Gonorhynchus latius Hamilton 1822
Creators: name: Ciccotto, Patrick J.
name: Page, Lawrence M.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy

description: Redescription of Gonorhynchus latius (Hamilton 1822)
Gangetic Latia
(Figures 2 A, 5, 7)
Cyprinus latius Hamilton 1822:345 (type locality: India / Bangladesh: Tista [Teesta] River, at base of Darjeeling Himalayas); no types known
Cyprinus sada Hamilton 1822:344 (type locality: India: Brahmaputra River, India); no types known
Cyprinus gohama Hamilton 1822:346 (type locality: India: Kosi [Koshi] and Ganges Rivers); no types known
? Cyprinus mosario Hamilton 1822:346 (type locality: India: Bengal); no types known
? Gonorhynchus gobioides M’Clelland 839:280, pl. 43, fig. 1 (type locality: India: Assam: Brahmaputra River); no types known
Gonorhynchus macrosomus M’Clelland 1839:282, pl. 43, fig.7 (type locality: India: Assam: cataracts of Brahmaputra River); no types known
Gonorhynchus fimbriatus M’Clelland 1839:282, pl. 43, fig. 3 (type locality: northern parts of Bengal), no types known
Gonorhynchus brevis M’Clelland 1839:373, pl. 43, fig. 6 (type locality: India: Kosi [Koshi] River and northwest Bengal and the Ganges River); no types known
Cyprinus sada.—Valenciennes 1842:385
Crossocheilus gohama.— Bleeker 1860:110
Crossocheilus latius.— Bleeker 1860:110
Crossochilus latius.— Günther 1868:71
Crossochilus gohama.— Günther 1868:72
Crossochilus rostratus Günther 1868:72 (type locality: India: Cossye [Kangsabati] River); holotype BMNH 1867.5.12.15
Crossochilus sada. — Günther 1868:74
Cirrhina latia.— Day 1877:548
Cirrhina gohama. — Day 1878:11
Crossocheilus latia.—Shaw & Shebbeare 1937:132
Crossocheilus latius latius.— Misra 1959:169
Cyprinus latius and C. gohama were originally described by Hamilton (1822) from the Teesta/Brahmaputra and Koshi/Ganges Rivers, respectively. Cyprinus gohama was differentiated from C. latius by a deeper body, clear (vs. yellow) pelvic and anal fins, circular (vs. oval) pupils, the lateral line descending from behind the operculum to the caudal peduncle (vs. straight along the middle of the body), and in possessing 8 (vs 7) rays in the anal fin. Plate 43 in M’Clelland (1839) picturing C. gohama and Gonorhynchus macrosomus (= G. latius) illustrates only a slightly deeper-bodied C. gohama, with the lateral line descending slightly more behind the operculum. None of the original specimens examined are available. We examined more recently collected specimens from streams where C. latius and C. gohama were initially described (Teesta and Koshi Rivers, respectively) and did not observe the differences noted by Hamilton (1822). All specimens possess a lateral line with a slight dip in the anterior portion behind the operculum, generally clear to yellow pelvic and anal fins with melanin on the rays of larger specimens, and no clear difference in pupil shape. Body depth overlaps between Koshi and Teesta River populations (Table 2). Principal component analysis of the morphometric and meristic data indicates substantial overlap between populations from the Ganges and Brahmaputra River basins in India, including specimens from the Koshi and Teesta Rivers (Fig. 4). Only those specimens in good condition for data collection were included in this analysis (see Table 2). Size accounted for 94.9% of the observed variance, with the second component accounting for 1.6% of the variance. Variables with the highest loadings on the sheared second principal component were body depth (- 0.48), caudal peduncle length (0.47), and orbit diameter (0.39). Variables with the highest loadings on the first principal component of the meristic data were total lateral-line scales (lateral-line scales plus scales on the caudal fin; 0.51), lateral-line scales (0.43), and scales between the pelvic-fin origin and the lateral line (0.40). A significant difference (ANOVA, p<0.05) was detected between specimens from the Ganges and the Brahmaputra River basins along the sheared second principal component axis, but not along the first principal component axis. However, there is overlap in morphometric traits values between these two populations as indicated by the substantial overlap in the minimum polygon clusters, and all measurements recorded have some overlap (Fig. 4, Table 2). Additionally, no fixed differences were observed in color pattern between populations. Several specimens from the Brahmaputra River basin possess a brown crescent in the humeral region, but this trait is observed in a specimen from the Ganges and from several other drainages in eastern India (as well as in G. b i co r n i s and G. burmanicus). Based on overall morphological similarity between all Ganges and Brahmaputra River specimens, Cyprinus gohama is recognized as a junior synonym of G. latius as first proposed by Day (1877).
19
incluđe the neotype.
