Trimma caesiura

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 : 19-21

Trimma caesiura Jordan & Seale, 1906

Caesiura Pygmygoby

Figs. 1 A, 6–7, Pl. 1 D

Trimma caesiura Jordan & Seale, 1906:391 (Apia, Samoa); Masuda et al., 1984:245 (Ryukyu Ids); Burgess et al., 1990:577; Shao et al., 1992:311; Myers, 1999: pl. 163; Hayashi & Shiratori, 2003:34 (x 2); Allen et al., 2004:330; Senou et al., 2004:101 (x 2); Randall, 2005:552 (photo from Palau); Aizawa, 2006:8; Allen & Erdmann, 2012:935 ( Japan to Samoa). Trimma caesiurum: Motomura et al., 2013:334 ( Japan) .

Trimma naudei (non Smith 1957): Shen, 1984:124 ( Taiwan); Fourmanoir & Laboute, 1985:143; Myers, 1999:pl.163.

Material. Hundreds of specimens, from southern Taiwan and the Ryukyus to Samoa via Palau, Great Barrier Reef, New Caledonia and Fiji to the west and northern Marianas and Marshalls to the east. The great extent of the holdings we have examined has prompted us to simply list the localities other than the Australian material with the acronym of the institution in which they are housed.

Australian Material. Queensland: Ashmore Reef: AMS I.33743-061, 8(8–16), 3– 13 m. Boot Reef: AMS I.33744-059, 9(8–16), 14–17 m; AMS I.33749-127, (15), 2– 6 m. Holmes Reef: AMS I.30465-114, 14(12.9–24.5), 10m; WAM P. 28541.043, 4(20–22), 12–14 m; WAM P. 29627.038, 17(17–26), 7– 8 m. Lihou Reef: WAM P. 29641.004, 3(19–23), 20– 23 m. Portlock Reef: AMS I.33752-059, 2(8–14), 12–16 m; AMS I.33751-070, 7(8–14), 5– 31 m. Lord Howe Rise: Elizabeth Reef: AMS I.27152-033, (23), 18 m.

Other material. Fiji: Bega Lagoon: AMS. Great Astrolabe Reef: ROM. Lau Group: USNM. Rotuma: USNM. Viti Levu: AMS, ROM. Yasawa Group: ROM. Japan: Ishigaki Id: BPBM. Iriomote Id: NSMT. Kiribati: Abaiang Atoll: AMS. Marianas: Guam: UGM. Maug Atoll: UGM. Marshalls: Bikar: USNM. Bikini: USNM. Enewetok: AMS, BPBM, USNM. Majuro: USNM. Rongelap: USNM. Micronesia: Kapingamarangi Atoll: CAS. Ifalik Atoll: CAS. Soral Atoll: CAS. Truk: AMS, BPBM. Ponape (= Pohnpei): CAS, USNM. Ulithi Atoll: AMS, BPBM, CAS. Yap: CAS. Niue: NMNZ. New Caledonia: Isle Puen: ROM. Vanuatu: Espiritu Santos: USNM. Futuna Id: AMS. Palau: BPBM, CAS, ROM. Philippines: Batan Id: USNM. Samoa: Upolu, (Apia): USNM 51772, (27 mm SL), holotype. Tuituila Id: USNM, AMS, BMNH. Rose Id: USNM. Solomons: Guadalcanal: ROM. Taiwan: southern part: BPBM, ROM, USNM.

Diagnosis. A species of Trimma with 7–9 predorsal scales; very deep, vertically-sided trenches between and posterodorsal to the eyes in adults ( Fig. 1 A); the second dorsal spine only slightly longer than the third; a uniformly dusky cheek without darker blotches or bars, sometimes with two narrow white bars below the eye; no dark bar on the base of the pectoral-fin and no fleshy lappets on the nape.

Description. Description based on 10 cleared and stained specimens (ROM 989CS, 11.2–23.9 mm SL) from the Great Astrolabe Reef, Fiji; other data from 10 specimens from Anguar Island, Palau (ROM 80560, 16.9–23.2).

