphology and coloration; this led Hora & Menon (1949) to consider the two species synonyms. Comparison with the figure prepared for the original description of G. telchitta (published as Pl. 21 Fig. 3 in Hora, 1929; Fig. 6) indicates that G. telchitta is the species with a deeper caudal peduncle, shorter adipose-fin base, a more triangular snout, and more uniform coloration without any distinct saddles. Day (1877) considered G. botius to be distinct from G. telchitta , and illustrated both species. His illustration of G. botius (Pl. CXIII Figs. 4 & 4a; Fig 7) matches that of G. telchitta , and his illustration of G. telchitta (Pl. CXVI Figs. 2 & 2a; Fig 8), matches that of the species with a more slender caudal peduncle, longer adipose-fin base, a more rounded snout, and a series of dark saddles on the dorsal surfaces of the body, even showing the broader folds of the skin on the thoracic adhesive apparatus.

Therefore, there is some confusion regarding the identity of G. botius . No illustration was prepared for the original description (Hora, 1929), nor is any mention made of the distinctive color pattern (the presence of dark saddles) in the original description (the color pattern is merely described as “...lurid brown, with a little yellowness intermixed...”). In fact, the description is sufficiently ambiguous that it could refer to any of the Glyptothorax species occurring in northeast India, although the statement that it is “...long in proportion to its breadth...” (this statement was also used in the description of G. telchitta but not in G. cavia , the only other Glyptothorax described by Hamilton) suggests that it is similar in overall morphology to G. telchitta . This confusion is heightened by the misidentification of G. telchitta as G. botius and vice versa by Day (1877), as explained above. The limited evidence available suggests that G. botius is the oldest (and only) available name for the Glyptothorax with a more slender caudal peduncle, longer adipose-fin base, a more rounded snout, and a series of dark saddles on the dorsal surfaces of the body, and the name is herein defined as such.

Given the confusion surrounding the identity of G. botius and the fact that type material does not exist for any of the Hamilton species as he did not retain any specimens used for his descriptions (Gudger, 1924; Hora, 1929), it is necessary to designate neotypes for Pimelodus botius and P. telchitta , and in accordance with the conditions stipulated in Article 75 of the International Code of Zoological Nomenclature, ZRC 50223, a specimen 74.6 mm SL collected from the Hooghly River at Kalna, West Bengal, India by H. H. Ng & D. C. J. Yeo on 24 January 1999 is hereby designated the neotype of Pimelodus botius Hamilton, 1822 , and UMMZ 244946, a specimen 69.2 mm SL collected from the Hooghly River at Kalna, West Bengal, India by H. H. Ng et al. on 20 April 2004 is hereby designated the neotype of Pimelodus telchitta Hamilton, 1822 . It is possible that G. botius sensu Hamilton may not be conspecific with the definition of the species used here, but the only alternative would be to make G. telchitta and G. botius objective synonyms by designating a common neotype and describing the species defined as G. botius here as new. However, the naming of another Glyptothorax species does nothing to resolve the confused taxonomy of the Indian Glyptothorax ; it is felt that stability in nomenclature can be best served by the course of action here.

As a result of the confused taxonomy of the Indian Glyptothorax , the exact number of valid Glyptothorax species occurring in the Ganges River drainage cannot be ascertained. Besides G. botius and G. telchitta , 12 other nominal species have been described from the Ganges River drainage: G. cavia (Hamilton, 1822) , G. pectinopterus (M’Clelland, 1842) , G. gracilis ( Guenther, 1864) , G. conirostre (Steindachner, 1867) , G. stolickae (Steindachner, 1867) , G. modestum (Day, 1872) , G. lineatum (Day, 1877) , G. brevipinnis Hora, 1923 , G. alaknandi Tilak, 1969 , G. garhwali Tilak, 1969 , G. dakpathari Tilak & Husain, 1976 , and G. indicus Talwar in Talwar & Jhingran, 1991 . I tentatively consider only seven of these to be valid: G. brevipinnis (with G. alaknandi as a junior synonym), G. cavia (with G. lineatum as a junior synonym), G. conirostre , G. garhwali , G. gracilis (with G. dakpathari , G. modestum and G. stolickae as junior synonyms), G. indicus , and G. pectinopterus . Besides the characters mentioned in the diagnosis, both G. botius and G. telchitta can be distinguished from G. brevipinnis and G. pectinopterus in having a longer thoracic adhesive apparatus (reaching immediately posterior to base of last pectoral-fin ray vs. to middle of pectoral-fin base), from G. cavia in having a shorter head (22.0-25.7% SL vs. 27.6-29.9), and from G. garhwali in having a narrower head (14.5-17.1% SL vs. 18.0-19.9). Both G. botius and G. telchitta further differ from both G. conirostre and G. gracilis in having a smooth (vs. serrated) posterior edge of the dorsal spine, and from G. indicus in having a shorter head (22.0-25.7% SL vs. 27.3-29.1) and the thoracic adhesive apparatus extending (vs. not extending) to the gular region.

Glyptothorax botius and G. telchitta occur syntopically in the Ganges River drainage. Both species were collected from the bottom of a large, fairly swift river (Hooghly River) with a mixed sand/mud bottom, along with the many other sisorids ( Bagarius yarrelli , Gagata cenia , G. sexualis , Nangra assamensis , N. nangra , Gogangra viridescens and Sisor rabdophorus ).

The differences in biometrics between G. botius and G. telchitta are not solely due to ontogeny. The biplots of caudal peduncle depth (Fig. 9) and length of the adipose-fin base (Fig. 10) against SL show that the regression lines are significantly different (ANCOVA; P<0.00000005).