Trimma anthrenum, Richard Winterbottom, 2006

Richard Winterbottom, 2006, Two new species of the gobiid fish Trimma from the coral reefs of the western Pacific Ocean (Pisces; Perciformes; Gobioidei)., Zootaxa 1331, pp. 55-68 : 56-61

Trimma anthrenum n. sp.

(Figs. 1-3, 4A)

Suggested common name: Honey-bee pygmy goby

Material examined

A total of 14 lots, 48 type specimens, 10.2-20.4 mm SL, from Fiji and Tonga.

Holotype: ROM 60677, 18.7 male, Tonga, Vava’u, southwest side off Mo’ungalafa mountain at latitude of Tu’ungasika islet, 18°39'30"S, 174°00'90"W, 37-40 m, J. Randall and K. Okamoto, 18 Mar 1983.

Paratypes: Fiji Islands: BPBM 40401, 1(16.2), Viti Levu Group, Viti Levu Island, Suva, outside of Suva Harbor, “Fish Patch”, 18°09'37"S, 178°23'57"E, vertical reef dropoff with vertical grooves and small holes and many sea fans, 55 m, J. L. Earle and D. F. Pence, 29 Jan 2002. BPBM 40402, 3(14.2-17.1), Viti Levu Island, Suva, outside of Suva Harbour, 100 m south of “Fish Patch”, 18°09'37.8"S, 178°23'57.6"E, large cave near base of groove in reef drop-off, 70-76 m, R. L. Pyle and J. L. Earle, 1 Feb 2002. BPBM 40403, 3(11.2-17.8), Viti Levu Island, Suva, outside of Suva Harbor, south of “Fish Patch”, 18°09'37"S, 178°23'57"E, southern wall, vertical reef drop-off, 52-55 m, J. L. Earle and J. Dituri, 3 Feb 2002. ROM 46011, 2(14.7-16.5), Nairai Island, off Tuilailai, 17°48' 58S, 179°23'46"E, 9-11 m, A. R. Emery and L. Payne, 13 Mar 1983. ROM 46016, 2(15.3-18.8), Great Astrolabe Reef, 2.7 km north of Dravuni Island, bommie, 18°43'48"S, 178°32'17"E, 5-10 m, R. Winterbottom and collaborators, 2 Apr 1983. ROM 46018, 1(18.6), Great Astrolabe Reef, lagoon south of Dravuni Island, 18°46'38"S, 178°31'57"E, bommie, 30 m, R. Winterbottom and collaborators, 6 Apr 1983. ROM 79529, 2(14.4-19.7), North Astrolabe Reef, northwest corner of Herald Pass, 18°45'19"S, 178°28'19"E, on outer reef, 4.1 km northwest of Yanu-Yanu-Sau Island, 10-20 m, R. Winterbottom and collaborators, 2 Apr 1983. ROM 79593, 3(15.1-17.3), Great Astrolabe Reef, Herald Pass on outer reef, 4.1 km northwest of Yanu-Yanu-Sau Island, 18°45'08"S, 178°28'26"E, 27 m, R. Winterbottom and collaborators, 4 Apr. 1983. ROM 79721, 4(13.3-19.4), Viti Levu Group, Viti Levu Island, Suva, outside of Suva Harbor, “Fish Patch”, 18°08'00"S, 178°25'00"E, groove in vertical reef drop-off with small holes and cracks, 58-67 m, R. L. Pyle and J. L. Earle, 28 Jan 2002. ROM 79722, 3(15.9-17.9), Viti Levu Island, Suva, outside of Suva Harbor, “Fish Patch”, 18°08'00"S, 178°25'00"E, vertical reef drop-off with vertical grooves and small holes and caves, 67-75 m, R. L. Pyle and J. Dituri, 29 Jan 2002. ROM 79723, 1(17.3),, Viti Levu Island, Suva, outside of Suva Harbor, “Fish Patch”, vertical reef drop-off with vertical grooves and small holes and many sea fans, 52-55 m, J. L. Earle and D. F. Pence, 29 Jan 2002. Tonga: USNM 341467, 9(10.8-20.4), Vava’u Group, north side of Nuku Island at top of vertical drop-off on sloping rock/sand bottom, 18°42'53"S 174°02'37"W, 12-26 m, J. Williams and collaborators, 19 Nov 1993. USNM 341468, 13(15.0-20.0), Vava’u Group, Luamoko Island, north coast at vertical drop-off, small cave in face of wall, lots of coral, 18°40'55"S 174°06'09"W, 21-31 m, J. Williams and collaborators, 15 Nov 1993.

