Trimma corerefum, Winterbottom, Richard, 2016

Winterbottom, Richard, 2016, Trimma tevegae and T. caudomaculatum revisited and redescribed (Acanthopterygii, Gobiidae), with descriptions of three new similar species from the western Pacific, Zootaxa 4144 (1), pp. 1-53 : 36-41

Trimma corerefum n.sp.

Colins’ Pygmygoby

Figs. 11 , 24–27 , 31

Trimma tevegae : (non Cohen & Davis, 1969:321)—Winterbotton et al., 2014:88 (Group 1 only).

Material examined. All type specimens collected off the main islands of Palau.

Holotype. ROM 100151, 15.2 mm SL female, Uchelbeluu Reef (aka the Short Drop-off), SE of Koror Island, vertical wall with small caves and crevices, hard corals ( Acropora , Montipora ), hydroids, 07°16'28.7"N, 134°31'32.1"E, 13.7−25.9 m , 21 May, 2004, R. Winterbottom et al.

Paratypes. ROM 74795, 48 (7.3–17.0), SW corner of Uchelbeluu Reef , hydroids, sea fans, variety of hard corals, 07°16'54.3"N, 134°31'38.7"E, 15.2–26.5 m, rotenone, 28 May, 2004, R. Winterbottom et al . ROM 80390, 23 (8.3–14.4), Uchelbeluu Reef near east tip, drop-off wall and steep gully with sand, numerous small caves, overhangs and crevices, 7°16'29.2"N, 134°31'32.0"E, 19.8–27.4 m, rotenone, 31 Mar., 2006, R. Winterbottom et al. (plus tissue specimen, ROM T00715) . ROM 81393, 37 (7.2–16.2), Uchelbeluu Reef , 07°15.963'N, 134°31.236'E, drop-off, 15 m, quinaldine, 10 May, 2007, P. Colin (all tissue specimens, ROM T07599–T07635) . ROM 99084, 37(7.8–15.7), collected with the holotype. ROM 99086, (17.1), outer reef off Ulong pass to N of Ngerumekaul Pass , hydroids, sea fans, various hard corals, 07°18'11.2"N, 134°14'06.2"E, 15.2–30.5 m, rotenone, 26 May, 2004, R. Winterbottom et al . ROM 99087, (13.0), just N of pass to W of Ulong Id outer reef, some gorgonians, Acropora , Pocillopora , sponges, 07°17'44.2"N, 134°14'18.9"E, 18.3–30.5 m, rotenone, 7 Jun., 2004, R. Winterbottom et al . ROM 99088, 43 (7.5–17.7), off SE coast of Koror Id, SW corner of Uchelbeluu Reef , corals, hydroids, 07°16'26.9"N, 134°31'29.3"E, 12.2–21.3 m, rotenone, 20 May, 2004, R. Winterbottom et al . ROM 1916CS, 4(13.2–19.7), collected with ROM 99088.

Other material: Indonesia, Sulawesi: ROM T12777–79, 3(11.8–13.2), Bunaken Id, Liang , south coast, 01°37.132'N, 124°45.473'E, 10 m, clove oil, 0 9 July, 2012, M. V. Erdmann . ROM 64645, 2 (11.5–14.7), Manado, Bunaken Id , north side, base of drop-off, 01°37'41"N, 124°45'36"E, 16 m, rotenone, 29 Oct., 1991, J. Randall et al.

Other material (identification not confirmed by genetic analysis): Philippines, Negros Oriental, ROM 101079, 6 (14.4–18.5), Siquijor Id, Tonga Point, 09°12'16"N, 123°27'16"E, 15.2–21.3 m, rotenone, 12 May,1987, R. Winterbottom et al . ROM 101080, 1 (16.2), Siquijor Id, Tonga Point, 09°12'17"N, 123°27'14"E, 9.1–21.3 m, rotenone, 22 May, 1987, R. Winterbottom et al.

