Wednesday, October 16, 2019

[Ichthyology • 2018] Silurus tomodai • A New Catfish (Siluriformes: Siluridae) from central Japan

Silurus tomodai 
Hibino & Tabata, 2018

A new catfish, Silurus tomodai, is described based on 37 specimens; 132-514 mm > 139-514 mm [132–514 mm standard length (SL)] collected from streams of Mie, Aichi, Gifu, Shizuoka and Nagano prefectures of central Honshu Island, Japan. Although S. tomodai is closely related to S. lithophilus (Tomoda, 1961) based on partial mitochondrial DNA sequences, the former can be distinguished from the latter by the position of dorsal fin (predorsal-fin length 28.5–32.1% vs. 30.1–33.7% SL), a shorter head (18.5–21.2% vs. 19.5–22.2% SL) that is more broadly rounded in ventral view, a more slender body (depth at 10th anal-fin ray 12.9–18.3% vs. 15.7–18.8% SL, and 86.8–100.3% vs. 97.2–109.7% of body depth at anal-fin origin), longer mandibular barbel [20.4–47.7% vs. 10.7–35.3% of head length (HL)], shorter anal-fin rays (10th anal-fin ray length 32.2–38.3% vs. 37.3–45.3% HL), eye slightly protruding laterally beyond profile in dorsal view, and the shape of medial depression on anterior face of mesethmoid (deep and narrow vs. shallow and wide). Silurus tomodai differs from S. asotus, a species widely distributed in Japan including central Honshu Island, in the shape of vomerine-tooth band (typically separated into two distinct lenticular patches vs. continuous), the shape and size of teeth (small and slightly recurved vs. relatively large and recurved), snout length (34.7–38.9% vs. 33.0–36.5% HL), the length of lower jaw (110–124% vs. 124–138% of snout length), interorbital width (53.0–61.3% vs. 46.3–52.8% HL), eye location (vertical through anterior margin of pupil usually posterior vs. anterior terminus of lips), inter-mandibular barbel width (24.7–32.5% vs. 21.7–26.7% HL), vertebral count (62–65 vs. 58–63), pigmentation on underside of head (usually mottled with dark pigmentation vs. uniformly white, rarely dark with pale band along posteroventral margin of lower jaw) and eggs yellow (vs. light green).

Keywords: Pisces, Siluridae, Silurus tomodai, Silurus lithophilus, cryptic species diversity, Japan

FIGURE 2. Live condition of Silurus tomodai sp. nov., FRLM 52893, holotype, 508 mm SL, Kushida River system, Mie Prefecture (photographed by R. Matsuo).

FIGURE 7. Variation in Silurus tomodai sp. nov. a. Live specimen, ANSP 203160, paratype, 255 mm SL, Shonai River system, Gifu Prefecture (photographed by T. Nishimura); b. live specimen, FRLM 52858, paratype, 210 mm SL, Shonai River system, Gifu Prefecture; c. fresh specimen, ANSP 203160 (just after death); d. fresh specimen (about six hours after death), FRLM 52858.

Silurus tomodai Hibino & Tabata, 2018, sp. nov.

New Japanese name: Tanigawa-namazu; 
new English name: Tomoda’s Catfish 

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.

Yusuke Hibino and Ryoichi Tabata. 2018. Description of A New Catfish, Silurus tomodai (Siluriformes: Siluridae) from central Japan.  Zootaxa. 4459(3); 507–524. DOI: 10.11646/zootaxa.4459.3.5