Trimma necopinum ( Whitley,1959 )

Winterbottom, Richard & Hoese, Douglass F., 2015, A revision of the Australian species of Trimma (Actinopterygii, Gobiidae), with descriptions of six new species and redescriptions of twenty-three valid species, Zootaxa 3934 (1), pp. 1-102 : 60-63

Trimma necopinum ( Whitley,1959)

Australian Pygmygoby

Figs. 33–34 , Pl. 2 G–H

Priolepis necopinus Whitley,1959:316 (Heron Id, Queensland, Australia).

Trimma necopina: Kuiter, 1993:354 (live); Kuiter & Debelius, 006:662 (live).

Material. Holotype. AMS IB.3991, (19), Heron Id, Great Barrier Reef.

Paratypes. USNM 177869, 2(20–22), Heron Id.

Australian Material. New South Wales: AMS I.19238-002, (19), Sydney Harbour; AMS IA.7066, 1(22), Sydney, 0– 1 m. AMS I.41858–038, (25), Iluka Marina. Queensland: off Cape Melville: AMS I.20774-111, 8(11–19), 8 m. Clack Reef: AMS I.20793-089, 14(10–26), 3– 7 m. Eagle Id: NTM S.11447-023, 3(20–21), 5–7 m; ROM 38756, 2(19–23), 5– 7 m. False Orford Ness, Cape York: AMS I.20776-016, (19), 0– 4 m. Great Detached Reef: AMS I.33693-082, 30(12–25), 19 m. Halfway Id, Cape York: AMS I.20769-017, 12(21–26), 4– 9 m. Heron Id: AMS I.15486-022, 3(15–22), 9 m; LACM 32820–3, (18). Lady Musgrave Id: AMS I.21495-017, 9(20–25), 5 m. Linnet Reef: AMS I.18767-057, 5(9–18), 6– 15 m. Lizard Id: AMS I.17686–005,(23), 6–9 m; AMS I.18739, 2(13–17), 3–10 m; AMS I.19108-088, 5(14–21), 1–11 m; AMS I.19473-157, 14(10–22), 2–7 m; AMS I.19473- 211, (23), 2–7 m; AMS I.19607, 14(18–25), 5–6 m; AMS I.20730-012, 3(13–24), 20–22 m; AMS I.20762-007, (15), 2–5 m; AMS I.20766-003, 9(14–21), 1–3 m; AMS I.21422, 7(16–23), 1–8 m; AMS I.21586-003, 3(9–22), 5–6 m; AMS I.21894-004, 4(13–21), AMS I.23702, 11(19–25), 2–6 m; NTM S.11448-017, (18); ROM 39330, 3(13–21), 2.0–4.0 m; ROM 52450, 5(15–25); ROM 52457, 3(23–25); ROM 52458, (22); ROM 52459, 6(22–26); ROM 52462, (20); ROM 52463, (22); ROM 68825, (20), 1–7 m;. McGillivray Reef: AMS I.18805-005, 2(17–17); AMS I.19482-137, 4(11–22), 25 m. One Tree Id: AMS I.15620-035, 4(21–24); AMS I.15641-051, 3(17–20), 1 m; AMS I.15642-041, (25), 4 m; AMS I.15681-080, 2(17–19); AMS I.15682-065, 15(11–24), 29 m; AMS I.18267- 0 0 6, 2(17–19), 30 m; AMS I.20201-010, 17(15–24), 2m; AMS I.20205-055, 11(13–20), 1–2 m; AMS I.20210-046, 2(20–21), 1–2 m; AMS I.20211-024, 11(15–23), 0–2 m; AMS I.20212-017, 7(9–23), 20 m; NTM S.11061-009, 7(18–23); LACM 33723-54, 2(22–24); ROM 52463, (22). Prince of Wales Id: AMS I.19356-002, 2(15–19), 1 m. Swain Reefs: AMS IB.6239, (22); AMS IB.6240, (20); QM I.37007, 7(15–24), 3– 5 m. Outer Barrier Reef off Townsville: AMS I.20965-016, 34(13–22), 10– 20 m. Tweed River mouth: QM I.31826, 5(16), 3– 5 m. Yonge Reef: AMS I.18740-078, (18), 12 m; AMS I.20784-053, (20), 1– 15 m.

