Trimma kalum, Winterbottom, 2020

Winterbottom, Richard, 2020, A new species of Trimma (Pisces: Gobiidae) from the northern Palauan Islands western Pacific Ocean, Zootaxa 4808 (3), pp. 582-588 : 583-587

Trimma kalum new species

Beautiful Pygmygoby

Figs. 1–3 .

Trimma sheppardi —non Winterbottom 1984:709 (Chagos Archipelago); Winterbottom 2019:48 ( Palau reference only, including Fig. 107a).

Material examined. Holotype. ROM 80355, 17.0 mm SL male, Palau, Koror State, Uchelbeluu Reef (aka Short Drop-Off), 7.27355, 134.02405, cave in steep reef slope, 73 m, quinaldine, 28 Mar., 2006, field # RW06-14, P. Colin.

Paratypes. AMS I.17936-003, 13(11.5–16.0), Palau, Ngemelis Group , Bailechesengel Island (aka Bairakaseru I.), approx. 7.104438, 134.25178, 40–53 m, 20 Feb., 1972, G. R. Allen & W. Starck. Includes a single, 15.5 mm SL male cleared and stained specimen .

Diagnosis. A species of Trimma with scales absent from the cheeks, opercle, and nape between the pectoral-fin base and the mid-base of the first dorsal fin, an elongate second dorsal spine reaching to the base of the 2 nd– 10 th ray of the second dorsal fin when adpressed, 17–18 pectoral-fin rays with 12–13 branched rays in the middle of the fin, a single dichotomous branch point in the 5 th pelvic-fin ray, which is 51–75% the length of the 4 th ray, 17–18 total gill rakers, 5 papillae in row c below the eye, a very well developed dermal crest in the midline between the base of the first dorsal spine and the posterior interorbital region, a U-shaped bony interorbital with no median fleshy ridge, and virtually no postorbital trench, which ends at or before papilla 5 in row p. When freshly collected, the new species has an overall yellow body grading to broad yellow and white bars/spots posteriorly, with two consecutive dark brown spots above the opercle, and three half pupil-width slanted yellow bars across the cheek.

