Erethistoides luteolus, Ng, Heok Hee, Ferraris, Carl J. & Neely, David A., 2012

Ng, Heok Hee, Ferraris, Carl J. & Neely, David A., 2012, The catfish genus Erethistoides (Siluriformes: Sisoridae) in Myanmar, with descriptions of three new species, Zootaxa 3254, pp. 55-68 : 60-63

Erethistoides luteolus new species

Figure 3 , Table 2

Type material. Holotype: NRM 61894, 26.1 mm SL; Myanmar: Mandalay Division, Sittang River drainage, Newin River at bridge, 438 km from Yangon on road to Mandalay, 20°4'46.9"N 96°15'17.9"E; S. O. Kullander & T.- Y. Liao, 25 March 2008.

Paratypes: NRM 58809 (3), 23.2–24.5 mm SL; collected with holotype.

Diagnosis. Erethistoides luteolus differs from all other congeners in the yellow (vs. cream or brown) base color. It is further distinguished from all congeners except E. vesculus in the length of the dorsal- and pectoral-fin spines (14–15% SL, vs. 15–27% and 21–24% SL vs. 23–35% respectively). It further differs from E. ascita , E.

cavatura , E. montana , E. pipri and E. sicula in lacking (vs. having) proximally-directed serrations on the anterior edge of the pectoral spine and in having the premaxillary tooth band only partially (vs. fully) exposed when the mouth is closed, from E. longispinis in the length of the caudal peduncle (22–25% SL, vs. 18–21%), and from E. vesculus in the length of the adipose-fin base (16–17% SL vs. 14–15%), the length and depth of the caudal peduncle (22–25% SL, vs. 19–21% and 6–7% SL vs. 4–5% respectively).

Description. Biometric data as in Table 2 . Body moderately elongate and somewhat compressed posterior of head. Cross section of body approximately triangular at dorsal-fin origin, ovoid further posteriorly. Profile slightly convex in lateral view from tip of snout to origin of dorsal fin, straight and evenly sloping ventrally between dorsal-fin base and adipose fin, and concave across caudal peduncle. Ventral profile horizontal to anal-fin origin, then straight, but dorsally angled from there to middle of caudal peduncle. Anus and urogenital openings located somewhat distant from anal-fin origin and at level of middle of adpressed pelvic fin.

Skin tuberculate, tubercles fine and either rounded or slightly anteroposteriorly elongated and many with an anteroposteriorly directed keel. Tubercles irregularly distributed over all surfaces of body; tubercles largest immediately ventral of dorsal fin and smallest on ventral surface of abdomen. Tubercles present on lateral surfaces of fin rays, but absent from interradial membranes. Lateral line complete and midlateral; lateral line extending onto dorsal portion of fleshy base of caudal fin, but not onto rayed portion of fin. Thoracic adhesive apparatus absent. Vertebrae 14+16=30* (2) or 15+15=30 (2).

Head depressed; lateral profile convex dorsally and straight ventrally; profile acutely triangular in dorsal view. Snout margin smoothly rounded anterior of nares. Anterior naris large and round; separated from larger, beanshaped posterior naris only by membranous base of nasal barbel. Gill openings moderately wide, extending anteroventrally from immediately ventral to posttemporal to isthmus but not to ventral midline. Skin of dorsal surface of head with large, elongated tubercles; skin of ventral surface of head with fine, rounded tubercles. Supraoccipital spine slender, with parallel lateral margins, posterior tip of extending nearly nuchal shield. Composite structure consisting of horizontal lamina of complex centrum and posterior process of supracleithrum visible beneath skin; process extending parallel to lateral margin of supraoccipital spine and extending to tip of spine. Eye small, horizontal diameter of orbit approximately one-third of length of snout; orbit ovoid, horizontal axis slightly longer than vertical axis. Eye located entirely in dorsal half of head and middle of pupil at approximately middle of HL. Orbit without free margin.

Mouth inferior, gape large and extending laterally beyond lateral mandibular-barbel origin. Premaxillary tooth band partially visible when mouth is closed. Lips covered with irregularly-distributed, blunt conical papillae. Oral teeth small and villiform, in irregular rows. Premaxillary teeth in crescentic patch with blunt medial margin that extends to midline. Dentary teeth in crescentic band narrower than that of premaxilla. Palate edentulous.

Barbels in four pairs. Nasal barbel short, extending to anterior margin of orbit. Maxillary barbel long and slender, extending to base of pectoral-fin spine; barbel with membranous base along medial surface of barbel that extends to level of middle of posterior naris. Mandibular barbels originate along lower-lip margin, at level of nasalbarbel base; barbels oriented in a nearly-transverse row. Medial mandibular-barbel origin slightly closer to lateral mandibular barbel than to midline; lateral mandibular barbel extending to two-thirds of distance between its base and base of pectoral-fin spine; medial mandibular barbel shorter and extending only to middle of orbit.

