Opistognathus reticeps, Smith-Vaniz, 2004

Smith-Vaniz, William F., 2004, Descriptions of Six New Species of Jawfishes (Opistognathidae: Opistognathus) from Australia, Records of the Australian Museum 56 (2), pp. 209-224 : 220-221

Opistognathus reticeps n.sp.

Figs. 2D, 3F, 11; Tables 1–4

Type material. HOLOTYPE: NTM S.10553-004, gravid female (99.4), Australia, Northern Territory, Darwin Harbour , east arm, 12°29'S 130°53'E, 0–1 m, sta. HL 82– 49, H. Larson and R. Williams, 6 Sep. 1982 . PARATYPES: 7 specimens, 19.4–117.3 mm. WAM P.24227 (113), Napier Broome Bay, Jul. 1973; NTM S.10158-003 (87.2), Van Diemen Gulf, Northern Territory Fisheries , 17 Jan. 1978, Sta. 11/9; AMS IA.7606, gravid female (117.3), Darwin , near jetty, from burrows on mud flat, M. Ward, 31 Jul. 1938; NTM S.10718-032 (63.7, C&S), Darwin Harbour , east arm, 1.5 m, H. Larson et al., 31 Dec. 1982, Sta. HL 82–91; NTM S.11242-002 (75.4), Darwin Harbour , Wood Inlet , 2 m, H. Larson and R. Williams , 16 Mar. 1984, Sta. HL 84–12; NTM S.10608-013 (19.4), N. Oxley Island , 11°00'S 132°49'E, 11–12 m, H. Larson et al., 21 Oct. 1982, Sta. HL 82–79; NTM S.13282-001 (84.2), Beagle Gulf, N. of Charles Point, 12°15.4'S 130°37.8'E, trawled in 23–29 m, R. Williams, 2 Sep. 1992, Sta. RW 92–2 .

Diagnosis. A species of Opistognathus with dorsal fin XII, 15 or 16; dorsal fin with 4 dark blotches, the first 2 extending onto distal half of fin; dorsum of head reticulated; lateralline terminus below verticals from 10th spine to 3rd segmented dorsal-fin ray.

Description. Dorsal-fin rays XII, 15 or 16. Anal-fin rays II, 13 or 14. Pectoral-fin rays 22 or 23. Caudal fin: procurrent rays 3–4+3–4, segmented rays 8+8, middle 12 branched, total elements 22–24; hypural 5 present. Vertebrae: 12+19; last pleural rib on vertebra 12; epineural ribs 15. Supraneurals absent, insertion pattern 0/0/1/1+1/1/. Gill rakers 9–10+17–19 = 26–29.

Scales absent on head, nape, pectoral-fin base (largest specimen with a few embedded scales) and breast; 3 or 4 rows of scales present above lateral line anteriorly and 1 or 2 rows posteriorly. Body with about 56–64 oblique scale rows in longitudinal series. Lateral-line terminus below verticals from 10th spine to 3rd segmented dorsal-fin ray (total element position 10–14). Lateral-line pores relatively sparse, mostly arranged in a single series along embedded lateral-line tubes. Cephalic sensory pores relatively numerous, except pores absent on most of nape; 1st mandibular pore position bipored, all other mandibulopreopercular pore positions occupied by multiple pores too small and numerous to count accurately; infra- and supraorbital pores also very numerous.

Anterior nostril positioned closer to posterior nostril than to margin of upper lip, and consisting of a short tube with a broad tentacle on posterior rim that when depressed extends to or nearly to posterior margin of posterior nostril; height of tentacle about 1.0–1.5 times maximum diameter of posterior nostril. Dorsal fin moderately low anteriorly, increasing in height posteriorly, with profile relatively uniform without change in height at junction of last spine and anterior segmented rays. Dorsal-fin spines relatively slender and only slightly curved, with flexible tips; skin covering tips of dorsal-fin spines somewhat rugose but without fleshy tabs; all segmented dorsal- and anal-fin rays branched distally, except first 1 or 2 anal rays usually unbranched. Outermost segmented pelvic-fin ray not tightly bound to adjacent ray, interradial membrane incised distally. Upper margin of opercle straight and slightly rounded posterodorsally; posterior margin of preopercle distinct, with a free margin. No papillae on inner surface of lips. Fifth cranial nerve passes over A1 section of adductor mandibulae.

Upper jaw not sexually dimorphic, extending about 0.7– 1.0 eye diameters behind posterior margin of orbit; maxilla widest at end and rounded, without flexible lamina posteriorly ( Fig. 2D); supramaxilla present, relatively small and terminally positioned. Jaws subequal, lower slightly included. Both jaws with an outer row of enlarged conical teeth that are relatively straight and slant forward, especially anteriorly; 1 or 2 irregular rows of much smaller inner teeth present anteriorly, those adjacent to premaxillary symphysis slightly enlarged and canted posteriorly. Vomerine teeth absent. Infraorbital bones relatively slender and tubular ( Fig. 3F); 3rd infraorbital with a slight suborbital shelf. Second pharyngobranchial rod-shaped with distal end slightly expanded.

Measurements of the 99.4 mm holotype (in parentheses) and 5 paratypes, 75–117 mm, as percentage of SL: predorsal length (39.0) 34.6–40.0; preanal length (63.9) 56.9–67.0; dorsal-fin base (62.6) 60.1–69.1; anal-fin base (26.6) 25.4– 30.1; pelvic-fin length (22.6) 20.4–25.3; caudal-fin length

(25.8) 24.1–29.8; depth at anal-fin origin (24.1) 22.9–25.5; head length (39.2) 37.1–41.2; orbit diameter (12.5) 12.5– 13.9; upper jaw length (25.7) 24.7–26.3. As percentage of head length: postorbital head length (61.8) 57.9–61.6; upper jaw length (65.4) 62.2–67.4; postorbital jaw length (30.1) 23.0–29.8; orbit diameter (31.8) 32.1–35.1.

Preserved coloration. Dorsum of head, snout, upper part of opercle, and nape reticulated with irregular pale markings or spots, remainder of head and body mostly pale to light dusky, except blotches in dorsal fin usually continue across the body as faint bands (best developed in smaller specimens), and a similar basicaudal band may be present on caudal peduncle; dorsal fin with four dark blotches that extend slightly onto dorsum; interradial membranes immediately adjacent to blotches lighter than rest of fin and almost clear in the smaller paratypes; anterior two blotches extending to or almost to distal margin of fin, others becoming progressively smaller in height; 1st blotch positioned between spines 3–6, 2nd between spines 9–12, 3rd between rays 3–6 and 4th between rays 10–14; dorsal and anal fins with narrow dark margins, widest posteriorly; remainder of anal fin pale or with one or two dark spots, slightly smaller than pupil diameter, in basal half of fin aligned with blotches in dorsal fin; caudal fin pale except for narrow dark margin; pelvic fins immaculate and pectoral fins faintly speckled.

Etymology. The specific epithet is from the Latin rete (net) and ceps (head), in reference to the reticulated dorsum of the head that is a distinguishing feature of this species. The name should be treated as a noun in apposition.

Distribution. Known only from northern Australia.

Remarks. Only Opistognathus reticeps and four other species of jawfishes have 12 dorsal-fin spines, and all have different colour patterns (see following identification key). Opistognathus reticeps apparently is much smaller (largest individual, a 117 mm SL gravid female) than the other four, all of which attain at least 200 mm. The largest specimens examined (mm SL) of the others are: O. inornatus (409); O. papuensis (339); O. reticulatus (368); O. latitabundus (216).