Mugilogobius hitam, Larson & Geiger & Hadiaty & Herder, 2014

Larson, Helen K., Geiger, Matthias F., Hadiaty, Renny Kurnia & Herder, Fabian, 2014, Mugilogobius hitam, a new species of freshwater goby (Teleostei: Gobioidei: Gobiidae) from Lake Towuti, central Sulawesi, Indonesia, Raffles Bulletin of Zoology 62, pp. 718-725 : 721-724

Mugilogobius hitam , new species

(English common name: Black Towuti Goby) ( Figs. 5 – 9 ; Tables 1, 2)

Material examined. Holotype: MZB 21456, 43 mm SL male, shallow gravel habitats of Lake Towuti , east of mouth of Tominanga River, Central Sulawesi, Indonesia (3°02.126'S, 119°53.232'E), August 2011, coll. H.-G. Evers, hand nets . Paratypes: MZB 21457, 3 (26–35.3); ZRC 54209, 2 (32.5–42.5); QM I.39127, 1(36.5) ; ZFMK 56701 , 1 (26) ; all with same data as holotype .

Diagnosis. A large Mugilogobius with second dorsal rays I,7 – 8, usually I,8; anal rays I,7 – 8, usually I,8; pectoral rays 15 – 16, usually 15; longitudinal scales 31 – 35; transverse scales backward 9 – 12; circumpeduncular scales 12 – 14; predorsal scales small, 17 – 21, reaching to slightly anterior of rear preopercular margin; ctenoid scales on sides of body extending forward in wedge to behind pectoral fin; sensory papillae on head in distinct transverse pattern; numerous short papilla rows along side of body; gill opening oblique, shoulder girdle smooth; first spine of dorsal fin longest in males, second spine longest in females, no spines elongate; head, body and fin rays plain dark brown to blackish; known only from Lake Towuti, central Sulawesi, Indonesia.

Relative to its congeners M. abei , M. adeia , M. latifrons , M. lepidotus , M. rexi and M. sarasinorum , the new species is characterised by seven fixed nucleotide substitutions in the 652 bp long mtDNA COI barcode region studied ( Table 1). Based on the complete COI fragment analysed, the mean smallest K2P distances to a congener is 4.7% to M. latifrons .

Description. Based on eight specimens, 25.6 – 42.5 mm SL. An asterisk indicates counts of holotype ( Figs. 5 , 6 ) if differing from paratypes.

First dorsal VI; second dorsal I,7 – I,8 (nearly always I,8*); anal I,7 – 8 (nearly always I,8*), pectoral rays 15; segmented caudal rays 15 – 16; caudal ray pattern 8/7* (in 7) or 9/7 (in 1); total branched caudal rays usually 15; unsegmented (procurrent) caudal rays 5/5* (in 5), 6/5 (in 1), 6/6 (in 1); longitudinal scale count 31 – 33; transverse scales backward 11 – 12; predorsal scales 17 – 19; circumpeduncular scales 12. Gill rakers on outer face of first arch 3+5* (in 1), 2+7 (in 1). Pterygiophore formula 3-12210. Vertebrae 11+16 (in 7), 10+17 (in 1). Neural spines of anterior vertebrae narrow and pointed, or second and third spine slightly broadened (first neural spine bifid in one). Two epurals present. Three anal pterygiophores anterior to haemal spine of first caudal vertebra ( Fig. 6 ).

