Exostoma ericinum, Ng, 2018

Ng, Heok Hee, 2018, Exostoma ericinum, a new glyptosternine catfish from southwestern China (Teleostei: Siluriformes: Sisoridae), Zootaxa 4420 (3), pp. 405-414 : 406-410

Exostoma ericinum , new species

urn:lsid:zoobank.org:act:4156F1E9-574E-4297-9C8B-6C2BDB415323

Figs. 1 , 2 , 4a , 5a , 6a

Holotype. KIZ 2006013041 , 88.2 mm SL; China: Yunnan Province, Tengchong County, Guyong township, Binglangjiang at Houqiao village , 25°22'47"N 98°12'8"E; DA Neely et al., 20 April 2006.

Paratypes. CAS 226058 (12), 73.3–115.5 mm SL; KIZ 2006013042 (1), 84.6 mm SL; KIZ 2006013043 (1), 87.2 mm SL; KIZ 2006013044 (1), 89.8 mm SL; KIZ 2006013045 (1), 103.7 mm SL; KIZ 2006013046 (1), 106.0 mm SL; data as for holotype. UF 168498 (2), 107.3–120.6 mm SL; China: Yunnan, Tengchong County, Dayingjiang at Guyong , 25°19'N 98°18'E; Y-W Zhou & X-F Pan , 26 February 2001 . ZRC 56672 (1), 97.0 mm SL; locality as for holotype; H Zhou, 21 July 2006 .

Diagnosis. Exostoma ericinum can be distinguished from all congeners except E. tenuicaudata in having more vertebrae (42–44 vs. 36–42) and a longer caudal peduncle (23.2–26.2% SL vs. 15.3–22.3), and from all congeners except E. chaudhurii , E. gaoligongense and E. vinciguerrae in having a longer adipose-fin base (39.5–43.0% SL vs. 25.8–35.8). It additionally differs from congeners in having a unique combination of the following characters: parallel striae on anterolateral surfaces of lips and lower surface of maxillary barbel; interorbital distance 26–31% HL; preanal length 67.7–70.5% SL; body depth at anus 10.4–12.0% SL (1.4–1.9 times in caudal peduncle depth); lacking an incision at posterior extremity of adipose-fin base; caudal peduncle depth 5.7–7.9% SL; and caudal-fin lobes with slightly concave posterior margin.

Description. Biometric data as in Table 1. Head and body broad, very strongly depressed, with paired fins greatly enlarged to form elongate ovoid adhesive disc with body. Rostral margin rounded in dorsal view, moderately curved in lateral view. Dorsal profile rising gently and evenly from anterior orbital margin to origin of dorsal fin, then sloping gently ventrally to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally to end of caudal peduncle. Single midlateral row of conical tubercles on body extending from posterior to opercular flap to vertical through tip of pelvic fin; scattered conical tubercles present on sides of body at predorsal region. Anus and urogenital openings located at posterior margin of adpressed pelvic fin. Mouth ventrally directed with broad, thin and papillate lips. Most of premaxillary tooth patches exposed when mouth is closed. Lower lip with prominent labial fold bearing entire posterior margin, notched at insertions of inner mandibular barbels. Anterolateral surfaces of lip with numerous fine, parallel striae. Postlabial groove on lower jaw present, uninterrupted. Dorsal surface of head with conical tubercles concentrated on dorsal surface of neurocranium, anterior and dorsal surfaces of maxillary barbels, and buccal region.

Jaw teeth distally flattened, oar-shaped and in two rounded triangular patches narrowly separated at midline on upper jaw. Teeth on lower jaw situated in two well-separated, roughly triangular patches. Palate edentulous.

Eyes small, dorsolaterally situated, subcutaneous. Gill openings narrow, extending from base of first pectoralfin ray to level dorsal to base of posteriormost pectoral-fin ray.

Barbels in four pairs. Nasal barbel long, reaching to middle of orbit. Maxillary barbel flattened, with flap of skin fringing posterior margin; its tip pointed; ventral surface with numerous striae; extending beyond base of first pectoral-fin ray. Inner mandibular barbel slightly flattened, very short; originating from notch on posterior margin of lower lip. Outer mandibular barbel situated lateral to inner mandibular barbel; slightly flattened, reaching to base of first pectoral-fin ray.

