Trimma bathum, Winterbottom, Richard, 2017

Winterbottom, Richard, 2017, Two new species of Trimma (Pisces; Gobiidae) from Fiji, south-western Pacific Ocean, Zootaxa 4269 (4), pp. 559-570 : 560-564

Trimma bathum new species

Deep-reef Pygmygoby Figs. 1–2 .

Trimma RW sp. 97— Winterbottom et al., 2014:83

Material examined. Holotype. ROM 101384 (ex-BPBM 40009), 16.4 mm SL male, Fiji, Viti Levu , Suva, outer reef, S of " Fish Patch " southern wall, vertical reef drop-off, 18.16° S, 178.40° E, 52.5 m, rotenone , 3 Feb., 2002, J. L. Earle & J. Dituri, Field # RLP-FIJI02–015.

Paratypes. BPBM 39900, 15.5 mm SL, Fiji, Viti Levu , outside of Suva Harbour; beyond " Fish Patch ", directly off bow of old shipwreck on top of reef, vertical reef drop-off with small ledges and holes, 18.1642° S, 178.40° E, 83–91 m, rotenone, 31 Jan., 2002, J. L. Earle & J. Dituri, Field # RLP-FIJI02–009 . BPBM 41320 (ex-BPBM 39712), 12.5 mm SL, Fiji, Viti Levu , Suva, outer reef, " Fish Patch ", 18.15983° S, 178.3993° E, 57–67 m, rotenone, 28 Jan., 2002, R.L. Pyle & J.L. Earle, Field # RLP-FIJI02–001 . ROM 101385 (ex-BPBM 40009), 15.8 mm SL female, collected with the holotype.

Tissues (non-types): KU:KUI T4454 (ex-ROM T02300; ex-BPBM 39849) and ROM T02301 (ex-KU:KUI T4458, ex-BPBM 39849), 17.6 and 16.4 mm SL respectively, Fiji, Viti Levu, Suva, outside of Suva Harbour, beyond "Fish patch", directly off bow of old shipwreck on top of reef, vertical reef drop-off with a large diagonal crack and over-hang, with some sea fans, 18.16422° S, 178.4003° E, 67–70 m, rotenone, 31 Jan., 2002, J.L. Earle & D.F. Pence, Field # RLP-Fiji02–007.

Diagnosis. A species of Trimma with scales absent from the cheeks, opercle and predorsal midline, 18–19 unbranched pectoral fin rays, an unbranched 5th pelvic fin ray that is 40–56% the length of the 4th ray, 17–18 total gill rakers, a U-shaped interorbital and a narrow slit-like postorbital trench, a low, median fleshy ridge extending half-way towards the orbit from the origin of the first dorsal fin, and, when freshly collected, a pink head and body with most body scales having an orange-brown spot or short bar at their centres.