Body rounded to slightly compressed anteriorly, compressed posteriorly. Body depth at anal-fin origin 19.0 – 22.0% (mean 20.7%) of SL ( Table 2). Head depressed anteriorly, HL 33.5 – 37.0% (mean 35.2%) of SL. Head width greater than head depth at posterior preopercular margin; depth 46.0 – 53.5% (mean 49.5%) of HL, width at posterior preopercular margin 61.2 – 68.7% (mean 65.9%) of HL; cheeks somewhat rounded. Mouth terminal, oblique, forming angle of about 30 – 40° with body axis; jaws reaching to below anterior part of eye. Upper jaw 31.5 – 41.4% (mean 35.0% in both sexes (two males, six females )) of HL. Lips smooth, moderately thick, with row of fine low fimbriae present on inner edges of both lips; lower lip free at sides, fused across front. Eyes relatively small, lateral, high on head, top forming part of dorsal profile, 18.1 – 23.0% (mean 20.5%) of HL. Snout blunt in dorsal view, flattened toward centre, not fleshy or overhanging, 25.8 – 30.6% (mean 28.8%) of HL. Interorbital broad and flat to slightly concave between bulges of eyes, 28.2 – 37.8% (mean 32.8%) of HL. Top of head anterior to nape scales with small, sparsely scattered villi, densest on interorbital area. Caudal peduncle compressed, length 22.2 – 24.5% (22.8%) of SL. Caudal peduncle depth 10.4 – 13.1% (mean 11.6%) of SL.

First dorsal fin low, triangular, tips of spines free, first spines longest in males (and two females), second spine longest in four females, but longest spine never much longer than others and never filamentous; fin falling short of second dorsal fin origin when depressed; longest spine 12.9 – 16.7% (mean 14.6%) of SL. Second dorsal and anal fins low, rounded posteriorly, anterior and posterior rays of about equal length; rays falling well short of caudal fin base when depressed. Pectoral fin pointed, central rays longest, 21.4 – 25.0% (mean 23.1%) of SL; uppermost ray shortest and unbranched. Pelvic fins short, oval; reaching somewhat more than half distance to anus, 17.8 – 20.2% (mean 19.3%) of SL; pelvic frenum edge irregular. Caudal fin rounded posteriorly, central rays longest, 17.2 – 26.2% (mean 21.0%) of SL.

No mental frenum, chin smooth. Anterior naris short, in thin tube, placed just behind upper lip, and oriented down and forward; preorbital slightly produced forward to accommodate naris tube. Posterior naris in small, round to oval pore, placed just above front centre margin of eye. Gill opening extending forward to under opercle, just behind preopercular rear margin. Inner edge of pectoral girdle smooth with low irregular fleshy ridge. Gill rakers on upper limb of outer face of first arch short and stubby (in one) or short and pointed (in one), unspined; rakers on ventral arm of arch low, short and slightly pointed (anteriormost rakers more blunt). Tongue tip blunt in two specimens. Outer row teeth in upper jaw moderately large, sharp and curved, largest teeth toward side of jaw; inner two to three rows of evenly sized, very small sharp teeth; rows narrowing at side of jaw. Lower jaw with outer row of slightly enlarged curved teeth and about four to five rows of evenly sized small sharp, curved teeth behind; rows narrowing toward side of jaw. Teeth size similar in male and female.

Predorsal scales small, cycloid, evenly sized, reaching anteriorly past preopercular margin in curved irregular pattern. Operculum covered with small cycloid scales; scales not always overlapping. Cheek naked. Pectoral base covered with small cycloid scales. Prepelvic area covered with small cycloid scales. Belly scales cycloid. Ctenoid scales on side of body in wedge extending up to behind pectoral fin, wedge narrowing in gap between dorsal fins; remainder of scales cycloid.

Genital papilla in male elongate, slightly rounded basally, becoming more flattened toward narrowly blunt tip; in female, papilla rounded, slender and bulbous.

Head pores absent as in all Mugilogobius .

Sensory papillae pattern transverse ( Fig. 7 ). Vertical cheek papilla rows numerous (and variable), probably resulting from proliferation of vertical rows c and a; two short s rows on snout, with longitudinal rows joining them; short curved row f of about six papillae on chin. Body with distinctive rows of vertical papillae on scale row along mid-side, with several similar short rows above and below mid-lateral scales anteriorly and near caudal fin base ( Fig. 8 ). Caudal fin with two longitudinal papilla rows and two short rows ventrally ( Fig. 8 ).

Live coloration. Body blackish brown to black; head reddish brown ( Fig. 9 ). Unpaired fin membranes blackish hyaline. Fin rays in first and second dorsal fin blackish to black, fin rays in caudal and anal fin reddish brown to blackish brown. Dorsal and anal fins with diffuse paler margin. Pelvic fin hyaline blackish. Pectoral fin membranes hyaline, pectoral rays light reddish brown.