Diagnosis. A species of Trimma with a very narrow interorbital, with a shallow groove before middle of eye, and no groove behind eye; predorsal largely naked, sides of nape scaled to above mid-operculum; operculum naked, segmented caudal rays usually 17; pectoral fin with central rays branched (usually 8–11 branched rays); pelvic fins broadly connected to or near tip of fifth ray; fifth ray short, about half length of fourth ray; fifth pelvic ray branched dichotomously, usually with 4 terminal tips (rarely 3); other rays with one or two sequential branches and 2–3 terminal tips; second and third dorsal spines subequal or second longest, second and third often elongated into short filaments; dorsal- and anal-fin rays usually I 9; head with large obliquely elongate spots (red in life), sloping upward posteriorly; pectoral-fin base with a red bar at base in life (absent in preserved material); body with 6–7 thin dark brown lines more prominent posteriorly.

Description. The description is based on specimens from the Great Barrier Reef. Dorsal fin VI + I 9 (rarely I 8 or I 10 in 6.5% of individuals), mean = I 9.0, n = 152, second to and third rays longest and subequal in length, reaching to between bases of first to fifth segmented dorsal-fin rays when adpressed, first segmented ray of dorsal fin branched or unbranched in adults, usually unbranched in specimens <15 mm SL, anterior element of last ray branched; anal fin I 9 (rarely I 8 or I 10, in 4.6% of individuals), mean = I 9.0, n = 152, first ray branched or unbranched, anterior element of last ray branched; pectoral-fin rays usually 18 or 19 (in 93 % of individuals); 17 in 2% of individuals, 20 in 5% of individuals), mean = 18.7, n = 140, reaching just posterior to a vertical in line between anal spine and third anal ray; upper 3–7 pectoral rays unbranched, central 7–13 branched; lower 4–7 rays unbranched; pelvic fin with two (outer) rays usually with 1 sequential branch, third and fourth ray usually with 1–2 branches (2–3 terminal tips); fifth ray usually with two dichotomous branches (3–4 terminal tips), 45–60% length of fourth ray; pelvic fin reaching posteriorly to just before anus in juveniles (below 15 mm SL) to about third segmented ray of anal fin in larger adults; fraenum absent, basal membrane present, usually connected to tip of fifth ray, but often torn; segmented caudal rays 16 (in 3), 17 (in 142); branched caudal rays 6/5 (72), 6/6 (20), 7/6 (7). Lateral scales 22–25, 22(1), 23(42), 24(42), 25(4), mean = 23.6, n = 90; transverse scale count usually 8, (rarely 7 in <7% of individuals), mean = 8.1, n = 86; scales on pectoral-fin base, breast, and sometimes anteriormost 1–2 scales on midline of belly cycloid, remaining scales ctenoid; a single median scale between bases of pelvic fins, covering part of basal membrane; head naked, scales extending anteriorly in arch from pectoral insertion upward and slightly forward to before first dorsal fin, with scales not reaching midline; anteriormost extent of scales above posterior fifth of first dorsal fin to above posterior end to middle of operculum; scales below posterior end of second dorsal fin with small accessory scales; pectoral-fin base with 8–11 large oval cycloid scales; prepelvic area with 8–10 rows of cycloid scales, extending well forward onto isthmus. Head moderately compressed, eyes dorsolateral; teeth in lower jaw consist of an enlarged outer row of curved, enlarged, evenly spaced canines anteriorly on dentary, followed by two inner rows of similar, but smaller canines tapering to a single row posteriorly; outer row of teeth in upper jaw similar to those of lower jaw, covering anterior half of premaxilla, with two small irregular inner rows of teeth; tongue tip rounded to emarginate, sometimes with minute central projection. Gill opening extending anteroventrally to below posterior margin of pupil to mid pupil; gill rakers on first arch 2–4 (rarely 2) + 12–15 = 15–19 (mean = 17.2, n = 43). Anterior nares a narrow tube, posterior nares a large pore with a raised rim; nasal sac distinctly elevated as a raised oval sac with anterior margin just above upper lip and posterior margin located midway between orbit and upper lip. Interorbital trough shallow, reaching interorbital papillae above middle of eye, no posterior or posterodorsal trough, bony interorbital narrow, width about one third or slightly less than pupil diameter; jaws form an angle of 45° with body axis; horizontal line from tip of upper jaw passes through lower margin of pupil; low nape crest from first dorsal origin to posterior opercular margin. Abdominal/caudal vertebral transition Type B.