Dorsal fin VI + I 8 (once 9, n = 20), second spine slightly longer than third but not elongated, reaching to between bases of spine to second fin ray of second dorsal fin when adpressed, first dorsal-fin ray usually unbranched (branched in 2 of 18), seventh ray usually longest and reaching posteriorly for two-thirds (half to almost full) length of peduncle; anal fin I 8, first anal-fin ray unbranched (branched in 1 of 16), seventh ray usually longest and reaching posteriorly for two-thirds (half to almost full) length of peduncle; pectoral fin 16–18 (mean = 16.8, n = 20), variable number of branched rays, none branched in specimens below about 16 mm SL, 3–6 dorsal (mean = 3.8, n = 18) and 2–6 (mean = 5.1, n = 16) ventral unbranched rays in larger specimens; pelvic fin I 5, fifth ray branched once dichotomously and 48–61% length of fourth (mean = 53.9, n = 10), fourth ray reaches posteriorly to base of first to fourth anal-fin element, rays 1–4 branched once sequentially, no fraenum, basal membrane absent or up to 7% length of fifth ray. Lateral scales 23 (n = 10); transverse 6 (once 7, n = 10); predorsal scales 7–9 (mean = 7.9, n = 10), first predorsal scales often somewhat larger than succeeding scales and cycloid; cycloid scales on midline of belly, breast, pectoral-fin base and opercle; rest of scales ctenoid; dorsal part of opercle of adults with a single horizontal row of 2–3 scales; pectoral-fin base margined by 3–4 scales (mean = 3.7, n = 6), middle scale largest; 4–5 (mean = 4.8, n = 8) prepelvic scales in midline. Outer row of teeth in both jaws of enlarged, curved, spaced canines, decreasing in size posteriorly, followed by several irregular rows of conical teeth about one-third the height of outer teeth. Innermost row of upper jaw teeth may be enlarged as far as bend of premaxilla. Enlarged teeth in outer row of lower jaw end at bend of dentary, those of innermost row are enlarged and about two-thirds the height of outer row, with teeth closest to symphysis about same height as outer row, and continuing posteriorly to coronoid process. Tongue narrow and rounded, half-pupil diameter in width. Gill opening extends anteroventrally to below middle of pupil; outer gill rakers of first gill arch 3–4 + 14–16 = 17–19 (means = 3.1 + 15.3 = 18.4; n = 19). Anterior nares a short tube, posterior nares pore-like with a raised rim, nasal sac slightly elevated, with nasal apparatus confined to anterior half of snout. A deep interorbital groove with vertical sides between and posterodorsal to eyes ( Fig. 1 A), best developed in adults; bony interorbital width less (26–39, mean = 31, n = 5) than pupil diameter; epaxialis inserting on bony flange that forms posterior wall of the interorbital/postorbital trenches. Vertebral pattern Type B.

Colour pattern. Live and freshly collected. Based on colour slides of freshly collected specimens from Fiji – including Rotuma (x 3), Coral Sea, Marshalls, New Caledonia, Palau ( Fig. 7 ) and Taiwan, and live specimens from Fiji, Guam, Japan, Palau, Philippines, Saipan (Pl. 1 D), Ulithi Atoll and Vanuatu. A red-brown to brick-red fish with silvery lines and spots. Upper half of body with a mixture of red and brown chromatophores and melanophores; scales below midlateral line with pockets strongly outlined with red and brown chromatophores and melanophores, and centres light; a zig-zag silvery-white line irregularly margined with melanophores beginning behind posterodorsal margin of eye and continuing to fifth dorsal-spine base, crossing midline at points just behind eye, at mid-nape, just anterior to origin of spinous dorsal fin and at base of fifth dorsal spine; silvery-white, pupilsized spots with irregular black margins centred on bases of spine of second dorsal fin and seventh dorsal-fin ray; a similar, but medial, spot half way along peduncle and another at bases of upper caudal-fin rays. A smaller white caudal spot as a ventral counterpart to upper one. Cheek and snout with red to reddish-brown chromatophores, mixed with melanophores. Some specimens with a short white bar on cheek below pupil, and second, slightly oblique such bar may be present from posterior margin of orbit. Iris red. Elongate spots may be present on bases of dorsal fin elements, and the second dorsal fin may have rows of similar or more rounded spots more distally in fin. Body colouration continues onto the bases of the more medial caudal fin rays, and a diffuse yellow to orange-red crescent may be present both above and below this just distal to bases of upper and lower caudal fin rays. An oval, silvery spot, a little less than pupil-diameter in width, on dorsal base of pectoral fin, often with another smaller white spot on ventral base of same fin. Body of live specimens translucent, but with same colour pattern.

