Erethistoides longispinis, 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 : 56-60

Erethistoides longispinis new species

Figure 1 , Table 1

Type material. Holotype: CAS 229022, 37.3 mm SL, Myanmar, Magway Division, Chindwin River, ca. 7.6 km SE of Pakangyi, 21°29'54.4"N 95°15'58.7"E, 9 Dec 2009, D. A. Neely, U Myint Pe, and local fishermen.

Paratypes: USNM 404360 (2), 39.5–41.0 mm SL, Myanmar: Mandalay Division, Chindwin River drainage, from fisherman at shore of Chindwin River, elevation: 76 m, 22°40'45"N 94°46'29"E; R. Britz, 27 March 2003. CAS 229023 (7), 31.9–37.7 mm SL; Mandalay Division, Irrawaddy River ca. 1 km upstream of Mingun, 22°3'29.5"N 96°1'24.6"E; D. A. Neely and local fishermen, 21 Nov 2009. CAS 233707 (2), 19.0– 35.8 mm SL; collected with holotype. CAS 229020 (1), 37.4 mm SL, Myanmar: Magway Division, large sandbar at Irrawaddy River, ca. 8 km SW of Pokokku, 21°17'46.7"N 95°1'11.3"E; D. A. Neely and local fishermen, 5 Nov 2009. CAS 229021 (1), 35.3 mm SL, Myanmar: Magway Division, Irrawaddy River, at head of sandbar just downstream of Nyaung Oo, 21°12'22.3"N 94°54'22.3"E; D. A. Neely and local fishermen, 7 Nov 2009.

Diagnosis. Erethistoides longispinis 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, and from E. infuscatus , E. luteolus , E. senkhiensis and E. vesculus in the length of the dorsal- and pectoral-fin spines (24–27% SL vs. 13–22% and 29–35% SL vs. 21–28% respectively). It is further distinguished from E. ascita in the length of the dorsal-fin spine (24–27% SL, vs. 15–21%), the pattern of divergence of the serrations along the leading edge of the pectoral fin spine (serrations pointed apically from middle of spine, vs. apically directed serrations only on distal one-fourth of spine), and the number of pectoral-fin rays (7, vs. 5 rarely 6), principal caudal-fin rays (16, vs. 12 or 13) and vertebrae (32–33, vs. 27–30), and from E. cavatura in eye diameter (13–17% HL vs. 18–21%), the length of the dorsal-fin spine (24–27% SL, vs. 18–21%), and the numbers of pectoral-fin rays (7, vs. 5), principal caudal-fin rays (16, vs. 13) and vertebrae (32–33 vs. 29–30). Erethistoides longispinis further differs from E. infuscatus in the pattern of coloration on body (with broad dark bands on a pale background, vs. almost uniformly dark), the predorsal length (42–45% SL, vs. 38–42%), and the number of principal caudal-fin rays (16, vs. 15), and from E. luteolus in the lengths of the adipose-fin base (10–14% SL vs. 16–17) and the caudal peduncle (18–21% SL vs. 22– 25%) and the number of vertebrae (32–33, vs. 30). It is further distinguished from E. montana in the numbers of pectoral-fin rays (7, vs. 6) and principal caudal-fin rays (16, vs. 13). Erethistoides longispinis further differs from E. pipri in length of the caudal peduncle (18–21% SL vs. 14%) and the head width (20–25% SL, vs. 16%), and from E. senkhiensis in the pattern of coloration on body (with broad dark bands on a pale background, vs. almost uniformly dark). It further differs from E. sicula in the length of the pectoral-fin spine (29–35% SL, vs. 15–28%), and the numbers of pectoral-fin rays (7, vs. 5 or 6) and principal caudal-fin rays (16, vs. 12 or 13), and from E. vesculus in the number of vertebrae (32–33, vs. 30).

Description. Biometric data as in Table 1 . 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 15+17=32 (4), 15+18=33 (1) or 16+17=33 (7).

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 to one-fourth 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 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 nearly to origin of pectoralfin 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 (1), II,5,i* (11) or II,6 (2) rays. Dorsal fin-spine straight, compressed, pungent, with sharply pointed tip, and extending almost to anterior origin of adipose fin when adpressed against body. Anterior margin of spine rough but without distinct serrations, posterior margin of spine with 2–7 distinct serrations.

