Enneapterygius gracilis Fricke, 1994

Dewa, Yuna, Tashiro, Satokuni & Motomura, Hiroyuki, 2023, A new species of the genus Enneapterygius (Perciformes: Tripterygiidae) from Japan and the Philippines, with a synopsis and synonymy of related species, Zootaxa 5374 (3), pp. 333-360 : 342-344

Enneapterygius gracilis Fricke, 1994

[English name: Northern Yellow-black Triplefin]

Figures 4 , 7 ; Tables 2 , 6 , 7

Enneapterygius gracilis Fricke, 1994: 209 , fig. 34 (original description; type locality: Danger Point, Cobourg Peninsula, Northern Territory, Australia); Larson and Williams, 1997: 367 (Nightcliff, East Point, and Lee Point Reef, Northern Territory); Fricke, 1997: 567 (Western Australia, Northern Territory, and Queensland); Hutchins, 2001: 41 (Western Australia); Hoese, 2006: 1520 (Gulf of Carpentaria, Northern Territory); Larson et al., 2013: 177 (Northern Territory: Burford Island; Trepang Bay, Cobourg Peninsula; North Oxley Island; East Vernon island; Veronica Island, Gove Peninsula; Yirrkala Reef).

Holotype. NTM S. 10431-027 , male, 19.7 mm SL, Danger Point , Cobourg Peninsula, Northern Territory, Australia, 11°08′S, 132°20′E, 0–1.5 m, 1 May 1982, B. Russell et al.

Paratypes. 8 specimens (15.8–20.7 mm SL). NTM S. 10431-034 , female, 16.5 mm SL, same data as holotype; AMS I. 17060-043 , 3 males and 3 females, 18.3–20.7 mm SL, Exmouth Gulf, Western Australia, 22°15′S, 114°15′E, 19 Jan. 1972, W. Ponder; AMS IB. 7075 , female, 15.8 mm SL, Bountiful Island, Gulf of Carpentaria , Queensland, 16°41′S, 139°50′E, Dec. 1963, J. Yaldwyn .

Non-type specimen. AMS I. 25500-005 , male, 19.5 mm SL, 5 km north of Learmouth, Exmouth Gulf , Western Australia, 22°20′S, 114°10′E, 10 Sept. 1985, D. Hoese & D. Rennis .

Diagnosis. A species of Enneapterygius ( Fig. 7 ) with the following combination of characters: 11 or 12 (modally 12) second dorsal-fin spines; 9–11 (9) third dorsal-fin rays; I, 16–18 (7) anal-fin rays; ii–iv (iii) + 4–6 (5) + vi–vii (vii) = 14–16 (15) pectoral-fin rays (iii + 5 + vii = 15 in holotype and 4 paratypes, iv + 4 + vii = 15 in 2 paratypes, iv + 5 + vii = 16 and ii + 6 + vi = 14 in single paratype specimen and non-type specimen); 12 or 13 (13) pored lateral-line scales; 19–22 (21) notched lateral-line scales; 31–34 (32) scales rows in longitudinal series; 2 or 2½ (2) scales above 1st pored lateral-line scale; 3 or 3½ (3) scales below 1st notched lateral-line scale; 8 circumpeduncular scales; mandibular pores 3–4 + 1–2 + 3–4 (usually 3 + 2 + 3) ( Fig. 8A ) (3 + 2 + 3 in holotype, 6 paratypes, and a non-type specimen, 3 + 1 + 3 and 4 + 2 + 4 in single paratype only); head relatively long, its length 29.2–32.5% (mean 30.6%) of SL; upper jaw length 9.2–11.7% (11.0%) of SL; 1st spine of first dorsal fin slightly longer than that of 2nd dorsal fin, its length 10.8–17.9% (13.9%) of SL; anterior nostril tentacle unbranched; orbital tentacle circular, the edge slightly pointed, its length slightly less than or subequal to pupil diameter; body generally yellowish or brownish with 6 or 7 bands, darker around lateral line; brownish blotches on each pectoral-fin ray, forming 3 or 4 narrow bands; anal fin with 7–9 brownish oblique bands; caudal fin translucent with 5 vertical bars; body yellowish, lower half of head and pectoral-fin base black in nuptial males.

