Glossogobius gnomus, Hoese & Allen & Hadiaty, 2017

Hoese, Douglass F., Allen, Gerald R. & Hadiaty, Renny K., 2017, Description of three new species of dwarf Glossogobius from New Guinea and northern Australia, Cybium 41 (2), pp. 179-193 : 182-184

Glossogobius gnomus , new species

( Figs 1A , 4A , 5, 6 , 12; Tabs I-V)

Material examined

Holotype. – MZB 23335 , 31.2 mm SL male, small creek at extreme eastern end of Etna Bay , West Papua Province, Indonesia, 03°57.01’S, 134°58.64’E, rock, sand and mud, G. Allen and K. Hortle, 30 Apr. 1997.

Paratypes. – AMS I.47260-001, 4(29-31); MZB 23336 , 4 (25-30) and WAM P.31302-010, 23(18-33), taken with holotype . MZB 23638 , 6 (19-34), AMS I.47263-001, 3(19- 34) and WAM P. 34655-001, 2(32-32) Prov. Maluku, Kab. Kepulauan Aru, Kec. Aru Selatan, Desa Jelia, P. Trangan: S. Gartanin. (= southern Trangan Island, Aru Islands ), G. Allen and R. Hadiaty, 4 Dec. 2016 .

Diagnosis

Mouth small, reaching to below a point between anterior margin of pupil and anterior margin of eye; mental fraenum with short lateral lobes attached to the chin; predorsal partly scaled, midline scaled forward to above or just behind posterior opercular margin; cheek and operculum naked; pectoral-fin base and prepelvic area naked; pelvic disc slightly thickened and oval, longer than wide, with most branching of first ray after middle of ray; first dorsal fin with black spot posteriorly, surrounding area near base of sixth dorsal spine, surrounded by large white area; second dorsal-fin rays usually I, 8; anal-fin rays usually I, 7; pectoral-fin rays 15-16; longitudinal scale count 24-28; predorsal scale count 8-14; transverse scale count (TRB) usually 7.5; vertebrae usually 11+16 = 27, preoperculum with 3 pores in adult, lateral canal tube above operculum present (LCT); lateral canal pore between infraorbital pore (LC1) and terminal lateral canal pore (TLC) present.

Description

Counts based on 36 specimens, measurements on 24 specimens 24-32.5 mm SL. First dorsal spines 6(30*); second dorsal rays I,8-9, usually I,8; anal rays I,6-7, usually I,7; pectoral rays 15-16; longitudinal scale count 24(1), 25(7), 26(12*). 27(8), 28(2); predorsal scale count 8-14; transverse scale count (TRB) 7/5(26*), 8.5(4); gill rakers on outer face of first arch 1+1+5(1), 1+1+6(3), 2+1+7(1), = 7-10; lower gill rakers on outer face of second arch 0+6(4), 0+7(2) = 6-7; segmented caudal rays 9/8(30*); branched caudal rays 7/6(5), 7/7(1), 8/7(24*). Other meristics shown in tables I-V.

