Robinsichthys nigrimarginatus, Tornabene & Manning & Robertson & Van Tassell & Baldwin, 2023

Tornabene, Luke, Manning, Rachel, Robertson, D. Ross, Van Tassell, James L. & Baldwin, Carole C., 2023, A new lineage of deep-reef gobies from the Caribbean, including two new species and one new genus (Teleostei: Gobiidae: Gobiosomatini), Zoological Journal of the Linnean Society 197 (2), pp. 322-343 : 337-340

publication ID	https://doi.org/ 10.1093/zoolinnean/zlac013
publication LSID	lsid:zoobank.org:pub:E0CDE4DB-E0CE-4171-A459-27D90F2566A5
DOI	https://doi.org/10.5281/zenodo.7622673
persistent identifier	https://treatment.plazi.org/id/9A75C72A-755F-FF8F-FF6A-AF68FADAE6FF
treatment provided by	Plazi
scientific name	Robinsichthys nigrimarginatus
status	sp. nov.

Treatment

ROBINSICHTHYS NIGRIMARGINATUS SP. NOV.

( FIGS 4B View Figure 4 , 8–11 View Figure 8 View Figure 9 View Figure 10 View Figure 11 )

Black-margined goby (English), gobio de margen negro (Spanish).

Zoobank registration: urn: lsid: zoobank. org:act: 9D9D60B1-2777-47FC-8CB0-6A7E0F70641C

Holotype: USNM 446953 , 21.0 mm female, tissue CUR19007, field number CURASUB19-02, 229 m depth, sandy bottom, East of Substation downline , Substation Curaçao, Bapor Kibra , Curaçao, 12.0838°, -68.8991°, quinaldine, HOV Curasub, Carole Baldwin, Luke Tornabene, Tico Christiaan, Sarah Yerrace, 7 May 2019. GoogleMaps

Diagnosis: First dorsal-fin pterygiophore pattern 3-22111*0 (last pterygiophore lacking an associated dorsal-fin spine; Fig. 4B View Figure 4 ); VI spines in first dorsal fin; 11 + 17 vertebrae; two modified basicaudal scales; head pores absent; second dorsal fin I,9; anal fin I,9; pelvic fins completely united by membrane to form a round disc with well-developed anterior frenum; pectoral-fin rays 19.

Description: Morphometric data are presented in Table 2 View Table 2 . Median and paired fins: First dorsal fin VI, no spines elongate; second dorsal fin I,9; anal fin I,9; pectoral-fin rays 19, extending posteriorly to a vertical through second dorsal-fin ray 2 or 3; pelvic fin I,5, all rays branched; pelvic fins connected via membrane forming a complete disk with well-developed anterior frenum connecting pelvic spines ( Fig. 8 View Figure 8 ); pelvic fin extending posteriorly to just before anus; tips of pelvicfin rays not ending in fleshy pads; caudal fin truncate; branched caudal-fin rays 14, segmented caudal-fin rays 17.

Scales: Scales on head and nape absent; ctenoid scales on side of the body present starting above pectoral fin base and ending at base of caudal fin rays; lateral scale rows 24, transverse scale rows six; pair of modified ctenoid scales with enlarged cteni present at base of caudal fin, one each at dorsal and ventral margins of fin; ctenoid scales present on abdomen, scales slightly larger than those on side of body.

Head: Jaw extending posteriorly to a vertical through midpoint of the pupil; anterior naris a short tube, posterior naris an opening with raised rim; cephalic lateralis pores absent; eyes large, 41% HL, dorsolateral. Both jaws with two rows of teeth, teeth thin, straight, pointed and evenly spaces posteriorly, becoming less regularly spaced, slightly more recurved anteriorly, with an occasional tooth in outer row slightly larger than others in row. Sensory papillae arranged as in Figure 9 View Figure 9 , with four prominent transverse rows, including rows 5i/5s present as a continuous single row.

Colour in life ( Fig. 10 View Figure 10 ): Body translucent with a silvery sheen, an internal white area around gut; body with five dark bars formed by aggregations of black chromatophores overlaying translucent yellow areas, the first bar strongest and widest, extending from the centre of the base of the first dorsal fin to the lower belly, the second to fifth only on the lower-half of the body, thin, formed by less dense aggregations of tiny black chromatophores, the last bar partly fused to the bar on the base of the caudal fin; upper-body profile with six small, translucent yellow blotches, each with a central area of tiny, black chromatophores, the first blotch between the two dorsal fins, the second under the front of the second dorsal fin, the third under the centre of that fin, the fourth to sixth on the caudal peduncle; two elongate internal areas of dark pigment with yellow tones along the spinal column, a short one under the second body bar, a longer one from third body bar to just behind the fourth body bar, with a suggestion of a third patch above the last body bar; when the fish is laterally oriented ( Fig. 10A View Figure 10 ), the silver sheen of the body is present in irregularly dispersed patches in the translucent areas, when the fish is oriented partly towards the viewer ( Fig. 10B View Figure 10 ) that iridescent colour is greenish silver, distributed in patches between the body bars and between the yellow dorsal-profile blotches, and as a distinct vertical greenish silver bar just before the upper-half of the first dark body bar.

