Monotaxis heterodon ( Bleeker, 1854 )

Shibuya, Shunta, Sakurai, You & Motomura, Hiroyuki, 2022, First Specimen-based Records of Redfin Emperor Monotaxis heterodon (Perciformes: Lethrinidae) from Japan, with New Diagnostic Characters Applicable to Identification of Preserved Specimens, Species Diversity 27 (1), pp. 45-51 : 46-49

publication ID	https://doi.org/ 10.12782/specdiv.27.45
persistent identifier	https://treatment.plazi.org/id/027D87C9-6F12-FFDD-8B7C-33C1FBA3F7FA
treatment provided by	Felipe
scientific name	Monotaxis heterodon ( Bleeker, 1854 )
status

Treatment

Monotaxis heterodon ( Bleeker, 1854) View in CoL

[English name: Redfin Emperor; new standard Japanese name: Kagutsuchi-yokoshima-kurodai] ( Figs 1 View Fig , 3 View Fig , 4A, C, E View Fig ; Tables 1, 2)

Pagrus heterodon Bleeker, 1854: 54 (type locality: Sindangole , Halmahera, Indonesia).

Monotaxis grandoculis View in CoL (not of Forsskål): Hiyama 1943: 449, fig. 31 ( Micronesia); Randall et al. 1996: 204, unnumbered fig. (in part; Coral Sea); Sato 1997: 358, unnumbered figs (in part; Kerama Islands, Okinawa, Japan; Saipan); Mansor et al. 1998: 186, fig. 236 (South China Sea); Carpenter 2001: pl. XVII, fig. 144 (Enewetak, Marshall Islands); Kuiter and Debelius 2006: 424, unnumbered figs [in part; locality unknown ( Indonesia, Maldives, or Australia)].

Monotaxis heterodon: Randall 2005: 281 View in CoL , unnumbered figs (Satonda, Indonesia; Marshall Islands); Allen and Erdmann 2012: 502, unnumbered figs ( Philippines; Indonesia; Papua New Guinea); Yoshino 2008: 195, unnumbered fig. (Sesoko-jima island, Okinawa Prefecture, Japan); Fricke et al. 2014: 94 (Madang, Papua New Guinea); Fricke et al. 2019: 173 (New Ireland, Papua New Guinea); Shimose 2021: 117, unnumbered fig. (Okinawa Prefecture, Japan); Zhao et al. 2021: 321, fig. 1 (Mischief Reef, Spratly Islands, South China Sea).

Material examined. 24 specimens (184.6–243.6mm SL), all from the southern Ryukyu Islands , Japan: KAUM –I . 88394, 215.0 mm SL, between Amami and Yaeyama islands, 17 May 2016, Y . Sakurai (obtained at fish market in Okinawa-jima island : detail locality unknown); URM-P 33254, 234.6 mm SL, Okinawa-jima island, 30 November 1994, Y . Sakurai et al.; URM-P 33447, 207.2 mm SL, URM-P 33448, 198.4 mm SL, URM-P 33449, 203.4 mm SL, Okinawa-jima island , 24 December 1994, M . Kume et al.; URM-P 34768, 189.1 mm SL, Okinawa-jima island , 25 November 1995, H . Yoshigou and M. Sekine; URM-P 38159, 197.4mm SL, Okinawa-jima island , 16 June 1996, N . Fujioka; URM-P 38170, 224.1mm SL, URM-P 38171, 230.4mm SL, Okinawa-jima island , 18 June 1997, N . Fujioka, URM-P 38211, 219.2mm SL, Okinawa-jima island , 4 July 1997, N . Fujioka; URM-P 38287, 191.8 mm SL, Okinawa-jima island , 1 August 1997, N . Fujioka; URM-P 38473, 191.5 mm SL, Okinawa-jima island , 22 August 1997, N . Fujioka; URM-P 39150, 235.6 mm SL, URM-P 39151, 227.3 mm SL, Okinawa-jima island , 27 October 1997, N . Fujioka; URM-P 39640, 220.4 mm SL, URM-P 39641, 231.8mm SL, URM-P 39642, 224.8 mm SL, Okinawa-jima island , 18 December 1998, N . Fujioka et al.; URM-P 39717, 226.7 mm SL, Okinawa-jima island , 13 February 1999, N . Fujioka; URM-P

39731, 212.0 mm SL, Okinawa-jima island , 12 March 1999, N . Fujioka et al.; URM-P 39977, 232.2 mm SL, Okinawa-jima island , 30 April 1999, N . Fujioka; URM-P 40070, 236.2mm SL, Okinawa-jima island , 15 July 1999, N . Fujioka; URM-P 40102 , 218.0mm SL, Okinawa-jima island , 5 August 1999, N . Fujioka et al.; URM-P 40307, 184.6 mm SL, Okinawa-jima island , 22 November 1999, N . Fujioka; URM-P 43626, 243.6mm SL, Okinawa-jima island , 8 November 1999, K . Shimada.

