Clarias microspilus , a new walking catfish ( Teleostei : Clariidae ) from northern Sumatra , Indonesia

Clarias microspilus, a new species of walking catfish is described from the short coastal rivers draining the western face of the Leuser Mountain Range and debouching into the Indian Ocean in Nangroe Aceh Darussalam province, northern Sumatra, Indonesia. It can be distinguished from Southeast Asian congeners in having a combination of the following characters: distance between the tip of the occipital process and the base of the first dorsal-fin ray 6.5–9.2 % SL; body depth at anus 14.9–18.9 % SL; head width 18.6–21.7 % SL; head depth 12.9–16.0 % SL; interorbital distance 40.5–44.5 % HL; occipital process width 31.7–40.8% HL; 64–68 dorsal-fin rays; 51–56 anal-fin rays; anterior tip of frontal fontanel reaching line through middle of orbit; anterior margin of pectoral spine with 22–34 serrations and posterodorsal margin smooth.


IntroductIon
The Old World catfish family Clariidae is a moderately diverse group of catfishes (113 species in 16 genera; Ferraris 2007).The family is diagnosed by the following autapomorphies: presence of well-developed mesial cartilage complex connecting the inner mandibular barbels at midline; pars lateralis lying completely dorsal to the pars ventralis of the protractor hyoideus; dorsolateral portion of cleithrum anterioposteriorly elongate; well-developed posterodorsal projection on the opercle; and a prominent ventrolateral crest on the anterior ceratohyal (Diogo 2007).The genus Clarias Scopoli, 1777 is the most speciose in the family Clariidae, accounting for almost half the diversity of the family (56 species; Ferraris 2007).Clarias is naturally distributed in inland water bodies in both Africa and Asia, with the bulk of the species being found in Africa.However, recent studies (e.g.Lim & Ng 1999;Teugels et al. 2001;Sudarto et al. 2003;Ng 2004) have uncovered a greater diversity of Asian taxa than previously known.The genus has also been shown to be paraphyletic, with the Asian species of Clarias needing to be assigned to a separate genus (Teugels & Adriaens 2003;Agnèse & Teugels 2005).
During ichthyological surveys of Nangroe Aceh Darussalam province in northern Sumatra, specimens of a Clarias species superficially resembling C. batrachus were collected.A detailed study of this material revealed them to belong to an undescribed species, which is named herein as Clarias microspilus, a new species.

MaterIal and Methods
Measurements were made point to point with dial calipers and data recorded to tenths of a millimeter.Counts and measurements were made on the left side of specimens whenever possible.Vertebrae and medianfin rays were counted from radiographs, while pairedfin rays were counted under a binocular dissecting microscope.Subunits of the head are presented as proportions of head length (HL).Head length and measurements of body parts are given as proportions of standard length (SL).Measurements follow those of Ng (1999) C. meladerma by a longer distance between the tip of the occipital process and the base of the first dorsal-fin ray (6.5-9.2 % SL vs. 2.8-5.6), from C. insolitus, C. olivaceus and C. planiceps by a deeper body (14.9-18.9% SL vs. 9.7-15.2) and wider head (18.6-21.7 % SL vs. 14.0-18.7).Clarias microspilus further differs from C. intermedius in having fewer rays in the median fins (64-68 vs. 70-72 dorsal-fin rays and 51-56 vs. 61-62 anal-fin rays), from C. insolitus in having a shorter distance between the tip of the occipital process and the base of the first dorsal-fin ray (6.5-9.2 % SL vs. 10.3-12.4), and from C. meladerma in having more serrations (22-34 vs. 14-22) on the anterior edge of the pectoral spine.It is further distinguished from C. olivaceus in having a more posteriorly situated frontal fontanel (the anterior tip of the frontal fontanel reaching to a line through the middle of the orbit vs. to anterior orbital margin), a smooth (vs.weakly serrated) posterodorsal margin of the pectoral spine, a shorter distance between the tip of the occipital process and the base of the first dorsal-fin ray (6.5-9.2 % SL vs. 9. 3-11.1) and a wider occipital process , and from C. planiceps in having a deeper head (12.9-16.0% SL vs. 9.5-11.5)and smaller interorbital distance .