Distribution. Enneapterygius gracilis is distributed only in northern Australia, where it ranges from Western Australia (Exmouth Gulf) to the Northern Territory (East Point, Nightcliff, Lee Point, East Vernon Island, Burford Island, Trepang Bay, North Oxley Island, Veronica Island, Yirrkala Reef) and Queensland (Bountiful Island) ( Fricke, 1994; Larson & Williams, 1997; Fricke, 1997; Hutchins, 2001; Hoese, 2006; Larson et al., 2013) ( Fig. 4 ).

Remarks. Although Fricke (1994) described the symphyseal mandibular pore of E. gracilis as single (mandibular pore formula 3 + 1 + 3), examination of specimens, including the holotype, in this study revealed that E. gracilis has double symphyseal mandibular pores, the mandibular pore formula being revised as 3 + 2 + 3, accordingly. Enneapterygius gracilis is similar to E. olivaceus n. sp. in having a long head [29.2–32.5% (mean 30.6%) of SL], 1st spine of the first dorsal fin [10.8–17.9% (13.9%) of SL], and orbital tentacles (slightly less than or subequal to pupil diameter) ( Figs 5 , 6 ). However, the former differs from the latter in notched lateral-line scale and scales below the 1st notched scale numbers, and mandibular pore formula ( Figs 5 , 6 ) (see E. olivaceus n. sp. Remarks.)

Figures

FIGURE 4. Distributional map of five species of Enneapterygius examined in this study.

FIGURE 5. Orbital tentacle shape of A Enneapterygius olivaceus n. sp., KAUM–I. 101347, holotype, male, 19.3 mm SL, Yoron-jima Island, Japan; B E. gracilis, AMS I. 25500-005, male, 19.5 mm SL, Western Australia; C E. nanus, NSMT-P 54443, male, 14.3 mm SL, Eroj Island, Marshall Islands; D E. minutus, lectotype, BMNH 1961.10.20.1, female, 20.4 mm SL, Apia, Western Samoa. Bars represent 1 mm

FIGURE 6. Lengths of A head, B upper jaw, and c 1st spine length of first dorsal-fin (% standard length) relative to standard length in five species of Enneapterygius. Yellow triangles, orange circles, red diamonds, blue squares, and a green star indicate E. gracilis, E. minutus, E. nanus, E. olivaceus n. sp., and E. philippinus, respectively

FIGURE 7. Photographs of preserved specimens of Enneapterygius gracilis. A NTM S. 10431-027, holotype, male, 19.7 mm SL, Northern Territory, Australia; B AMS I. 17060-043 (1), paratype, male, 19.9 mm SL, Western Australia; C AMS I. 17060- 043 (3), paratype, female, 19.5 mm SL; D NTM S. 10431-034, paratype, female, 16.5 mm SL, Northern Territory

FIGURE 8. Illustrations of mandibular pore system of Enneapterygius gracilis and Enneapterygius minutus. A double symphyseal mandibular-pores (3 + 2 + 3) (Enneapterygius gracilis, AMS I. 25500-005, male, 19.5 mm SL), B single symphyseal mandibular-pore (mandibular pore formula: 3 + 1 + 3) (Enneapterygius minutus, BMNH 1961.10.20.1, female, 20.4 mm SL) Bars represent 1 mm

Tables

TABLE 2. Counts and morphometric measurements (as % of SL) of specimens of Enneapterygius gracilis