MORPHOMETRICS Neotype Teesta River (n=11) Brahmaputra River (n=3) Koshi River (n=6) Ganges River (n=27)
CAS-SU CAS-SU 41131, UMMZ 244747, 244772 KU 28563 KU 28639, 28688, 28725, 69910 UMMZ 244858 29006, 29031, 29037 Mean Range Mean Range Mean Range Mean Range MORPHOMETRICS Mahanadi River (n=2) Orissa, India (n=2) Hooghly River Surma River Range Range Images of the type specimen of Crossochilus rostratus (BMNH 1867.5.12.15) from the Kangsabati River (Haldi/ Hooghly River basins) show characters diagnostic of Gonorhynchus. Even though no formal diagnosis was given, based on the original description by Günther (1868) this specimen was differentiated from G. latius by lacking maxillary barbels, having more transverse scale rows (12½), four scale rows between the lateral line and the pelvic-fin insertion, presence of a spot on the fifth and sixth scales of the lateral line (Fig. 5), and a longer snout. Several specimens of G. latius examined also lack maxillary barbels. Additionally, these scale counts are not unique to G. latius examined, and the presence of a spot on the anterior portion of the lateral line does not distinguish this specimen from G. latius as this character is also observed in specimens from the Teesta River and other localities. Based on a measurement of a digital image (Fig. 5), the snout is longer than the average snout length of G. latius (42% HL), but is not greater than the maximum (47% HL, Tables 2 and 3). A single specimen from the Hooghly River (UMMZ 244942, Table 3) was also not distinguishable from other G. latius specimens. We thus retain the synonymy of Crossochilus rostratus with G. latius first proposed by Day (1877).
Diagnosis. Member of Gonorhynchus as diagnosed above. Gonorhynchus latius is differentiated from its congeners by the following combination of characters: absence of rostral flaps on tip of snout (vs. present in G. bicornis); large specimens without tubercles on snout and cheek (vs. present in G. p e r i ya re n s i s and G. wattanah); thick midlateral stripe absent (vs. present in G. burmanicus). Gonorhynchus latius generally has more vertebrae (mode 37, range 35–38) compared to G. diplochilus (34–35), G. b i c o r n i s (34–36), and G. burmanicus (35), greater total lateral-line scale counts (mode 40, range 36–40) compared to G. diplochilus (35–38), G. b i c o r n i s (36), G. burmanicus (35–38) and G. macmahoni (35–36), and greater circumpeduncular scale counts (mode 20, range 16– 24) compared to G. diplochilus (mode 16, range 16–18), G. b i c o r n i s (16), and G. burmanicus (16). The postorbital length of G. latius is generally smaller (mean 31.9, range 26.6–36.4 % HL) than that of G. diplochilus (mean 38.0, range 34.5–42.3 % HL). The orbit diameter of G. latius is also generally larger (mean 29.6, range 24.4–38.1 % HL) than that of G. diplochilus (mean 24.8, range 22.1–29.6 % HL).
In a limited number of specimens, we did not find raker counts on the first gill arch to be diagnostic as reported in Bănărescu (1986). Two specimens of G. latius from the Teesta River (CAS-SU 41131), which Bănărescu (1986) had examined, and several specimens from the Ganges River basin have counts of 21–26 vs. 37–39 as initially reported. The count given by Bănărescu may be a typographical error as it matches the lateral-line scale counts reported therein. Gonorhynchus diplochilus specimens examined here have gill raker counts in the range of 21–26, whereas two G. burmanicus specimens have counts of 22. These data are in accordance with gill raker counts reported in Sharma et al. (2014) and Su et al. (2000) for G. diplochilus and G. burmanicus, respectively.
Description. Morphometric and meristic data presented in Tables 2 and 3. Ventral profile from tip of snout to anal fin flat to slightly concave. Snout conical, rounded at end. Head short, longer than wide. Eyes dorsolateral. Dorsal-fin origin anterior of pelvic-fin origin. Pectoral fin reaching approximately halfway between pectoral-fin insertion and pelvic-fin origin. Pelvic fin reaching to or slightly beyond anus. Anal fin not reaching base of caudal fin. Axillary pelvic lobe well-developed. Caudal fin deeply forked with pointed lobes, approximately equal in length.