Head translucent with silver sheen on cheeks; top rear corner of opercle with a translucent orange patch about half pupil size and a larger patch of tiny, welldispersed, black chromatophores over area of pink gills, an indistinct, irregularly shaped translucent orange patch behind centre of eye extending on to nape; mouth translucent, top jaw with silver sheen and a transverse line of black chromatophores across its centre, an indistinct yellow blotch on the snout immediately behind its centre; iris with most of its anterior and rear part overlaid by a dense silvery yellow sheen, top edge of the eyeball silvery yellow; a curved black bar formed by densely aggregated black chromatophores, passing from upper-rear of iris through the pupil and down to rear corner of the mouth, section of bar under eye with relatively large chromatophores overlaying a translucent yellow area, that bar bounded anteriorly and posteriorly by patches of silver iridescence.

Base of caudal fin with long, thin, vertical yellow bar with an aggregation of black chromatophores down its centre that partly fuses with last body bar, fin itself translucent with patches of tiny black chromatophores along interradial membranes – two small patches along top of fin, a subterminal band down upper-half of posterior of the fin; a small, vertical patch of black-dotted yellow pigment just behind upper-half of the basal dark bar; first dorsal fin translucent with a large, horizontally oval, solid black blotch covering the outer third of fin between spines 1 and 5, and extending partly towards spine 6, base of fin with short extension of first yellow and black body bar; base of second dorsal fin with two yellow, black dotted extensions of third and fourth yellow body blotches, a black spot immediately above fin base between first two rays, a small, black-dotted, yellow spot on lower third of the fifth ray and another between bases of last two rays, outer edge of fin with a narrow band of dense black chromatophores on interradial membranes; anal fin translucent with scattered, tiny, black chromatophores on interradial membranes, particularly on anterior twothirds of fin; pectoral fin base translucent with a large greenish silver blotch that extends on to basal one-fifth of fin, base of the dorsal ~8 rays of pectoral fin covered with a yellow, black-dotted blotch; remainder of the fin translucent; pelvic fins translucent with small black dots on interradial membranes.

Colour in preservation ( Fig. 11 View Figure 11 ): Body pale yellowish; side of head below eye with curved, black, vertical bar formed by densely aggregated black chromatophores ending at rear corner of the mouth; operculum covered with scattered chromatophores; chromatophores more densely concentrated on posterior half, forming vertical bar of pigment that extends dorsally on to and across nape; side of body with four concentrations of chromatophores that form vertical bars, first bar complete and positioned beneath centre of first dorsal fin; second bar positioned below origin of second dorsal fin, not extending to dorsal midline, third and fourth bars positioned over end of anal fin and centre of caudal peduncle, respectively, both bars beginning at lateral midline and extending ventrally to ventral midline; a series four or five small patches of chromatophores along dorsal midline, beginning at origin of second dorsal fin and extending to end of caudal peduncle; a singular vertical row of chromatophores over base of caudal fin rays, followed by a small patch of chromatophores on upper-half of caudal fin on anterior one-third of rays; first dorsal fin with distinct black oval on outer third of fin, and smaller dark black spot on middle of fin that is an extension of vertical bar on body; second dorsal fin with three or four small, isolated dark patches of chromatophores on lower-half of fin, distal margin of fin bordered with dark chromatophores; anal fin uniformly covered with scattering of chromatophores; pelvic and pectoral fin without pigment.

Genitalia: Female papillae short and conical; male papilla unknown.

Habitat: Collected on open sand bottom at 229 m depth.

Distribution: Known only from type locality off southwest coast of Curaçao, Caribbean Netherlands.

Etymology: The specific epithetic nigrimarginatus is an adjective (black-margined) formed from the Latin niger, glossy black, and marginatus, bordered, in reference to the black margins on the dorsal and caudal fins.

Remarks: The new species is placed in the genus Robinsichthys based on the following characters: first dorsal-fin pterygiophore pattern 3-22111*0, with the last pterygiophore lacking an associated dorsal-fin spine ( Fig. 4B View Figure 4 ); VI spines in first dorsal fin; 11 + 17 vertebrae; two modified basicaudal scales; head pores absent; side of body with ctenoid scales; lack of fusion between hypurals 1–2 and hypurals 3–4 and the terminal vertebral element; body with several narrow, dark bands or saddles, head with dark triangular marking below eye. The new species differs from R. arrowsmithensis , and thus the original description of Robinsichthys , most notably in the following ways: (1) having pelvic fins fused to form a complete disk with well-developed anterior frenum vs. having pelvic fins completely separate, lacking frenum; (2) having a large dark blotch on the margin on the first dorsal fin vs. dorsal fin without blotch; (3) having 19 vs. 21–24 (usually 22–23) pectoralfin rays; and (4) having I,9 elements in both the second dorsal fin and anal fin vs. predominately I,10 (I, 9 in one specimen) in both fins of R. arrowsmithensis .

Because R. arrowsmithensis was not included in our phylogenetic analysis, we cannot confirm with molecular data that Robinsichthys is monophyletic with regards to Birdsongichthys , and thus whether a new genus is required for B. rectus . However, there are two characters that we regard as apomorphic for Robinsichthy s that are not present in Birdsongichthys . A count of VI dorsal spines (in most specimens) is unique to Robinsichthys among other Gobiosomatini genera (a reduction from the plesiomorphic state of VII spines). Counts of 11 + 17 vertebrae are also considered apomorphic for Robinsichthys , with these counts also being independently derived in members of the Barbulifer subgroup ( Elacatinus and allies). Birdsongichthys possesses neither of these synapomorphies. Birdsongichthys has head pores, while both Robinsichthys do not, but head pores and many other morphological characters that may be useful for defining genera of Gobiosomatini have more complex evolutionary histories and may be of limited phylogenetic utility (see Discussion below).