	Holotype	Paratypes		Non-type
	NTM S. 10431-027	n = 3	n = 5	AMS I. 25500-005
	Australia	Australia	Australia	Australia
	Male	Males	Females	Male
Standard length (SL; mm)	19.7	18.3–19.9	15.8–20.7	19.5
Counts
Dorsal-fin rays	III, XII, 10	III, XI, 9–11	III, XI–XII, 9–10	III, XII, 9
Anal-fin rays	I, 17	I, 16–18	I, 16–17	I, 17
Pectoral-fin rays	iii + 5 + vii = 15	iii + 5 + vii = 15	ii–iv + 4–6 + vi–vii = 14–15	iv + 5 + vii = 16
Scale rows in longitudinal series	32	33–34	32–34	31
Pored lateral-line scales	12	13	13	12
Notched lateral-line scales	21	21–22	21–22	19–20
Scales above of 1st PLL	2	2	2–2½	2
Scales below 2nd dorsal fin	3	2½–3½	2½–3½	2½
Scales below of 1st NLL	3	3–3½	3–3½	3
Circumpeduncular scales	8	8	—	8
Mandibular pore formula	3 + 2 + 3	3 + 2 + 3	3–4 + 1–2 + 3–4 (usually 3 + 2 + 3)	3 + 2 + 3
Measurements (% SL)
Body depth	21.0	20.8–22.2 (21.6)	19.8–21.1 (20.3)	20.5
Body width	18.6	17.3–19.8 (18.7)	17.3–20.0 (18.1)	21.0
Head length	30.5	30.5–31.1 (30.7)	30.0–32.5 (30.9)	29.2
Snout length	9.4	7.9–8.9 (8.3)	7.7–8.6 (8.2)	10.3
Orbit diameter	10.9	10.7–10.9 (10.8)	10.2–11.0 (10.5)	10.3
Interorbital width	2.7	2.4–2.8 (2.7)	2.1–2.9 (2.5)	3.1
Upper-jaw length	11.7	11.5–11.7 (11.5)	10.3–11.2 (10.9)	9.2
Postorbital length	13.5	13.5–14.3 (13.9)	13.7–14.2 (13.8)	13.3
Pre-1st-dorsal-fin length	26.6	24.6–25.9 (25.4)	23.6–26.5 (25.2)	26.2
Pre-2nd-dorsal-fin length	38.0	37.6–39.6 (38.7)	36.9–38.1 (37.7)	37.4
Pre-3rd-dorsal-fin length	71.6	72.5–74.1 (73.4)	68.8–72.1 (70.9)	70.3
Pre-anal-fin length	48.8	50.7–52.6 (51.9)	50.1–53.9 (52.6)	52.3
Anal-fin base length	43.5	40.8–43.3 (42.4)	39.1–43.5 (41.1)	37.9
Pre-pectoral-fin length	31.5	32.2–33.0 (32.6)	31.9–33.5 (32.9)	31.3
Pre-pelvic-fin length	23.7	24.5–24.9 (24.7)	22.1–24.8 (23.6)	23.6
Caudal peduncle length	9.2	8.1–9.9 (9.2)	8.5–10.4 (9.6)	14.9
Caudal peduncle depth	8.6	9.2–10.7 (10.1)	8.2–10.3 (9.2)	9.2
1st spine length of 1st dorsal fin	15.6	13.0–14.9 (13.7)	12.8–17.9 (14.3)	10.8
2nd spine length of 1st dorsal fin	12.5	10.2–11.6 (10.7)	10.1–14.7 (11.8)	10.3
3rd spine length of 1st dorsal fin	9.8	8.4–9.3 (8.9)	8.9–10.8 (9.9)	7.2
1st dorsal-fin base length	6.6	6.4–7.3 (6.8)	5.9–6.8 (6.5)	5.1
1st spine length of 2nd dorsal fin	15.1	13.3–13.8 (13.6)	13.2–13.9 (13.6)	12.8
2nd spine length of 2nd dorsal fin	16.2	13.6–14.6 (14.1)	13.8–15.5 (14.9)	14.9
3rd spine length of 2nd dorsal fin	16.9	13.9	14.1–15.8 (15.2)	14.9
2nd dorsal-fin base length	34.5	29.1–32.8 (30.7)	26.8–30.4 (28.9)	29.2
1st ray length of 3rd dorsal fin	damaged	18.9	16.2–18.5 (17.6)	15.9
2nd ray length of 3rd dorsal fin	16.0	16.3–18.4 (17.3)	17.2–17.7 (17.4)	15.9
3rd dorsal fin base length	20.1	17.2–21.1 (19.2)	damaged	16.4
Pectoral-fin length	33.1	33.6–37.3 (35.3)	33.9–37.3 (36.0)	29.7
1st ray length of pelvic fin	17.2	16.2–19.9 (18.5)	17.2–20.3 (18.5)	damaged
2nd ray length of pelvic fin	25.0	25.7–27.7 (26.8)	25.6–28.0 (26.6)	damaged

Means in parentheses