Trimma fishelsoni Goren, 1985

Bogorodsky, Sergey V., Suzuki, Toshiyuki & Mal, Ahmad O., 2016, Description of a new species of Priolepis (Perciformes: Gobiidae) from the Red Sea, a new record of Priolepis compita, and a distributional range extension of Trimma fishelsoni, Zootaxa 4150 (2), pp. 168-184 : 178-181

Trimma fishelsoni Goren, 1985

Fishelson’s Pygmygoby

Figures 4 , 5 , 6 A, Table 1

Trimma fishelsoni Goren, 1985: 64 , Figs. 1–3 ("University Reef", Sinai, Egypt, Gulf of Aqaba , Red Sea) - Goren & Dor, 1994: 66 (Red Sea, checklist); Winterbottom, 1995: 96 ( Gulf of Aqaba to southern Egypt at Ras Banas); Golani & Bogorodsky, 2010: 49 (Red Sea, checklist); Hoese et al., 2015: 538 (Red Sea) .

Material examined. SMF 35735 (KAU 14-857), 20.0 mm SL, female, stained with alizarin red, Saudi Arabia, Al Lith, reef wall to depth of about 35–40 m, 27–29 m, St. 41, 20°11'632''N, 40°03'137''E, 17 November 2014, coll. S.V. Bogorodsky & T.J. Alpermann ; SMF 35737, 21.6 mm SL, male, and KAUMM 368 (KAU14-858), 15.4 mm SL, sex unknown, collection data the same as for specimen SMF 35735.

Diagnosis. Trimma fishelsoni differs from the other species of the genus in the following combination of characters: dorsal-fin rays VI + I,7–8, second spine elongate and filamentous; anal-fin rays I,7–8; pectoral-fin rays 14–17 (usually 15–16); longitudinal scale series 25–28; median predorsal scales 9–14, scales reaching to interorbital area. Head scaled, with 1–2 rows of scales on cheek and 3–4 rows on opercle. Bony interorbital width broad, about half pupil diameter. Pelvic fins separated, without basal membrane or frenum, fifth ray unbranched, its length 46–56% length of fourth ray. Pale greenish yellow densely dotted with melanophores on postorbital head, along back, and on lower half of body, with faint broad purple stripe above midside of body. Dorsal and anal fins broadly striped with pale yellow and blue, caudal fin yellow with blue margins and with two large bright yellow blotches in vertical alignment at base.

Head papilla pattern. This species has a reduced transverse pattern of sensory papilla rows, shown in Fig. 5 , with number in each row (in parentheses) as follows: a (6), b (4), c (6), cp (1), cs (2), d (7), d’ (9), ea (13), ep (14), f (3), g (1), ia (8), ip (7), m (1), n (4), ot (12), os (6), oi (4), p (7), r (3), s (1), u (5), x (9), and z (6).

Coloration of freshly collected specimen shown in Fig. 4 A.

Distribution and habitat. Trimma fishelsoni was originally described based on 20 specimens from the Gulf of Aqaba by Goren (1985). Winterbottom (1995) extended the range of distribution south to Ras Banas, southern Egypt. The range is here extended to the central Red Sea, at Al Lith, about 250 km south from Jeddah. The species is typically seen hovering a few centimeters above the substratum, often upside down, forming small groups with each goby about 10–30 cm from other. Reported from coral reefs at depths of 15–47 m; the specimens from Al Lith were collected from a cave at a depth of 27–29 m, together with Priolepis melanops n. sp. and Trimma taylori .

Remarks. The three specimens from Al Lith generally matches the description and diagnosis provided by Goren (1985) and Winterbottom (1995). They differ, however, in having all pectoral-fin rays unbranched (versus upper and lower 5–7 rays unbranched). More specimens from southern part of the distribution are needed to determine whether unbranched rays represent intraspecific variation or are related to separate northern and southern populations.

The colour of live fish ( Fig. 6 A) is slightly different from that of freshly collected specimens ( Fig. 4 A): a broad stripe above midside of body dark purple; iris mainly dusky yellow with an oblique blue line across upper edge of pupil; each dorsal and anal fins with yellow stripe, rest of fin blue; and caudal fin with blue margins. Goren (1985) described presence of four faint saddle-like dusky blotches, one under each dorsal fin and two on the caudal peduncle which were apparent in preserved specimen; such blotches not visible in live gobies or in fresh specimens. Body along back in preserved specimens from Al Lith ( Fig. 4 B) densely covered with melanophores but not form patches or saddle-like blotches.

