Wednesday, November 8, 2017

[Ichthyology • 2017] Review of the Chromis xanthura Species Group (Perciformes: Pomacentridae), with Description of A New Species; Chromis anadema


Chromis anadema
 Motomura, Nishiyama & Chiba, 2017 


Abstract
A taxonomic review of the Chromis xanthura species group, defined here as having 13 dorsal-fin spines, three upper and three lower procurrent caudal-fin rays, two black bands at the preopercular and opercular margins, and a yellow caudal fin when juvenile, resulted in the recognition of three species, Chromis xanthura (Bleeker 1854), Chromis opercularis (Günther 1867), and Chromis anadema sp. nov. Chromis xanthura and C. opercularis, the Pacific and Indian Ocean paired sister species, respectively, are redescribed, with confirmation of two color types of C. xanthura (having a white or black caudal peduncle and fin) as a single species on the basis of morphological and molecular analyses. Chromis anadema sp. nov., described from the oceanic islands of the Pacific Ocean on the basis of 21 specimens, is characterized by having 28–33 gill rakers; longest dorsal-fin soft ray length 20.0–24.7% of standard length (SL); first anal-fin spine length 5.0–6.1% of SL; caudal-fin length 33.4–43.8% of SL; posterior tips of caudal-fin lobes not filamentous in adults; broad black bands along preopercular and opercular margins, sum width of two bands 28.9–38.7% of head length; distal half of soft-rayed portion of dorsal fin transparent in adults; triangular black blotches at upper and lower caudal-fin base in adults; caudal peduncle and fin bluish black in adults; and body grayish, and all fins (except for pectoral fin) bright yellow in juveniles.

Keywords: Teleostei, Chromis anadema, Chromis opercularis, Damselfish, Taxonomy, Morphology 


Fig. 2 Photographs of Chromis anadema sp. nov.
ab Fresh holotype from Yoron-jima island, Ryukyu Islands, Japan (KAUM–I. 42229, 101.3 mm SL);
c live individual from Ishigaki-jima island, Ryukyu Islands, Japan, 15 m depth (photo: T. Uchida); d live juvenile from Hachijo-jima island, Izu Islands, Japan, 12 m depth (photo: S. Kato)

Chromis anadema sp. nov.
(New English name: Short-tail Doublebar Chromis;
new standard Japanese name: Kanzashi-suzumedai) 

Diagnosis. A species of Chromis with the following combination of characters: dorsal-fin rays XIII, 10 or 11 (mode 11); anal-fin rays II, 10–12 (11); pectoral-fin rays 18–20 (19); upper and lower procurrent caudal-fin rays 3; pored lateral-line scales 17–19 (18); gill rakers 7–9 (8) + 20–24 (22) = 28–33 (30); longest dorsal-fin soft ray length 20.0–24.7% (mean 22.3%) of SL; first anal-fin spine length 5.0–6.1% (5.6%) of SL; caudal-fin length 33.4–43.8% (38.4%) of SL; posterior tips of caudal-fin lobes not filamentous in adults; broad black bands along preopercular and opercular margins, sum width of two bands 28.9–38.7% (33.1%) of head length; distal half of soft-rayed portion of dorsal fin transparent in adults; triangular black blotches at upper and lower caudal-fin base in adults; caudal peduncle and fin bluish black in adults; body grayish and all fins (except for pectoral fin) bright yellow in juveniles.

Distribution. Known from the vicinity of oceanic islands in the tropical Pacific Ocean (Fig. 4). The specimens were collected from the Ryukyu, Mariana, Marquesas, Society, Gambier, and Pitcairn islands at depths of 3–45 m. Records by published underwater photographs are: Hachijo-jima island (Izu Islands, off Pacific coast of Japanese mainland), Saipan, and Palau (Kato 2011),Guam (Myers 1989), Minna-jima, Ie-jima, and Okinawa-jima islands (Okinawa Islands, Ryukyu Islands) (Yoshino 2008; Araga 2009), Yaku-shima island (Osumi Islands, north of Ryukyu Islands) (Motomura and Harazaki 2017), and Tahiti (Society Islands) (Randall 2005) (Fig. 4).

Etymology. Derived the Latin anadema meaning “hair band”, with reference to two black bands at the preopercular and opercular margins of the species.


Chromis opercularis (Günther 1867 in Playfair and Günther 1867)
(English name: Doublebar Chromis)

Chromis xanthura (Bleeker 1854)
(English name: Paletail Chromis;
standard Japanese name: Mon-suzumedai)


Hiroyuki Motomura, Hajime Nishiyama and Satoru N. Chiba. 2017. Review of the Chromis xanthura Species Group (Perciformes: Pomacentridae), with Description of A New Species. Ichthyological Research.  DOI: 10.1007/s10228-017-0601-8

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