Diagnosis. A species of Trimma with a bony interorbital about three-quarters pupil diameter (68–85%), a fully scaled nape with the anterior rows cycloid in adults, a second dorsal spine that usually reaches the middle of the second dorsal fin, only two cephalic sensory papillae in row f on the chin and in row r on the top of the snout, 2–5 (usually 4) papillae in row d ʹ immediately behind the maxilla, usually 13 (range = 12–14) unbranched pectoral-fin rays, and an unbranched fifth pelvic-fin ray that is 34–45% the length of the fourth ray. Freshly collected specimens have a reddish head and anterior nape except below a line bounded by the horizontal limb of preopercle, where they are white, the opercular region and abdomen are red with a liberal sprinkling of large, dark brown melanophores, a pupil-diameter wide white band across peduncle anterior to the caudal spot, which is an approximately pupildiameter dark marking on the posterior part of the peduncle and extending onto the bases of the caudal fin rays. Preserved specimens have four distinct groupings of small round black melanophores situated at the 3, 4:30, 6 and 9 o’clock positions around the eye.

Description. The description is based on up to 22 specimens, 13.0– 17.3 mm SL (mean 15.7) from four collections from the main islands of Palau. Dorsal fin VI + I 8 (once I 7, n = 21), second spine elongated, usually reaching to about middle of second dorsal fin (adpressed tip of spine to bases 2– 4 –7th rays of second dorsal fin, mean 4.1, n = 20, see also Table 1 ), all fin rays branched except for posterior element of last (first dorsal ray unbranched in two specimens), last ray 28– 37 –39% (mean 33.5%, n = 13) of distance between its base and first dorsal procurrent caudal fin ray; anal fin I 8 (n = 21), first ray usually branched (unbranched in 5 of 21 specimens), last ray 22– 35 –37% (mean 30.0, n = 12) of distance between its base and first ventral procurrent caudal fin ray; pectoral fin 12– 13 (mean 12.8, n = 21), rays unbranched, reaching posteriorly to vertical line above urogenital papilla to base of second element of anal fin; pelvic fin I 5, fifth ray unbranched and 34–45% (mean 39.2%, n = 17, broken in holotype) length of fourth ray, which reaches posteriorly to between bases first to fourth anal ray, pelvic rays 1–4 with a single sequential branch point; basal membrane only just forms a fold across midline beneath last prepelvic scale or attaches to sides of body near midline; no fraenum. Lateral scales 23; anterior transverse scales 8– 10 (mean 9.1, n = 11); posterior transverse scales 7– 9 (mean 8.1, n = 12); predorsal midline scales 10 –11 (mean 10.4, n = 14), anteriormost scales cycloid ( Fig. 24 B) but may be up to five scales with at least some cteni in posterior part of series, scales rimming orbit usually cycloid, scales reaching anteriorly to above anterior to middle of pupil; cheek with 1 –2 rows of cycloid scales, uppermost row (if present) of one scale, row below it of 6 –7 scales (mean 6.8, n = 8); opercle with 2–3 horizontal rows of 5–10 mostly cycloid scales (mean 6.8, n = 4, scales missing in holotype), often with 1–2 very small supernumerary cycloid scales dorsally, some larger scales may be ctenoid, dorsalmost row with 3–4 scales (mean 3.3, n = 4), second row 2–4 (mean 2.8, n = 4), third row, if present, 1–2 (mean 1.7, n = 3); pectoral base with 2– 3 vertical rows of cycloid scales, with 0– 3 in anterior row (if present), 2– 4 in next row, and 3 –4 in outer row; 6– 7 cycloid prepelvic scales in midline; area between pelvic spine and ventral margin of pectoral fin base, midline of belly and sometimes anteriormost row beneath axil of pectoral fin base with cycloid scales, those adjacent to bases of dorsal and anal fins may be cycloid or ctenoid. Upper jaw with outer row of closely spaced, slightly curved conical teeth, decreasing slightly in size and becoming less curved posteriorly, reaching almost to posteroventral tip of premaxilla, inner row of conical teeth, larger near symphysis, decreasing in size posteriorly, reaching almost to end of premaxilla. Lower jaw with outer row of about 5–7 enlarged, slightly curved, spaced canines ending at bend in dentary, a single row of smaller conical teeth from symphysis to anterodorsal tip of coronoid process of dentary, additional short irregular inner row ending a little posterior to bend of dentary (description of teeth based on cleared and stained specimens). Tongue truncately pointed. Gill opening extending anteroventrally to below mid-pupil; gill rakers 2– 3 + 12– 14 –15 = 14– 17 –18 (mean 2.9 + 14.2 = 17.1, n = 20). Anterior nares a short tube reaching anteriorly to above anterior margin of upper lip, posterior opening porelike with raised rim, separated from bony front of orbit by 3– 4 times its diameter (mean 3.6, n = 8), nasal sac raised and on anterior one-third of snout. Bony interorbital 68– 85 % (mean 74.5%, n = 11) pupil diameter; shallowly concave with slightly raised median fleshy ridge forming broadly rounded W in cross section; epaxialis extending anteriorly to point above posterior of pupil. Caudal peduncle depth as percentage caudal peduncle length 28.6–42.7 (mean 36.8, n = 11); head length as percentage SL 30.4–33.5 (mean 31.8, n= 17); as percentage head length, horizontal eye diameter 32.2–38.5 (34.6, n = 17); snout length 20.8–27.7 (mean 24.1, n = 17), cheek depth 9.0–15.9 (mean 12.4, n = 14). Cephalic sensory papillae as in Fig. 24 , number of papillae in each row given in Table 2 , occasional supernumerary papillae may be present. Abdominal/caudal vertebral transition Type A, with haemal arches of first two caudal vertebrae expanded (based on 4 cleared and stained specimens).

