Trimma stobbsi Winterbottom, 2001

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 : 78-81

Trimma stobbsi Winterbottom, 2001

Stobbs’ Pygmygoby

Figs. 44–45 , Pl. 3 F

Trimma stobbsi Winterbottom, 2001:20 ( New Caledonia, also Maldives, Indonesia, the Philippines, Papua New Guinea, Solomon Ids, New Caledonia, and western Australia); Hayashi & Shiratori, 2003:42; Anderson, 2005:105; Allen et al., 2004:331; Allen & Erdmann, 2012:947 (western Pacific).

Australian material. Western Australia: Ashmore Reef: WAM P.31437-033, (13), 1– 7 m.

Other material. The following lists material we examined from localities that had not previously been reported for this species: Indonesia: Flores: AMS I.34500-027, 14(12–17), 29– 30m. Raja Ampat: ROM 84882, 3(16–17), 70 m; ROM 84889, 11(13–17), 56 m; ROM 84900, 18(10–16), 8–25 m; ROM 85086, 2(10–15), 50 m; ROM 85135, 14(8–14), 20–23 m; ROM 85146, 3(10–16), 42 m; ROM 85157, (13), 20–23 m; ROM 85188, (17), 52 m; ROM 85203, 3(9–14), 18–23 m; ROM 85229, (15), 12–16 m; ROM 85244, (12), 12–26 m; ROM 85276, 5(8–15), 15–22 m; ROM 85291, 3(9–17), 2–28 m; ROM 85316, 4(12–15); ROM 85329, 10(8–17), 18–21 m; ROM 85332, 13(10–17), 66 m; ROM 85345, 11(10–17), 20–27 m; ROM 85359, 9(10–17), 60 m; ROM 85368, 5(11–17), 55 m; ROM 85373, 5(12–17), 14–18 m; ROM 85392, 22(12–17), 45 m; ROM 87422, 4(9–17), 6–21m; ROM 87455, 5(10–16), 15– 18 m. Palau: Main Ids: ROM 74938, (16), 12–21 m; ROM 74786, (15), 14–26 m; ROM 74787, 3(17–19), 15–27 m; ROM 76416, 2(8–13), 18– 30 m. South West Ids: ROM 82982, 4(15–175), 20–36 m; ROM 82994, 10(9–20), 16–33 m; ROM 83018, 7(16–19), 20–31 m; ROM 83028, 4(18–19), 7–15 m; ROM 83041, 6(15–18), 20–35 m; ROM 83045, 6(15–19), 12–30 m; ROM 83060, 2(15–21), 18–30 m; ROM 83069, 10(16–19), 16–28 m; ROM 83148, (17), 8–20 m; ROM 83257, 3(8–16), 20–35 m; ROM 83270, 2(17–18), 22–34 m; ROM 83295, 3(13–15), 24–32 m; ROM 83395, 3(16.1–17.0), 22– 35 m. Papua New Guinea: Rabaul: ROM 88137, 6(12–15), 16 m; ROM 8157, 4(12–16), 19 m; ROM 92132, 5(10–17), 26 m; ROM 92245, 7(12–15), 20 m; ROM 92284, 10(8–16), 18 m. Vietnam: ROM 73196, (18), 23– 29 m.

Diagnosis. A species of Trimma with a yellow head, a grey-brown body, and a distinct oval dark spot above and just anterior to the posterodorsal corner of the operculum. This spot is preceded by a shallow groove which extends along the dorsal margin of the operculum. No predorsal scales, posterior half of the nape with a slightly developed longitudinal ridge in the midline, scales present on either side of the ridge with a very narrow scaleless gap between them; slight interorbital trench which extends posteriorly barely beyond mid pupil, no postorbital trench; fifth pelvic-fin ray unbranched and 50–70% of the length of the fourth.

Description. The following is based on the original description because only a single specimen is currently known from Australian waters. Dorsal fins VI + I 9–10, (mean = 9.1, n = 47), second spine not elongated or occasionally slightly elongated, reaching posteriorly to base of spine or first ray of second dorsal fin when adpressed, first ray of second dorsal fin branched or unbranched, all remaining rays except posterior half of last ray branched; A I 8–9 (mean = 9.0, n = 47, 8 twice); P 16–19, (mean = 17.6, n = 47, 16 twice, 19 twice), variable number of uppermost and lowermost rays unbranched with branched rays in between, may all be unbranched in smaller specimens <13 mm SL, reaching posteriorly to vertical through base of first anal fin ray or just anterior to this; V I 5, no fraenum, basal membrane vestigial, first four rays with a single sequential branch, fifth ray unbranched (one dichotomous branch on one side in three specimens), 50–70% of length of fourth ray, fourth ray reaching posteriorly to first to fifth elements of anal fin. Lateral scales 22–24 (mean = 23.4, n = 38), transverse scales 7–8 (mean = 7.4, n = 43); no predorsal scales in midline; a slightly developed, raised, longitudinal fleshy ridge from anterior of dorsal fin to mid-nape, scales on either side of ridge with a narrow scaleless gap between them, gap widens towards head where ridge ends; two specimens with one and two scales respectively across nape anterior to ridge; no scales on cheek or opercle; scales on breast (usually five rows), belly, and pectoral-fin base (4 vertical rows) cycloid; scales extend anteriorly 1/2 to one scale width posterior to eye. Ventral attachment of gill opening anywhere between vertical through posterior margin and mid-point of pupil. Teeth in both jaws of outer row of curved, evenly spaced, enlarged canines, with inner row of smaller conical teeth. In some specimens large outer canines on lower jaw appear to be in pairs, with gap between each pair. Tongue truncate or rounded. Gill rakers on first arch 2–4 (2 twice) + 11–15 (11, 15 once each; mean = 3.5 + 12.9, n = 34). Anterior nares long narrow tube, posterior nares pore with raised rim. Bony interorbital quarter to half pupil width, with poorly developed interorbital trench which does not extend posteriorly beyond posterior third of pupil; no postorbital trench. Abdominal/caudal vertebral transition Type B.