Diagnosis

Trimma anthrenum is characterized by the presence of scales in the predorsal midline, second and third dorsal spines either slightly or not elongate, an unbranched fifth pelvic fin ray, both interorbital and postorbital trenches moderately well developed, and the absence of opercular scales. The scale margins of preserved specimens are very finely outlined with melanophores across the top half of the body, which is otherwise almost devoid of visible pigment cells. When alive, T. anthrenum is yellow with a pair of blue/black inverted triangles with their bases against the anterior and posterior margins of the pupil, the posterior triangle continuing anteroventrally around the pupil margin (giving the pupil a slit-like appearance). Both living and preserved specimens have a dark basal stripe in the medial fins and a blaze of brown pigment on the upper portion of the pectoral-fin base.

Description

The description is based on the holotype and up to 28 paratypes. Dorsal fins VI + I 8 -9 (n=29, mean = 8.9), second and third spine not or very slightly elongate and not reaching the second dorsal fin when adpressed, rays branched except the first and/or last fin-ray; anal fin I 7 -8-9 (n=29, mean = 8.0), anal fin rays branched except the first and/or last fin ray; pectoral fin 16-18 (n=29, mean = 17.4) with 7-11 branched rays in the approximate centre of the fin, reaching posteriorly to a vertical line varying from in line with the genital papilla to the first few elements of the anal fin; pelvic fin I 5, no frenum, basal membrane no more than 10% of the length of fourth ray, often vestigial, first four rays with one sequential branch, fifth ray unbranched and 50-60% the length of the fourth, fourth ray reaching posteriorly in a vertical line varying between the second to sixth element of the anal fin. Lateral scales 23-26, (n=25, mean = 23.6), anterior transverse scales 6-7-8 (n=16, mean = 7.2), posterior transverse scales 6-7, (n=16, mean = 6.9); predorsal scales 2-7-9, (n=26, mean = 6.2), if fewer than six scales are present they are centred on the nape, often with naked areas before and after the scaled patch; 3-7 rows of cycloid scales on breast, 6-15 cycloid scales on pectoral base in 2-4 vertical rows, scales on the head extend to the postorbital trench, cheek and opercle scaleless. Gill opening extending anteroventrally to below the posterior margin of the pupil to mid pupil. Upper and lower jaws with an outer row of widely spaced enlarged canines with irregular inner rows of small conical teeth. Tongue round, or parenthesis shaped. Gill rakers on first arch 3-5 + 13-14-15 = 16-19, (mean =17.7, n=10). Anterior nasal opening a tube adjacent to upper lip, posterior opening a pore with a raised rim, both openings on a raised oval sac confined to the anterior half of the snout. Bony interorbital 1/4-1/3 pupil width, with moderately to well developed interorbital and postorbital trenches (both trenches deeper than wide), cephalic sensory papillae pattern as illustrated for T. preclarum , except that the two papillae in row r on the dorsal surface of the snout are better developed (all shown in Fig. 3).

Colour pattern (from slides of freshly collected specimens from Fiji, Figs. 1, 2): Background colour bright yellow with two somewhat darker brownish streaks on the posterior half of the body running above and below the midlateral septum, which extend onto the caudal peduncle. A pair of blue-black inverted triangle shapes, their bases against the pupil, occur at the anterior and posterior margins of the orbit, imparting the impression of a horizontally slit iris. The ventral margin of the posterior triangle continues around the anteroventral margin of inner edge of the iris. Nape sprinkled with melanophores. Scale pockets faintly outlined with melanophores. Red-brown pigment concentrated along the dorsal edge of the operculum and at the top of the pectoral base. A wide (half-pupil width), black basal stripe in the dorsal and anal fins, remaining portion of the fins yellow. Caudal fin primarily yellow, two pale streaks in centre of fin, tips of fin-rays hyaline. Preserved (ethyl or isopropyl alcohol): background colour straw yellow with scale pockets very finely outlined (often a single line of melanophores) across the dorsal portion of the body (Fig. 4A). Melanophores are scattered evenly on the snout. A loose collection of melanophores lies just above the opercle and there is a patch of them at top of the pectoral base; the cheek may have a scattering of melanophores or may be immaculate; the remainder of the body is virtually free of visible pigment cells. The thick black basal stripe in the dorsal and anal fins remains obvious, and the tips of fins may or may not have melanophores; the pectoral fins are hyaline.

