Enneapterygius atriceps
Creators: name: Motomura, Hiroyuki
name: Ota, Ryohei
name: Meguro, Masatoshi
name: Tashiro, Satokuni
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Perciformes
Tripterygiidae
Enneapterygius
Enneapterygius atriceps

description: Enneapterygius atriceps (Jenkins, 1903)
[English name: Hawaiian Blackhead Triplefin]
(Figs 6–7, 8 C–D, 9; Tables 1 –3)
Tripterygium atriceps Jenkins, 1903: 505, fig. 46 (type locality: Honolulu, Oahu, Hawaiian Islands).
Enneapterygius atriceps: Fricke 1997: 161, 566, figs 25, 26 (Hawaiian Archipelago, including French Frigate Shoals, Laysan Island, and Midway Atoll); Williams and Fricke 2001: 3534 (name only); Fricke 2009: 38 (Hawaiian Islands, north to Midway Atoll); Randall 2007: 373, unnumbered figs (Hawaiian Islands); Meguro and Motomura in Motomura and Matsuura 2010: 6 (name only).
Holotype. USNM 50719, male, 22.1 mm SL, Honolulu, Oahu, Hawaiian Islands, 1889, O. Jenkins.
Non-type material examined. 46 specimens, 14.9– 26.9 mm SL, all from the Hawaiian Archipelago. ANSP 28022, 3 males, 15.7–19.4mm SL, Honolulu, Oahu, Hawaiian Islands, 1900, O. Jenkins; ANSP 95035, male and female, 14.9–20.8 mm SL, Waikiki, Oahu, Hawaiian Islands, 1992, C. Edmondson; BPBM 3465, male, 25.8 mm SL, Waikiki Reef, Honolulu, Oahu, 1923, V. Pietschmann; BPBM 19658, male and female, 19.0– 20.9 mm SL, Kaneohe Bay, Oahu, 2 m, 13 September 1975, B. Carlson et al.; BPBM 34846, 13 males and 5 females, 19.5–23.9 mm SL, southeast side of Sand Island, Midway Atoll, 8 m, 16 September 1991, J. Randall et al.; FMNH 47658, male, 22.1 mm SL, Kaneohe Bay, Oahu, April–May 1935, Shedd Aquarium; FMNH 63605, 9 males and 5 females, 17.0– 26.9 mm SL, Kahuku, Oahu, 21 April 1961, L. Woods et al.; ROM 28022, 3 males (one in poor condition, its SL not included), 16.0– 18.5 mm SL, Honolulu, Oahu, US Fish. Commission; ROM 95035, 2 males, 15.6– 20.4 mm SL, Waikiki, Honolulu, Oahu, 1922, C. Edmondson.
Diagnosis. A small-sized species of Enneapterygius with the following combination of characters: 12–15 (mode 14) second dorsal-fin spines; 9–11 (9) third dorsal-fin soft rays; 14–17 (15) pectoral-fin rays; 19–21 (19) anal-fin soft rays; 35–37 (36) scale rows in longitudinal series; 17–20 (19) pored lateral-line scales; 16–20 (18) notched lateral-line scales; 1 or 2 scale rows between last pored lateral-line scale and first notched lateral-line scale; mandibular pore formula 4–6+1+4–5 (4+1+4); short dorsal-fin spines and rays [e.g., lengths of second spine 8.0–11.3% of SL (mean 9.2%) and third spine 6.5–9.1% of SL (7.8%) in first dorsal fin; first spine 12.5–14.2% of SL (13.4%), second spine 12.9–15.3% of SL (14.2%), and third spine 13.6–15.8% of SL (14.8%) in second dorsal fin; first soft ray 14.2–17.3% of SL (15.9%), second soft ray 13.6–16.7% of SL (15.6%), and third soft ray 13.4–16.2% of SL (14.8%) in third dorsal fin]; long second dorsal-fin base [27.4–38.1% of SL (mean 31.8%)]; long anal-fin base [39.5–47.5% of SL (mean 43.1%)]; nasal tentacle bilobed (Fig. 8C, D; rarely unbranched; 2 of 47 specimens with unbranched tentacle); lower two-thirds of head, including lower half of eye, snout, lips, cheek, and opercle, and pectoral-fin base dense black in nuptial males; upper head and body reddish-brown in females and males, reddish in nuptial males, with 4–6 H-shaped and/or upside-down Y-shaped oblique brown bars on lateral surface of body; caudal-fin base with vertical brownish band, its width subequal to pupil diameter, narrow vertical white band behind brownish band; narrow, indistinct, white line along posterior margin of black area on pectoral-fin base; no fins black.
Distribution. Known only from the Hawaiian Archipelago (Fricke 1997; this study).