Diagnosis. A species of Monotaxis with the following combination of characters: scale rows below lateral line 13 or 14; mid-dorsal snout profile concave; snout short, its length (excluding lips) 8.9–11.1% (mean 9.9%) of SL; spinous anal-fin base long, its length 4.6–5.9% (5.0%) of SL; both lips reddish-gray; distinct black blotch absent; 2 vertical narrow white bands on lateral surface of body (usually indistinct in preserved specimens over ca. 185 mm SL), width of each band including 1 or 2 longitudinal scale rows; black blotches on soft-rayed bases of dorsal and anal fins absent; all fins red or yellowish-red; dark brown stripe across occipital region in preserved specimens; and inner surface of pectoral-fin base blackish-brown in preserved specimens.

Description. Counts and measurements given in Tables 1 and 2. Body slightly compressed, deepest at base of third dorsal-fin spine. Dorsal profile of head and body generally elevated from snout tip to base of third spine of dorsal fin (concave above middle of snout), thereafter gradually decreasing to uppermost point of caudal-fin base. Ventral profile decreasing from lower-jaw tip to pelvic-fin origin, thereafter gradually rising to lowermost point of caudal-fin base. Eye and pupil round. Anterior and posterior nostrils close to each other, former with membranous tube; both located before anterior margin of eye. Both lips thick. Posterior tip of maxilla reaching to vertical through anterior margin of pupil. Gill rakers short, knob-like. Teeth on both jaws conical anteriorly, molariform laterally. Body completely covered with stout ctenoid scales, not extending onto fin bases, except for caudal fin. Head partially covered with stout scales, anterior margin of scaled area reaching to level with through posterior margin of eyes in dorsal view. Snout and suborbital region naked. Lateral line complete, extending from posterior tip of opercle to caudal-fin base. Cheek and inner surface of pectoral fin covered with scales. Pelvic fin with axillary scale.

Dorsal-fin origin above uppermost point of pectoral-fin base; end of dorsal-fin base reaching posteriorly to vertical through end of anal-fin base. Lowermost point of pectoralfin base below base of second dorsal-fin spine. Posterior tip of pectoral fin slightly pointed, reaching to below between bases of 10th dorsal-fin spine and first dorsal-fin soft ray. Pelvic-fin origin below lowermost point of pectoral-fin base. Posterior tip of depressed pelvic fin reaching to anus. Analfin origin below between bases of 9th and 10th dorsal-fin spines. Caudal fin forked, upper and lower tips rounded.

Coloration. Fresh condition ( Fig. 1A View Fig ). Body brown dorsally, brownish-gray ventrally, with two faint pale white bands on lateral surface; anterior and posterior bands extending from base of third dorsal-fin spine and first dorsalfin soft ray, respectively, to middle of body through lateral line; width of bands relatively narrow, including 1 or 2 longitudinal scale rows. Head brownish-gray, a single yellowish-brown band on middle of nape. Snout tip faint blackish, both lips reddish-gray. Upper and posterior margins of eye reddish-gray and yellowish-brown, respectively. Pupil black, a small faint red blotch above pupil. Upper point of posteri- or margin of opercle reddish-gray. Spinous portion of dorsal fin reddish-yellow, soft rayed portion red. Pectoral fin red, upper part of fin base widely margined with black, middle portion blackish-gray. Pelvic fin reddish-white anteriorly, white posteriorly. Anal fin whitish-red. Caudal fin ground color red, upper and lower lobes widely margined with yellowish-brown, a few narrow reddish-black streaks along rays (particularly in middle of fin).

a–h

Based on 17, 23, 18, 14, 11, 12, 10 and 15 specimens, respectively

Preserved condition ( Fig. 1B View Fig ). Body blackish-brown dorsally, light brown ventrally, two faint white bands (in fresh condition) becoming less distinct (not visible in 22 specimens, probably due to long-term preservation). Head light brown with single dark brown stripe across postorbital region. Snout tip faint blackish. Single yellowish-brown band on middle of nape (in fresh condition) usually retained as faint whitish band (not visible in 9 specimens). All fins (except caudal fin) pale brown. Caudal fin yellowish-brown, a few narrow black streaks along rays (particularly in middle of fin). Inner surface of pectoral-fin base blackish-brown.

Distribution. Widely known from the Indo-West Pacific: Seychelles east to southern Japan and New Caledonia ( Sato 1997; Randall 2005; Yoshino 2008; Allen and Erdmann 2012; Fricke et al. 2014, 2019, 2021; Zhao et al. 2021; Shimose 2021). In Japanese waters, specimen-based records are known only from Okinawa-jima island, Ryukyu Islands. Photograph-based Japanese records are known only from Okinawa Prefecture, including Sesoko-jima island and the Kerama Islands ( Sato 1997; Yoshino 2008; Shimose 2021).

