Akysis fontaneus, Ng, Heok Hee, 2009

Ng, Heok Hee, 2009, Akysis fontaneus, a new species of catfish (Siluriformes: Akysidae) from Sumatra, Zootaxa 1973, pp. 41-50 : 42-45

Akysis fontaneus sp. nov.

( Figs. 1 , 2 , 5 a)

Type material. Holotype: MZB 10989, 23.5 mm SL; Sumatra: Jambi, Sungai Jernih at Desa Jernih, ca. 25 km on road to Sarolangun after turnoff at Pauh, 2°00.215'S 102°42.475'E; M. Kottelat & H. H. Ng, 19 May 2008.

Diagnosis. Akysis fontaneus is distinguished from congeners by a combination of the following characters: weakly emarginate caudal fin, convex dorsal surface of neurocranium making predorsal profile appear steeply sloping, presence of 4 large serrations on posterior edge of pectoral spine that are more than half width of spine, predorsal length 34.5% SL, pectoral-fin length 21.7% SL (not reaching pelvic-fin origin), length of adipose-fin base 18.7% SL and interorbital distance 42.3% HL.

Description. Morphometric data are in Table 1. Body moderately compressed. Dorsal profile gently convex from tip of snout to origin of dorsal fin, sloping gently ventrally to end of caudal peduncle. Ventral profile flat to anal-fin base, sloping gently dorsally to end of caudal peduncle. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin tuberculate. Vertebrae 16+17=33.

%SL

Predorsal length 34.5 Preanal length 60.9 Prepelvic length 45.5 Prepectoral length 19.6 Length of dorsal-fin base 17.9 Length of anal-fin base 18.7 Pelvic-fin length 15.7 Pectoral-fin length 21.7 Pectoral-spine length 18.7 Caudal-fin length 23.4 Length of adipose-fin base 18.7 Caudal-peduncle length 19.6 Caudal-peduncle depth 8.9 Body depth at anus 14.5 Head length 22.1 Head width 26.4 %HL

Snout length 40.4 Interorbital distance 42.3 Eye diameter 11.5 Nasal barbel length 84.6 Maxillary barbel length 138.5 Inner mandibular barbel length 57.7 Outer mandibular barbel length 119.2 Head depressed and broad, with rounded snout margin when viewed from above. Anterior nostril tubular, base of nostril not in contact with base of nasal barbel. Gill openings narrow, extending from immediately ventral to posttemporal to point immediately lateral to ventral midline of body. Bony elements of dorsal sur face of head covered with thick, tuberculate skin. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel long and slender, extending to middle of pectoral-fin base. Nasal barbel slender, extending to base of pectoral spine. Inner mandibular-barbel origin close to midline, extending to base of pectoral spine. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to middle of pectoral-fin base.

Mouth subterminal, premaxillary tooth band not exposed when mouth closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band gently arced, of equal width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally.

Dorsal fin located above anterior third of body, with I,5 rays; fin margin convex; spine short, straight. Adipose fin with dorsal margin slightly concave, posterior margin angular; origin at vertical through middle of pelvic-fin base. Caudal fin weakly emarginate, with i,5,5,i principal rays. Procurrent rays symmetrical, extending slightly anterior to fin base. Anal-fin origin just posterior to vertical through origin of adipose-fin base. Anal fin with convex margin and iii,7 rays. Pelvic-fin origin at vertical through posterior end of dorsalfin base. Pelvic fin with slightly convex margin and i,5 rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,6 rays; fin margin posteriorly convex; anterior spine margin smooth, posterior margin with 4 large serrations; serrations more than half width of spine.

Coloration. In ethanol: dorsal surface and sides of head dark chocolate-brown. Irregular v-shaped yellow band encircling nape, with apex at base of dorsal spine. Dorsal surface and sides of body dark chocolatebrown. Belly, chest and ventral surfaces of head and body light brown. Dorsal half of body with two yellow saddle-shaped patches: first on body at anterior third of adipose-fin base, second between adipose-fin base and caudal flexure. Ventral half of body with two similar yellow saddle-shaped patches: first between anal and pelvic fins and second between posterior base of anal fin and caudal flexure. Dorsal-fin membrane chocolatebrown, with coloration more diffuse on distal third. Anal and pelvic fins hyaline with brown spots forming 3–4 indistinct transverse bands through middle of fins. Pectoral fin with brown spots on fin rays forming irregular bands. Caudal fin chocolate-brown with proximal one third of both upper and lower lobes with mostly hyaline spot (with scattered melanophores) on each lobe; very thin hyaline margin on distal edge of fin. Adipose fin dark chocolate-brown, except where yellow saddle-shaped patches on body run through fin. Barbels yellow, annulated with brown rings.

Live coloration similar, but with more intense yellow color ( Fig. 2 ).

Distribution. Presently known only from the type locality in the Batang Hari drainage in central Sumatra ( Fig. 3 ).

Habitat. The type locality is a spring-fed stream that flows into the Tembesi River (a tributary of the Batang Hari) via the Air Hitam River. The stream is approximately 10 m wide and about 1.5 m deep ( Fig. 4 ). The bottom consists of clay and highly degraded woody plant debris; the water was clear, with pH of 6.8.

Etymology. The specific epithet comes from the Latin adjective fontaneus , meaning of or from a spring, in reference to the nature of a type locality (a spring-fed stream).

Figures

FIGURE 1. Akysis fontaneus, MZB 10989, holotype, 23.5 mm SL; Sumatra: Sungai Jernih.

FIGURE 2. Holotype of Akysis fontaneus (right side reversed), MZB 10989, 23.5 mm SL showing live coloration.

FIGURE 3. Map showing distribution of Akysis species from Sumatra.

FIGURE 4. Type locality of Akysis fontaneus (Sungai Jernih).

FIGURE 5. Lateral views of head in: a. Akysis fontaneus, MZB 10989, holotype, 23.5 mm SL; b. A. heterurus, ZRC 51430, 24.6 mm SL, showing differences in predorsal profile. Images not to scale.