Silurus tomodai Hibino & Tabata 2018, sp. nov.
Creators: name: Hibino, Yusuke
name: Tabata, Ryoichi
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Siluridae
Silurus
Silurus tomodai

description: Silurus tomodai sp. nov.
New Japanese name: Tanigawa-namazu; new English name: Tomoda’s Catfish
Type material. All type specimens were collected from central Hunshu Island, Japan.
Holotype. FRLM 52893, female, 508 mm SL, 18 May 2016, Kushida River system, Mie Prefecture.
Paratypes. 36 specimens, 139–514 mm SL. FRLM 22119, male, 183 mm SL, 17 July 1998, FRLM 52842, female, 453 mm SL, FRLM 52843, female, 412 mm SL, FRLM 52844, male, 295 mm SL, 26 April 2016, FRLM 52862, female, 357 mm SL (dissected specimen), 1 May 2016, Kamo River system, Mie Prefecture; FRLM 32656, female, 226 mm SL, 20 July 2006, FRLM 53217, female, 196 mm SL, BMNH 2018.5.29.1 (formerly FRLM 53218), female, 159 mm SL, FRLM 54428, female, 325 mm SL (skeletal specimen), 26 July 2016, Isuzu River system, Mie Prefecture; FRLM 52882 [voucher specimen used in Tabata et al. (2016)], male, 174 mm SL, September 2012, FRLM 53565, female, 276 mm SL, USNM 440398 (formerly FRLM 53566), male, 170 mm SL, FRLM 53567, female, 161 mm SL, 10 September 2016, NSMT-P 128085, female, 139 mm SL, 8 December 1989, Miya River system, Mie Prefecture; FRLM 52892, male, 457 mm SL, FRLM 52894, female, 312 mm SL, Kushida River system, Mie Prefecture, collected with holotype; FRLM 52939, female, 514 mm SL, Kumozu River system, Mie Prefecture, 4 June 2016; FRLM 52911–52914, four specimens, female, 315–431 mm SL, 22 May 2016, NSMT-P 128084, male, 179 mm SL, 21 September 1992, Kiso River system, Gifu Prefecture; FRLM 52858, male, 210 mm SL, ANSP 203160 (formerly FRLM 52860), FRLM 52859, two specimens, female, 214–255 mm SL, 3–7 May 2016, Shonai River system, Gifu Prefecture; FRLM 52874, 52876, 52877, 52909, 52910, five specimens, female, 204–499 mm SL, 14 May 2016, FRLM 52875, male, 228 mm SL, 14 May 2016, HMNH 12752 [voucher specimen used in Tabata et al. (2016)], female, 194 mm SL, 5 October 2011, NSMT-P 128083, female, 190 mm SL, 9 September 1992, Yahagi River system, Aichi Prefecture; NSMT-P SK 216, female, 141 mm SL, 16 September 1948, Chikuma River system, Nagano Prefecture.
Non-type materials. All specimens collected from central Hunshu Island, Japan. KYUM-PI 5340, sex unknown, 194 mm SL, 1 October 2017, Tenryu River system, Shizuoka Prefecture (only distributional record); NSMT-P 2297, two specimens, male, 252 mm SL, female, 278 mm SL, 11–16 May 1962,? Yui River system, Shizuoka Prefecture.
Diagnosis. A species of Silurus with the following combination of characters: vomerine-tooth band typically separated into two distinct lenticular patches; head 18.5–21.2% SL; body slender, body depth at 10th anal-fin ray 12.9–18.3% SL; snout 34.7–38.9% HL; lower jaw relatively slender, its length 110–124% of snout length; mandibular barbel 20.4–47.7% HL; inter mandibular barbel width 24.7–32.5% HL; all teeth small, slightly recurved; dorsal-fin length 24.9–43.3% HL, 4.7–7.9% SL; predorsal-fin length 28.5–32.1% SL; eye slightly protruded laterally; dorsal-fin rays 4–5; anal-fin rays 72–91; total vertebrae 62–65; total gill rakers 8–11; mesethmoid bone moderately expanded with a deep depression; underside of head and belly mottled with dark pigmentation; eggs yellow.
Description. Body elongate, skin smooth, covered by a strong mucous membrane; trunk subcylindrical, laterally compressed towards tail (Fig. 2). Belly somewhat convex, its ventral profile gently curved; tail tapered posteriorly.
