Erethistoides vesculus, 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 : 64-67

Erethistoides vesculus new species

Figure 4 , Table 3

Type material. Holotype: UMMZ 249554, 28.8 mm SL; Myanmar: Rakhine state, headwaters of Ann Chaung drainage, approx 19 km E by S of Ann, 19°43'N 94°11'E; Than Kyaw Toe, 5 April 2008.

Paratypes. UMMZ 249555 (1), 27.9 mm SL; ZRC 53246 (1), 29.2 mm SL; collected with holotype.

Diagnosis. Erethistoides vesculus differs from all other congeners except E. luteolus in the length of the dorsal- and pectoral-fin spines (15% SL, vs. 15–27% and 22–23% SL vs. 23–35% respectively). It differs from E. luteolus in the length of the adipose-fin base (14–15% SL vs. 16–17%), the length and depth of the caudal peduncle (19–21% SL, vs. 22–25% and 4–5% SL vs. 6–7% respectively), and a cream (vs. yellow) base color. 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. infuscatus and E. senkhiensis in having a distinctly banded (vs. almost uniform) coloration, and from E. longispinis and E. infuscatus in having fewer vertebrae (30 vs. 31–33).

Description. Biometric data as in Table 3 . 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 (3).

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 small, scattered, 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 past 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 very short, falling short of 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 nasal-barbel base. Mandibular barbels originate along lower-lip margin, slightly past posterior margin of posterior naris; 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 midway between its base and base of pectoral-fin spine; medial mandibular barbel shorter and extending only to vertical through anterior orbital margin.

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,6 (3) 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 4–6 distinct serrations.

Pectoral fin pointed, with fin spine longest; fin margin slightly concave distally. Pectoral fin with I,7 (3) rays; pectoral-fin spine stout and blade-like, not reaching pelvic-fin origin when adpressed against body. Spine with 17– 22 fine distally- or anteriorly-directed serrations along lateral margin and 7–8 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 at approximately middle of SL. Pelvic fin with slightly concave distal margin, with first branched ray longest; fin with i,5 (3) rays; tip of adpressed fin falling just short of anal-fin origin.

Adipose fin small, its base approximately as long as anal-fin base; fin origin at 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,6,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 (3) 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 brown, color somewhat unevenly distributed; tubercles along anterior part of lateral line cream. Snout with dusky appearance imparted by cream base color overlain by melanophores. All ventral surfaces of head and body cream. Dorsal and lateral surfaces of body posterior to dorsal fin cream, with scattered melanophores imparting dusky appearance. Two brown vertical blotches on body extending almost to ventral midline: first immediately ventral to adipose-fin base and second at posterior half of caudal peduncle. Dorsal fin dusky brown, caused by irregular distribution of melanophores on fin rays and fin membranes. Pectoral fin with basal third hyaline and broad subdistal brown band. Pelvic fin hyaline, with thin brown band in middle third of fin. Anal fin hyaline with broad brown band in middle third of fin. Caudal fin hyaline, with broad irregular transverse brown band subdistally. All barbels cream.

Distribution. Known only from Ann Chaung River basin in western Myanmar ( Fig. 2 ).

Etymology. The specific epithet comes from the diminutive form of the Latin adjective vescus, meaning small, thin or feeble. This is used in reference to the relatively small dorsal- and pectoral-fin spines of this species.

Figures

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

FIGURE 4. Erethistoides vesculus, holotype, UMMZ 249554, 28.8 mm SL; Myanmar: Ann Chaung River drainage. Scale bar represents 10 mm.

Tables

TABLE 3. Biometric data for E. vesculus (n = 3).

%SL Predorsal length Preanal length	Holotype UMMZ 249554 41.7 71.2	Paratype UMMZ 249555 40.9 68.8	Paratype ZRC 53246 37.7 64.0
Prepelvic length Prepectoral length Dorsal-fin base length Dorsal-spine length	50.3 22.2 15.3 15.3	50.2 21.5 15.4 15.4	48.6 26.4 14.7 15.4
Anal-fin base length Pelvic-fin length	13.5 16.3	12.9 14.7	13.4 12.7
Pectoral-fin length Pectoral-spine length Caudal-fin length Adipose-fin base length	25.7 22.6 23.3 13.9	26.2 21.9 23.3 14.7	damaged 22.9 damaged 14.7
Dorsal-to-adipose distance Post-adipose distance	12.8 15.6	12.2 15.4	9.6 18.5
Caudal-peduncle length Caudal-peduncle depth Body depth at anus Head length	18.8 4.5 10.1 25.3	20.8 3.9 10.0 25.8	20.2 4.8 8.2 25.3
Head width Head depth %HL Snout length Interorbital distance Eye diameter Nasal-barbel length Maxillary-barbel length	20.8 16.7 53.4 28.8 19.2 6.8 75.3	21.1 16.1 50.0 27.8 16.7 5.6 62.5	18.2 15.8 52.7 29.7 17.6 damaged damaged
Inner mandibular-barbel length Outer mandibular-barbel length	34.2 38.4	31.9 45.8	damaged damaged