Description. The description is based on the holotype and 13 paratypes. Dorsal fin VI + I 10– 11 (10.8, 14; Figs. 1–2 ), second spine reaching to base of 2 nd– 7 th –10 th fin-ray of second dorsal-fin, third dorsal spine reaching posteriorly to base of spine– 2 nd –5 th dorsal fin-ray, first ray of second dorsal fin branched or unbranched, remaining fin rays branched except for posterior element of last ray, which reaches posteriorly 53– 65 –78% (63.3%, 9) distance between its base and first exposed dorsal procurrent caudal-fin ray; anal fin I 9 –10 (9.8, 14), first two rays unbranched or branched, last ray reaching posteriorly 48– 60.1 –70% (60.0%, 9) distance between its base and first exposed ventral procurrent caudal-fin ray; pectoral fin 17– 18 (17.9, 14) with 3 dorsal and 2– 3 ventral unbranched rays and 12 –13 branched rays in central portion of fin, fin reaching posteriorly to vertical above urogenital papilla to base of 3 rd anal ray; pelvic fin I 5, fifth ray branched once dichotomously and 51– 62 –75% (61.1%, 12) length of fourth ray, which reaches posteriorly to base of 2 nd –5 th anal fin-ray, pelvic rays 1–4 with single sequential branch point; basal membrane forming fold across midline posterior to last pre-pelvic scale, about 8– 10 % length of 4 th pelvic-fin ray (8.6%, 9); no fraenum. Lateral scales 24– 26 (25.2, 11); anterior transverse scales 10– 13 (12.1, 10); posterior transverse scales 9–11 (10.4, 9); cheek, opercle and predorsal midline scaleless; anteriormost extent of scales to a line between middle of first dorsal fin and pectoral-fin base; 4 vertical rows of cycloid scales on pectoralfin base with 2 in anteriormost row, 3 (once 4) in second row and 5 in outer two rows (once 6 in outermost row); 7– 8 (7.4, 8) cycloid scales in midline anterior to pelvic-fin base; area between pelvic spine and ventral margin of pectoral-fin base with cycloid scales; anterior few rows of scales in midline of belly cycloid; anteriormost row of body scales beneath axil of pectoral-fin base of either cycloid or ctenoid scales. Circumpeduncular scales 12, scale rows in midline between base of last anal ray and first ventral procurrent caudal-fin ray 8– 9 (8.7, 7). Upper jaw with outer row of spaced, enlarged curved canines to distal end of premaxilla, space between adjacent teeth about equal to canine height, gradually decreasing in size posteriorly; several irregular rows of small conical teeth behind outer teeth, gradually decreasing in size and becoming reduced to single row, continuing posteriorly to distal tip of premaxilla; innermost few teeth near symphysis slightly larger and posteriorly oriented. Lower jaw with 3–5 enlarged, spaced, curved canines in outer row to bend of dentary, space between adjacent teeth about equal to canine height; 2–3 irregular rows of slightly curved small teeth at symphysis to dentary bend; innermost row half-length of outer and reaching posteriorly to dorsal rim of coronoid process. Tongue narrow, with broadly pointed or rounded tip. Gill opening extending anteroventrally to below mid-pupil; gill rakers 3– 4 + 13– 14 = 17– 18 (3.8 + 13.8 = 17.6, 13). Anterior naris in short tube reaching anteriorly to above anterior margin of upper lip, posterior opening porelike with raised rim, separated from bony front of orbit by 1.5 –2 times its diameter, nasal sac raised and on anterior one-third of snout. Bony interorbital width 39– 40 –53% (45.0%, 10) pupil diameter; moderate U-shaped interorbital trench with no median raised fleshy ridge; narrow, poorly developed postorbital groove ending between papillae 4-5 of row p ( Fig. 3 B ); epaxialis reaching anteriorly in midline to vertical above posterior margin of pupil; well-developed narrow dermal ridge in midline of nape extending anteriorly from origin of first dorsal fin to above posterior margin of pupil ( Fig. 3A ). Caudal peduncle depth as percentage of caudal peduncle length 45.9– 46.6 –60.7 (50.8, 10); head length as percentage of SL 31.7 –34.4 (32.6%, 10); as percentage head length: horizontal eye diameter 31.3– 34.7 –37.9 (34.3%, 10); snout length 19.8– 22.3 –23.7 (22.2%, 10); cheek depth 22.7– 29.7 –30.2 (27.4%, 10). Cephalic sensory papillae as in Fig. 3 . Number of papillae in each row: a = 6; b = 6– 7 –8 (7.1, 14); c = 5; cp = 1; d = 7 –9 (7.6, 14); dʹ = 8 –10 (8.6, 14); e-anterior = 12 –18 (15.7, 13); e-posterior = 12 –18 (15.5, 13); i-anterior = 7 –9 (8.4, 13); i-posterior = 8 –9 (8.2, 13); p = 6; r = 2; f = 3 –4 (3.5, 13); cs ″ = 3; g = 7– 9 (8.5, 11); n = 1; x = 5 –6 (5.1, 14); u = 5; z = 5– 6 (5.7, 13); ot = 13– 14 –15 (13.6, 14); os = 5– 6 (5.7, 11); oi = 3 –4(3.8, 12). Caudal fin of holotype with 3 dorsal and 2 ventral segmented unbranched rays, and 6 dorsal and 6 ventral branched rays (apparently the postero-ventral segmented unbranched ray is branched); other specimens with 3 ventral segmented unbranched and 5 ventral branched rays. Abdominal/caudal vertebral transition type B, although separation of two haemal canals on first caudal vertebra poorly developed (based on single cleared and stained paratype).

Colour pattern. Live, based on 35 mm colour slide by Hiroshi Nagano ( Fig. 1 ). Yellow nape and trunk grading to diffuse yellow and translucent bars/spots posteriorly, last one a pupil-diameter yellow spot with a few black melanophores over ural complex, bipartite dark spot above the opercle/pectoral base, each a little larger than pupil-width in diameter, anterior half mostly dark red with numerous black melanophores and above posterodorsal margin of opercle, second spot just posterior to attachment of opercular membrane to body dorsally, made up mostly of melanophores, three approximately pupil-width slanted yellow bars on cheek, first below anteroventral eye to end of maxilla, second from otic region to interopercle below middle of eye, third slanted over posterior margin of vertical limb of preopercle. Diffuse, yellowish stripe along base of dorsal-fins, fin membranes translucent. Anal fin with very diffuse yellow suffusion basally. Caudal fin with two or three vague, somewhat oblique, yellow stripes formed by yellow spots on fin rays. Iris yellow speckled with a few melanophores, with diagonal cerise stripe from anteroventral to posterodorsal across middle of eye and diffuse cerise stripes along dorsal and ventral margins, a large patch of melanophores below pupil. Posterodorsal region of nape immediately behind eye suffused with pinkish red.