Remarks. Counts and measurements of the above-listed holotype and non-types of E. atriceps are given in Tables 1 –3. The cephalic sensory pore system of the species is illustrated in Fig. 7. Color photographs of male and female specimens were published by Randall (2007: 373).
Comparisons. Enneapterygius phoenicosoma n. sp. is similar to the Hawaiian endemic species E. atriceps in sharing the following features: 16–20 pored lateral-line scales; a single scale row between the last pored lateral-line scale and the first notched lateral-line scale; the lower two-thirds of the head, including the lower half of the eye, snout, lips, cheek, and opercle, and the pectoral-fin base dense black in nuptial males; the upper head and body reddish in nuptial males but reddish-brown in females and non-nuptial males, with H-shaped or upside-down Y-shaped oblique brown bars on the lateral surface of the body; the caudal-fin base with a vertical brownish band, its width subequal to the pupil diameter, and a vertical narrow white band behind the brownish band; a narrow, indistinct, white line along the posterior margin of the pectoral-fin base; and no black fins. With the exception of E. phoenicosoma and E. atriceps, no nominal species with combination of the above-mentioned characters have been reported in the genus (Fricke 1997; this study).
The new species is clearly distinguished from E. atriceps by having a simple nasal tentacle (vs bilobed in the latter; Fig. 8) and 16–18 (mode 17) anal-fin soft rays [vs 19–21 (19); Tables 1–2]. Enneapterygius phoenicosoma further differs from E. atriceps in having 11–13 (mode 12) second dorsal-fin spines [vs 12–15 (14); Tables 1–2], 15–17 (16) pectoral-fin rays [vs 14–17 (15); Tables 1–2], 32–35 (33) scale rows in the longitudinal series [vs 35–37 (36); Tables 1, 3], and 16–19 (17) pored lateral-line scales [vs 17–20 (19); Tables 1, 3].
In morphometrics, E. phoenicosoma tends to have slightly longer spines and rays of the dorsal fins than E. atriceps: e.g., lengths of the second spine (mean 10.1% of SL vs 9.2% in E. atriceps; Table 1, Fig. 9A) and third spine (8.5% vs 7.8%; Table 1) in the first dorsal fin; lengths of the first spine (15.2% vs 13.4%; Table 1, Fig. 9B), second spine (15.9% vs 14.2%; Table 1, Fig. 9C), and third spine (15.8% vs 14.8%; Table 1, Fig. 9D) in the second dorsal fin; and the lengths of the first soft ray (17.3% vs 15.9%; Table 1), second ray (16.9% vs 15.6%; Table 1), and third ray (15.9% vs 14.8%; Table 1) in the third dorsal fin. In contrast, the lengths of the second dorsal-fin base and anal-fin base in E. phoenicosoma tend to be slightly shorter than those of E. atriceps (mean 29.2% of SL and 40.5%, respectively, vs 31.8% and 43.1%, respectively, in E. atriceps; Table 1, Fig. 9E, F).
Enneapterygius phoenicosoma grows larger than E. atriceps (largest recorded size, 37.2 mm SL vs 26.9 mm SL; this study). Fricke (1997) examined 87 specimens of E. atriceps ranging from 11 to 26 mm SL. On the basis of examination of otoliths of E. atriceps, Longenecker and Langston (2005) determined the age of the oldest individual of E. atriceps as 117 days, with sexual maturity occurring at about 55 days and 15 mm SL. No biological information on E. phoenicosoma is known. These two species are allopatrically distributed in the Pacific Ocean (Fig. 6).
Enneapterygius etheostoma (Jordan and Snyder, 1902) co-occurs with E. phoenicosoma through at the entire distributional range of the latter in Japanese waters. Coloration of females and pale males in the two species is very similar to each other either in life or when fresh. Besides the coloration of nuptial males, however, E. phoenicosoma differs from E. etheostoma in the following features: nasal tentacle simple (vs bilobed in the latter), 11–13 (mode 12) second dorsal-fin spines [vs 12–16 (14)], 16–18 (17) anal-fin soft rays [vs 17–20 (19)], 2½–4 (3½) scale rows between base of first spine of second dorsal fin and pored lateral-line scale [vs 4–7½ (6)], and 2–3 (2½) scale rows above last pored lateral-line scale [vs 3½–5½ (4)] (Fricke 1997; Meguro and Motomura unpub. data).
description: Published as part of Motomura, Hiroyuki, Ota, Ryohei, Meguro, Masatoshi & Tashiro, Satokuni, 2015, Enneapterygius phoenicosoma, a New Species of Triplefin (Tripterygiidae) from the Western Pacific Ocean, pp. 1-12 in Species Diversity 20 (1) on pages 10-11, DOI: 10.12782/sd.20.1.001, http://zenodo.org/record/4583130