Amamiichthys matsubarai ( Akazaki 1962 )

Tanaka, Fumiya & Iwatsuki, Yukio, 2015, Amamiichthys, a new genus for the sparid fish Cheimerius matsubarai Akazaki 1962, and redescription of the species, with designation of a neotype, Zootaxa 4007 (2), pp. 195-206 : 199-205

Amamiichthys matsubarai ( Akazaki 1962)

Proposed English name: Japanese blue-spotted seabream Japanese Name: Hoshirenko

Figures 1 A–3A, 4; Table 2

Cheimerius matsubarai Akazaki, 1962:132 , 347, Fig. 31 (Amami-oshima I., Ryukyu Is, Japan); Akazaki 1984: 177, pl. 166 (Amami-oshima I., Japan); Hayashi 2002: 859, upper right figure on p 859 (Amami-oshima I.); Hayashi & Ogihara 2013: 959, upper right figure on p 959 (Amami-oshima I., Japan)

Neotype ( Fig. 3A ). MUFS 30984, 268 mm SL, off Naze, Amami-oshima Island, Ryukyu Islands, Japan.

Non-type specimens (212–437 mm SL, n = 30). MUFS 2022, 30983, 33157–33159, 33292–33311, 43227, 26 specimens, 212–437 mm SL, off Naze, Amami-oshima Island, Ryukyu Is, Japan; MUFS 33160–33161, 2 specimens, 190–201 mm SL, off Setouchi, Amami-oshima I., Ryukyu Is, Japan; URM-P at OCF 7414, 36931, 2 specimens, Amami-oshima I., Ryukyu Is, Japan.

Diagnosis. Distinguishing characters are given in Table 1 and indicated in Figures 1 A–3A and 4. Amamiichthys matsubarai is distinguished by the following combination of characters: dorsal-fin rays XII, 10; anal-fin rays III, 8; pored lateral-line scales 56–61; first and second dorsal-fin spines very short, third and fourth (usually) dorsal-fin spines extremely elongated and filamentous; scales absent on preopercular flange; head and body uniformly pinkish; upper body with small distinct blue spots (sometimes overlapping pairs); no black margin on caudal fin ( Fig. 3A ).

Description. Counts and proportional measurements of the neotype and 30 non-type specimens of Amamiichthys matsubarai are shown in Table 2 . Data for the neotype are presented first, followed by other specimen data in parentheses.

Body elliptical from deep to somewhat slender; anterior profile of head somewhat convex, usually arched evenly between snout tip and dorsal-fin origin; interorbital scaly, scales extending anteriorly to slightly beyond level of posterior nostrils; anterior nostril oval, posterior nostril slit-like, just in front of eye; no scales on preoperculer flange; posterior tip of maxilla reaching just beyond vertical with anterior margin of eye; snout length greater than orbit diameter; four canines on upper jaw; six canines on lower jaw, two median canines small; a single outer row of molariform teeth on upper and lower jaws, two rows of small molariform teeth on medial aspect of upper jaw, teeth on anteromedial aspect of lower jaw villiform, becoming small molariform posteriorly; gill rakers elongate; dorsal fin originating above pectoral-fin origin; first and second dorsal-fin spines very short, third and fourth dorsal-fin spines distally filamentous (rarely only third dorsal-fin spine filamentous); first dorsal-fin soft ray longer than last dorsal-fin spine; first anal-fin spine much stronger than first dorsal-fin spine; second anal-fin spine slightly stronger than third; first anal-fin soft ray subequal to third anal-fin spine; anal fin with scaly sheath along its base; pectoral-fin tip clearly reaching to level with first anal-fin spine base when depressed, its length clearly greater than head length; pelvic fin-spine longer than snout; caudal fin forked; three supraneural bones arranged as 0/0 + 0/2 + 1/1; vertebrae 10 + 14.

Color of fresh specimens ( Figs. 3A , 4 ). Head and body pinkish; chin and belly silvery-white; eye yellow, iris black; upper part of eye blue; posterior margin of operculum yellowish-red; first to fourth dorsal-fin spines pinkish, remainder muddy white, soft rays hyaline, fin membranes hyaline, whitish-yellow; pectoral fin pinkish-yellow; pelvic fin pinkish, anal fins dusky gray; caudal fin yellowish-pink with no black posterior margin; upper body with small distinct, sometimes paired (overlapping slightly) blue spots.

