Parakysis hystriculus, Ng, Heok Hee, 2009

Ng, Heok Hee, 2009, Parakysis hystriculus, a new species of catfish (Siluriformes: Akysidae) from Sumatra, Zootaxa 1977, pp. 39-48 : 40-43

Parakysis hystriculus , sp. nov.

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

Type material. Holotype: MZB 10985, 27.6 mm SL; Sumatra: Sumatera Selatan, Lalang drainage, swamp forest at Sentang, ca. 5 km after turnoff ca. 12 km after Bayung Lencir on Bayung Lencir–Jambi road, 1°56.192'S 103º42.532'E; M. Kottelat & H. H. Ng, 17–20 May 2008.

Paratypes: CMK 20676 (10), 23.9–27.6 mm SL; ZRC 51418 (9), 23.0–28.2; data as for holotype. MZB 10986 (10), 20.7–25.8 mm SL; UMMZ 248763 (12), 22.6–27.1 mm SL; ZRC 43088 (68), 17.4–29.2 mm SL; locality as for holotype; H. H. Tan, 27 July 1997.

Diagnosis. Parakysis hystriculus is distinguished from other members of the genus in having a combination of: branched pelvic-fin rays with anterior branch always shorter than posterior branch (vs. almost same length in congeners), lateral edges of head evenly sloping in dorsal view (vs. gently curving in congeners), anteriormost pair of accessory inner mandibular barbels longer than (vs. equal to or shorter than in congeners) distance separating bases of left and right barbel, outer mandibular barbel with one accessory barbel (vs. absent in P. anomalopteryx ), mandibular laterosensory pore between bases of inner and outer mandibular barbels present (vs. absent in P. anomalopteryx ), margin of lower lip with medial concavity (vs. entire in P. anomalopteryx ), anal fin rounded (vs. polygonal or rectangular in P. grandis ), caudal fin with narrow lobes having evenly-tapering posteromedial margins (vs. broad lobes with curved posteromedial margins in P. grandis and P. longirostris ) and 10 (vs. 11 in P. verrucosus ) branched rays without secondary branches (vs. with secondary branching in P. grandis ).

Description. Morphometric data are in Table 1 . Body slightly compressed, becoming more so toward caudal peduncle. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin and sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile horizontal to posterior end of anal fin base, then sloping very gently dorsally from there to end of caudal peduncle. Skin rugose, covered with evenly distributed, rounded tubercles of uniform size. Lateral line absent, with postcranial laterosensory system on body consisting only of single pore on lateral surface of body immediately posterior to vertical through base of last pectoral-fin ray. Mandibular laterosensory canals with two pairs of pores: one medial to base of inner mandibular barbel and another between bases of inner and outer mandibular barbels. Vertebrae 18+12=30 (1), 19+12=31 (5), 19+13=32 (3), 20+12=32* (6), or 19+14=33 (1).

Head slightly depressed, dorsal surface covered with thick, rugose skin; dorsal profile convex; lateral margins of head straight in dorsal view, making head look broadly triangular. Eye very small and ovoid, subcutaneous, horizontal axis longest; located entirely in dorsal half of head. Gill openings restricted, extending from just above to just below cleithral process. Gill membranes united with isthmus.

Mouth subterminal, fleshy upper lip with anterior medial lobe projecting anteriorly; lower lip with medial concavity in outline through which lobe on upper lip is visible. Oral teeth small, villiform, and in irregular rows on all tooth-bearing surfaces. Premaxillary and dentary tooth bands narrow and of equal width throughout. Vomerine teeth absent.

Barbels in four pairs. Nasal barbel slender, extending to two thirds of distance between its base and anterior base of dorsal spine. Maxillary barbel long and slender, with broad base originating at rictus of jaws and continuous with both upper and lower lips; extending to vertical through anterior base of dorsal spine. Inner mandibular barbel origin close to midline; barbel thicker and longer than nasal barbel and extending to horizontal line through anterior bases of pectoral spine. Base of inner mandibular barbel with two accessory barbels (branches) not confluent at base; anterior accessory barbel longer than distance between bases of left and right barbel. Outer mandibular barbel origin close to midline of ventral surface of head, thicker and longer than nasal barbel, and extending to vertical line through bases of posteriormost pectoral fin ray. Base of outer mandibular barbel with one accessory barbel.

