Opistognathus ensiferus, Smith-Vaniz, William F., 2016

Smith-Vaniz, William F., 2016, Opistognathus ensiferus, a new species of jawfish (Opistognathidae) from the Gulf of Mannar, India, with redescription of O. solorensis Bleeker, Zootaxa 4196 (2), pp. 278-288 : 279-282

Opistognathus ensiferus new species

( Figures 1‒2 A; Tables 1‒4)

Holotype. (only known specimen) FMNH 71365, 61.5 mm SL, male, India, Gulf of Mannar, Manauli Reef, Musal Tivu Island ( Hare Island ), 9°12'N, 79°55'E, ca. 1.0 m, living and dead coral, sand and rubble, Loren P. Woods, 22 February 1964.

Diagnosis. A species of Opistognathus with an elongate supramaxilla and maxilla with flexible lamina posteriorly, widest before end and sword-shaped in adult males,; inner lining of upper jaw and adjacent membranes with a single black stripe and no dark oral pigmentation; dorsal and anal fins XI,14 and III,14, respectively; lateralline terminus ends below dorsal-fin segmented rays 6 or 7.

Description. Dorsal-fin rays XI,14. Anal-fin rays III,14. Pectoral-fin rays 20. Caudal fin: procurrent rays 5+4, segmented rays 8+8, middle 14 branched, total elements 25; hypural 5 present. Vertebrae: 10+18; last rib on vertebra 10; epineurals 13. Supraneural bones 1. Gill rakers (right/left) 9/10+18/19 = 27/29.

Scales absent on head, nape, area above lateral line, pectoral-fin base and breast; belly completely scaly. Body with about 48–52 oblique longitudinal scale rows. Lateral line ends below verticals from 6th (left) or 7th (right) segmented dorsal-fin rays. Lateral line pores numerous, arranged in multiple series above and below embedded lateral-line tubes. Cephalic sensory pores numerous, completely covering most of head, including all of predorsal area except a small area immediately adjacent to dorsal-fin origin ( Fig. 2 A); mandibular pore positions 1–2 occupied by relatively large, single pores, 3rd position with 5 or 6 pores, 4th with 8 pores, and 5th position with at least 15 pores.

Anterior nostril slightly closer to posterior nostril than to dorsal margin of upper lip, and with a simple, flattened tentacle on posterior rim that when depressed reaches margin of posterior nostril; height of tentacle about 1.5 times maximum of diameter of posterior nostril. Dorsal fin moderately low anteriorly, gradually increasing in height posteriorly; profile relatively uniform with only a slight change in fin height at junction of spinous and segmented rays. Dorsal-fin spines relatively slender and curved distally with flexible tips; all segmented dorsal- and anal-fin rays branched distally. Outermost segmented pelvic-fin ray not tightly bound to adjacent ray, interradial membrane incised distally. Posterior margin of preopercle indistinct without a free margin. No papillae on inner surface of lips. Fifth cranial nerve passes under A1β branch of adductor mandibulae.

Upper jaw extends 2.2 eye diameters behind posterior margin of orbit; maxilla with flexible lamina posteriorly, widest before end and sword-shaped in adult males; supramaxilla moderately large, elongate and subterminally positioned. Premaxilla with an outer row of stout conical teeth that become progressively smaller posteriorly, an inner row of smaller conical teeth anteriorly that are canted backwards, except 2 teeth on each side of premaxillary symphysis, which are as large or larger than adjacent outer teeth. Dentary with an outer row of moderate teeth, largest mid-laterally, and 1 or 2 irregular inner rows of smaller conical teeth anteriorly that are slightly canted backwards. Vomerine teeth absent.

Measurements of the 61.5 mm SL male holotype, as percent of SL: predorsal length 31.5; preanal length 58.4; dorsal-fin base 64.6; anal-fin base 35.9; pelvic-fin length 16.7; caudal-fin length 24.2; depth at anal-fin origin 18.1; caudal-peduncle depth 11.2; head length 35.3; postorbital-head length 24.0; upper-jaw length 27.8; postorbital-jaw length 18.7; orbit diameter 8.6. As percent of head length: postorbital-head length 68.0; upper-jaw length 78.8; postorbital-jaw length 53.0; orbit diameter 24.2.

