Xenisthmus polyzonatus ( Klunzinger, 1871 )

Gill, Anthony C., Bogorodsky, Sergey V. & Mal, Ahmad O., 2017, Review of Red Sea Xenisthmus Snyder (Teleostei: Gobioidei: Xenisthmidae), with description of a new species, Zootaxa 4286 (2), pp. 203-214 : 211-213

Xenisthmus polyzonatus ( Klunzinger, 1871)

Bullseye wriggler

Figures 3 , 5 ; Tables 1–2

Eleotris polyzonatus Klunzinger 1871: 482 (type locality, Al-Qusair , Red Sea Governorate, Egypt, Red Sea; two syntypes ZMB 8018 ).

Xenisthmus polyzonatus ; Clark 1968: 5, 7 (key; Ghardaqa, Egypt); Dor 1984: 88 (list); Goren & Dor 1994: 67 (list); Golani & Bogorodsky 2010: 50 (list).

Diagnosis. A species of Xenisthmus with the following combination of characters: second dorsal-fin rays usually I,11 (rarely I,12); anal-fin rays I,10–11; tongue rounded to truncate; and posterior nostril with well-developed anterior flap.

Description (based on eight Red Sea specimens, 13.4–22.1 mm SL). Dorsal-fin rays VI + I,11–12, all segmented rays branched; first dorsal-fin pterygiophore formula 3-22110; anal-fin rays I,10–11, all segmented rays branched; pectoral-fin rays 17–18, upper 1–2 and lower 1–2 rays unbranched; pelvic-fin rays I,5, inner ray unbranched; segmented caudal-fin rays 9 + 8; branched caudal-fin rays 6–8 + 6–7; upper unsegmented caudal-fin rays 6–8; lower unsegmented caudal-fin rays 6–8; total caudal-fin rays 29–32; scales in lateral series 54–66; scales in transverse series counted anterodorsally from anal-fin origin 20–26; scales in transverse series counted posterodorsally from anal-fin origin 20–26; circumpeduncular scales 27–32; predorsal scales 17–20; gill rakers 3– 4 + 9–10 = 12–14; pseudobranch filaments 4; vertebrae 10 + 16; epurals 2.

Morphometric data are given in Table 1.

Body covered with small, cycloid scales anteriorly, and ctenoid scales posteriorly, the anteriormost ctenoid scales on midside more-or-less below origin of second dorsal fin in specimens larger than about 15 mm SL (ctenoid scales mostly restricted to caudal peduncle in smaller specimens); ventral contour of body fully scaled, except for narrow area beneath branchiostegal membranes; predorsal scales extending anteriorly to or slightly posterior to vertical through posterior edge of preopercle, sometimes with 1–2 additional median scales anterior to main scales; operculum scaled at least dorsally, sometimes with scales covering most of opercle; cheek with at least some scales, often fully scaled; cycloid scales present on pectoral-fin base; narrow band of scales on fleshy portion of caudal-fin base, these usually cycloid, but sometimes with several, irregularly distributed ctenoid scales; no scales on dorsal- or anal-fin bases.

Head pores A’BC D(S)EFHIJK’ M’NOPQ’ (head pores incompletely developed in some specimens smaller than 15 mm SL); lower lip fleshy and protruding, with uninterrupted, free ventral margin; anterior nostril in short tube; posterior nostril with raised rim, with prominent membranous flap anteriorly; tongue rounded to truncate anteriorly; gill opening extending anteriorly to about midway between verticals through posterior edge of preopercle and posterior edge of eye.

Upper jaw with 2–3 (anteriorly) or 2 (posteriorly) rows of small, conical teeth, the outer-row teeth largest and slightly curved; lower jaw with 3 (anteriorly) or 2 (posteriorly) rows of small, conical teeth, the outer-row teeth largest and slightly curved; vomer, palatines and tongue edentate.