Affinities

Trimma anthrenum is very similar to Trimma milta Winterbottom, 2002 and Trimma preclarum when preserved in alcohol. The three share many characteristics including nine dorsal-fin rays in the second dorsal fin, eight anal-fin rays in T. milta and eight or nine anal-fin rays in T. anthrenum and T. preclarum , a similar numbers of pectoral-fin rays, no scales on the cheek, a few scales on the pectoral base, and a dark basal stripe in the median fins. The body of T. milta is more heavily pigmented with high concentrations of chromatophores at the insertion points of the scales, a lighter area beneath each scale and then a band of melanophores at the outer edge of each scale (Fig. 4C). This often creates a rough pattern of half moons down the side of the body. Trimma anthrenum (Fig. 4A) and T. preclarum (Fig. 4B) are not as heavily pigmented and the scale pattern on the dorsal half of the body is outlined with melanophores to create a diamond pattern. This pattern in T. anthrenum is more finely defined when compared to T. preclarum , as each scale is usually only outlined by a single row of melanophores. Trimma anthrenum is also characterized by a line of melanophores just above the opercle and a patch of melanophores at the top of the pectoral base. In T. preclarum , a diffuse stripe of large, light brown chromatophores passes across the abdomen and fades out above the anal fin. All three have a background colour of straw yellow (although T. milta may often be reddish-brown, particularly the eastern populations). Pigment on cheek is often patchy, with lighter bars extending down from the eye in both T. preclarum and T. milta . In T. anthrenum , the cheek is often immaculate, or there may be a darker spot directly below the centre of the eye and another larger spot directly posterior to this. Trimma milta has a moderate sprinkling of chromatophores and melanophores on the opercle and pectoral base, but they are not evenly distributed. Trimma preclarnum has evenly spaced chromatophores and melanophores on the pectoral base and often a heavier concentration of pigment on the upper half of the opercle than the lower half, whereas T. anthrenum has very little pigment on the pectoral base except for the patch at the top of the base. When alive, T. preclarum has three yellow stripes, which extend down the body on a dirty white to grey background, and is easily distinguished from T. milta and T. anthrenum , which are more uniform in body colour, with T. milta either yellowish or a red brown with the centres of each scale being a lighter orange red colour. Trimma anthrenum is uniformly canary yellow. Slides of living T. preclarum show a bright red or cerise iris with four yellow spots compared to dull red iris seen in T. milta , while T. anthrenum has the blue and black triangles anterior and posterior to the pupil, and has a bold yellow stripe in each of the three medial fins. In T. milta , the yellow spots on the fin rays may or may not coalesce to form a yellow stripe in the medial fins, and in T. anthrenum the medial fins are yellow. All three species have a black basal stripe in the medial fins.

Trimma milta has two to three scales on the upper portion of the opercle, a very heavy body and a stubby face. Trimma anthrenum and T. preclarum have no scales on the opercle, a more slender body and a more pointed face. The spines of the first dorsal fin of T. milta and T. anthrenum are either not elongate or just slightly so, while the second and third fin spines of T. preclarum are often but not always elongate, reaching as far as the middle of the second dorsal fin. The postorbital trench of T. anthrenum (Fig. 3) is much better developed (deeper than it is wide) than that of T. preclarum (Fig 7 B) or T. milta (where it is wider than it is deep).

Distribution

Trimma anthrenum has been found at Fiji and Tonga Islands, at depths of between 5-76 m.

Etymology

From the Greek 'anthrene', a wild bee, wasp or hornet, in a perhaps fanciful allusion to the aposematic colouration of yellow with black stripes (at the bases of the dorsal and anal fins) that characterize the new species.

Trimma anthrenum has been referred to informally as Trimma RW sp 84 .