Forsterygion gymnota Scott, 1977

Jawad, Laith A., 2008, Second revision of the New Zealand triplefin genus Forsterygion Whitley and Phillips, 1939 (Pisces: Tripterygiidae), Journal of Natural History 42 (47 - 48), pp. 2943-2989 : 2967-2969

Forsterygion gymnota Scott, 1977

Robust triplefin

Forsterygion gymnota Scott 1977, p. 158 –161, Fig. 3 (Montague Bay, SE Tasmania); Last et al., 1983 p. 428–429, Fig. 30.99 (South-eastern Tasmania; mainly shallow, estuary near Hobart).

Forsterygion ? robustum: Paulin and Roberts 1992, p. 177 , Figs 88, pls.32.

Grahamina gymnotum . Fricke and Roberts 1993, p. 12–14, Fig 7 (Tasmania); Clements et al. 2000, p. 373–384; Francis 2001, p. 85, pl.175.

Grahamina signata . Fricke and Roberts 1993, p. 15.

Tripterygion robustum Syms 1995, p. 31 –43

Grahamina signata . Clements et al. 2000, p. 373–384.

Diagnosis

A species of Forsterygion with the following set of characters: snout profile steep, line drawn through tip of premaxilla across ventral margin of orbit touches or passes anterodorsal to dorsal extremity of preoperculum. Transverse groove in front of first dorsal fin containing cephalic sensory pore. Scales absent in front of first dorsal fin first spine, naked immediately adjacent to first dorsal, but many small ctenoid scales adjacent to post-temporal. First lateral line scale with one group of ctenii at upper posterior edge, second scale onward, with two groups of ctenii at upper and middle posterior edges. Dorsal fin formula V-0N-0-1-0-1 (36).

Description

The following counts and proportions (given as times in standard length unless otherwise stated) are based on the paratype and, in parentheses, the range for 94 non-type specimens of 27–93mm SL. F. gymnota differs from F. varium in the following combination of characters: Steeply angled, blunt snout. Medium sized species. First dorsal fin low, shorter in height than second dorsal.

Head length 4.2 (3.6–4.4); predorsal length 3.3 (3.2–3.6); preanal length 2.3 (2.3– 2.4); peduncle length 1.7 (1.7–1.8); peduncle depth 12.8 (11.7–12.8); pectoral fin length 3.2 (3.2–4.0); eye diameter 3.3 (3.3–3.6) in HL; upper jaw length 2.5 (2.5–2.6) in HL; snout length 3.0 (2.9–3.4) in HL.

Dorsal fin spines VII (VI–VIII); second dorsal fin spines XX (XIX–XXII); third dorsal fin rays 17 (14–16); pectoral fin rays 17 (15–18); anal fin with 2 spines and 26 (25–27) fin rays. Discontinuous lateral line with 23(20–26) tubular scales, 20–25 notched scales. Total vertebral number 45 (44–46). Transverse groove in front of first dorsal fin first spine.

Head sensory canals. Postocular canal extending backward toward postemporal. Supratemporal canal with few small pores. Preoperculo-mandibular canal with a single sensory pore line. No sensory papillae on frontal, temporal and upper part of otic areas. Ventral part of the preoperculo-mandibular canal with eight sensory pores, four at base of preoperculum, three at tip of upper jaw and one at lower jaw symphysis.

Squamation. Head, nape and base of pectoral fin naked. Naked immediately adjacent to first dorsal, but several small ctenoid scales adjacent to post-temporal. Six to seven scales between the anterior end of second dorsal fin and lateral line. Two to three scales between second and third dorsal fins. Scales with crenate anterior scale margin. Secondary radii present in scales from all body regions. Lateral line canal scales with straight anterior end and C-shaped posterior end. First lateral line scale (counting from the anterior side of fish body) with one group of ctenii at upper posterior edge, remainder with two groups of ctenii at upper and middle posterior edges. Narrow-based denticles on circuli. Rounded focus with complete circulus and with coarse bumps.

Osteology. Post-temporal smooth, not exposed. Four infraorbitals variable in size. Orbital edge of lacrimal smooth, second, third and fourth infraorbitals with wavy ventral edges with smooth orbital edge. Short, club-shaped basihyal, with straight anterior edge. Basibranchials separated by narrow gap. Second hypobranchial with no phalanges. Shallow gap between legs of third hypobranchial. Oppositely arranged, non-stalked gill rakers. Phalanges at lateral end of first epibranchial directed anteriorly and posteriorly. Usual inverted boat shape uroyal (lateral view), elongated posteriorly, with central notch at anterior edge. Poorly developed, nonelevated basibranchial attachment. Pterygiophore supporting first segmented ray of third dorsal fin anterior to neural spine of twenty seventh vertebra. One free pterygiophore between second and third dorsal fins. Dorsal fin formula V-0N-0-1-0- 1 (36). Dorsal edges of both hypural plates curved. Parhypural with rounded free end. Blunt neural spine of second preural vertebra. Broad, short, pointed, haemal spine of second preural vertebra, not reaching posterior edge of lower hypural. Epurals straight, similar width and different length. Eight procurrent rays in upper caudal lobe, seven in lower lobe; in upper lobe, one procurrent ray between upper lobe and posterior epural, five opposite epurals, one opposite neural spine of third preural vertebra; in lower lobe, five rays opposite haemal spine of second preural vertebra, one ray opposite haemal spine of third preural vertebra and one ray anterior haemal spine of third preural vertebra.

