Trimma nubarum, Winterbottom & Bogorodsky & Alpermann, 2023

Winterbottom, Richard, Bogorodsky, Sergey V. & Alpermann, Tilman J., 2023, A new species of Trimma of the T. taylori species group (Teleostei: Gobiidae) from the Red Sea, Indian Ocean, Zootaxa 5353 (3), pp. 250-264 : 254-260

Trimma nubarum new species

Rift Pygmygoby

Figs. 1–5 .

Trimma taylori (non Lobel 1979: 3) — Randall 1994: 270 (Suakin Archipelago, Sudan); Winterbottom 1995: 97 (Ras Banas, Egypt); Bogorodsky et al. 2016: 181 (Al Lith, Saudi Arabia); Golani & Fricke 2018: 162 (Red Sea, listed).

Trimma cf. taylori — Ryanskiy 2022: 110, (El Quseir, Egypt).

Holotype. SMF 35730 , 1 , 15.8 mm SL, female, Red Sea , Saudi Arabia, Al Lith, Malathu Island, 19°45.108'N, 39°54.552'E, reef wall with small caves, 22–23 m, St 37, 15 November 2014, T. J. Alpermann & S. V. Bogorodsky.

Paratypes. KAUMM 469 (sample tissue KAU14-795), 1, 14.6 mm SL, Red Sea , Saudi Arabia, Al Lith , Malathu Island, 19°45.108'N, 39°54.552'E, reef wall with small caves, 22–23 m, St 37, vial 13, 15 November 2014 , T.J. Alpermann & S. V. Bogorodsky; KAUMM 470 , 3 , 16.1-17.8 mm SL, Red Sea , Saudi Arabia, Al Lith, 20°11.632'N, 40°03.137'E, reef wall with small caves, 27–29 m, St 41, 17 November 2014 , T.J. Alpermann & S. V. Bogorodsky; KAUMM 471 (sample tissue KAU14-860), 1, 15.5 mm SL, Red Sea , Saudi Arabia, Al Lith, 20°11.632'N, 40°03.137'E, reef wall with small caves, 27–29 m, St 41, vial 15, 17 November 2014 , T.J. Alpermann & S. V. Bogorodsky; SMF 35729 (sample tissue KAU14-794), 1, 13.4 mm SL, Red Sea , Saudi Arabia, Al Lith, Malathu Island, 19°45.108'N, 39°54.552'E, reef wall with small caves, 22–23 m, St 37, vial 11, 15 November 2014 , T.J. Alpermann & S. V. Bogorodsky; SMF 35732 (sample tissue KAU14-859), 1, 17.0 mm SL, Red Sea , Saudi Arabia, Al Lith, 20°11.632'N, 40°03.137'E, reef wall with small caves, 27–29 m, St 41, vial 14, 17 November 2014 , T.J. Alpermann & S. V. Bogorodsky; SMF 35734 , 2 , 16.3–19.6 mm SL, Red Sea , Saudi Arabia, Al Lith, 20°11.632'N, 40°03.137'E, reef wall with small caves, 27–29 m, St 41, 17 November 2014 , T.J. Alpermann & S. V. Bogorodsky.

Non-types. ROM 66697 , 16.4 mm SL, Red Sea, Eritrea, Saunders Reef, 17° 10'N, 39° 12'E, 16 m, quinaldine, 11 May 1993 , J.E. Randall; ROM 72052 , 2 , 13–13.5 mm SL, Red Sea, Saudi Arabia, 150 m north of Obhur Creek entrance, just north of Jeddah, 21° 42.4704'N, 39° 4.0674'E, second reef face, 01 October 1999 , R. Field .

Diagnosis. A species of Trimma with scales in the predorsal midline; 5 th pelvic-fin ray with one dichotomous branch point (total of two branch tips); the middle 1–9 pectoral-fin rays branched; a bony interorbital of>80% pupil width; caudal fin not forked, but with the longest ray in the dorsal half of the caudal fin longer than the equivalent ray in the ventral half; upper-cheek papillae in two horizontal lines (a and c); 9 and 8–9 dorsal- and anal-fin rays respectively; 13 pectoral fin rays; and cycloid scales covering the entire predorsal region anterior to a convex line from the upper base of the pectoral fin to just lateral to the base of the sixth first dorsal-fin spine. The differences in the COI gene from other Trimma in the T. taylori species group are detailed in the Discussion.