description
Biometric data in Table 1.Head depressed; dorsal profile slightly convex and ventral profile almost straight.Bony elements of dorsal surface of head covered with thick skin; bones not readily visible, but sutures sometimes evident.Anterior pair of nostrils tubular and medial to maxillary barbel base.Posterior pair of nostrils bordered by nasal barbels anteriorly and fleshy membrane posteriorly; posteromedial to maxillary barbel base.Eye ovoid, horizontal axis longest, subcutaneous; located dorsolaterally on head.Anterior fontanel short and squat ("shoe-shaped" of Teugels, 1986); anterior tip reaching to line through middle of orbits.Occipital process rounded.Gill openings narrow, extending from dorsal-most point of pectoral-fin base to isthmus.Gill membranes free from isthmus but united to each other with 8 (n=5) branchiostegal rays.First branchial arch with 5+13 (n=2) or 5+14* (n=3) gill rakers.
Mouth subterminal, with fleshy, plicate lips.Oral teeth small and in irregular rows on all tooth-bearing surfaces.Premaxillary tooth band rectangular, with median notch on posterior edge.Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally.Vomerine tooth band unpaired, continuous across midline, crescentic and smoothly arched along anterior and posterior margins.Premaxillary and dentary teeth viliform; vomerine teeth subgranular.Barbels in four pairs; long and slender with thick fleshy bases.Maxillary barbel extending to base of fifth or sixth dorsal-fin ray.Nasal barbel, extending nearly to level of base of last pectoral-fin ray.Inner mandibular-barbel origin close to midline; barbel thicker and longer than nasal barbel and extending beyond base of last pectoral-fin ray.
Outer mandibular barbel originating posterolateral to

coloration
In 70% ethanol: Dorsal and lateral surfaces of head and body violet-gray, fading to pale gray on ventral surfaces.Dorsal, anal and caudal fins violet-gray with very thin hyaline distal margin.Pectoral-fin rays violet-gray, with hyaline interradial membranes.Pelvic fins hyaline.Barbels and pectoral spines violetgray dorsally and light grey ventrally.

distribution
Known from the short coastal rivers that drain the western face of the Leuser Mountain Range (Fig. 1).
Besides the species mentioned in the diagnosis, there are four species of Asian Clarias with a serrated anterior edge of the pectoral spine (C.brachysoma, C. dussumieri, C. fuscus, and C. magur).These species are not found in Sundaic Southeast Asia, and brief comparisons are made with the new species below.Clarias microspilus differs from C. brachysoma (from Sri Lanka) and C. dussumieri (from southern India) in having a shorter distance between the tip of the occipital process and the base of the first dorsal-fin ray (6.5-9.2 % SL vs. 9.0-11.1).Clarias microspilus is distinguished from C. fuscus (from northeastern Laos, northern Vietnam, China, Taiwan and Japan) in having more anal-fin rays (51-56 vs. 43-52), a longer distance between the tip of the occipital process and the base of the first dorsal-fin ray (6.5-9.2 % SL vs. 4.8-6.5)and broader occipital process , and from C. magur (from the Indian subcontinent) in having a short and squat (vs.long and thin; "sole-shaped" vs. "knife-shaped") anterior fontanel.
We have examined material from the Alas River drainage (which drains the eastern face of the Leuser Mountain Range) that is not conspecific with C. microspilus.These specimens differ from the type series of C. microspilus in having a long and thin ("knife-shaped" vs. short and squat, "sole-shaped") frontal fontanel and the presence of irregular asperities (vs.serrations) on the anterior edge of the pectoralfin spines.Current evidence indicates the Alas River material is conspecific with material from Java identified as C. batrachus (fide Ng & Kottelat, 2008).
inner mandibular barbel, extending nearly to base of first pelvic-fin ray.Body cylindrical, becoming compressed towards caudal peduncle.Dorsal profile rising very gently from tip of snout to origin of dorsal fin and thereafter almost horizontal to end of caudal peduncle.Ventral profile slightly convex to middle of head and thereafter almost horizontal to end of caudal peduncle.Skin smooth.Lateral line complete and midlateral in position.Vertebrae 20+40=60* (n=1), 19+42=61 (n=3), or 20+42=62 (n=1).Dorsal fin with long base, spanning posterior three-quarters of body; with 64* (n=1), 66 (n=3), or 68 (n=1) rays covered by thick layer of skin and without spine.