Comprehensive Description

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Chromis circumaurea ZBK , new species

urn:lsid:zoobank.org:act:8ADC4817-8F1C-4C88-8B8A-5372A84CAEC9

Gold-rim Chromis

(Figs. 3a -3c, Ta b l e 4; Morphbank105; GenBank106; Barcode107)

Holotype. BPBM 40836108 (98.2 mm SL), Caroline Islands; Yap, S end; "Magic Kingdom" (9°26'3.41"N, 138°2'5.96"E): among boulders on sloping shelf above deep drop-off, 98-100 m, hand net, R.L. Pyle and B.D. Greene, 20 April 2007 [PCMB 3080109].

Paratypes. BMNH 2007.10.31.3110 (102.4 mm SL) [PCMB 3081111]. CAS 225757112 (97.6 mm SL) [PCMB 3078113]. MNHN 2007-1924114 (92.5 mm SL) [PCMB 3076115]. USNM 391138116 (94.2 mm SL) [PCMB 3077117]. WAM P.32900-001118 (96.6 mm SL) [PCMB 3079119]. All with same data as holotype.

Diagnosis. Dorsal rays XIV,12-13 (usually 13); anal rays II, 13-14 (usually 13); pectoral rays 18-19; spiniform caudal rays 3; tubed lateral-line scales 16-17; gill rakers 6-7+20-21 (total 26-27); body depth 1.68-1.86 in SL; color when fresh mahogany brown with bright yellow distally on spinous portion of dorsal fin; soft portion of dorsal fin, caudal fin, and anal fin bright yellow.

Description. Dorsal rays XIV,13 (12 in one paratype); anal rays II,13 (14 in one paratype); all dorsal and anal rays branched, the last to base in some specimens; pectoral rays 19 (18-19), the upper 2 and lowermost unbranched; pelvic rays I,5; principal caudal rays 8+7=15; upper and lower procurrent caudal rays 5, the anterior3 spiniform, the posterior 2 segmented and unbranched; tubed lateral-line scales 16|17 (16-17); posterior midlateral scales with a pore or deep pit 8 (5-8); scales above dorsal fin to origin of dorsal fin 3.5 (3-3.5); scales below lateral line to origin of anal fin 10 (9-10.5); gill rakers 6+21=27 (6-7+20-21= 26-27); surpaneural(predorsal) bones 3; vertebrae 12+13.

Body moderately deep, depth 1.71 (1.68-1.86) in SL, and compressed, the width 3.02 (2.93-3.22) in body depth; head length 3.28 (3.18-3.37) in SL; dorsal profile of head with slight convexity anterior to eye, slight concavity dorsal to eye, and slight convexity on nape; snout shorter than orbit diameter, its length 3.71 (3.82-4.30) in head length; orbit diameter 2.61 (2.35-2.63) in head length; interorbital space convex, its width 2.61 (2.54-2.74) in head length; caudal-peduncle depth 2.04 (2.02-2.04) in head; caudal-peduncle length 3.19 (2.72-3.40) in head.

Mouth terminal, small, oblique, the upper jaw forming an angle of about 40º to horizontal axis of head and body; posterior edge of maxilla reaching slightly beyond a vertical at anterior edge of pupil, the upper jaw length 3.09 (2.86-3.22) in head; teeth multi-serial, an outer row of conical teeth in each jaw, largest anteriorly; about 32 upper and about 26 lower teeth on each side of jaw; a narrow band of villiform teeth lingual to outer row, in 2-3 irregular rows anteriorly, narrowing to a single row on side of jaws; tongue triangular with rounded tip; gill rakers long and slender, the longest on lower limb near angle about three-fourths length of longest gill filaments; nostril with a fleshy rim, more elevated on posterior edge and located at level of middle of pupil, slightly less than one-third distance from front of snout to base of upper lip.

Opercle ending posteriorly in a flat spine, the tip relatively obtuse and obscured by a large scale; margin of preopercle smooth, the posterior margin extending dorsally to level of upper edge of pupil; suborbital with free lower margin extending nearly to a vertical at posterior edge of pupil.

Scales finely ctenoid; anterior lateral line ending beneath rear portion of spinous dorsal fin (between 12th and 13th dorsal-fin spines); head scaled except lips, tip of snout, and a narrow zone from orbit to edge of snout containing nostrils; a scaly sheath at base of dorsal and anal fins, about two-thirds pupil diameter at base of middle of spinous portion of dorsal fin, progressively narrower on soft portion; a column of scales on each membrane of dorsal fin, narrowing distally, those on spinous portion of dorsal progressively longer, reaching about two-thirds distance to spine tips on posterior membranes; scales on anal-fin membrane in two columns, progressively smaller distally; small scales on caudal fin extending slightly more than two-thirds distance to posterior margin; small scales on basal one-fifth of pectoral fins; a median scaly process extending posteriorly from between base of pelvic fins, its length about half that of pelvic spine; axillary scale above base of pelvic spine slightly more than one-third length of spine.