Remarks. Although M. heterodon was regarded as a junior synonym of M. grandoculis by Carpenter and Allen (1989), Randall (2005) demonstrated differences (color patterns of lips and fins, and width of body stripes) between the two species and resurrected the former as a valid species. The present specimens agreed closely with M. heterodon [sensu Randall (2005) and Allen and Erdmann (2012)] in having scale rows below the lateral line 12.5 (vs. 13.5 in M. grandoculis ), reddish lips (vs. yellowish), relatively narrow vertical white bands on the lateral surface of the body (width including 1 or 2 longitudinal scale rows) (vs. broad, including 3 or 4 longitudinal scale rows), and all fins red or yellowish-red (vs. dark brown or dusky red), and lacking black blotches on the soft-rayed bases of the dorsal and anal fins [vs. some blotches on soft-rayed bases (between membranes) of fins] ( Figs 1 View Fig , 2 View Fig ). Zhao et al. (2021) analyzed the COI sequences of M. heterodon and M. grandoculis , and detected two monophyletic clades that differed by 8.71% sequence divergence.

Although the above-mentioned characters are useful for distinguishing between M. heterodon and M. grandoculis (reconfirmed in this study), they are restricted to fresh specimens (except for black blotches on the dorsal and anal fins) and/or small individuals [e.g., white bands on the lateral body surface usually indistinct in large preserved specimens (>ca. 185 mm SL) in both species; Figs 1 View Fig , 2 View Fig ]. However, the present study disclosed new diagnostic characters which can be used for preserved specimens, as well as large individuals, as follows: mid-dorsal profile of snout concave (except in juveniles: see Randall 2005; Yoshino 2008; Allen and Erdmann 2012) (vs. straight; Figs 1 View Fig , 2 View Fig ); snout short, its length (excluding lips) 8.9–11.1 (mean 9.9) % of SL [vs. 10.3–12.1 (11.2) % SL; Fig. 3A View Fig ]; spinous anal-fin base long, its length 4.6–5.9 (5.0) % of SL [vs. 3.9–4.9 (4.4) % SL; Fig. 3B View Fig ]; a distinct black blotch above pupil absent (vs. single black blotch present–note, both species with a small red blotch above pupil in fresh specimens; Fig. 4A, B View Fig ); a dark brown stripe across occipital region in preserved specimens (vs. occipital stripe absent; Fig. 4C, D View Fig ); and inner surface of pectoralfin base blackish-brown in preserved specimens (vs. light brown; Fig. 4E, F View Fig ). Randall (2005) and Allen and Erdmann (2012) described the counts of scale rows below the lateral line of M. grandoculis and M. heterodon as 13.5 and 12.5 (equivalent to 14 and 13 in counting method in this study), respectively. The counts of the present specimens were 15 or 16 in M. grandoculis and 13 or 14 in M. heterodon ( Table 1). Although the range of the scale counts slightly overlapped, the modal values still differed between the two species ( Table 2).

Monotaxis heterodon has previously been recorded from Japanese waters by Yoshino (2008) and Shimose (2021), based only on photographs from Okinawa Prefecture. Sato (1997) published an underwater photograph of a juvenile fish as M. grandoculis from the Kerama Islands and the photographed fish was re-identified here as M. heterodon based on two longitudinal black stripes on the lateral surface of the body (diagnosis of juveniles of M. heterodon ; Randall 2005). Therefore, the present Ryukyu Islands specimens represent the first specimen-based records of M. heterodon from Japan.

Hiyama (1943) reported M. grandoculis from Micronesia and proposed the new Japanese name “Dokudai” (meaning “venomous sea bream”) for the species. Hiyama’s (1943) M. grandoculis was reidentified here as M. heterodon , having a concave snout, no black blotches above the pupil, and a yellowish caudal fin based on figure. Subsequently, Matsubara (1955) apparently overlooked Hiyama (1943) and proposed the Japanese name “Yokoshima-kurodai” for M. grandoculis , based on a single juvenile specimen (85 mm total length) which reported by Fowler (1946) from the Ryukyu Islands. The identity of Fowler’s (1946) specimen was confirmed here as M. grandoculis (based on his description, viz., having olive brown band from interorbital through eye to lower margin of cheek) (such a band absent in juveniles of M. heterodon ; Randall 2005; Yoshino 2008; Allen and Erdmann 2012).

Recently, “Yokoshima-kurodai” has been widely used in papers that have treated fishes belonging to Monotaxis (e.g., Carpenter and Allen 1989; Sato 1997), whereas “Dokudai” has been rarely used (e.g., Baba 1983; Wu et al. 1999) since its proposal by Hiyama (1943). In addition, Hiyama’s (1943) “Dokudai” was superseded by Matsubara’s (1955) “Yokoshima-kurodai” (although both were considered to represent M. grandoculis at that time). In his review of Japanese lethrinids, Shimada (2000, 2002, 2013) followed Matsubara (1955) and used “Yokoshima-kurodai” as the standard Japanese name for both M. grandoculis and the genus Monotaxis . We also follow Matsubara’s (1955) and Shimada’s (2000, 2002, 2013) treatment, and suppress “Dokudai” to avoid further confusion. The new standard Japanese name “Kagutsuchi-yokoshima-kurodai” was therefore proposed for M. heterodon , based on KAUM–I. 88394, “Kagutsuchi” is the god of fire in Japanese mythology, and is associated with the reddish fins of this species.