Colour pattern. Freshly collected. From 35mm colour slides of living specimens from Ataoru, Flores, Raja Ampat (Pl. 3 F) and Sabah. Distinct round to oval spot (vivid red to dark red-brown) above and just anterior to posterodorsal corner of opercle. Head yellow, with brown chromatophores, yellow pigment extending around eyes and along sides of head just beyond opercular spot. Tinges of pink on opercle (probably from gill filaments) and pectoral base. Body ranging from light yellowish-brown to dull grey brown, with colour extending anteriorly to behind pectoral-fin base and along nape just posterior to eye. Scale pockets faintly outlined with brown chromatophores. Dorsal fins with brown chromatophores, a yellow stripe just above base. Specimen from Flores with yellow head and body appears to be bright salmon pink, although brown chromatophores present. Iridocytes present on pectoral fins of Flores specimen only.

Freshly dead. From 35mm colour slides of specimens from Vietnam ( Fig. 44 ), the Philippines, Palau, Indonesia, and New Caledonia. Background colour of head and body uniform orange or yellow, with numerous brown chromatophores throughout. Distinct black spot (third pupil size) above and anterior to posterodorsal corner of opercle, preceded by groove which runs along two-thirds of dorsal margin of opercle. Greatest concentration of brown chromatophores on body just above pectoral fin and posterior to opercular spot. Scale pockets outlined with orange or yellow and brown chromatophores. Base of dorsal and anal fins with brown chromatophores, single row of orange or yellow spots on fin rays of both dorsal fins, similar spots on base of caudal fin; opercle, pectoral-fin base, and pectoral fin pinkish.

Preserved. Background colour of head and body pale straw yellow sprinkled heavily with brown chromatophores, body appears straw yellow to light brown, head and belly (with fewer chromatophores) straw yellow. Dorsal and anal fins dusky, with row of light spots just above bases of dorsal fin rays; pectoral fins hyaline.

Caudal and pelvic fins sprinkled lightly with chromatophores; scale pockets clearly outlined on anterior half of body.

Etymology. Named for Robin E. Stobbs, friend, guru, and colleague of RW, whose expertise in so many things was instrumental in launching RW’s career (especially the field-work aspects) many years ago at the JLB Smith Institute of Ichthyology in Grahamstown, South Africa.

Distribution. The species has been found in the Indian Ocean at the Maldive Islands. In the Pacific it has been recorded from Western Australia (a single specimen from Ashmore Reef), Indonesia, the Philippines, Vietnam, Papua New Guinea, Solomon Islands, Vanuatu, and New Caledonia ( Fig. 43 ). The specimens have been collected in 1–40 m of water, on reefs and drop-offs, and in caves.

Comparisons. Trimma stobbsi shares the characteristics of a distinct opercular spot and no scales in the predorsal with T. agrena , T. fangi , T. sheppardi , and T. winterbottomi , but the less complex colour pattern of T. stobbsi easily distinguishes it from these four species in both the live and the preserved state. Trimma fangi and T. agrena differ from T. stobbsi in possessing a pattern of yellow, orange or red spots and blotches on the head (which remain as light areas in preserved material), usually a full basal membrane, and a fifth pelvic-fin ray which branches dichotomously at least twice. Trimma winterbottomi can be distinguished from T. stobbsi by the dark banding pattern on the upper part of the body, well developed interorbital and postorbital trenches, full basal membrane and a fifth pelvic fin ray which is sub-equal to the fourth and branched dichotomously twice. Trimma sheppardi and T. stobbsi both have a raised longitudinal ridge that runs anterior from the dorsal fin to the mid-nape and the dark spot above the opercle. The spot on T. sheppardi is an elongate oval (or two rounder spots side by side) and tends to be more posterior on the body so that much of the spot is above the pectoral-fin base, rather than just above the opercle as in T. stobbsi . Trimma sheppardi also has vertical bars on the head, dark internal blotches along the vertebral column, and no interorbital trench.

A barcode analysis of 11 specimens identified morphologically as T. stobbsi was divided into three haplogroups ( Winterbottom et al., 2014). The first, from Palau and Raja Ampat (Group 1; n = 2) differed from the other two groups by a minimum of 12%; the second group ( Palau only, Group 2; n = 3) differed from the third group from New Caledonia, Rabaul and Raja Ampat (Group 3; n = 6) by 8% sequence divergence. The third group probably represents the same haplogroup as the holotype, which was collected at New Caledonia. These results suggest that there may be at least two other undescribed species currently identified as T. stobbsi . No tissue samples are currently available from Australia, and we use the name here with some reservations.

This species has been informally referred to as Trimma DFH sp. 36 or RW sp. 23.

Figures

FIGURE 43. Distribution map for Trimma readerae (solid diamonds).

FIGURE 44. Trimma stobbsi, 17.9 female, ROM 73196, Nha Trang, Vietnam. Photo by R. Winterbottom.

FIGURE 45. Distribution map for Trimma stobbsi (solid circles with white stars).