Head slightly depressed, length 26.4-31.9% SL; cheeks bulbous in adults over 22 mm SL, slightly bulbous in juveniles, head width at posterior preopercular margin 18.8- 21.3% SL; depth at posterior preopercular margin 14.7- 17.5% SL. Snout rounded in dorsal view; concave in side, with distinct notch formed from ascending processes premaxilla just before eye; 7.4-9.6% SL. Eye slightly longer than snout in juveniles and subequal to snout in adults above 20 mm SL, 6.9-8.0% SL in adults. Small bump between nostrils below anterior nostril present, but very low. Anterior nostril at end of short tube, slightly less than one nostril diameter above upper lip. Posterior nostril pore without elevated rim, about 1-2 nostril diameters from eye and 1-1.5 from anterior nostril. Preoperculum short, distance from end of eye to upper posterior preopercular margin slightly less than snout length. Postorbital moderate, subequal to distance from tip of snout to a point above end of pupil to just behind end of eye. Gill opening reaching to below a point just behind posterior preopercular margin. Jaws forming an angle of 30-40° with body axis; upper margin of upper jaw in line with or just below lower margin of eye, upper jaw length 12.6-14.4% SL in adult males and 9.7-11.9% SL in adult females. Teeth in upper jaw: outer row of teeth conical, slightly enlarged teeth extending full length of premaxilla; an inner row of smaller conical teeth developed anteriorly only and a third innermost row of small depressible teeth anteriorly. Teeth in lower jaw: teeth in outer row conical, slightly enlarged and close-set confined to anterior half of dentary; a second inner rows of slightly smaller teeth extending the full length of the dentary coming larger posteriorly; an innermost row of posteriorly directed depressible teeth anteriorly on inner face of dentary. Tongue tip distinctly bilobed. Gill rakers on outer face of first arch triangular, very short, much less than filament length. Rakers on inner face of first arch and other arches shorter than rakers on outer face of first arch and denticulate. Body covered mostly with large ctenoid scales, anteriormost one or two rows cycloid; midline of belly naked or with a few cycloid scales before anus and a large naked patch behind pelvic fin insertion and a few rows of cycloid scales extending forward to below pectoral fin insertion ventrally. First dorsal fin low and rounded in both sexes, lower than body depth at anal fin origin, fourth to sixth spines reaching to about the same point just before to just beyond origin of second dorsal fin when depressed; dorsal origin above a point just behind pelvic fin insertion. Second dorsal fin slightly higher than first dorsal fin, but lower than body depth at anal fin origin. Anal fin slightly lower than second dorsal fin, posterior most rays slightly elongate in mature males, reaching about half way to caudal fin when depressed, reaching less than half way to caudal fin in mature females. Pectoral fin with rounded to pointed margin, reaching to above a point between anus and just behind anal fin origin, (24.3-31.9% SL). Pelvic fin thick and rounded, reaching to or just beyond anus in males (21.7-23.4% SL) and usually well short of anus in females, reaching anus only in females over 30 mm SL (17.4-21.7% SL), fifth ray with few short branches and about 8-12 terminal tips, second ray with most sequential branches behind middle of

ray.

from jaws to end of preoperculum. Line 9 (LL cheek row) short extending from below front half middle of eye arching upward then downward to near posterior preopercular margin. Line 10 (LL cheek row) extending from jaws to just beyond end of eye and not reaching preopercular margin. Line 11 (LT row d) extending to below posterior end of eye. Line 12 (Outer POP-mandibular) continuous from chin to near lower preopercular pore, usually without a gap of no papillae behind posterior tip of jaws. Line 13 (Inner POP-mandibular) continuous from chin to lower preopercular pore. Line 20 (Opercular VT) composed of single row of papillae extending from just behind upper preopercular pore to lower margin of operculum. Line 21 (Upper OT) separate from Line 20 short and sloping downward posteriorly, ending well before posterior opercular margin. Line 22 (Lower OT) short, almost horizontal and composted of few papillae, usually only 3 or 4. Other papillae shown in figure 1A.

Figures

Figure 1. – Sensory papillae in three dwarf species of Glossogobius, composite drawing, based largely on holotypes. A: G. gnomus; B: G. nanus; C: G. pumilus. Numbers indicate papilla lines after Akhito and Meguro (1975) and in descriptions here. Scale bar = 5 mm.

Figure 4. – Dark area indicating anterior extent of predorsal and prepelvic scales and head pores in various populations and species of dwarf Glossogobius. A: Glossogobius gnomus; B: G. nanus, Australia; C: G. nanus, Fly River; D: G. pumilus, Bensbach River; E: G. pumilus, Timika region. Scale bar = 5 mm.

Figure 6. – Live individuals of Glossogobius gnomus. A: Etna Bay, Photo G. Allen; B: Aru Islands, Photo R. Hadiaty.