Trimma preclarum Winterbottom, 2006

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 : 73-74

Trimma preclarum Winterbottom, 2006

Exquisite Pygmygoby

Figs. 40–41 , Pl. 3 C

Trimma preclarum Winterbottom, 2006:63 ( Fiji, also Palau); Allen & Erdmann, 2012:944 ( Indonesia to Fiji). Trimma sp.: Hayashi & Shiratori, 2003:44, Saipan.

Australian material. New South Wales: Coff’s Harbour: AMS I.30456-003, (22.8). Queensland: Ashmore Reef: AMS I.33717-083, 4(9.8–16.0), 1– 32 m. AMS I.33720-063, 10(9.6–17.0), 2– 32 m. Escape Reef: AMS I.22627- 0 17, 2(18–21). Herald Cays: WAM P.28537-004, 2(13.2–16.2); WAM P.28537-006, 5(12.5–18.7); WAM P.29630- 0 0 9, 2(17.4–17.7). Holmes Reef: WAM P.28541-046, 15(10.6–18.2); WAM P.28541-047, 3(15.5–17.6); WAM P.29627-040, 3(19.0–20.0). Lihou Reef: WAM P.29641-014, (20.1).

Other material. In addition to the type material from Fiji and Palau, we have also examined specimens from the following localities: American Samoa: AMS. Kiribati: Abaiang Atoll: AMS. Indonesia: Raja Ampat: ROM. Papua New Guinea: Ninigo Ids: USNM. Hermit Ids: USNM. Vanuatu: AMS. Micronesia: Ponape: USNM. Kapingamarangi Atoll: CAS. Marshalls: Kwajalein: BPBM.

Diagnosis. Trimma preclarum is characterized by the presence of scales in the predorsal midline, second and third spines of the first dorsal fin usually elongated, moderate interorbital and postorbital trenches, no opercular scales, and scales pockets outlined with pigment, especially across the dorsal half of the body. The fifth pelvic fin ray is branched sequentially once or unbranched depending on the locality. When alive T. preclarum has three yellow stripes on a grey background which extend along the body, two stripes in the dorsal and anal fins (one dark basal stripe and a more distal yellow one), and a red or cerise iris with four large, irregularly-spaced yellow spots.

Description. The description is based on 10 specimens from the Australia for comparison with the original description. Dorsal fins VI I 9 (one specimen deformed, lacking sixth dorsal spine and anal spine), second and sometimes third spine longest, with second spine reaching between spine and third ray of second dorsal fin, all rays branched except posterior element of last fin-ray, and sometimes first ray, and once first and seventh to ninth rays; anal fin I 8–9 (mean = 8.7); pectoral fin 17–19 (mean = 18.0), with 3–6 (mean = 4.5) and 4–8 (mean = 6.1) unbranched dorsal and ventral unbranched rays respectively, reaching posteriorly to vertical line with first few elements of anal fin; pelvic fin I 5, no fraenum, basal membrane vestigial, with small membrane from inner base of fifth ray that does not reach midline, first four rays with one sequential branch, fifth ray unbranched and 48–56% (mean = 51.6) length of fourth, fourth ray reaching posteriorly to a vertical line with second to fifth element of anal fin. Lateral scales 22–23 (mean = 22.7), transverse scales 6–8, (mean = 6.8); midline predorsal scales 7–8 (mean = 7.9), pectoral-fin base with 2–3 vertical rows of cycloid scales, with 3–5 in outer row, 2–5 in middle row and 2–3 in inner row (if present); 5–7 (mean = 5.4) cycloid scales in midline anterior to pelvic fin; scales on head extend anteriorly to above vertical with posterior half of iris; cheek and opercle scaleless. Gill opening extending anteroventrally to below mid to posterior margin of pupil. Upper jaw with outer row of widely spaced enlarged canines extending to about bend of jaw, with few irregular inner rows of small conical teeth that grade to single row posteriorly. Lower jaw with outer row of enlarged widely spaced canines across front of jaw, one or two middle rows of small closely spaced canines, and inner row of widely spaced medium-sized canines. Inner rows of teeth on lower jaw extend around whole jaw as far as coronoid process, where they may be reduced to single row. Tongue round, or rounded with central tip. Gill rakers on first arch 3–4 + 14 = 17–18 (mean = 17.9). Anterior nares short tube adjacent to upper lip, posterior nares pore with raised rim, both nares on raised oval sac confined to anterior half of snout. Bony interorbital 1/3 to 1/2 pupil width, with moderately developed interorbital and postorbital trenches (both wider than deep), but with postorbital trench poorly developed (especially posterolaterally) in smaller specimens. Abdominal/caudal vertebral transition of Type B.

