Trimma emeryi Winterbottom, 1985

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 : 25-28

Trimma emeryi Winterbottom, 1985

Emery's Pygmygoby

Figs. 11–12

Trimma emeryi Winterbottom, 1985:752 (Chagos Archipelago) ; Kuiter, 1998:207 ( Maldives); Hayashi & Shiratori, 2003:37; Kimura & Matsuura, 2003:191 (Bitung, N. Sulawesi); Senou et al., 2004:102 (x 2); Randall, 2005:552 (photo from Fiji); Satapoomin, 2007:121 (Andaman Sea); Allen & Erdmann, 2012:936 ( Comores to Marshall Ids., south to Tonga). Trimma mendelssohni (non Goren, 1978:195): Winterbottom, 1984:706 (Chagos Archipelago, central Indian Ocean; colour photo (misidentification recognized at end of text, p. 714).

Material. The type material (363 specimens, 9.6–19.0 mm SL) from Chagos, plus over 400 additional specimens from the following localities and museums:

Australian material. Queensland: Ashmore Reef: AMS I.33717-081, 16(9–18), 1– 32 m. Dunk Id., No Name Reef: AMS I.20965-014, 21(10–18), 10– 20 m. Escape Reef: AMS I.22573-039, 4(11–18), 14–17 m; AMS I.22581-046, 2(14–15), 10–14 m; AMS I.22612-030, (17), 20 m; AMS I.22619-041, 2(12–16), 19–22 m; AMS I.22631-062, (20), 3–6 m; AMS I.22633-081, (18), 2–11 m; AMS I.22637, 3(12–17), 3– 15 m. Escape Reef North: AMS I.22612-030, (17), 20 m; AMS I.22619-041, 2(12–22), 19–22 m; AMS I.22631-062, (20), 3–6 m; AMS I.22633-081, (18), 2– 11 m. Lihou Reef: WAM P. 29638.024, 2(9–10), 20–35 m; WAM P. 29640.018, 4(16–17), 20– 21 m. Osprey Reef: AMS I.25109-077, (19), 1–3 m; AMS I.25113-047, 4(10–18), 9– 11 m. Outer Barrier Reef off Townsville: AMS I.20965, 4(14–17), 10–20 m; AMS I.20965-014, 24(10–18), 10– 20 m. Yonge Reef: AMS I.19480-032, 2(17–18), 20– 30 m. Western Australia: Ashmore Reef: WAM. Cartier Reef: NTM S.12883-011, 6(14–17), 13–14 m; NTM S.13408-010, (19); NTM S.12884-011, (12), 12– 13 m. Timor Sea: Hibernia Reef: NTM S.13425-057, 3(13–17); NTM S.13428-044, 2(12–16). Rowley Shoals: WAM. Scott Reef: NTM S.11370-024, (17), 18– 20 m. Seringapatam Reef: NTM S.11388-022, (18), 0– 1 m. Christmas Id, Indian Ocean: AMS I.20430- 0 14, 4(17–19), 5–10 m; WAM P.26080-015, 7(17–19), 20–30 m; WAM P.26085-021, 9(14–18), 15–20 m; WAM P.26092-026, (19), 14 m; WAM P. 26098.010, 3(13–14), 6–10 m; WAM P.26109-015, 5(19–20), 6– 7 m. Cocos (Keeling) Ids: ANSP 134952, 3(15–19), 46– 49 m.

Other material. In addition to the above, we have examined material from the following localities: Comores: CAS, ROM. Fiji: Bega Lagoon: AMS; Great Astrolabe Reef: ROM; Lau Group: USNM; Nairai: ROM; Rotuma: USNM; Viti Levu: AMS; Viwa Id: USNM; Yasawa Ids: ROM. Indonesia: Moluccas: USNM. Japan: Ishigaki: AMS. Maldives: ROM. Marianas: Guam: AMS. Marshalls: Enewetok: BPBM. Mauritius: BPBM. Micronesia: Ant Atoll: USNM; Ponape: USNM; Ulithi Atoll: CAS. Papua New Guinea: Bouganville Id: WAM; Hermit Ids: USNM; Madang: AMS. New Britain: USNM; Ninigo Ids: USNM. Philippines: Palawan: USNM; Siquijor: ROM. Samoa: Tutuila Id: AMS. Seychelles: Amirante Ids: ANSP. Palau: Uchelbeluu Reef: AMS, CAS, ROM. Tonga: Vava'u: ROM. Vanuatu: Banks Group: AMS.

Diagnosis. A member of the species group defined by a scaled predorsal midline and scale pockets outlined with melanophores and/or chromatophores, T. emeryi can be recognized by the low number of dorsal-fin rays (8), all pectoral-fin rays unbranched, a branched fifth pelvic-ray which is subequal to the fourth, a uniform distribution of the chromatophores on the snout and cheek, and scale pockets which are strongly outlined with dark chromatophores to form a mesh-like pattern on the body.