Body entirely scaled; scales large. Lateral-line scales and pored scales on caudal fin 34–40 + 1–4 (mode 37 + 3), predorsal scales 8-11 (mode 10), scale rows above lateral line 4½–6½ (mode 5½), scale rows below lateral line 4½–5½ (mode 5½), circumpeduncular scales 16–24 (mode 20), 3½–4½ scale rows between lateral line and pelvicfin origin (mode 4½), 4½–7 scales between anus and anal-fin origin (mode 6). Dorsal fin with 3 simple and 8½ branched rays; anal fin with 3 simple and 5½ branched rays; pelvic fin with 1 simple and 8 branched rays; pectoral fin with 1 simple and 13–16 branched rays (mode 14); caudal fin with 10+9 principal rays, 9+8 branched, except one specimen with 9+9 principal rays, 8+8 branched rays (UMMZ 208722). Abdominal vertebrae 23–25, caudal vertebrae 11–13, total vertebrae 35–38 (vertebrae data from BMNH 1867.5.12.15, CAS 24234, CAS-SU 41131, CAS-SU 69910, FMNH 5716, and KU 28563). Rakers on first gill arch 21–26.
Rostral cap covering upper lip which is not visibly separated from snout by groove and not attached to lower lip; rostral cap with 11–22 fimbriae superficial to upper jaw, fewer fimbriae observed in smaller specimens as fimbriae appear to be fused along sides. Mouth inferior; upper lip very thin or absent, widening substantially at corner of mouth connecting upper jaw to lower; lower lip free only on anterior and lateral edges, posterior edge connected to underside of head (not modified into rounded mental disc), central region equally thick as lateral edges, anterior edge with large papillae; sublachrymal groove uniformly narrow from corner of mouth to rostral barbel, not expanding anteriorly to contain rostral lobe. Rostral barbels shorter than eye diameter; maxillary barbels present or absent; if present, tiny, sometimes hidden in corner of mouth.
Color in 75% Ethanol. Dorsally light to dark brown. Most specimens with dark stripe on midline of dorsum. Flanks and lateral portions of head mottled dark brown, with irregular clusters of black spots. Very thin stripe (less than one scale height) on midline of flank present in some specimens. Ventral surface of rostral cap and barbels stippled brown in some specimens. Venter cream to yellow. Some specimens with faint dark stippling on the dorsal-fin, caudal-fin, pelvic-fin, and pectoral-fins rays; inter-radial membranes otherwise clear. Anal fin clear. Lower lobe of caudal fin with dusky blotch in most specimens, darkest along distal edges of fin. Some larger specimens with dark humeral spot on 5th–6th lateral-line scale and scales directly above and below it, forming a crescent or semi-circle.
Color in Life. Silvery ventral half, brassy dorsal half of body. Black speckles overlay head and body. Fins as described above (R. Thoni and T. Sado, pers. comm.).
Distribution and Ecological Notes. The species is distributed in streams of the Ganges, Brahmaputra, and Meghna River basins in Nepal, India, Bhutan, and Bangladesh, as well as the Subarnarekha and Mahanadi Rivers draining into the Bay of Bengal in eastern India (Fig. 6). Gonorhynchus latius was recently reported by Khedkar et al. (2014) in the Narmada River draining into the Arabian Sea in western India, although specimens from this locality warrant examination to confirm species status. Singh & Agarwal (2013) reported observations of G. latius in a variety of microhabitats in a headwater stream in the Ganges River basin, with a stronger preference for pools. Spawning in a Himalayan population occurred during July–September, possibly triggered by high turbidity and stream velocities from seasonal rains (Negi & Dobriyal 1997). The diet of G. latius consists of macrophytes, algae, and diatoms (Sharma 1984). Gonorhynchus latius was listed as “Vulnerable,” i.e., considered to be at a substantial extinction risk, in India by Lakra et al. (2010), although specific threats to this species were not discussed.
Neotype Designation. There is no mention of the type material of Gonorhynchus latius in the original description by Hamilton (1822), nor in any subsequent discussions of the species. Furthermore, an examination of museum records does not indicate the presence of any of the original specimens, suggesting this material is lost. As G. latius is the senior synonym of the type species of the genus Gonorhynchus and will likely be included in future taxonomic research in the group, we herein designate a neotype in accordance with the conditions of Article 75 of the Code (ICZN 1999). The following specimen is selected as the neotype: CAS-SU 69910, collected by S.L. Hora at the Teesta River near Kalimpong Duars and Siliguri Terai, (26.794276°N, 88.561392°E), West Bengal, India, November 1938 (Fig. 7). This specimen possesses the characters diagnostic of G. l a t i u s described here (morphometric and meristic data presented in Table 1) and is topotypical in being from the Teesta River where G. latius was originally described by Hamilton (1822).
description: Published as part of Ciccotto, Patrick J. & Page, Lawrence M., 2016, Revised diagnosis of the genus Gonorhynchus McClelland (Teleostei: Cyprinidae: Labeonini) with redescription of G. latius (Hamilton) and revalidation of G. wattanah (Sykes), pp. 471-492 in Zootaxa 4127 (3) on pages 478-483, DOI: 10.11646/zootaxa.4127.3.4, http://zenodo.org/record/271777