Head depressed, broadly rounded dorsal view, cheek slightly convex (Fig. 3a); snout bluntly pointed in lateral view; snout length more than three times orbital diameter; anterior nostril tubular, length of tube almost equal or slightly longer than a horizontal diameter of pupil; posterior nostril as opening with an extremely low crown-like flap, located at or slightly anterior of transverse line through anteriormost margin of eye; eye relatively small, vertically oblong, its rim weakly developed; mouth large; lips well developed, posterior corner not reaching a vertical through anterior margin of pupil; two pairs of barbels: maxillary barbel relatively robust, beginning at midsnout along upper lip and finishing well behind insertion of pectoral fin; mandibular barbel relatively thin, about 1/ 2 to 1/5 of head length; lower jaw relatively slender, weakly curved dorsally, its anterior tip protruding well beyond anterior tip of snout; posterior margin of opercle smooth.
Sensory-canal pores present on head; lateral line with 13–16 branched canals dorsally (15 left side and 16 right side in holotype).
Teeth small, conical, slightly recurved; jaw teeth forming continuous tooth-band; mandibular teeth almost invisible when mouth closed; vomerine-tooth band typically as two lenticular patches (incl. holotype) that may touch medially (Fig. 4a) or remain completely separate (Fig. 4b); otherwise, vomerine-tooth band continuous with large posterior notch medially (Fig. 4c).
Gill arches stout; gill rakers rigid, relatively well separated.
Dorsal fin small, origin usually at or anterior to vertical through posterior tip of pectoral fin (rarely slightly behind); anal-fin base long, height of fin slightly tapered posteriorly, anal-fin rays mostly covered by thick skin; caudal fin short, scarcely bi-lobed with shallow notch in distal margin, both lobes broadly rounded, upper lobe usually slightly longer than lower, anteriormost procurrent ray of lower lobe joined to last anal-fin ray by membrane, but two fins clearly separable by distinct notch; pectoral fin rounded with robust, stout spine; pectoralfin spines with distinct anterior and posterior serrations; serrations more highly developed in males than that of females (Fig. 5); pelvic fin rounded, origin well behind a vertical through posteriormost base of dorsal fin.
Mesethmoid bone moderately expanded with a deep medial depression (Fig. 6a).
Coloration when alive (Figs. 2, 7a, b): body black or brown, mottled with irregular pattern of golden blotches especially numerous on dorsal head and body, more scattered on sides and extending onto dark anal fin; underside of head and belly mottled with irregular lines, vermiculations and spots, sometimes ground color dark with irregular pale markings (Fig. 8 a-c); iris silvery gray; barbels usually brown, sometimes mandibular barbels pale to gray; caudal and paired fins brown to dark brown. Eggs yellow (Fig. 9a). Prominent patterns fade rapidly and become darker after death (Fig. 7c) or obscured by subsequent change in mucous membrane to yellow (Fig. 7d). Just after capture, body often appears paler than normal condition and patterns become faded, presumably due to stress.
Size. Maximum size recorded 459 mm SL for males (FRLM 52892) and 514 mm SL for females (FRLM 52939).
Etymology. The scientific name tomodai honors Dr. Yoshio Tomoda, the author of “Two New Catfishes of the Genus Parasilurus found in Lake Biwa-ko” (1961). The Japanese standard name, Tanigawa-namazu, refers to the mountain stream (means "Tanigawa" in Japanese) habitat of S. tomodai.
Distribution. Distributed in Mie, Aichi, Gifu, Shizuoka and Nagano prefectures, central Honshu Island of Japan (Fig. 1); potentially in Niigata Prefecture (Shin-ichiro S. Matsuzaki, pers. comm.).
Notes on habitat and biology. Species generally inhabits the upland portions of streams rather than their alluvial-fans, taking refuge under large stones or cavities in the rocky bed (Fig. 10). Often observed with Liobagrus reinii Hilgendorf, 1878, Nipponocypris temminckii (Temminck and Schlegel, 1846), Rhinogobius flumineus (Mizuno, 1960), and Tachysurus ichikawai (Okada and Kubota, 1957).
description: Published as part of Hibino, Yusuke & Tabata, Ryoichi, 2018, Description of a new catfish, Silurus tomodai (Siluriformes: Siluridae) from central Japan, pp. 507-524 in Zootaxa 4459 (3) on pages 509-512, DOI: 10.11646/zootaxa.4459.3.5, http://zenodo.org/record/1458841