Dorsal fin located above middle of body; origin nearer to tip of snout than to caudal flexure. Dorsal fin margin convex, with I,3,i (30) rays; spine short and robust, lacking serrations on posterior edge. Pectoral fin with I,5 (2), I,5,i* (24), I,6 (3) or I,6,i (1) rays; branched fin rays with anterior branches shorter than posterior branches. Pectoral-fin spine short and stout; anterior and posterior spine margins smooth and without serrations. Pectoral fin margin straight anteriorly, convex posteriorly. Pelvic fin origin at vertical through posterior end of dorsal fin base; with i,4,i (30) rays. Posterior branch of branched pelvic-fin rays markedly longer than anterior branch; tip of adpressed fin not reaching anal fin origin. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Long dorsomedian adipose ridge originating just posterior to dorsal fin and confluent with upper procurrent caudal fin rays. Anal fin base ventral to posterior half of adipose fin; fin with iii,3,i (3), iii,4,i *(8), iii,5 (1), iv,3,I (1), iv, 4 (4), iv,4,i (8), iii,5,i (3), iii,6 (1) or iv,5 (1) rays. Anal-fin shape sexually dimorphic: fin in males more ventroposteriorly produced than in females ( Fig. 2 a). Caudal peduncle moderately slender. Caudal fin deeply forked, with i,6,4,i (30) principal rays; upper and lower lobes pointed. Procurrent rays symmetrical, extending only slightly anterior to fin base. Mature male with long, conical genital papilla located immediately posterior to anus. Immature males with shorter papilla. Female lacking genital papilla, but with short, tubular extension of genital opening.

Color. In 70% ethanol: dorsal and lateral surfaces of head and body dark brown. Belly, chest, and ventral surface of head cream. A series of about five to six light brown spots on dorsolateral surface of body, arranged longitudinally from below dorsal fin base to caudal peduncle, frequently partially coalescent with elongate light brown patch on dorsal surface of body running along entire postdorsal length. Proximal three-quarters of dorsal fin dark brown, with distal one-quarter hyaline. Pectoral, pelvic, anal, and caudal fins hyaline with scattered brown spots, denser on rays than on membranes. Barbels cream with dark brown rings.

Distribution. Known from the Lalang River drainage in southern Sumatra ( Fig. 3 ). Etymology. From the Latin adjective hystriculus , meaning hairy or bearded; in reference to the long accessory mandibular barbels of this species.

Figures

FIGURE 1. Parakysis hystriculus, MZB 10985, holotype, 27.6 mm SL; Sumatra: swamp forest at Sentang.

FIGURE 2. Posterior portion of bodies in: a. Parakysis hystriculus, ZRC 51418, male paratype, 26.0 mm SL (above) and ZRC 51418, female paratype, 25.7 mm SL (below); b. P. grandis, ZRC 38632, male paratype, 24.2 mm SL (above) and ZRC 39178, female paratype, 29.3 mm SL (below), showing difference in anal-fin shape. Images not to scale.

FIGURE 3. Map showing distribution of Parakysis species in Sumatra.

Tables

TABLE 1. Morphometric data for Parakysis hystriculus (n = 16).

	Holotype	Range	Mean±SD
%SL
Predorsal length	34.8	33.5–37.6	35.6±1.52
Preanal length	71.0	69.4–75.0	72.6±1.95
Prepelvic length	49.3	47.7–53.6	50.9±2.11
Prepectoral length	17.0	17.0–20.0	18.6±0.95
Length of dorsal-fin base	10.5	9.4–14.1	11.3±1.42
Dorsal-spine length	12.0	7.9–14.5	10.7±1.98
Length of anal-fin base	13.8	11.4–13.8	13.0±0.93
Pelvic-fin length	17.4	15.7–21.9	17.7±2.18
Pectoral-fin length	18.8	18.8–22.7	20.5±1.55
Pectoral-spine length	14.9	12.5–15.2	13.6±1.01
Caudal-fin length	27.2	25.9–35.2	29.1±3.36
Caudal peduncle length	14.9	14.0–17.0	15.4±1.00
Caudal peduncle depth	10.9	9.3–13.2	10.9±1.08
Body depth at anus	14.5	13.3–15.6	14.2±0.73
Head length	23.9	21.6–25.2	23.1±1.14
Head width	21.4	21.4–24.4	23.2±1.05
Head depth	14.5	11.9–15.4	14.1±1.03
%HL
Snout length	34.8	29.6–36.8	33.9±2.80
Interorbital distance	40.9	36.6–41.7	40.0±1.77
Eye diameter	9.1	8.5–10.5	9.5±0.61
Nasal barbel length	65.2	65.2–112.7	92.8±14.82
Maxillary barbel length	116.7	115.8–144.4	130.2±11.54
Inner mandibular barbel length	28.8	28.8–66.7	52.4±12.29
Outer mandibular barbel length	86.4	86.4–124.2	102.5±12.69