Origin of dorsal fin over fourth lateral-line scale, the pre-dorsal distance 2.31 (2.30-2.47) in SL; base of spinous portion of dorsal fin contained 2.14 (2.09-2.18) in SL; base of soft portion of dorsal fin contained 6.16 (5.68-6.35) in SL; first dorsal spine 12.62 (9.91-10.88) in SL; second dorsal spine 6.83 (6.13-6.88) in SL; third dorsal spine 5.52 (4.81-5.53) in SL; fourth dorsal spine 4.88 (4.73-5.09) in SL; fifth dorsal spine 4.86 (4.66-5.02) in SL; sixth dorsal spine 4.82 (4.63-5.08) in SL; last dorsal spine 6.40 (6.13-6.57) in SL; membranes of spinous portion of dorsal fin moderately incised; fourth dorsal soft ray longest, its length 4.20 (4.18-4.67) in SL; first anal spine 11.98 (10.50-11.05) in SL; second anal spine 3.77 (3.89-4.15) in SL; first anal soft ray the longest, its length 4.18 (4.31-4.56) in SL; caudal fin forked, its length 3.17 (2.68-3.39) in SL, the caudal concavity 5.46 (5.20-6.44) in SL; fourth pectoral-fin ray longest, 2.77 (2.62-2.83) in SL; pelvic spine 5.78 (5.09-5.52) in SL; first soft ray of pelvic fin without long filamentous extension, usually not reaching anal fin, its length 3.89 (3.82-4.20) in SL.

Color when fresh mahogany brown, appearing slate brown underwater; lateral line faintly brownish cream-colored; scales below lateral line with faint brownish cream-colored broad center area, forming approximately eight horizontal stripes visible underwater; spinous portion of dorsal fin same color as body, becoming bright yellow distally on first spine; second through last dorsal spines and membranes abruptly yellow distally, yellow portion increasing from distal one-fourth of fin at third spine to distal half at eleventh spine; soft dorsal fin entirely bright yellow except for posteriorly diminishing thin brown area basally on anterior6 rays; caudal region from posterior base of dorsal fin to posterior tip of caudal fin uniform bright yellow; brown body color extends posterior to anal fin to lower anterior caudal peduncle; anal fin spines yellowish white; anal fin rays and membranes bright yellow; scales along ventral margin from anus to origin anal fin yellow; pectoral fin translucent; pelvic-fin spine translucent, medial yellow wash on anterior 3 pelvic rays, rays otherwise translucent; pelvic-fin membranes mahogany brown basally, translucent distally; iris brown with yellow wash.

Color in alcohol similar to fresh color, except yellow portions are much paler yellow, and brown portions are slightly paler brown (much paler brown on thorax).

Distribution. Observed from submersibles in the Marshall Islands and Mariana Islands, but only collected from Yap.

Etymology. Named circumaurea ZBK , an adjective derived from the Latin words circum (meaning "around") and aurea (meaning "golden, of gold"), in reference to the golden-yellow anal fin, caudal fin, and outer margin of the dorsal fin.

Remarks. This species was first observed and photographed from a submersible by Patrick L. Colin at Enewetak in the Marshall Islands. An unconfirmed sighting and video clip of this species from the Mariana Islands requires verification. It was observed at Yap at depths of 98-120 m, in a group of about a dozen individuals living among large (~1-2 m) rock boulders just above the upper edge of a precipitous drop-off. A juvenile of approximately 40 mm SL was observed by the first author at a depth of 120 m, below the site where the type specimens were collected; its color pattern was consistent with that of the adults.

Two photos appearing on p. 390 of Kuiter & Tonozuka (2001), labelled as Chromis analis ZBK 120 (Cuvier 1830), bear a remarkable resemblance to C. circumaurea ZBK , but differ in number of dorsal-fin spines (XIII vs. XIV) and color of body (paler in C. analis ZBK ), caudal peduncle (dark centrally vs. entriely yellow), and central region of caudal fin (transparent vs. yellow). This species also bears a superficial resemblance in color to Chromis ZBK flavicauda121 (Guenther 1880) from the western Atlantic Ocean, but is readily distinguished from that species on the basis of body color (blue in C. flavicauda ZBK vs. brown in C. circumaurea ZBK ), dorsal-fin rays (XIII,11-12 vs. XIV,12-13, usually 13), anal-fin soft rays (11 vs. 13). Similarities with other deep-dwelling species with XIV dorsal-fin spines, including the new speciesC. abyssus ZBK described herein, are discussed in the Remarks section of C. abyssus ZBK .

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