Live coloration (based on live and freshly dead specimens from the Red Sea; Figure 5 ): head and body pale greenish grey to olive, becoming pale pink to white on lower head and abdomen; four short, reddish brown to dark grey-brown bars extending from eye, one from mid-anterior part of orbital rim to mid-side of upper lip, one from below mid-ventral part of orbital rim to behind posterior edge of maxilla, one from midposterior part of orbital rim to mid-upper part of preopercle, and one from behind eye to upper part of pectoral-fin base; mid-side of lower lip and adjacent inner part of lower jaw reddish brown to dark grey-brown; upper and sometime anterior part of operculum with irregular reddish brown to dark grey-brown markings; iris mottled reddish brown to grey-brown; upper half of body with 12–13 reddish brown to dark olive-brown slightly oblique bars, the first passing just anterior to pectoral-fin base and the last just anterior to caudal-fin base; area between bars sometimes with indistinct white spots or bars; upper part of pectoral-fin base with irregular reddish brown to dark grey-brown spot, with second spot on mid-ventral part of fin base; first dorsal fin hyaline with two rows of reddish brown to dark grey spots on each spine, one along base of fin and the other through middle of fin; second dorsal fin and anal fin hyaline with one (anteriorly) to three (posteriorly) curving rows of dark spots along each fin ray; caudal fin hyaline with large (almost eye-sized) black spot near middle of fin base, rimmed anteriorly by narrow yellow to white curved bar and preceded by broader orange to reddish brown or grey arc-like bar; remainder of caudal fin with 5–6 convex (anteriorly) to vertical (posteriorly) reddish brown bars; pectoral fins hyaline, white basally, with two large orange-brown to grey-brown spots, one near base of mid-upper rays and the other near base of mid-lower rays; pelvic fins pale pink to white.

Preserved coloration: similar to live coloration; dark markings remain, becoming pale greyish brown to dark grey-brown.

Habitat and distribution. Xenisthmus polyzonatus is currently regarded as a widespread species, ranging from the Red Sea and East Africa to French Polynesia, with Luzoneleotris nasagbua Herre (1938; type locality Nusagbua, Luzon, Philippines) considered a synonym. However, detailed comparison of specimens from throughout this range has not been completed (currently underway by the first author), and it is possible that there is a complex of closely related species involved. Preliminary molecular analyses also showed that specimens from the western Pacific identified as X. polyzonatus represent distinct lineages. We therefore restrict our treatment of the species to specimens from the Red Sea, where it is widely distributed ( Figure 3 ). It typically inhabits crevices close to the base of fringing reefs in the depth range of 1.5– 16 m.

Remarks. Clark (1968) reported on a 40 mm SL specimen of X. polyzonatus from Ghardaqa (= Hurghada), Egypt. Details given in her key indicate the specimen was correctly identified to the present species, but the size is large for the species. Although our examined Red Sea specimens do not exceed size 22.1 mm SL, an uncatalogued specimen from El Quseir measured 36.0 mm SL ( Figure 3 A). Clark’s specimen (deposited in the Marine Biological Station at Hurghada), was not examined by us.

Material examined. RED SEA. Egypt: USNM 270680, 1 : 22.0 mm SL male, ca. 1 mile N of Ras Burqa, 0– 7.5 m, V.G. Springer et al., 21 July 1969 . Eritrea: USNM 270677, 1 : 20.3 mm SL female, 1: 21.5 mm SL male, S shore of Difnein I., 16°36’N 039°20’E, 0–4 m, V.G. Springer et al., 15 August 1969 ; USNM 270681, 1: 18.9 mm SL female, collected with USNM 270677. Saudi Arabia: KAUMM 419 (field number KAU13-34), 1: 14.6 mm SL juvenile, Al Khoreybah , st 38, unnamed island, seaward reef, corals at base of fringing reef, 8–12 m, S.V. Bogorodsky, 23 June 2014 ; SMF 35839 (tissue sample KAU11-291), 1: 22.1 mm SL male, Al Qunfudhah , reef flat, 1.5 m, S.V. Bogorodsky & T.J. Alpermann, 30 March 2011 ; KAUMM 418 (field number KAU13-29), 1: 13.4 mm SL juvenile, st 31, Duba , bay with coral wall, 12–16 m, S.V. Bogorodsky, 21 June 2013 ; SMF 35838 (field number KAU13-21), 1: 14.8 mm SL juvenile, st 24, Duba , base of fringing reef, 10–12 m, S.V. Bogorodsky, 19 March 2013 .

Figures

FIGURE 3. Distribution records for Xenisthmus oligoporus (closed circles), X. balius (open circles) and Red Sea X. polyzonatus (triangles).

FIGURE 5. Xenisthmus polyzonatus, A: uncatalogued, 36.0 mm SL, Mangrove Bay, El Quseir, Egypt, Red Sea; B: SMF 35838, 14.8 mm SL juvenile, Duba, Saudi Arabia, Red Sea. Photographs by S. V. Bogorodsky.