Trimma fishelsoni may be distinguished from other Red Sea congeners by a combination of scaled predorsal area, cheek and opercle, a very long second dorsal-fin spine, a moderately broad interorbital area, no spots on the head and body, body with an indistinct, dark purple stripe above midside, and each dorsal and anal fin with a yellow band. Trimma fishelsoni is assigned to the T. tevegae species group and is most similar to T. gigantum Winterbottom & Zur, 2007 , described from Palau, western Pacific. It differs in having fewer predorsal scales (11– 14 versus 14–18), in the presence of two yellow blotches at the caudal-fin base (versus only thin yellow line), and in having the lower half of the body and pectoral-fin base densely pigmented with melanophores (versus a few scattered melanophores on body and pectoral-fin base).

The similarity of Trimma fishelsoni with T. tevegae led confusion in identification of specimens collected from the vicinity of Jeddah, Saudi Arabia. Winterbottom (1995) included T. tevegae in his review of the Red Sea Trimma ( ANSP, without catalogue number) and used an underwater photograph of T. caudomaculatum Yoshino & Araga, 1975 , taken by J.E. Randall at the Maldives, as T. tevegae . In fact, six specimens of this lot ( ANSP 158831 , labeled Trimma sp.) are T. flavicaudatum (Rick Winterbottom, pers. comm.). Three specimens from the Western Australian Museum ( WAM 25787.008 ) were collected by Randall and Vine in 1977 from Jeddah, and were identified by D. Hoese as T. tevegae . Recently specimens of this lot were examined and re-identified as T. fishelsoni (Winterbottom, pers. comm.). Trimma tevegae and T. caudomaculatum thus currently not known from the Red Sea. Trimma fishelsoni differs from T. caudomaculatum and T. tevegae in having more pectoral-fin rays (usually 15–16 versus usually 14), and in lacking a dark blotch on the caudal peduncle (dark blotch, covering the posterior caudal peduncle and the basal two-fifths of the caudal fin, present in the other two species).

The three specimens of T. fishelsoni from Al Lith were collected together with T. taylori ( Fig. 6 B) close to the entrance of a small cave on a reef wall. These two species can be easily confused under water. In the Gulf of Aqaba they are not observed together, with individuals of T. fishelsoni often swimming in a dispersed group close to the substrate and quickly retiring inside a cave or holes when alarmed, whereas T. taylori forms small groups swimming at some distance from reef, and usually swim away when alarmed.

Figures

FIGURE 1. Priolepis melanops, n. sp., SMF 35728, holotype, female, 24.0 mm SL, Al Lith, Saudi Arabia, Red Sea A: freshly collected; B: preserved; C: ventral view of region between pelvic and anal fins; red line indicates basal membrane, yellow lines show fourth and fifth pelvic-fin rays. Photos by S. V. Bogorodsky (A) and T. Suzuki (B, C).

FIGURE 2. Priolepis melanops n. sp., SMF 35728, holotype, cephalic sensory papillae of head. Dorsal (top), lateral (middle) and ventral (bottom) views of head. Dots represent the sensory papillae; AN = anterior nares, PN = posterior nares; arrow shows position of lower end of gill opening. Photo and drawing by T. Suzuki.

FIGURE 3. A: Priolepis compita, live individual, Sharm el Moya, at entrance of the Gulf of Aqaba, Red Sea; B: Priolepis semidoliata, fresh specimen, BPBM 41242, 21.0 mm SL, Dahab, Gulf of Aqaba, Red Sea. Photos by S. V. Bogorodsky.

FIGURE 4. Trimma fishelsoni. A: SMF 35735, fresh specimen, 20.0 mm SL, female, Al Lith, Saudi Arabia, Red Sea; B: SMF 35737, preserved specimen, 21.6 mm SL, male, Al Lith, Saudi Arabia, Red Sea. Photo by S. V. Bogorodsky (A) and T. Suzuki (B).

FIGURE 5. Trimma fishelsoni, SMF 35737, cephalic sensory papillae of head. Dorsal (top), lateral (middle) and ventral (bottom) views of head. Dots represent the sensory papillae; AN = anterior nares, PN = posterior nares; arrows show position of lower end of gill opening. Photo and drawing by T. Suzuki.

FIGURE 6. Underwater photographs of alive individuals. A: Trimma fishelsoni, Dahab, Gulf of Aqaba, Red Sea; B: Trimma taylori, Al Lith, Saudi Arabia, Red Sea. Photos by S. V. Bogorodsky.