Preserved coloration. Head and body plain blackish to brownish black, paler on belly ( Fig. 5 ). First dorsal fin dark grey to blackish, with first spine white and other spines usually darker than membrane; tips of spines white to dusky; one female with two dark-margined oval translucent spots at edge of fin between third and fourth spines and fourth and fifth spines respectively. Second dorsal fin plain dark grey to blackish. Anal fin plain dark grey to blackish; spines darker than membrane. Caudal fin dusky to dark grey, spines blackish. Pectoral fin membrane translucent to whitish, with dusky to dark grey rays. Pelvic fins with membrane translucent to pale dusky, with dusky to dark grey rays; base of fin darker than remainder.

Distribution. This species is so far known only from Lake Towuti, near Tominanga in central Sulawesi, Indonesia ( Figs. 1 – 3 ).

Ecology. This species hides in the warm shallows, deep among coarse gravel substrate (see Fig. 3 ). It was recorded down to 2 m depth, where it was rare during fieldwork in 2011. In contrast to other Mugilogobius species of the Malili Lakes, M. hitam is very shy, and difficult to find and collect (H.-G. Evers, pers. comm.). Syntopic goby species in its shallow gravel habitats are M. latifrons and Glossogobius flavipinnis . It is uncertain if this species is restricted to this depth and habitat; an extended focus in sampling effort in suitable areas within Lake Towuti is required to answer this question.

Etymology. The specific name, hitam , is the Bahasa Indonesia word for black.

Comparisons. Mugilogobius hitam differs from all other known species of the genus other than M. rexi by having rows of transverse papillae on the cheek. It is easily distinguished from M. rexi by its larger size, complex transverse sensory papillae pattern and having uniformly plain brownish black colouring; M. rexi is small, has only short transverse papillae rows under the eye and is pale in colour, yellow to yellowish grey with darker reticulate pattern on scale margins when alive. Mugilogobius hitam could possibly be confused with the large plain dark (and possibly extinct) Mugilogobius amadi from Lake Poso, but has far fewer lateral line scales (31 – 34), while M. amadi has 52 – 65 ( Larson, 2001).

Remarks. This species has successfully been kept in aquaria and has reportedly spawned several times in captivity (H.- G. Evers, pers. comm.). Like other closely related species of the genus, M. hitam deposits and guards its small eggs on hard substrates. The larvae are minute, and have so far not been successfully reared. Photographs on an aquarium website show this species spawning in captivity (http:// www.aqualifestyle-france.com/t8498p15-reproductionmugilogobius-cf-amadi). The species has apparently been traded in Europe as Mugilogobius amadi (see http:// photobucket.com/images/mugilogobius?page=1 and http:// www.aqualifestyle-france.com/t8498p15-reproductionmugilogobius-cf-amadi).

Figures

Fig. 5. Mugilogobius hitam, new species.A, MZB 21456, holotype, 43 mm SL male (photograph by S. Hüllen); B, ZRC 54209, paratype, 42.5 mm SL female (right side reversed) (photograph by H. H. Tan).

Fig. 6. Mugilogobius hitam, new species, radiograph of MZB 21456, holotype.

Fig. 7. Sensory papillae rows on head of Mugilogobius hitam, new species, ZRC 54209, 42.5 mm SL female paratype (scales indicated only). A, lateral view; B, dorsal view.

Fig. 8. Diagram of papillae rows on body and caudal fin of Mugilogobius hitam, new species, QM I.391271, 36.5 mm SL male paratype (scales omitted).

Fig. 9. Mugilogobius hitam, new species, captive specimen (photograph by H.-G. Evers).

Fig. 1. Map of the Malili Lakes in Sulawesi. The type locality of Mugilogobius hitam, new species,is denoted by an asterisk (modified Map © T. von Rintelen).

Fig. 2.Type locality ofMugilogobius hitam, new species, at northern Lake Towuti, east of the mouth of Tominanga river (photograph by H.-G. Evers).

Fig. 3. Cobble and gravel substrate at type locality, Lake Towuti (photograph by H.-G. Evers).