Description. The description is based on 4 specimens, 12.5–16.4 mm SL (mean =15.1) from 3 lots collected off Suva Harbour, Viti Levu, Fiji in 2002. An additional two specimens of this species were collected for analysis of the COI gene (see Discussion). Dorsal fin VI + I 8– 9 (mean = 8.8, n = 4), second spine slightly elongated, reaching to base of spine of second dorsal fin, first ray of second dorsal fin branched (n = 2) or unbranched (n = 2), remaining fin rays branched except for posterior element of last ray, which reaches posteriorly 68– 79 % (mean = 73.7%, n = 2) distance between its base and first exposed dorsal procurrent caudal fin ray; anal fin I 8– 9 (mean = 8.8, n = 4), first ray branched (n = 2) or unbranched (n = 2), last ray reaches posteriorly 65– 66 % (n = 2) distance between its base and first exposed ventral procurrent caudal fin ray; pectoral fin 18– 19 (mean = 18.8, n = 4), rays unbranched, fin reaching posteriorly to region above urogenital papilla to anal spine; pelvic fin I 5, fifth ray unbranched and 40 –56% (mean = 49.5, n = 3) length of fourth ray, which reaches posteriorly to between bases of second to fourth anal rays, pelvic rays 1–4 with a single sequential branch point; basal membrane apparently absent; no fraenum. Lateral scales 23 (n = 3); anterior transverse scales 9– 10 (n = 2); posterior transverse scales 8– 9 (n = 2); cheek, opercle and midline of predorsal without scales; anteriormost scale on side of nape reaching anteriorly to one scale width posterior to upper margin of eye; 3 vertical rows of cycloid scales on pectoral fin base with 1– 2 in anteriormost row, 4 in second row and 5 in outer row (n = 2); 6 cycloid scales in midline anterior to pelvic fin base (n = 2); area between pelvic spine and ventral margin of pectoral fin base, midline of belly and sometimes anteriormost row of body scales beneath axil of pectoral fin base with cycloid scales. Circumpeduncular scales 12, scales rows in midline between base of last anal ray and first ventral procurrent caudal fin ray 7 (n = 2). Upper jaw teeth: outer row of enlarged, curved, spaced canines, decreasing in size posteriorly to distal end of premaxilla, several irregular inner rows of small, short conical teeth near symphysis, number of rows decreasing to a single row at bend of jaw. Lower jaw teeth: outer row of enlarged, curved, spaced canines reaching to bend of dentary, several irregular rows of small conical teeth at symphysis, decreasing to single row of somewhat enlarged (½ height of outer teeth), slightly curved teeth reaching to coronoid process. Tongue truncate with rounded edges. Gill opening extending anteroventrally to below mid-pupil; gill rakers 3 –4 + 13– 14 = 17 –18 (mean = 3.5 + 13.8 = 17.3, n = 4). Anterior nares in short tube reaching anteriorly to above anterior margin of upper lip, posterior opening pore-like with raised rim, separated from bony front of orbit by 4 times its diameter, nasal sac raised and on anterior one-third of snout. Bony interorbital width 36.0– 39.5 % (n = 2) pupil diameter; moderate U-shaped interorbital trench and narrow, groove-like postorbital slit; epaxialis extending anteriorly to point above middle of pupil ( Fig. 1 B); narrow ridge of skin from origin of first dorsal fin extending along anterior midline of nape halfway to orbit. Caudal peduncle depth as percentage caudal peduncle length 52.3 –57.4; head length as percentage SL 32.1 –32.9; as percentage head length: horizontal eye diameter 37.4– 39.4; snout length 19.5– 22.3; cheek depth 20.2– 25.1. Cephalic sensory papillae as in Fig. 1 , number of papillae in each row given in Table 1. Abdominal/ caudal vertebral transition presumed to be Type B (inferred from the narrow bony interorbital width of less than 80% pupil-diameter).

Colour pattern. Freshly collected, based on photograph of two specimens saved as tissues ( Fig. 2 ). Head and anterior body pink, fading gradually posteriorly until almost translucent at end of caudal peduncle. Centres of most body scales with orange-brown spot or short bar, spots/bars may join each other, becoming a diffuse, slightly lighter wash dorsally and ventrally on peduncle. Second dorsal fin (and possibly anal fin) with a basal orangebrown stripe, posterior half of fin with similarly-coloured mottling. Caudal fin with ill-defined scattered lighter spots and blotches, about one-third pupil-diameter in size. Iris with narrow white ring around pupil, yellowishblack below pupil, and broad, very diffuse dark, pupil-width oblique stripe from anterodorsal to posteroventral across pupil.

Preserved. Holotype straw-yellow and faded, with fairly even scattering of very small melanophores on head and anterior nape (fewer on cheeks), none on ventral surface of head and abdomen. Melanophores also tend be concentrated along anterior margins of scale pockets on body so that they show through at middle of scale in front (note: most body scales have been abraded off specimens), melanophores decreasing in number posteriorly. A few slightly larger melanophores along base of second dorsal fin which may indicate a basal stripe in life. Paratypes similar, but with few small melanophores on lips and ventral surface of head.