Preserved: The same pattern remains, but reds and browns no longer apparent. Note that pattern may be disrupted in specimens that have lost their scales.

Etymology. Not given. Apparently derived from the Latin “caesio”, a cut, and the Greek “oura”, a tail. This compound word is a noun, and we retain it here in its original orthography as a noun in apposition.

Distribution. Found at most of the Melanesian and Micronesian islands ( Fig. 6 ), north to the Ryukyu Islands, west to the southern Philippines and central South China Sea (Pratas Reef), the northern Philippines, eastern Papua New Guinea and the Great Barrier Reef north of about 15˚S.

Comparisons. Trimma caesiura belongs to a species complex defined by the presence of predorsal scales and vertically-walled and deep interorbital and posterodorsal orbital trenches. These trenches were hypothesized to be independently derived from the similar looking trenches in Priolepis eugenius ( Jordan & Everman 1903), a Hawaiian endemic ( Winterbottom & Burridge 1989:2402). The species complex was revised by Winterbottom & Villa (2003), who included T. mendelssohni ( Goren, 1978) from the Red Sea and western Indian ocean (distinguished by a pair of fleshy nape lappets and pelvic rays branched 3–5 times); T. lantana from Australia, Solomons, New Guinea and southern Indonesia (which has an elongated second spine and dark spots on the cheek and opercle, and a yellow caudal peduncle and fin); T. naudei from the western Indian ocean through Indonesia and the northern Philippines to Japan (distinguished by an elongated second dorsal spine in the first dorsal fin and a dark bar or blotch over the pectoral-fin base), and T. winterbottomi from the Persian Gulf to the west coast of Thailand (distinguished by the lack of scales in the predorsal midline, two dichotomous branch points in the fifth pelvic-fin ray, and a small dark spot above the posterodorsal margin of the opercle). Trimma unisquame differs in having seven dorsal fin rays, the walls of the interorbital trench lined with ctenoid scales, (usually) a single scale on the cheek and none in the prepelvic region, and black margins to the dorsal fins.

A DNA analysis of the cytochrome c oxidase I gene included five specimens (2 from Palau, 3 from New Caledonia). The phenetic (genetic distance) network groups these specimens together, with a within group variance of 0.9% of the CO1 genome ( Winterbottom et al., 2014).

Discussion. Two specimens, one in excellent condition, the other in very poor condition (USNM 295234), were identified as this species. The bottle label states " Indonesia, Netherlands Indies, Longley". We have some reservations about the accuracy of this locality information given the apparent absence of T. caesiura from most of the Philippine and Asian plates, and its marginal presence on the eastern edge of the Australian plate. Longley is known to have made collections of fishes at Samoa in 1926-27, although none of his specimens has yet been found with Samoan locality data ( Springer, 1971:43). Samoa is the type locality of T. caesiura , and we suspect these specimens were collected there.

Trimma caesiura has been informally referred to as Trimma DFH 8. The species is known from depths of 1–50 m, normally in depths of less than 10 m. In Australia it is found only on clean water reefs on islands of the outer Great Barrier Reef, the Coral Sea and Timor Sea. The largest specimen from Australian waters that we examined was 23 mm SL; elsewhere the species can reach 33 mm SL.

Figures

FIGURE 1. Dorsal view of heads of A: Trimma caesiura, (26.3 mm SL male, ROM 64124, New Caledonia) to show fleshy interorbital width and interorbital and postorbital trenches; B: T. hoesei (21.7 mm SL female, ROM 83303, Palau) to show wide fleshy interorbital and fleshy median interorbital ridge. Photos by R. Winterbottom.

FIGURE 6. Map of the distributions of Trimma benjamini (solid squares) and T. caesiura (solid stars). A black diamond indicates localities at which both species occur.

FIGURE 7. Trimma caesiura, 21.5 mm SL male, ROM 74988, Palau. Photo by R. Winterbottom.