Distribution. Amamiichthys matsubarai is known only from Amami-oshima Island, Ryukyu Islands, Japan ( Fig. 6 ).

Ecological note. Amamiichthys matsubarai inhabits relatively deepish waters (between 50 and 200 m) along the continental shelf ( Akazaki 1962; Hayashi 2002; Hayashi & Ogihara 2013; Iwatsuki et al. 2014; this study), being a similar habitat to that occupied by Dentex abei Iwatsuki, Akazaki & Taniguchi 2007 . Both species are sometimes caught together by long-line fishing ( Iwatsuki et al. 2014). February is a possible spawning season of A. matsubarai , suggested by many larger specimens being caught in relatively shallow waters (ca. 80 m depth) at that time of year, according to local fishermen (M. Fujiyama, pers. comm.).

Amamiichthys matsubarai is apparently distributed over an extremely limited area around Amami-oshima Island (supported by surveys conducted by F. Tanaka in July 2010 and July 2013), extending less than 100 km from north to south and 60 km from east to west. It has not been reported from Okinawa Island, approximately 200 km south of Amami-oshima Island, or elsewhere (Iriomote Islands and Miyako-jima Island) in the Ryukyu Islands, nor from southern Japan or Taiwan (Gushiken 1975; Shen 1984; Motomura & Matsuura 2010, Motomura et al. 2013; Motomura & Matsuura 2014). Under the name Cheimerius matsubarai , it has been designated as Vulnerable (VU) in the Red List of the International Union for Conservation of Nature ( Iwatsuki et al. 2014).

Remarks. A neotype of Amamiichthys matsubarai Akazaki 1962 (MUFS 30984, 268 mm SL, type locality: off Naze, Amami-oshima Island, Japan) is designated herein so as to avoid future taxonomic confusion, since the original type specimens (MIKU 1962, holotype: 477 mm SL and MIKU 1961, paratype: 532 mm SL) of Cheimerius matsubarai Akazaki 1962 were lost (T. Nakabo and Y. Kai of FAKU, pers. comm.) when the collection of MIKU was moved to FAKU, when MIKU was closed.

Comparative materials. An asterisk indicates specimen dissected. All specimens were X-rayed. Cheimerius nufar : HUJ 18419, 235 mm SL, Oman; MUFS 21009*, 22693 (2 specimens), 229–236 mm SL, Durban, South Africa; MUFS 29088*, 329 mm SL, Oman; SAIAB 8576, 215 mm SL, Algoa bay, South Africa; SAIAB 14917, 179 mm SL, Eastern Cape, South Africa; SAIAB 16574, 314 mm SL, KwaZulu-Natal, South Africa; SAIAB 37252, 292 mm SL, Durban, South Africa. Evynnis tumifrons : MUFS 11723, 11725, 11727, 11740*, 11743, 11745, 12252–12254, 12569 (10), 126–240 mm SL, Meitsu, Nango, Miyazaki, Japan. Evynnis cardinalis : MUFS 22504, 206 mm SL, Kagoshima Bay, Kagoshima, Japan. MUFS 22711, 171 mm SL, Meitsu, Nango, Miyazaki, Japan; MUFS 38700–38703 (4), 161–175 mm SL; NSMT-P 54732, 134 mm SL, China; NSMT-P 66122, 67834 (3), 68580 (5), 81–88 mm SL, Vietnam. Argyrops bleekeri : MUFS 2034, 2677–2678, 4445, 6343, 109– 175 mm SL, Okinawa Island, Japan. Argyrops spinifer : FAKU A784–A788, 33045 (6), 151–211 mm SL, Off India; MUFS 134*, 236 mm SL, Indian Ocean. Pagrus auratus : MUFS 22821–22822 (2), 127–130 mm SL, Wellington, New Zealand; MUFS 29102*, 286 mm SL, New Zealand; NMNZ-P 1812(2), 107–129 mm SL, Gisborne, New Zealand; NMNZ-P 16116 (4), 228–243 mm SL, Karewa Island, New Zealand. Pagrus major : MUFS 22504*, 206 mm SL, Kagoshima Bay, Kagoshima, Japan; MUFS 22536–22541 (6), 184–203 mm SL, Kitagawa, Miyazaki, Japan; MUFS 22673–22674 (5), 111–117 mm SL, Meitsu Fish Market, Nango, Miyazaki, Japan; MUFS 22706–22710 (5), 166–171 mm SL, Oro Island, Fukuoka, Japan; MUFS 22917, 82 mm SL, Aoshima, Miyazaki, Japan; MUFS 22944–22946 (3), 181–205 mm SL, Shintyu, Taiwan.