Description. The description is based on the holotype and nine paratypes 13.4–19.6 mm SL (16.3, 10). Dorsal fin VI + I 9, second spine of first dorsal fin extending beyond end of second dorsal fin to 2 nd – 3 rd –5 th scale in dorsal midline on peduncle, third dorsal spine reaching posteriorly to between 1 st – 3 rd –6 th ray bases of second dorsal fin, all rays of second dorsal fin branched except for posterior element of last ray, fin reaches posteriorly 56– 72 –95% (66.7%, 8) distance between base of last ray and first exposed dorsal procurrent caudal-fin ray; anal fin I 8– 9 (8.3, 10), first ray unbranched, fin reaching posteriorly 59– 75 –96 % (72.1, 8) distance between base of last ray and first exposed ventral procurrent caudal-fin ray; pectoral-fin rays 13, with 2– 3 –6 dorsal (3.3, 8) and 2– 5 –6 ventral (4.4, 8) unbranched rays, and 1– 5 –9 branched (5.4, 8) rays in central portion of fin (one specimen, the smallest, with all rays unbranched), fin reaching posteriorly to vertical at base of anal-fin spine (n = 7); pelvic fin I 5, fifth ray with 1 dichotomous branch point with a total of 2 branch tips, and 63– 65 –76% (67%, 8) length of fourth ray, which reaches posteriorly to between 1st–4th anal-fin bases, pelvic rays 1–4 with 1–3, usually 2, sequential branch points (maximum of 4 terminal tips); basal membrane delicate and usually torn, but where present at least 50–80% (65, 5) length of fourth pelvic-fin ray; no fraenum. Caudal fin with 3 dorsal and 3 ventral segmented unbranched rays, and 6 dorsal and 5 ventral segmented branched rays (7)—note, first ray in each half may be only partially segmented, or even unsegmented, fin wedge-shaped in lateral view, longest ventral caudal-fin ray approximately 85% length of longest dorsal caudal-fin ray ( Fig. 1A ).

Scales in mid-lateral series 23, anterior transverse scales 8–9 (8.7, 9), posterior transverse scales 7–8 (7.7, 9), cheek and opercle scaleless; predorsal midline crossed by 9 –10 (9.1, 10) irregular scale rows, anteriormost scales extending forwards to just posterior to a vertical with posterior margin of eye; 2 vertical rows of cycloid scales on pectoral-fin base with 1–3 scales in innermost row, and 3 in outer row; 6 –7 (6.2, 9) scales in midline anterior to pelvic-fin base; cycloid scales on head in area anterodorsal to convex line joining upper pectoral-fin base with origin of second dorsal fin (anterior extent of ctenoid body scales shown by series of green dots in Fig. 2 ); between pelvic spine and ventral margin of pectoral-fin base, anterior few rows of scales in midline of belly, and anteriormost row of body scales beneath axil of pectoral-fin base. Body scales ctenoid. Circumpeduncular scales 12; scale rows in midline between base of last anal-fin ray and first ventral procurrent caudal-fin ray 8 (8).

