Trimma nasa Winterbottom, 2005a

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 : 58-60

Trimma nasa Winterbottom, 2005a

Nasal-bar Pygmygoby

Figs. 31–32 , Pl. 2 F

Trimma nasa Winterbottom, 2005a:34 (Siquijor Id, Philippines; also Palau and widespread in the SW Pacific east to Fiji, x 2); Allen & Erdmann, 2012:942 (Kalimantan to Fiji).

Trimma griffithsi : (non Winterbottom, 1984): Kuiter & Tonozuka, 2004:707 ( Indonesia). Trimma sp. 13: Kuiter & Tonozuka, 2004:707 (x 3, Indonesia).

Australian material. Queensland: Ashmore Reef: AMS I.33717-077, 2(11–14), 1–32 m; AMS I.33731-089, 7(13–18), 1– 18 m. Lihou Reef: WAM P. 29638.025, 3(23–24), 20– 35 m. Tijou Reef: AMS I.20779-144, (17), 25 m. Timor Sea: Cartier Reef: NTM S12883 -064, 3(13–16).

Other material of this species is reported in the original description ( Winterbottom, 2005a), with the additional material at the ROM from Helen Reef, Palau, Raja Ampat, Indonesia, and Rabaul, Papua New Guinea.

Diagnosis. A species of Trimma with a broad bony interorbital (equal in width to pupil diameter); nape scales all cycloid; a branched fifth pelvic-fin ray; 13 or fewer outer gill rakers on the lower limb of the first gill arch; last ray of dorsal and anal fins split to its base with both elements unbranched; an eye-sized, dark blotch over the hypural region of the caudal peduncle; and, in all but Fiji specimens and one specimen from the Moluccas, a thin, median, dark, stripe from the upper lip to the mid-region of the interorbital.

Description. The description is based on the 10 specimens from the Philippines (ROM 49229, 53043–046, 53048 and 60234), and 10 cleared and stained specimens from the Solomons (ROM 835CS). Dorsal fins VI + I 8 (once 7), second spine of first dorsal fin elongated, reaching posteriorly to caudal peduncle when adpressed, anterior half of last fin ray unbranched, all other rays branched, last ray often elongated, sometimes almost reaching procurrent-fin rays; anal fin usually I 8 (twice 7, once 9, in holotype), all rays branched except anterior half of last ray, last ray often elongated, sometimes almost reaching procurrent-fin rays; pectoral fin usually 14 (once 13, once 15, both sides of holotype), all rays unbranched; pelvic fin I 5, first four rays with single sequential branch, fifth ray branched once dichotomously and about 60% the length of fourth ray; basal membrane complete but often damaged; no fraenum. Scales apparently very deciduous because few specimens have many scales left, and none appears to be fully scaled. Lateral scales 23 (n = 7); predorsal scales 5, 6 or 7 (n = 5); transverse scales 6 (n = 3); scales cycloid anterior to lines between pelvic- and ventral pectoral-fin base, and dorsal pectoral-fin base and base of fifth dorsal spine dorsally; ctenoid posterior to these lines; anterior extent of first predorsal scale approximately in line with posterior margin of pupil; opercle of one specimen with a cycloid scale at posterodorsal corner, and possibly larger scale anterior to this (scales of this area probably occur regularly, but are so deciduous that they are absent in all other specimens, and even scale pockets cannot be identified with confidence); vertical row of three scales (middle largest) on pectoral-fin base (n = 1). Outer row of teeth of upper jaw enlarged, curved, spaced canines, followed by several rows of small conical teeth; lower jaw with 2–3 straight canines projecting anterodorsally on each side followed by several irregular rows of small conical teeth. Tongue truncately rounded with central point, about two-thirds pupil diameter in width. Gill opening extending anteroventrally to below midpupil; outer gill rakers on first arch 1–3 + 10–13 (mean = 2.0 + 11.8, n = 12). Anterior nares short thin tube, posterior opening small pore, nasal sac virtually flat; entire organ difficult to distinguish from surrounding area of snout. Bony interorbital pupil-diameter in width, shallowly concave with low median fleshy ridge (forming broad 'W' in cross section), epaxialis musculature reaching anteriorly to above posterior margin of pupil. Abdominal/ caudal vertebral transition of a modified Type A, with no ‘haemal canal’ at the base of the ninth vertebra, first caudal vertebra with separate small basal haemal canal with much enlarged second canal distally, and haemal canal of third caudal vertebra slit-like and not enlarged (n = 3).