Colour pattern. Live ( Fig.25 A). Sulawesi specimens overall reddish with a greenish-gold tinge dorsally below dorsal fin bases, dark blotch over width of end of peduncle and onto bases of caudal fin rays where it grades to dark red posteriorly, slate-blue lateral stripe tapering anteriorly and continuing over top of eye, constricted over dorsal margin of pupil to form two rounded spots connected by thin stripe, specimen on left of Fig. 25 A with dorsoventral expansion of stripe to form light peduncular bar just anterior to dark blotch, lateral stripe somewhat expanded dorsally below beginning and end of second dorsal fin, top of snout orange-red with no central blue stripe, lower half of head just below eye abruptly white, which continues posteriorly over abdomen, a light spot at top of pectoral fin base, an orange stripe in anal and dorsal fins at middle of height, caudal fin with traces of yellowish stripes in membranes, other fins apparently hyaline.

Freshly collected. Only one image available (from Palau), specimen distorted with right eye displaced downwards and inwards into buccal cavity, and gut extruded from body cavity between pelvic and anal fin bases ( Fig. 25 B). Head, lips and anterior nape reddish with some dark, round melanophores, except below line bounded by horizontal limb of preopercle, where white, opercular region and abdomen red with liberal sprinkling of large, dark brown, irregularly rounded chromatophores ending at pupil-diameter sized white band containing a few dark melanophores across peduncle anterior to caudal blotch; dorsum varying from off-white to reddish- or yellowishbrown, with scattered dark chromatophores and some scale pockets outlined with small round black melanophores, becoming lighter in region above mid-lateral septum; an approximately pupil-diameter dark blotch made up of both amorphous dark and more clearly rounded and even darker melanophores on a red background on posterior peduncle, extending onto bases of caudal fin rays. Dorsal fin elements reddish, no apparent colouration in membranes of any fin (other than extension of caudal blotch onto bases of caudal fin rays).