Upper jaw with outer row of spaced, slightly enlarged and curved canine teeth which decrease in size posteriorly and reach distally to tip of premaxilla, space between adjacent teeth about equal to canine height, an irregular inner row of smaller straight teeth reaching to distal tip of premaxilla. Lower jaw with outer row of about 4 similarly spaced, slightly enlarged and curved canines, about 2 irregular inner rows of smaller teeth, grading to single row at posterior tip of coronoid process of dentary. Tongue narrow and rounded or pointed. Gill opening extending anteroventrally to below posterior one-third of pupil; gill rakers 3– 4 + 13 –14 = 16– 17 (3.1 + 13.3 = 16.4, 8; Fig. 1B ). Anterior naris in short tube, not or only just reaching anteriorly to above upper lip, posterior opening pore-like with raised rim, separated from bony front of orbit by 2.5– 3 times its diameter, nasal sac slightly raised. Bony interorbital width 91– 100 –110% pupil diameter (100.1, 9); interorbital trench with rounded W-shaped profile with median, rounded fleshy ridge ( Fig. 3B ); epaxialis reaching anteriorly in midline to vertical above posterior portion of pupil; no dermal ridge in midline of nape extending anteriorly from origin of first dorsal fin. Caudal peduncle depth as percentage of caudal peduncle length 38.5– 45.2 –50 (43.3%, 7); head length as percentage of SL 20.6– 28.5 –29.8 (28.9%, 7); as percentage head length: horizontal eye diameter 32.2– 41 (34%, 7); snout length 20.6– 29.8 (25.1%, 7); cheek depth 15.7– 16.0 –24.9 (18.2%, 7).

Cephalic sensory papillae as in Fig. 3A & B . Number of papillae in each row: a = 6 (9); b = 4 –6 (4.4, 8); c = 7; cp = 1; d = 4– 5– 6 (4.8); dʹ = 4– 5 –6 (5.1); e-anterior = 8– 9 –11 (9.5); e-posterior = 9– 11 –13 (11.3); i-anterior = 6– 7 –8 (7.1); i-posterior = 7 –9 (7.5); p = 6; r = 2; f = 2– 3 (2.4, 9); cs" = 3; g = possibly absent; n = 1; x = 6– 7 –8 (6.9, 9); u = 4 –5 (4.2, 9); z = 4 –5 (4.3, 9); ot = 9– 11 –13 (10.6, 9); os = 5– 6 –8 (6.5, 4); oi = 4 (5).

Abdominal/caudal vertebral transition type unknown, but probably type A given broad bony interorbital and the apparent backward extension of the swimbladder posterior to the anal-fin origin (as is apparent in Fig. 4C ).

Colour pattern. Live, based on 11 images from Saudi Arabia and Egypt (two of which are reproduced here as Fig. 4B & C ). A specimen from Al Lith, Saudi Arabia ( Fig. 4B ) has a translucent body with scales outlined with red, mixed with melanophores dorsally, and a tapering reddish wedge below the vertebral column. Midline of snout with narrow white stripe from above upper lip to orbit. Snout, upper and lower lips, cheek and opercular region red; area below lower lip, eye and branchiostegal region white. Anterior two-thirds of braincase with heavy sprinkling of melanophores, with a crescent-shaped dark band at posterior margin, anterior half of nerve chord with intermittent yellow stripe, posterior half with intermittent dark stripe, peritoneum heavily invested with melanophores, dark stripe in ventral midline from base of last anal-fin ray to first procurrent caudal-fin ray. First dorsal fin mostly red with melanophores; second dorsal-fin rays reddish, fin membrane translucent with melanophores and iridocytes, two irregular lines of oval yellowish spots with melanophores at posterior margins of fin rays, lines at about one-third and two-thirds length of fin rays. Anal fin similar to second dorsal fin but spots indistinct. Caudal-fin rays outlined with red, fin membranes translucent. Pectoral fin with reddish outline to fin rays and translucent membranes, pelvic fin plain with some melanophores. Iris dark reddish brown or brown, with many melanophores, somewhat lighter dorsally. A second photograph ( Fig. 4C ), from Ras Banas, Egypt, is similar but paler, with nerve chord a yellow stripe until about end of second dorsal fin and dorsal surface of swim bladder highlighted by a series of yellow spots and ovals, apparently separated by the haemal arches and heads of the pleural ribs, which extends posteriorly about one-third of length of anal-fin base. Peritoneum not as heavily pigmented, oval yellow spots in dorsal- and anal-fins not apparent. Dorsal one-third of pupil with light blue arc (but most specimens with a white arc one-fifth pupil width). One specimen (Jeddah, Saudi Arabia) with whitish margins to dorsal, anal, caudal and pelvic fins, and a short posteroventral counterpart to dorsal blue arc on pupil. In another specimen from Sharm El Naga, Egypt whole fish very pale, with red colouration confined to a lateral stripe from anterior eye to above upper lip and most of pupil (apart from white dorsal arc), vertebral column pinkish, white oval spots in both dorsal fins as well as the caudal and anal fins.