Colour pattern. Freshly collected. Ground colouration is off-white, the snout yellow to orange ( Fig. 32 ). Ring of melanophores surrounding outside of eye, yellow ring around pupil, and some red pigmented spots or red suffusion on iris. Pinkish blush-like stripe passes along side of body, resulting from red chromatophores on an offwhite background. Yellow stripe along upper edge of pink stripe, reaching dorsal surfaces on nape and caudal peduncle, but leaving off-white area around bases of dorsal fins. Similar stripe present along ventral margin of body, beginning on abdomen and ending at caudal spot. Eye-sized, dark, orange-red spot heavily invested with melanophores present on hypural region of caudal peduncle, extending onto caudal fin rays, melanophores within spot particularly concentrated on hypural plate and area immediately anterior to it, where they form pupil-diameter sized darker area. Line of red chromatophores along base of anal fin and continue to caudal spot. Similar line on dorsal surface, beginning at first dorsal fin, but not as intense. First and second dorsal fins with yellow basal stripe and sprinkling of red chromatophores in interradial membranes. Some yellow and red chromatophores present in anal fin, sometimes forming basal yellow stripe. Procurrent rays of caudal fin suffused with pink, pelvic and pectoral fins hyaline. Peritoneum heavily pigmented with melanophores, creating dark patch along side of body beneath pinkish band. Melanophores present on braincase.

Live. Body translucent, with sprinkling of red chromatophores on head and snout (Pl. 2 F). Yellow chromatophores present on margin of eye bordering interorbital space, and white stripe from anterior portion of snout right through interorbital region to posterior margin of pupil. Large, eye-sized, dark red-brown spot on hypural region of peduncle, with rounded spot of melanophores in centre. Red colouration begins immediately behind eye and passes down side of body to mid peduncle region and appears to be entirely internal. Iridescent green suffusion present on peritoneum and along most of vertebral column (could be artefact of electronic flash photography). Sprinkling of red chromatophores present around bases of first two dorsal spines, with some red pigment present in fin rays of first dorsal and pectoral fins. Pigment pattern in other fins difficult to determine from available photographs.

Preserved. Ground colouration pale straw-yellow. Approximately eye-diameter sized black spot over hypural region on caudal peduncle, consisting primarily of dark brown chromatophores; thin medial blotch on peduncle just posterior to last anal-fin ray consisting of brown chromatophores and some centrally located melanophores, few scattered chromatophores on belly; peritoneum with numerous melanophores and brown chromatophores, especially dorsally; dorsal surface of braincase covered with melanophores and chromatophores except for clear, medial area; distinct medial stripe of melanophores and/or chromatophores from snout tip to posterior margin of pupil; margins of few predorsal and dorsal peduncular scales may be outlined by melanophores.

Etymology. Derived from the old English word 'nasal', a bar descending from the front of many medieval helmets to protect the nose of the wearer, in allusion to the snout stripe of the species. Treated as a noun in apposition.

Distribution. Found from Flores, Indonesia north to Siquijor Island in the Philippines east to Palau and southeast through the Bismarck Archipelago, the Solomons, Vanuatu to Fiji and New Caledonia, north-west to the northern Great Barrier Reef ( Fig. 31 ).

Comparisons. Among the species possessing a broad bony interorbital, only T. tevegae , T. xanthochrum and T. griffithsi have a dark mark on the hypural region of the caudal peduncle. These species lack the snout stripe and the post-anal blotch, and the peduncular spot in T. griffithsi equals the pupil in diameter (rather than the eye). In addition, T. tevegae and T. xanthochrum have an unbranched fifth pelvic-fin ray, more gill rakers on the lower limb of the first gill arch (15–16 vs. 10–13), ventral half of body darker than dorsal half (vs. uniform), and have scales on the cheek (vs. absent). Trimma marinae is very similar to T. nasa , but has virtually no caudal spot and has a nasal pit rather than the nasal sac present in all other species of Trimma .

Winterbottom et al. (2014) analysed the CO1 gene of 16 specimens. The results suggested that there were four haplogroups. Group 1 occurred at Raja Ampat and Timor, Indonesia (n = 4), Group 2 in New Caledonia (n = 1), Group 3 in Palau (n = 9) and Group 4 at Rabaul, New Britain (n = 2). These groups were separated from each other by between 5.5–16.8% of the base pairs. There are no tissue samples from the type locality (Siquijor Id, Philippines). In the absence of genetic material from Australia, we provisionally retain the name T. nasa for the Great Barrier Reef material.

Discussion. The snout stripe is of variable occurrence in juveniles (<15 mm SL), and appears to be entirely absent from the Fijian population, in which the post-anal blotch is also weakly developed.

Winterbottom & Southcott (2008) reported a maximum longevity of 87 days, settlement at about 8 mm SL, a maximum recorded length about 18 mm SL, and a daily mortality rate of 4.7% based on 110 specimens of T. nasa from Palau. The pelagic duration was found to be about 34 days, and males were significantly smaller than females and juveniles when corrected for age. The largest specimen measured, 24 mm SL, was collected at Lihou Reef, Coral Sea.

The species is known from depths of 13– 40 m. In Australia it is known only from a single reef on the outer Great Barrier Reef. This species has been referred to informally as Trimma DFH sp. 16 or Trimma RW sp. 22.

Figures

FIGURE 31. Map of the distribution of Trimma milta (solid inverted triangles) and T. nasa (solid circles with white star).

FIGURE 32. Trimma nasa, 22.6 mm SL female, ROM 63925, Port de Goro, New Caledonia. Photo by R. Winterbottom.