Colour Pattern. Freshly collected. Helen Larson (NTM) provided the following notes made from freshly collected specimens from Ashmore Reef (AMS I.33717-083): “Dusky grey with pink heads. Three yellow lines on body converge on caudal base. Bluish lines on bases of second dorsal and anal”. This description essentially agrees with that provided in the original description ( Fig. 41 ; Pl. 3 C), and rules out the possibility that Australian specimens are Trimma anthrenum (these two species are difficult to tell apart when preserved).

Preserved. A 22.8 mm SL female with yellow-brown body, scale pockets strongly outlined with dark brown chromatophores (pigmentation about twice width of dorsal spines); small brown chromatophores on posterior cheek, snout, opercle and pectoral base; body with larger, pale brown chromatophores mostly below scale pockets and more concentrated over abdomen and above anal fin, but no discrete, wedge-shaped pattern as in original description of Palauan specimens; one-third pupil-diameter dark stripe of chromatophores at bases of second dorsal and anal fins, with few scattered chromatophores in interradial membranes. Female (16.3 mm SL) similar, but whole cheek pigmented, melanophores on body scales, and subdermal chromatophores virtually confined to abdomen and lower body above anal fin. This specimen similar to 17.0 mm SL female, but melanophores widely distributed over body, especially outlining scale pockets, and subdermal chromatophores present over whole body (although still more concentrated on abdomen).

Etymology. From the Latin word “preclarus”, meaning splendid or very beautiful, in reference to the wonderful colouration when alive, especially the multi-hued iris.

Distribution. Found though the western Pacific from Palau and Guam in the north to Samoa and west to the eastern coast of Australia ( Fig. 40 ). In Australia it is known from outer barrier reef islands in depths of 50–60 m and reefs in the Coral Sea in depths of 12– 25 m.

Comparisons. This species is most easily confused, when preserved, with Trimma anthrenum (see Winterbottom 2006). The specimens from Australia differ from the original description in that none of them has an elongated second dorsal spine, which is often, but not always, present in the Fijian and Palauan type material. (We note that only 3 of 44 specimens identified as this species from the Kiribati had the second dorsal spine elongated beyond the base of the fifth dorsal fin ray). In addition, the wedge of chromatophores above the anal-fin origin is not as apparent in these specimens as the illustration provided in the original description ( Winterbottom, 2006, fig. 4B), although it is still discernible. The well developed outlining of the scale pockets and the relatively poorly developed posterior interorbital trench are, however, consistent with T. preclarum to the exclusion of T. anthrenum , as is the colour pattern of freshly collected specimens. Although it is certainly possible that the Australian and, perhaps, the Kiribati material represent an undescribed species allied to T. preclarum , we prefer to await collection of fresh material and subsequent genetic analyses to resolve this issue. Two tissue samples of T. preclarum , both from Palau, were available for genetic analysis, and exhibited no variation in CO I ( Winterbottom et al., 2014).

Figures

FIGURE 40. Distribution map for Trimma pentherum (open triangles) and T. preclarum (solid squares). A solid star indicates localities at which both species occur.

FIGURE 41. Trimma preclarum, 21.3 mm SL female, ROM 83037, Merir Id, Palau. Photo by R. Winterbottom.