Freshly collected, based on the holotype ( Fig. 4A ), and one other specimen from Maqna, Saudia Arabia. Translucent/white areas of holotype white or off-white, whole body below vertebral column suffused with red; only tip of lower jaw red; nerve chord and top of swim bladder without colour; proximal areas of peduncle near vertebral column with sprinkling of melanophores, especially ventrally; basal row of oval yellow spots in second dorsal fin, which has narrow distal white margin; anal fin with three rows of elongated oval yellow spots, fin membrane with many melanophores and a wider white distal margin; a few vague yellow spots in caudal fin; pectoral fin with narrow white crescent at bases of fin-rays, pelvic-fin membrane mix of melanophores and iridocytes. No light arc over iris. Genital papilla reddish. Second image very similar, but no melanophores above vertebral column on peduncle, and no trace of white crescent on pectoral-fin base.

Preserved. All yellows and reds lost, head and body uniform straw-yellow. A few small distinct melanophores just lateral to nasal capsule on snout, in an irregular short line of melanophores along midline of snout, along either side of the midline on peduncle and along base of anal fin, and on bases of more central caudal-fin rays. A scattering of somewhat larger melanophores across interorbital region just anterior to insertion of epaxialis. Large amorphous melanophores on dorsal surface of brain case, in peritoneum, and in dorsal- and anal-fin membranes.

Etymology. The name “nubarum” is derived from a combination of the first three letters of the Nubian and the first two letters of the Arabian continental plates (= “nubar”) whose divergence forms the great rift of which the Red Sea is a part. The suggested common name for the species is “Rift Pygmygoby”.

Distribution and Habitat. Positively recorded only from the Red Sea, from the Gulf of Aqaba at Dahab (SVB) south to central Saudi Arabia and to Saunders Reef off Eritrea in 16– 29 m. We currently consider the new species to be endemic to the Red Sea. It has been observed hovering in aggregations up to 15 individuals near the roof of caves and moving to shelter in the cave roof when approached by divers.

Comparisons. This species keys out to couplet 7 in Winterbottom's (2019) key to the species of Trimma . It has (following the sequence of the key): scales in the midline of the predorsal, a single branch point in the 5 th pelvic-fin ray, at least some pectoral-fin rays branched, a bony interorbital width of>80% pupil width, fifth pelvic-fin ray <75% length of fourth, a caudal fin that is not deeply forked but rather is wedge-shaped with the rays in the upper lobe longer than those in the ventral lobe, the predorsal midline with <10 scales, and upper-cheek papillae in two horizontal lines (a and c).

There are two species in couplet 7, T. taylori Lobel, 1979 and T. multiclitellum Allen, 2015 . The latter is immediately and easily distinguishable from the new species, T. nubarum , and from T. taylori in having 8 dorsal-fin and anal-fin rays (vs. 9 or more), 17 pectoral-fin rays (vs. 13–15), and a dark body with white bars (vs. a plain or yellowish body without white bars on a dark background). It is currently known only from Milne Bay, Papua New Guinea. Differences between T. nubarum and T. taylori include 9 and 8–9 dorsal- and anal-fin rays respectively in the former (vs. means of 10 and 10 rays), 13 pectoral fin rays (vs. mean of 14 rays), and cycloid scales covering the entire predorsal (nape) region from the upper base of the pectoral fin to just lateral to the base of the sixth first dorsal-fin spine (vs. most or all scales ctenoid in this region in all other groups identified as T. taylori ). We note that 1 of 14 and 1 of 22 specimens from the Chagos Archipelago and the Great Barrier Reef (GBR) respectively had 9 fin rays in the second dorsal fin. In the anal fin, we found 3 of 14 from Chagos with 9 rays, and 1 with 8, 1 with 9 rays among the 22 specimens from the GBR. The GBR specimen with 8 anal-fin rays had the fin distorted and apparently damaged. All 14 Chagos samples had 14 pectoral-fin rays, while 2 of 22 specimens from the GBR had 13 pectoral-fin rays, the remainder had 14 pectoral-fin rays.