Pectoral fin pointed, with fin spine longest; fin margin slightly concave distally. Pectoral fin with I,5,ii (1), I,6 (1), I,6,i* (10) or I,7 (2) rays; pectoral-fin spine stout and blade-like, extending slightly beyond pelvic-fin origin when adpressed against body. Spine with 20–28 fine distally- or anteriorly-directed serrations along lateral margin and 7–12 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 (14) 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 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 iii,4,ii (1), ii,6,i (1), iii,6 (1), iii,6,i* (10) or iii,8 (1) 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 (14) 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 cream. Dorsal and lateral surfaces of body posterior to dorsal fin cream. 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. Maxillary barbel cream, sometimes with faint brown annulations; all other barbels cream.

Distribution. Known only from the Irrawaddy River basin in central Myanmar ( Fig. 2 ).

Habitat. This species was collected over sand and fine gravel substrates, in areas of moderate current up to approximately 2 m in depth. Collections at two stations (CAS 229020 and 229021) used a 3-m mini-Missouri trawl ( Herzog et al. 2005) to sample deeper runs; other stations were primarily collected by seines or cast nets.

Etymology. The specific epithet comes from the Latin adjective longus, meaning long, and the noun spina, meaning a thorn. The name is used in reference to the relatively long dorsal spine of this species when compared to congeners.

Remarks. The two paratypes collected from the Chindwin River (USNM 404360) roughly 150 river kilometers upstream of the mouth have a shorter pectoral fin than the rest of the type series collected from the Chindwin near the mouth (type locality) and adjacent Irrawaddy River (29–31% SL vs. 32–36). However, we were unable to find any other consistent morphological populations between these populations and consider them conspecific.

Figures

FIGURE 1. Erethistoides longispinis, holotype, CAS 229022, 37.3 mm SL, Myanmar: Chindwin River. Scale bar represents 10 mm.

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

Tables

TABLE 1. Biometric data for E. longispinis (n = 14).

%SL Predorsal length Preanal length	Holotype CAS 229022 42.6 65.1	Range 42.1–44.8 64.6–70.6	Mean±SD 43.7±0.91 67.0±1.88
Prepelvic length Prepectoral length Dorsal-fin base length Dorsal-spine length	46.6 23.1 15.3 25.5	46.6–51.0 22.9–28.0 14.4–18.5 23.8–27.0	49.3±1.49 24.7±1.68 16.1±1.36 25.4±1.01
Anal-fin base length Pelvic-fin length	16.4 14.5	11.6–16.4 14.1–17.6	14.4±1.60 15.8±1.06
Pectoral-fin length Pectoral-spine length Caudal-fin length Adipose-fin base length	32.4 30.0 25.5 13.7	29.1–36.1 29.3–35.3 24.3–29.0 10.2–14.1	33.0±2.34 31.6±1.66 26.1±1.51 12.5±1.24
Dorsal-to-adipose distance Post-adipose distance	14.7 15.0	13.3–16.4 15.0–20.4	15.1±1.09 17.3±1.75
Caudal-peduncle length Caudal-peduncle depth Body depth at anus Head length	19.8 4.8 8.0 26.3	17.7–21.4 4.8–6.1 8.0–11.9 26.3–30.0	19.5±1.07 5.5±0.49 9.9±1.32 27.9±1.07
Head width Head depth %HL Snout length Interorbital distance Eye diameter Nasal-barbel length Maxillary-barbel length	20.4 15.5 52.0 33.7 16.3 11.2 91.8	19.5–25.1 14.7–17.8 49.5–54.4 29.1–33.7 13.3–16.5 8.8–17.5 71.6–105.5	21.5±1.75 15.8±0.88 52.1±1.54 30.3±1.42 14.7±1.22 13.5±2.68 89.8±10.77
Inner mandibular-barbel length Outer mandibular-barbel length	41.8 55.1	26.2–47.7 49.0–63.1	37.5±6.91 54.8±3.84