Figures

FIGURE 1. Teeth of upper and lower jaws. A. Amamiichthys matsubarai, MUFS 30983, 257 mm SL, Amami-oshima Island, Japan; B. Cheimerius nufar, MUFS 22693, 236 mm SL, Oman.

FIGURE 4. Diagnostic coloration of dorsolateral body surface of Amamiichthys matsubarai. MUFS 43227, 212 mm SL, Amami-oshima Islands, Japan.

FIGURE 6. Collection localities of Amamiichthys matsubarai along the coast of Amami-oshima Island, Ryukyu Islands, Japan.

FIGURE 3 A. Amamiichthys matsubarai, MUFS 30984, neotype, 268 mm SL, Amami-oshima Islands, Japan. B. Cheimerius nufar, 250 mm SL, Durban, South Africa, photographed by J. E. Randall.

Tables

TABLE 2. Counts and proportional measurements of Amamiichthys matsubarai, expressed as percentages of standard length (means in parentheses).

Standard length (mm) Counts:	Amamiichthys matsubarai Neotype MUFS 30984 n = 1 264 mm	Non-type specimens n = 30 212–437 mm
Dorsal-fin rays Anal-fin rays Pectoral-fin rays	XII, 10 III, 8 16	XII, 10 III, 8 15–16
Pored lateral-line scales Scale rows above/below lateral line Scale rows between fifth dorsal-fin spine base and lateral line	60 7½ / 17½ 6½	56–61 6½–8½ / 16½–18½ 5½–7½
Scale rows on cheek Gill rakers Proportions:	5 8 + 12 = 20	5–7 6–8 + 10–12 = 16–20
Body depth Body depth at first anal-fin spine origin Head length	45.2 38.7 32.7	43.2–47.6 (45.2) 35.7–39.6 (37.6) 31.1–34.2 (32.4)
Body width at pectoral-fin base Snout length Orbit diameter	16.0 14.8 10.3	14.9–17.0 (15.8) 13.7–15.8 (14.4) 7.2–10.8 (9.6)
Dermal eye opening Bony interorbital width Upper-jaw length	8.9 10.6 11.4	6.6–9.9 (8.7) 9.9–11.1 (10.4) 8.1–11.9 (11.3)
Caudal-peduncle depth Caudal-peduncle length Predorsal length	11.2 20.1 45.2	10.1–11.3 (10.6) 18.8–21.1 (20.0) 43.6–47.3 (44.6)
Preanal length Prepelvic length Dorsal-fin base	62.1 38.6 52.6	61.4–69.9 (67.0) 36.4–39.8 (38.1) 52.2–55.2 (53.9)
Anal-fin base Caudal-fin length Pelvic-fin spine	20.0 33.5 18.3	18.1–20.1 (19.5) 26.9–35.7 (31.1) 14.7–18.9 (17.2)
First pelvic-fin ray Longest pectoral-fin ray First dorsal-fin spine	28.5 40.1 3.3	21.0–30.0 (27.3) 37.4–41.4 (39.0) 2.6–3.9 (3.3)
Second dorsal-fin spine Third dorsal-fin spine Fourth dorsal-fin spine	5.6 41.4 29.4	3.7–7.4 (5.7) 20.1–48.6 (30.0) 15.0–36.8 (20.0)
Fifth dorsal-fin spine	13.8	11.4–13.9 (12.8) ......continued on the next page