Description. The following description is taken mostly from Winterbottom (1984, 1985), with corrections made for differences in methodology, omissions and errors in text and figure. Dorsal fin VI + I 8, second spine longest but not elongated, reaching to base of first dorsal-fin ray when adpressed, but may reach base of fourth ray in mature males, first ray and anterior element of last ray unbranched; anal fin I 8 (once 7), first ray and anterior element of last ray unbranched; pectoral fin 16–18 (mean = 17.5), all rays unbranched, reaching posteriorly to a point above anus or anterior few elements of anal fin; pelvics I 5, fifth ray branched once dichotomously and subequal to fourth, which reaches posteriorly to between anus and anterior few elements of anal fin, other rays branched once sequentially, no fraenum, full basal membrane. Lateral scales 23; predorsal scales 6–8, first predorsal scale up to twice as large as others, scales reaching anteriorly to a vertical in line with posterior margin of eye; transverse scales 6–6.5; cycloid scales may be present on opercle; pectoral-fin base margined by a vertical row of two large cycloid scales; scales on breast anterior midline of belly cycloid; those posteriorly on belly may be cycloid or ctenoid; other scales ctenoid. Teeth in outer row of both jaws consist of enlarged, curved, evenly spaced canines followed by several irregular rows of small conical teeth; inner row of lower jaw intermediate in size. Tongue truncate with rounded edges, almost pupil diameter in width. Gill opening extending anteroventrally to a vertical between middle and anterior of pupil, outer gill rakers on first gill arch 2–3 + 11–13. Anterior nares in a short tube, posterior pore-like with a raised rim, nasal sac slightly elevated, rather small and confined to posterior two-thirds of anterior half of snout. Interorbital trough moderate, grading to shallow or absent posterodorsal to eye, bony interorbital width equal or less than half pupil-diameter; epaxialis musculature reaching to a vertical in line with posterior margin of eye. Vertebral pattern is Type B.

Colour pattern. Freshly collected. Based on colour slides of specimens from Chagos, Christmas Island, Philippines, Great Barrier Reef (2, see Fig. 11 ) and the Marshalls Islands. Chagos: body translucent, liberally sprinkled with brown chromatophores, scale pockets strongly outlined with dark chromatophores and melanophores, a light yellow suffusion on head and lower half of body, chromatophores evenly distributed on cheek and snout, median fins yellowish with numerous brown chromatophores, paired fins light yellow, iris with an inner red ring grading irregularly to yellow mixed with brown chromatophores at periphery. Christmas Island specimens similar, with scale pockets more emphatically outlined with brown melanophores with some yellow tinges. The Philippines specimen has scale pockets indistinctly outlined and less yellow on body, and the iris is red with a central narrow ring of yellow. The Great Barrier Reef specimens ( Fig. 11 ) are similar to Philippine example, but scale pockets moderately well outlined, and elements of dorsal fin are red-brown to brown. Enewetok specimen with scale pockets strongly outlined with only a few chromatophores scattered in interspaces. Body, and especially head, suffused with orange-red. A narrow yellow stripe just above base of dorsal and anal fins.

Preserved: greyish body with scale pockets obvious, yellows and reds absent.

Etymology. Named for Alan Roy Emery, colleague, field companion and friend of RW, in appreciation of his many contributions to science, administration and fieldwork.

Distribution. Broadly distributed across the Indo-West Pacific ( Fig. 12 ), from the Comores and Mauritius to the Ryukyu Islands, and the Marshall Islands to Samoa, Tonga and New Caledonia. It is present on the northern half of the Great Barrier Reef and in northwestern Australia. It appears to be absent from mainland Asia with the exception of western Thailand.

Comparisons. Among the species with outlined scale pockets, a branched fifth pelvic-fin ray and unbranched pectoral-fin rays, Trimma emeryi is morphologically virtually identical to T. flavicaudatum ( Goren 1982) , differing only in that the fifth pelvic-fin ray of the latter is about 75% the length of the fourth (vs. subequal). However, in life, T. flavicaudatum has red spots on the cheek and a yellow caudal peduncle and fin. Traces of these spots remain on preservation as light areas on the cheek. Snout pigmentation is also irregular, and the fleshy dorsal margin of the eye has a narrow band of melanophores and/or chromatophores from the anteroventral to the posterodorsal positions. In T. emeryi the cheek and snout are uniformly covered with chromatophores, and the fleshy dorsal margin of the eye is unpigmented. Trimma emeryi differs from T. pentherum sp. nov. in lacking the dark bar on the pectoral-fin base and the 6 grey saddles over the dorsum, in being brown rather than yellow in life, and in having, modally, fewer pectoral-fin rays (17.5 vs. 19.7).

An analysis of the CO1 genome of eight specimens from five localities revealed five groups differing from each other by between 14–22%, suggesting the presence of cryptic species ( Winterbottom et al., 2014). The single specimen sampled from the Great Barrier Reef grouped with two specimens from Palau in Group 5. We provisionally retain the Australian specimens in T. emeryi because there are no specimens available for genetic analysis from the type locality (Chagos Archipelago, central Indian Ocean), and we are currently unable to separate them morphologically from the type material.

Discussion. Further studies of this species are clearly needed to resolve the variation encountered. The variation in freshly collected colouration has been documented above. In addition, the degree of scalation of the opercle varies from none in specimens from the western Indian ocean, to a few specimens possessing such scales at Chagos, to invariably with 1–2 scales for the eastern Australian/Coral Sea population (a single scale was present on the opercle of an 11.5 mm SL juvenile from Dunk Island). Further, the eastern Australian/Coral Sea specimens frequently possess 19 pectoral-fin rays (one more than recorded for other populations), and are considerably darker in overall colouration (especially the head) than specimens from elsewhere.

The specimens from the Gulf of Tadjoura tentatively identified as T. emeryi by Winterbottom (1985) proved, on further analysis, to be T. flavicaudatum . The characters listed in that paper to suggest that the Fijian specimens might be different have here been shown to be labile (anterior extent of gill opening, and tongue shape).

The largest specimen from Australia is 22 mm SL, the largest we have examined is 24 mm SL.

Figures

FIGURE 11. Trimma emeryi, 17.5 mm SL female, AMS I. 9480 - 032, Yonge Reef, Queensland. Photo by D. F. Hoese.

FIGURE 12. Map of the distributions of Trimma emeryi (solid inverted triangles) and T. fangi (solid pentagons). A solid circle with a white star indicates localities at which both species occur.