In addition, the partial COI gene sequences of representatives of T. nubarum differ from the four other phenetic haplogroups of T. taylori recognized by Winterbottom et al. (2020) by a minimum distance of between 8.4–18.5% of the base pairs (see below). The phylogenetic gene tree based on COI sequence data estimated herein (see Fig. 6 ) shows that the new species forms a monophyletic lineage, well divergent from other congeners. This lineage forms the sister to a clade composed of three lineages. One lineage is composed of specimens from the Maldives ( T. taylori group 1d sensu Winterbottom et al. 2020), which is the sister group of a single available specimen from the Seychelles, herein designated T. taylori Group 1f, following the scheme introduced by Winterbottom et al. (2020). These two species together form the sister group of specimens of a widespread western Pacific clade (designated T. taylori Group 1e sensu Winterbottom et al. 2020).

Figures

FIGURE 1. Trimma nubarum. A: Left lateral view of caudal fin and peduncle showing the wedge-shape fin, SMF 35730 (holotype), 15.8 mm SL, female. B: Dorso-lateral view of right first gill arch and gill rakers, SMF 35734, 16.3 mm SL, male. Specimens stained with cyanine blue. Photos: R. Winterbottom.

FIGURE 2. Trimma nubarum, left lateral view of body from behind head to just anterior to caudal fin to show distribution of cycloid scales on the nape. Green dots denote the anteriormost ctenoid scales, scales anterodorsal to these are primarily cycloid. SMF 35730 (holotype), 15.8 mm SL. Specimen stained with cyanine blue. Photos: R. Winterbottom.

FIGURE 3. Trimma nubarum, head papillae of SMF 35734, 19.6 mm SL, female. Left lateral (A) and dorsal (B) views of head to show head papillae. Papillae in any given row connected by a thin green line. Specimen stained with cyanine blue. Photo: R. Winterbottom.

FIGURE 4. Trimma nubarum. A: Freshly collected holotype, SMF 35730, 15.8 mm SL, female, Al Lith, Saudi Arabia, Red Sea. B: Live specimen, Al Lith, Saudi Arabia, Red Sea. C: Live specimen, Ras Banas, Egypt, Red Sea. Photos: A & B—S. V. Bogorodsky; C—G. Barrall.

FIGURE 5. Various examples of freshly collected Trimma taylori from throughout its geographic range. Group numbers (“Gr.1 x”) denote haplogroups. A: Marquesas, Gr. 1a. B: Helen Reef, Palau, Gr. 1b. C: Raja Ampat, Indonesia, Gr. 1b. D: Oahu, Hawaiian Islands, Gr. 1b. E: Hithadhoo, Maldives, Gr. 1d. F: Sonsorol I., Palau, Gr. 1e. G: St. Joseph’s Atoll, Seychelles, Gr. 1f. H: ChagosArchipelago, Indian Ocean, Gr. designation unassigned. Photos:A—J.T. Williams. B, C, F and H—R. Winterbottom. D—J.E. Randall. E—M.V. Erdmann. G—R. Daly.

FIGURE 6. Maximum likelihood tree based on mitochondrial COI barcoding sequences of members of the Trimma taylori group including the new species T. nubarum and sequences from T. filamentosus, T. flavicaudatum, T. mendelssohni and T. quadrimaculatum as the outgroup. Group assignment (Groups 1a – 1e) follows Winterbottom et al. (2020) with Group 1f from Seychelles added accordingly. Values on branches indicate bootstrap support from 1,000 replicates in percent; bootstrap support values below 50 percent are not shown. The bar shows the average rate of nucleotide substitutions.