Color pattern in alcohol ( Fig. 1 ): head and body various shades of brown; head mostly uniformly pigmented except a few scattered dark spots, much smaller than pupil diameter; lips without bands and inside of mouth pale except inner lining of upper jaw and adjacent membranes with posterior dark stripe that is externally visible; body with irregular, mid-lateral, dark stripe that extends on to base of caudal fin, stripe bordered above and below by series of 6–8 faint pale spots that do not extend on to fin bases, upper spots smaller and more complete; dorsal fin with large ocellus centered between spines 3–6 followed by a similar sized, indistinct dark blotch extending to distal margin of fin, and soft portion of fin unmarked except for dark stripe, approximately width of pupil, centered on about basal third of fin; anal fin with narrow pale basal area, otherwise uniformly dark; caudal fin mostly pale with faint band on anterior third of fin; pelvic fin uniformly dark. Life coloration unknown.

Dorsal-fin spines and rays Anal-fin spines and rays Caudal vertebrae

Species X XI 14 15 III 13 14 15 17 18 19

ensiferus 1 1 1 1 1

solorensis 2 83 80 5 85 83 2 2 81 2

verecundus 2 2 7 2 6 3 2 9 1 2 7 1 2 8 1

Caudal-fin rays

Procurrent rays Branched rays Total pectoral-fin rays Upper Lower Total

Species 34 35 36 37 38 39 40 4 5 6 3 4 5 7 8 9 10 11 12 13 14

ensiferus 1 1 1 1 1

solorensis 1 ─ 5 2 43 7 9 14 55 3 1 45 26 14 33 22 3 13 7 35

verecundus 15 6 8 15 9 4 19 1 3 13 7 1 4 6 12 Total gill-rakers

Species 23 24 25 26 27 28 29 30 31 32 33 mean ensiferus 1 ─ 1 2 8.0 solorensis 9 1 8 2 4 1 6 5 1 1 2 9.0 verecundus 5 1 1 7 1 2 4.2 44 46 48 50 52 54 56 58 60 62 64 66 68

Species 45 47 49 51 53 55 57 59 61 63 65 67 69 mean SD ensiferus 1 ─ 1 5 0.0 2.8 solorensis 1 ─ ─ 3 5 1 5 1 4 5 2 6 3.0 2.8 verecundus 2 ─ 3 3 3 1 4 9.4 3.1 Lateral-line terminus position

Species 1 2 3 4 5 6 7 mean ensiferus 1 1 6.5 solorensis 10 30 24 11 2.5 verecundus 3 1 7 7 3.1 Remarks. The new species is most similar to Opistognathus solorensis and O. verecundus but differs from both species in having a lateral line that ends below the 6th or 7th segmented dorsal-fin ray (vs. below the 1st to 4th ray), inner lining of upper jaw and adjacent membranes with a single dark stripe (vs. two stripes) and no dark oral pigmentation (vs. with distinct oral pigmentation, Fig. 3 ). Opistognathus verecundus further differs in lacking a black blotch or spot on the spinous dorsal fin and in having fewer total gill rakers 23–26 (vs. 27–33). Distribution. Known only from the type locality, Manauli Reef , Gulf of Mannar, India ( Fig. 4 ). Etymology. The specific epithet, from the Latin ensifer (sword-bearing), is in allusion to the scimitar-shaped upper jaw.

Figures

FIGURE 1. Opistognathus ensiferus n. sp., holotype, FMNH 71365, male, 61.5 mm SL, India, Gulf of Mannar, Manauli Reef. Drawn by Jack R. Schroeder.

FIGURE 2. Cephalic sensory pores in two species of Opistognathus: A, O. ensiferus n. sp., holotype and B, O. solorensis, WAM P. 33117 – 001, male, 48 mm SL, Brunei.

FIGURE 3. Diagrammatic illustrations of oral pigmentation in two species of Opistognathus: A, O. solorensis and B, O. verecundus.

FIGURE 4. Distribution of Opistognathus solorensis species group. Collections from closely adjacent localities are represented by single symbols.