Sisor rheophilus, Ng, 2003

Ng, H. H., 2003, A revision of the south Asian sisorid catfish genus Sisor (Teleostei: Siluriformes), Journal of Natural History 37 (23), pp. 2871-2883 : 2877-2878

Sisor rheophilus n. sp.

(figures 2c, 4c, 6)

Sisor rhabdophorus (non Hamilton, 1822): (?)Motwani and David, 1957: 12; Majumdar, 1958: 368; Misra, 1976: 312, figure 54 (in part); Menon, 1977: 83 (in part); Talwar and Jhingran, 1991: 681, figure 217 (in part); Jayaram, 1999: 301 (in part); Menon, 1999: 234 (in part); Karmakar, 2000: 34 (in part).

Sisor rabdophorus (non Hamilton, 1822): Mahajan, 1967b: 281, figures 1, 2; Husain, 1997: 609.

Material examined

H. UMMZ 189651, 115.9 mm SL; India: Uttar Pradesh State, Kali Nadi River, near Muzaffarnagar; C. L. Mahajan, date unknown.

P    . CAS 211745 , 27 specimens , 61.0– 84.6 mm SL; India: Bihar State, Ganges River at Patna ; T. R. Roberts, April to May 1996 .

Diagnosis

Sisor rheophilus can be distinguished from its congeners in having a narrower nuchal plate (width equal to length vs width 1.2–1.3 times length; figure 2c), larger eye (13.2–16.3% HL vs 6.9–12.2) and (except for S. torosus ) a longer snout (56.2–60.3% HL vs 53.9–55.9). It further differs from S. rabdophorus and S. chennuah in having a narrower head (14.5–14.8% SL vs 15.1–17.7).

Description

General appearance as for genus. In % SL: body depth at anus 4.2–5.3, predorsal length 30.5–32.0, preanal length 64.6–68.3, prepelvic length 35.8–39.3, prepectoral length 16.9–18.8, length of dorsal-fin base 13.0–14.5, length of dorsal spine 9.0–9.5, length of anal-fin base 7.0–7.1, length of pelvic fin 11.8–13.9, length of pectoral fin 18.7–21.9, length of pectoral spine 16.9–17.7, depth of caudal peduncle 1.4–1.5, length of caudal peduncle 26.0–28.0, length of caudal fin 10.1–12.1, head length 18.0–20.6, head width 14.5–14.8, head depth 7.0–8.2; in % HL: snout length 56.2–60.3, interorbital distance 20.1–23.0, eye diameter 13.2–16.3, length of maxillary barbel 62.5–92.3, length of inner mandibular barbel 45.6–54.1, length of outer mandibular barbel 54.6–58.9. Branchiostegal rays five (6). Vertebrae 18 + 13 = 31 (1), 19 + 13 = 32 (1), 20 + 13 = 33 (2) or 21 + 13 = 34 (2). Lateral line ossicles 72–77. Nuchal plate with long and narrow central process and broad lateral lobes, width equal to length (figure 2c).

Fin-ray counts: dorsal I, 6 (6); pectoral I, 9 (5) or I, 10, i (1); pelvic i, 6 (6); anal ii, 4 (6); caudal 5/6 (3) or 5/7 (3). Anterior edge of pectoral spine with 32–49 long and narrow serrations on anterior edge, and 17–22 smaller, more recurved serrations on posterior edge (figure 4c).

Ecology

The ecology of this species was studied by Mahajan (1967b). Sisor rheophilus has been found in swift-flowing rivers with sandy bottoms.

Etymology

From the Greek rheos, meaning flow, and philus, meaning to love, in reference to the habitat of this species. Used as an adjective.

Distribution

Known from the middle and upper parts of the Ganges River basin in Bihar and Uttar Pradesh States, India .