Preserved. (Note: specimens which have lost scales tend to have a somewhat distorted colour pattern). Body pale straw-yellow, head with four diffuse round to oval groupings made up of small rounded black melanophores around eye at the 3, 4:30, 6 and 9 o’clock positions (circumscribed by red ovals in Fig. 26), a few slightly larger black rounded and diffuse brown melanophores on cheek, and few of latter on side of snout and on lips. Pigment on top of snout primarily of small, round dark brown to black melanophores ( Fig. 24 B), with scattered larger, brown, amorphous pigment cells anteriorly, and more or less confined to central ridge in interorbital region. Posterior edges of scale pockets on nape and dorsal margin of pectoral fin base with small black round melanophores, a few irregular brown pigment cells on nape and opercle, becoming more concentrated on lower pectoral fin base and between it and pelvic fin origin. On body ( Fig. 27 ), posterior margins of scale pockets above midlateral scale row with diffuse bands of small black rounded melanophores with a scattering of larger, light brown amorphous pigment cells more concentrated near the dorsal margin, midlateral scale row with a few small rounded black melanophores on dorsal half and even fewer large light brown irregular pigment cells on ventral half; body below midlateral scale row with only latter pigmentation with number of cells decreasing towards ventralmost scale row. Caudal spot as for fresh specimen, but red colouration not apparent and at least some of pigmentation appears to be internal.

Etymology. The name corerefum is an arbitrary combination of letters reflecting the Coral Reef Research Foundation in Palau. This organization, established and operated by Pat and Lori Colin, has not only spearheaded marine research in Palau through the efforts of its founders, but has also provided laboratory and research facilities while acting as a home away from home for innumerable scientists working on marine organisms of the Palauan Islands for almost a quarter of a century. The name is to be treated as a noun in apposition, and is pronounced “core-ref-um”.

Distribution. Based only on material examined in this study, the range of T. corerefum is, with two exceptions, confined to sheltered outer reefs in the central one-third of the main archipelago of the Palauan islands, from off Ulong Island in the south-west to Uchelbeluu Reef in the north-east ( Fig. 11 ). It was not collected during a three week expedition to the South West Islands of Palau, nor at any other localities in the main islands. Two formalinfixed specimens, identified by morphology only, were collected on the north coast of Bunaken Island, northern Sulawesi. Three tissue samples from Liang (on the south coast of Bunaken Island) were analysed for COI, and nest within the 38 tissue samples of T. corerefum from Palau. Six formalin-fixed from Siquijor Island, Philippines, were identified as this species (see “Other Material” above). It appears to prefer depths of 12– 30 m.

Comparisons. See under Trimma tevegae for differences between various similar-looking species.

Discussion. Females of this species appear to reach a larger maximum size than the males (17.2 vs. 14.6 mm SL in the type series). The largest specimen, an 18.6 mm SL female, is from the Philippines, as is the largest male (16.6 mm SL). Too few males were available to permit testing for sexual dimorphism in the length of the second dorsal spine of the first dorsal fin.

Figures

FIGURE 11. Map of the distributions of the Trimma tevegae subgroup. Inverted triangle = T. burridgeae; square = T. caudomaculatum; triangle = T. corerefum; diamond = T. hollemani; circle = T. tevegae. Pink fill = tissue specimens available; blue fill = formalin-fixed specimens only; green fill = literature / photographic records only.

FIGURE 24. Trimma corerefum, head papillae. A: left lateral view, 15.2 mm SL female, ROM 99084; B: dorsal view, 16.3 mm SL female, ROM 74795; C: ventral view, as for A. Papillae in a given row joined by yellow lines. Photos by R. Winterbottom.

FIGURE 25. Trimma corerefum. A: Live specimens, Liang, Bunaken, Sulawesi. B: Freshly collected, lateral view of 14.4 mm SL female paratype, ROM 80390, Uchelbeluu Reef, Palau. Note displacement of right eye below left eye, and extruded gut between pelvic and anal fin bases. Photos: A by M. V. Erdmann, B by R. Winterbottom.

FIGURE 27. Trimma corerefum, 16.3 mm SL female, ROM 74795, Uchelbeluu Reef, Palau, left lateral view of flank. Diffuse violet areas denote missing scales. Photo by R. Winterbottom.

FIGURE 31. Trimma hollemani, preserved specimens. A: Left lateral view of body, 27.6 mm SL male paratype, ROM 85341, Raja Ampat; B: dorsal view of snout pigmentation, 17.4 mm SL male paratype, ROM 85256; C: dorsal view of snout pigmentation, 17.1 female paratype, ROM 84886. Photos by R. Winterbottom.