Dorsal fin without spine, with i,6 (19) rays; surfaces of fin rays covered with conical tubercles. Adipose fin with long base; anterior extremity at vertical through middle of adpressed pelvic fin, posterior extremity separate from upper procurrent caudal-fin rays, without incision at base. Anal fin with ii,4 (8) or ii,5* (11) rays, surfaces of fin rays covered with small, conical tubercles. Caudal fin weakly forked, posterior margin of fin lobes slightly concave, with i,7,7,i (3) or i,7,8,i* (16) rays; lower lobe slightly longer than upper; surfaces of fin rays with scattering of conical tubercles. Pelvic fin greatly enlarged, with convex distal margin and i,5 (19) rays; first ray greatly flattened, with numerous parallel striae on ventral surface; dorsal surfaces of fin rays covered with conical tubercles. Pectoral fin greatly enlarged, without spine and with i,10 (14) or i,11* (5) rays; first ray greatly flattened, with numerous parallel striae on ventral surface; scattered conical tubercles present on fleshy portion of pectoral- fin base. Dorsal surface of pectoral-fin rays entirely covered with conical tubercles. Vertebrae 25+17=42 (4), 24+19=43 (2), 25+18=43* (11) or 25+19=44 (1).

Coloration. In 70% ethanol: grayish brown on dorsal and lateral surfaces of head and dorsal surface of body, dark yellow on ventral region. Pale brown on lateral surfaces of body immediately dorsal and ventral to lateral myoseptum, giving impression of two diffuse brown lines on body: one on lateral myoseptum and another along inter-dorsal region and adipose-fin base. Dorsal fin grayish brown; dorsal surfaces of pectoral and pelvic fins grayish brown, with ventral surfaces of pectoral and pelvic fins dark yellow. Anal-fin rays grayish brown, fin membrane dark yellow. Caudal fin with large irregular grayish brown spot at base; distal half of distalmost 4–5 principal fin rays grayish brown, fin membranes and remainder of fin rays dark yellow. Dorsal surface of nasal and maxillary barbels grayish brown, ventral surface dark yellow. Mandibular barbels dark yellow. Coloration in life similar, but with darker overall body color ( Fig. 2 ).

Distribution. This species is known from the Binglangjiang and the Dayingjiang (=Taping River) in Yunnan, China ( Fig. 3 ) [the Binglangjiang joins the Danzhahe to become the Dayingjiang]. The Taping River is a left-bank tributary of the Irrawaddy River, originating in Yingjiang County, Yunnan and entering the Irrawaddy immediately upstream of Bhamo, Myanmar.

Etymology. The specific epithet comes from the Latin adjective ericinus, -a, -um, meaning “of the hedgehog”. This is used in allusion to the strongly tuberculate head, predorsal region and pectoral fins of this species, which imparts a spiky appearance (in the manner of a hedgehog).

Figures

FIGURE 1. Exostoma ericinum, holotype, KIZ 2006013041, 88.2 mm SL. Dorsal, lateral and ventral views.

FIGURE 2. Exostoma ericinum, paratype, ZRC 56672, 97.0 mm SL. Lateral view showing coloration in life. Photograph courtesy of H Zhou.

FIGURE 3. Map of Irrawaddy River drainage showing collection localities of Exostoma ericinum (solid circle represents more than one locality).

FIGURE 4. Lateral views of pectoral fins of: a. Exostoma ericinum, CAS 226058, paratype, 82.6 mm SL; b. E. sectile, MHNG 2767.061, holotype, 78.2 mm SL (condition in other Exostoma species from the Irrawaddy River drainage similar). Tubercles are visible as small, pale dots. Images not to scale.

FIGURE 5. Dorsal views of heads of: a. Exostoma ericinum, KIZ 2006013041, holotype, 88.2 mm SL; b. E. chaudhurii, CMK 26291, 62.2 mm SL; c. E. stuarti, CMK 25604, 42.4 mm SL; d. E. vinciguerrae, CMK 26330, 62.9 mm SL. Images not to scale.

FIGURE 6. Ventral views showing mouths and oral structures in: a. Exostoma ericinum, CAS 226058, paratype, 82.6 mm SL; b. E. sectile, CMK 26439, paratype, 63.8 mm SL; c. E. vinciguerrae, CMK 26330, 62.9 mm SL. Images not to scale.