Etymology. From the Greek word ‘bathos’ (βάΘος), meaning deep or deep water, in reference to the depth at which these specimens were collected (50–90 m). The name is treated as an adjective in the nominative singular.

Distribution. Currently recorded only from the Fiji Islands in the vicinity of Suva, Viti Levu.

Comparisons. The colour pattern combination of a pink head and body with orange-brown spots/short bars in the centres of the scale rows on the body is unique to T. bathum . Four other valid species of Trimma lack predorsal, cheek and opercular scales, and have unbranched pectoral and 5th pelvic fin rays [ T. anaima Winterbottom, 2000 ; T. grammistes ( Tomiyama, 1936) ; T. sanguinellus Winterbottom & Southcott, 2007 ; and T. sostra Winterbottom, 2004 ]. This species differs further from T. anaima in usually having 9 dorsal and anal fin rays (vs. 8), 18–19 pectoral rays (vs. 15–17), 13–14 lower gill rakers (vs. 11–12), a narrower bony interorbital (about 40% pupil-width vs. 60%), a U-shaped trench between the eyes with a narrow slit-like post-orbital trench (vs. both absent), and a dermal fold in the dorsal midline anterior to the first dorsal spine (vs. absent). Trimma grammistes differs most prominently in colour pattern, with a brownish body (darker above) and a pupil diameter black stripe from the upper jaw through the eye and just above the pectoral fin base which curves gently down to end at the middle of the caudal peduncle and fades into the base of the caudal fin (vs. no such stripe); it also has higher mean values for number of dorsal and anal fin rays (9.8 and 9.5 vs. 8.8 and 8.8 respectively), a longer fifth pelvic fin ray (mean = 80 % length of fourth ray vs. 49.5%), and fewer total gill rakers (13–16 vs. 17–18). Trimma sanguinellus is a plain orange-red species with a somewhat elongate second spine in the first dorsal fin (to bases of 2nd to 4th rays of second dorsal fin vs. base of spine), and 15–17 total gill rakers (vs. 17–18). Trimma sostra has a white body with six large, red midlateral blotches on the body with another over the opercular region (vs. blotches absent), a very elongate second spine of the first dorsal fin (vs. spine not elongate), usually (in 30 of 32 specimens) at least some pectoral fin rays branched (vs. all unbranched) and no fleshy ridge in midline anterior to first dorsal fin (vs. ridge present).

The phenetic relationships from an analysis of the COI gene (see below) suggest that T. stobbsi Winterbottom, 2001 and T. kardium Winterbottom et al., 2015 are most similar to the new species. The colour pattern of T. stobbsi is overall brownish background (vs. pink) with a prominent, half-pupil diameter black spot over the posterodorsal region of the opercle (vs. black spot absent), and branched rays are present (vs. absent) in the pectoral fin. Trimma kardium is overall yellow with a pinkish head, and a prominent, heart-shaped red blotch over the hyoid arch (vs. not as above). In addition, the fifth pelvic fin ray of T. kardium may be branched (vs. unbranched), and it usually has at least some scales in the predorsal midline (vs. scales absent), and a row of scales on the opercle (vs. opercular scales absent).

Discussion. A Neighbour-Joining analysis of available COI data for Trimma places the specimens of T. bathum sequenced (listed as T. RW sp 97) as being phenetically closest to T. kardium (listed as T. RW sp 98), these two species together being phenetically closest to T. stobbsi (Box J of Fig. 1 in Winterbottom et al., 2014: 85). The new species differs from T. kardium by almost 10% of the COI base pairs, and these two species together differ from the T. stobbsi complex by slightly more than 11%.

Figures

FIGURE 1. Trimma bathum, 16.4 mm SL male holotype, Suva, Fiji. Lateral (A, image reversed) and dorsal (B) views of head papillae, specimen stained with cyanine blue. Papillae in a given row connected by thin yellow lines. Photos by R. Winterbottom.

FIGURE 2. Trimma bathum, 17.6 (UK T 4454) & 16.4 (ROM T 02301) mm SL, Viti Levu, Fiji. Photo by R. Pyle.