Otolith. Lateral surface smooth. Posterior end with two rounded projections. Crista inferior absent. Antirostrum broad.

Colour. Body grey-brown to reddish-brown with dark brown or black blotches dorsally. Head with greenish-yellow mottling pattern extending from the dorsal side, surrounding eyes and covering snout. Large yellow/white blotches along the posterior edge of preoperculum and operculum, and sometimes on sides of body. Occasionally, mottling pattern is not clear and blotches on preoperculum and operculum are faint. First dorsal fin blackish with yellow/orange broad blotch at its anterior and central part. Base of the second dorsal fin with a series of yellow blotches, sometimes forming a continuous broad line; fin tip clear, sometimes with a dark or brown colouration. Third dorsal fin transparent, sometimes with few basal yellow blotches. Base of pectoral fin dark, with broad cream arc distally. Anal fin with a dark broad line across it.

Size. 93mm SL.

Distribution

Throughout New Zealand, from Cape Reinga to Stewart Island , including Chatham Islands. Introduced to Tasmania , it is now found in the Derwent Estuary ( Edgar et al. 1982) and is common in a range of habitats around Hobart ( Kendall Clements , Auckland University , personal observation). In New Zealand usually found on exposed rocky coasts with sand, but also common on wharf piles among encrusting invertebrates. Depth to at least 7m.

Material examined

Museum specimens (n 594): holotype of G. signata, NMNZ P. 30569, 1, 73mm SL, Tauranga Bay, S side, opposite seal colony, 3km SSW Cape Foul wind, 41 ° 479S 171 ° 279E, rock pool and 0–1.5m depth, rocks, sand and algae, exposed area, 21 Nov 1992 , paratypes; NMNZ P. 30570, 4, 51–62mm SL, same data as holotype; 2, southeastern Tasmania, Aug 1976 ; QVMT 1976 /5/205, 206, QVMT Type Nos. 233 and 234, paratypes; NMNZ P. 13557, 4, 36–58mm SL, Muriwai Beach , Auckland, 36 ° 509S 174 ° 269E, intertidal pools, 17 Jan 1962 ; NMNZ P. 17082, 3, 43–68mm SL, Castle Rock, Seal Rocks, Sugar Loaf Islands , New Plymouth, 39 ° 0.359S 174 ° 00.29E, 25 Mar 1985 ; NMNZ P. 24347, 10, 36–66mm SL, Higgins Wharf, Napier Harbour , 22 Mar 1988 ; NMNZ P. 25282, 1, 47mm south-eastern Tasmania, Aug 1976 ; NMNZ P. 25422, 2, cleared and stained, Kettering Jetty , S. Bell, 11 Jan 1966 ; NMNZ P. 30579, 3, 80–93mm SL, Wrest Point, Hobart, Derwent River Estuary , 1982; NMNZ P. 30580, 2, 47–82mm SL, Wrest Point , Hobart , Derwent River estuary, 1982; NMNZ P. 25422, 2, cleared and stained, Kettering Jetty, S. Bell , 11 Jan 1966 ; NMNZ P. 30579, 3, 80–93mm SL, West Point, Hobart, Derwent River Estuary , 1982; NMNZ P. 30580, 2, 47–82mm SL, Wrest Point , Hobart , Derwent River estuary, 1982; 2, 55– 56mm SL, same data as holotype. Auckland University specimens: 2, 45– 71mm SL., Musick Point , 31 Mar 1998 ; 2, 56– 65mm SL., Whatipu, North Head , Manukau Harbour, 14 Aug 1999 ; 11, 50– 75mm SL., Whatipu, North Head Manukau Harbour , 5 Sept 1999 ; 15, 27– 70mm SL, Te Arai Point , 15 Dec 1999 ; 3, 43.4–48.7mm SL, Orapiu Wharf, Waiheke Island , 29 Dec 1999 ; 3, 47.9–49.9mm SL, Orapiu Wharf, Waiheke Island , 30 Dec 1999 ; 6, 47.4–56.4mm SL, Orapiu Wharf, Waiheke Island , 1 Jan 2000 ; 11, 36– 85mm SL, Queens Wharf , Wellington, 23 Apr 2000 .

Figures

Figure 3. Pattern of head sensory canals of F. varium. (A) Lateral view; (B) Dorsal view; (C) ventrolateral view. Scale bar51 mm.

Figure 7. SEM micrograph of F. varium (53 mm, SL) otolith (mesial surface). Scale bar5500 Mm.