Freshly collected, based on 35 mm colour slide of the holotype ( Fig. 2 ). Very similar to live colouration, but yellow nape and trunk grading to broad yellow and white bars/spots posteriorly, two dark brown spots in a row above the opercle/pectoral base, each about half pupil-width in diameter, with numerous black melanophores, anterior spot above posterodorsal margin of opercle, second spot just posterior to attachment of opercular membrane to body dorsally (see Fig. 3 A , dashed yellow ovals), three slanted yellow bars on cheek about half pupil-width. A few scattered melanophores on upper pectoral-fin base. Diffuse, elongate yellowish spots on dorsal-fin spines and anterior rays just distal to their bases, fin membranes with iridocytes and tiny black melanophores. Anal fin with yellow suffusions. Caudal fin with two vague, somewhat oblique, yellow stripes. Iris yellow speckled with small melanophores, with diagonal purple stripe from anteroventral to posterodorsal across middle of eye and diffuse purple patches along dorsal and ventral margins. Posterodorsal region of nape immediately behind eye, and area above two dark spots suffused with pinkish red.

Preserved. Pale straw-yellow, no trace of colouration except for concentration of small black melanophores representing the two shoulder spots, and a very light sprinkling of tiny black melanophores on nape and anterior body.

Etymology. From the Greek word “kalos” (καλός), meaning beautiful, in reference to the delicate colouration of the new species. This species has been informally known as Trimma RW sp 47 or T. DFH sp 23.

Distribution. Currently positively recorded only from the deep (40–73 m) drop-offs in the main islands of Palau.

Comparisons. The new species splits the identification key of Winterbottom (2019) at couplet 102. Trimma kalum is almost identical in live/fresh colouration to T. sheppardi Winterbottom 1984 , sharing the overall yellowto-red head and body with faint dark internal blotches along the vertebral column, a dark horizontal “double spot” above the end of the opercle, and three slanted yellow-to-red bars on the head ( Fig. 4 ). However, these two species differ substantially in morphology: the second spine of the first dorsal-fin is more elongate and reaches the base of the 2 nd– 10 th fin-ray of the second dorsal fin in T. kalum (vs. to the spine-to-3 rd fin ray in T. sheppardi ), 10–11 fin-rays in the second dorsal fin (vs. 8–9), scales not extending anterior to a line between the middle of the first dorsal-fin and the pectoral-fin base (vs. 1–2 scale-widths behind eye), a trough in the interorbital with no central fleshy ridge (vs. ridge present), a long dermal crest in the midline between the posterior margin of the pupil and the origin of the first dorsal-fin (vs. to the posterior margin of the eye), 5 (vs. 6) papillae in row c, and 6 (vs. 7) papillae in row p. No other species have the dark markings above the posterior part of the opercle split into two sub-equal spots. However, four other species do have a single discrete dark spot in approximately this position— T. agrena Winterbottom & Chen 1984 , T. fangi Winterbottom & Chen 1984 , T. stobbsi Winterbottom 2001 and T. winterbottomi Randall & Downing 1994 . None of these has an elongate second dorsal-fin spine, nor do any of them have yellow-to-red bars across the cheeks. Only T. stobbsi has 5 papillae in cheek row c (the other three species have 6 or 7 such papillae) and a dermal crest, which only reaches anteriorly to within two scale widths of the posterior margin of the eye (vs. to posterior margin of the pupil in T. kalum ).

Discussion. The holotype of the new species was taken from a cave in 73 m that produced most of the type specimens of T. gigantum Winterbottom & Zur 2007 . This collection also contained specimens of another undescribed species allied to T. xanthochrum Winterbottom 2011 , but lacking the dark caudal spot. Collections from below about 50 m invariably contain undescribed species of Trimma . While numerous such collections have been made in the western Pacific (especially by M.V. Erdmann), virtually none has been made in the Indian Ocean, and it will be extremely interesting to see what species they contain. For example, a photograph taken in a cave off Mayotte in the western Indian Ocean by Patrick Plantard shows specimens of what appear to be T. nomurai Suzuki & Senou 2007 . If correctly identified, this would represent the first record of that species from the Indian Ocean.

Figures

FIGURE 1. Trimma kalum live, Palau. Photo: Hiroshi Nagano.

FIGURE 2. Trimma kalum fresh, 17.0 mm SL male holotype, ROM 80355, Palau. Photo by R. Winterbottom.

FIGURE 3. Trimma kalum, 17.0 mm SL male holotype, ROM 80355, Palau. Left lateral (A) and dorsal (B) views of head to show head papillae, specimen stained with cyanine blue. Papillae rows connected by thin blue lines. Two dark spots above opercle in A delineated by yellow dashed ovals. Photos by R. Winterbottom.

FIGURE 4. Left lateral view of: A) Trimma sheppardi, 17.6 mm SL female paratype, ROM 41222, Chagos Archipelago, central Indian Ocean. B) Trimma sheppardi, 15.0, WAM P.33357-008, Cenderawasih Bay, West Papua, G. R. Allen.