Dorsal fin with first branched ray located at vertical through middle of SL, with posterior insertion of fin posterior of vertical through pelvic-fin origin; fin shape retrogressive, with anterior rays longest and straight distal margin; fin with II,5 (4) rays. Dorsal fin-spine straight, compressed, pungent, with sharply pointed tip, not reaching anterior origin of adipose fin when adpressed against body. Anterior margin of spine rough but without distinct serrations, posterior margin of spine with 3 distinct serrations.

Pectoral fin pointed, with fin spine longest; fin margin slightly concave distally. Pectoral fin with I,6* (2), I,6,i (1) or I,7 (1) rays; pectoral-fin spine stout and blade-like, not reaching pelvic-fin origin when adpressed against body. Spine with 23–28 fine distally- or anteriorly-directed serrations along lateral margin and 7–9 larger, proximally-directed serrations along medial margin. Coracoid with moderately long posterior process that extends to vertical through anterior tip of nuchal shield.

Pelvic-fin origin at vertical through middle of dorsal-fin base and slightly anterior to middle of SL. Pelvic fin with slightly concave distal margin, with first branched ray longest; fin with i,5 (4) rays; tip of adpressed fin not reaching anal-fin origin.

Adipose fin small, its base approximately as long as anal-fin base; fin origin slightly anterior of vertical through anal-fin origin. Fin shape regressive, anterior edge longest.

Anal-fin base approximately equal in length and position with adipose-fin base. Anal-fin distal margin convex; fin with ii,5,i (1) or iii,5,i* (3) rays.

Caudal peduncle slender. Caudal fin forked, middle rays approximately one-half length of longest ray of lower lobe; tips of lobes rounded. Fin asymmetrical, with ventral lobe distinctly longer than dorsal lobe. Caudal fin with i,7,7,i (4) principal rays. Procurrent rays short, symmetrical in number and size dorsally and ventrally, and extending only slightly anterior of fin base.

Coloration. In 70% ethanol: dorsal and lateral surfaces of head and body in front of and at level of dorsal fin light chocolate-brown, color somewhat unevenly distributed; tubercles along anterior part of lateral line cream. Snout cream. All ventral surfaces of head and body yellow. Dorsal and lateral surfaces of body posterior to dorsal fin yellow. Two chocolate brown saddle-shaped markings on body: first immediately ventral to adipose-fin base and second at base of caudal fin. Dorsal fin hyaline, with proximal one-third or one-quarter chocolate brown and faint irregular transverse brown band subdistally. Pectoral, pelvic and anal fins hyaline, sometimes with scattered melanophores. Caudal fin hyaline, with irregular transverse brown band subdistally. All barbels yellow.

Distribution. Known only from upper Sittang River basin in central Myanmar ( Fig. 2 ).

Etymology. The specific epithet comes from the Latin adjective luteolus , meaning yellowish. This is used in reference to the presence of yellow in the color pattern of this species, which is its chief diagnostic feature.

Figures

FIGURE 2. Map showing collection localities of Erethistoides species in Myanmar. Each point may represent more than a single collection locality.

FIGURE 3. Erethistoides luteolus, holotype, NRM 61894, 26.1 mm SL; Myanmar: Newin River. Scale bar represents 10 mm.

Tables

TABLE 2. Biometric data for E. luteolus (n = 4).

%SL Predorsal length Preanal length	Holotype NRM 61894 36.0 65.5	Range 36.0–40.5 64.1–67.2	Mean±SD 38.5±1.86 65.4±1.33
Prepelvic length Prepectoral length Dorsal-fin base length Dorsal-spine length	47.1 27.6 18.0 14.9	45.7–48.3 23.7–27.6 13.8–18.0 13.5–15.2	46.8±1.20 25.9±1.85 15.8±1.73 14.4±0.83
Anal-fin base length Pelvic-fin length	16.9 16.1	13.1–16.9 14.7–16.8	15.1±1.55 15.7±0.93
Pectoral-fin length Pectoral-spine length Caudal-fin length Adipose-fin base length	28.7 21.8 20.3 16.5	28.7–29.4 20.8–23.7 20.3–26.7 15.9–17.2	29.1±0.31 21.8±1.34 23.5±4.53 16.5±0.54
Dorsal-to-adipose distance Post-adipose distance	11.1 19.2	11.1–13.5 18.5–20.4	12.3±0.98 19.6±0.87
Caudal-peduncle length Caudal-peduncle depth Body depth at anus Head length	21.5 6.1 10.7 27.2	21.5–24.6 5.6–6.5 10.7–11.6 25.3–27.2	23.1±1.27 6.1±0.37 11.1±0.37 26.5±0.91
Head width Head depth %HL Snout length Interorbital distance Eye diameter Nasal-barbel length Maxillary-barbel length	20.7 16.9 46.5 26.8 16.9 8.5 94.4	19.4–22.0 15.9–17.7 46.5–51.6 26.8–29.7 16.9–19.4 7.4–11.3 94.4–104.7	20.9±1.10 16.8±0.74 50.1±2.45 28.5±1.24 18.2±1.15 9.2±1.66 98.6±4.42
Inner mandibular-barbel length Outer mandibular-barbel length	39.4 50.7	34.9–41.9 50.7–64.1	38.8±2.90 58.7±5.68