Colour pattern. Freshly collected. From slides of specimens from the Great Barrier Reef (see Fig. 33 ). Head and body with red or orange spots on dirty white to grey background; spots often darkest at edges. Spots on side of head obliquely elongate, sloping upward posteriorly; spots on nape rounded; spot forming bar from anteroventral margin of eye to middle the upper jaw and similar spot from ventral margin of eye extending forward over end of jaws; distinctly curved bar below posteroventral margin of eye; round spot below middle of eye just behind jaws, elongate bar on cheek just before posteroventral margin of preoperculum; oblique bar crossing center of operculum extending to posterodorsal margin of operculum and one or two spots ventrally. Nape with 5–6 rounded spots. Isthmus with scattered small red or orange spots, branchiostegal membranes with some traces of red or orange, but no distinct and large red spots. Each scale on body with vertically elongate red or orange spot, often concave and sometimes interconnected to spots on scale above and/or below; 4–6 bluish grey lines most distinctive posteriorly on body. First dorsal fin clear to whitish, with spot centered on each dorsal spine near base of fin. Second dorsal fin clear to whitish with 3–5 rows of red or orange spots on basal two-thirds of fin. Anal fin clear to whitish, with red spot along each ray at base, often with some orange or red scattered on rest of fin. Caudal fin clear to whitish, with 2–3 vertical rows of red to orange spots on basal half of fin. Pectoral-fin base with red or orange bar posteriorly, extending on to bases of pectoral rays; pectoral fin largely whitish with some traces of orange or red. Pelvic fin clear to whitish, with small red or orange spot at base of each fin.

Live. (Pl. 2 G–H). Similar to above, but body purplish-grey in adults, spots not usually darker around edges, red or orange spots in median fins not as apparent, and small white spot present on upper margin of pectoral-fin base. Body of juveniles more translucent (Pl. 2 G), spots on nape in form of ovoid blotches, and red or orange spots on body represented by diffuse bars.

Preserved. Background colour straw yellow with brown chromatophores. Spots (reddish or orange) in fresh material becoming pale, without pigment; interspaces grey to dusky. Dark lines on body sometimes visible; bar at pectoral-fin base not distinctive, fins largely clear of pigment.

Variation. Comparison of specimens from the southern and northern Great Barrier Reef did not show any major differences. For example the pectoral-ray count for 60 specimens from the northern Great Barrier Reef (Lizard Island to off Townsville) averages 18.6 whereas the count averages 18.7 in 60 specimens from the southern Great Barrier Reef (One Tree and Heron islands).

The spots on the body are normally red in photos of live individuals, but often orange in specimens photographed shortly after preservation.

Etymology. From the Latin ‘necopinus’, meaning ‘unexpected’.

Distribution. Trimma necopinum is known only from Australia, from the tip of Cape York to the southern border of Queensland, the Coral Sea and from Sydney, New South Wales ( Fig. 34 ). It is most common on midreefs, but is found on Swains Reefs in the Coral Sea and in back reef areas on the outer barrier islands. The species is found in depths of 1– 30 m.

Comparisons. The species is close to Trimma macrophthalmus in fin-ray and scale counts and general reddish head and body colouration. Both occur in Australia, but Trimma necopinum typically is most abundant on coastal and midreefs, while T. macrophthalmus is confined to the outer barrier islands and the Coral Sea. Trimma necopinum differs in having the spots on the head elongate and sloping upward posteriorly (especially the oblique short bars on the cheek below the posteroventral margin of the eye and the one on midregion of the operculum), these spots are rounded in T. macrophthalmus . In T. necopinum , there is a reddish band at the base of the pectoral fin and no dark spots on the branchiostegal membranes, while T. macrophthalmus has three dark spots on the pectoral-fin base and two dark spots ventrally on the branchiostegal membranes. Trimma necopinum also has less branching of the pelvic rays and a slightly deeper interorbital trough. The species also reaches a larger size than T. macrophthalmus , with a maximum size of 26 mm SL, while T. macrophthalmus reaches a size of 22 mm SL, rarely over 18 mm SL in Australia.

Discussion. Currently the species is known only from Australia, but it may be expected to occur on reefs of southern New Guinea. It may also occur in other areas of the south-west Pacific. Insufficient samples are available of Trimma from the south-west Pacific (except Fiji) to accurately determine distributions of Trimma in this region. The species has been informally referred to as T. RW sp. 74 or DFH sp. 51.

Four specimens from the Great Barrier Reef were analysed for variation in the CO1 gene, which was about 0.7% of the sampled genome.

Figures

FIGURE 33. Trimma necopinum, 20.0 mm SL male, AMS I. 20784 - 053, Yonge Reef, GBR. Photo by D. F. Hoese.

FIGURE 34. Distribution map for Trimma necopinum (solid circles with white stars) and T. nomurai (solid squares with white circles).