Chromis degruyi, Pyle, R. L., Earle, J. L. & Greene, B. D., 2008

Pyle, R. L., Earle, J. L. & Greene, B. D., 2008, Five new species of the damselfish genus Chromis (Perciformes: Labroidei: Pomacentridae) from deep coral reefs in the tropical western Pacific., Zootaxa 1671, pp. 3-31 : 18-21

Chromis degruyi , new species

urn:lsid:zoobank.org:act:1859B68B-340C-44F9-BEAB-D75BAED300F2

DeGruy's Chromis

(Figs. 4a -4c; Table 5; Morphbank122; DigiMorph123; GenBank124; Barcode125)

Holotype. BPBM 40842126 (81.0 mm SL), Belau (Palau) Islands; Kayangel Atoll, W side; on outer reef dropoff near tip of small reef extension (8°4'16.64"N, 134°40'54.52"E): rocky ledge with holes at base of steep sandy slope with many gorgonians, 85 m, hand net, R.L. Pyle, 22 April 2007 [PCMB 3086127].

Paratypes. BMNH 2007.10.31.4128 (38.7 mm SL), Caroline Islands; Yap, S end; "Magic Kingdom" (9°26'3.41"N, 138°2'5.96"E): deep rubble on rocky slope, 85 m, quinaldine and hand net, R.L. Pyle, 20 April 2007 [PCMB 3084129]. CAS 225758130 (38.3 mm SL), Caroline Islands; Puluwat Atoll; Alet Islet, S side (7°21'15.44"N, 149°10'47.03"E): outer reef drop-off with small caves and holes, 100-103 m, quinaldine and hand net, R.L. Pyle and B.D. Greene, 11 April 2007 [PCMB 3032131]. USNM 391139132 (76.6 mm SL), Belau (Palau) Islands; off Ngemlis Island; below and slightly to the N of the Blue Holes cave system (7°8'16.49"N, 134°13'18.5"E): in coral and rubble at the base of a large boulder offset from the drop-off, 88 m, hand net, R.L. Pyle, 27 April 2007 [PCMB 3114133]. WAM P.32901-001134 (82.4 mm SL), Belau (Palau) Islands; Ngaruangl Atoll, S end (8°8' 50.39"N, 134°37'3.47"E), 115 m, hand net, R.L. Pyle, 23 April 2007 [PCMB 3088135].

Diagnosis. Dorsal rays XIII -XIV,11-12 (usually XIV,12); anal rays II,11-12 (usually 12); pectoral rays 18; spiniform caudal rays 3; tubed lateral-line scales 15-17; gill rakers 7+20-21 (total 27-28); body depth 1.84-1.99 in SL; color of adults when fresh dull brownish yellow with nine thin lavender-gray stripes on side of body, with a prominent black spot on dorsal half of pectoral-fin base.

Description. Dorsal rays XIV,12 (one paratype with XIII, another with 11); anal rays II,12 (one paratype with 11); all dorsal and anal rays branched, the last to base in some specimens; pectoral rays 18, the upper 2 and lowermost unbranched; pelvic rays I,5; principal caudal rays 8+7=15; upper and lower procurrent caudal rays 5, the anterior 3 spiniform, the posterior 2 segmented and unbranched; tubed lateral-line scales 16|15 (15-17, one paratype with 17); posterior midlateral scales with a pore or deep pit 8|9 (5-9); scales above dorsal fin to origin of dorsal fin 3; scales below lateral line to origin of anal fin 9 (one paratype with 8); gill rakers 7+20=27 (7+20-21=27-28); surpaneural (predorsal) bones 3; vertebrae 12+13.

Body moderately deep, depth 1.84 (1.92-1.99) in SL, and compressed, the width 2.87 (2.73-3.29) in body depth; head length 3.10 (2.95-3.18) in SL; dorsal profile of head with slight convexity anterior to eye, very slight concavity dorsal to eye, and very slight convexity on nape; snout shorter than orbit diameter, its length 4.05 (3.63-4.38) in head length; orbit diameter 2.77 (2.12-2.95) in head length; interorbital space convex, its width 2.73 (2.73-3.15) in head length; caudal-peduncle depth 2.18 (2.11-2.27) in head; caudal-peduncle length 2.83 (2.69-3.37) in head.

Mouth terminal, small, oblique, the upper jaw forming an angle of about 37º 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 2.91 (3.05-3.18) in head; teeth multi-serial, an outer row of conical teeth in each jaw, largest anteriorly; about 20 upper and about 20 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 13th and 14th 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 about one-half length of spine.

Origin of dorsal fin over third lateral-line scale, the pre-dorsal distance 2.39 (2.30-2.41) in SL; base of spinous portion of dorsal fin contained 2.17 (2.14-2.34) in SL; base of soft portion of dorsal fin contained 6.66 (6.54-7.17) in SL; first dorsal spine 12.33 (9.51-12.14) in SL; second dorsal spine 8.15 (6.84-7.96) in SL; third dorsal spine 5.88 (5.53-6.39) in SL; fourth dorsal spine 5.23 (5.04-5.87) in SL; fifth dorsal spine 5.08 (5.17-5.76) in SL; sixth dorsal spine 5.07 (4.93-5.79) in SL; last dorsal spine 6.27 (6.14-7.04) in SL; membranes of spinous portion of dorsal fin moderately incised; fourth dorsal soft ray longest, its length 4.95 (4.54-5.04) in SL; first anal spine 11.30 (10.99-13.08) in SL; second anal spine 3.84 (3.76-4.52) in SL; first anal soft ray the longest, its length 4.48 (4.34-5.15) in SL; caudal fin forked, its length 2.84 (2.26-3.29) in SL, the caudal concavity 5.63 (4.37-5.46) in SL; fourth pectoral-fin ray longest, 2.99 (2.79-3.20) in SL; pelvic spine 5.36 (5.66-6.12) in SL; first soft ray of pelvic fin filamentous, usually reaching to first or second analfin ray (when not broken or otherwise damaged), its length 2.94 (2.95-4.17) in SL.

Color of adults when fresh dull brownish yellow with nine thin lavender-gray stripes, some faint, the middle4 or 5 extending onto caudal peduncle; nape area olive-brown, lighter on thorax and ventrally to anus, becoming yellowish white; black spot slightly smaller than orbit at upper pectoral axil; faint diffuse lavender blotch smaller than orbit on opercle edge at level of lower orbit, not apparent underwater; olivaceous with brown stripes and greenish olive in nape area when observed underwater; spinous portion of dorsal fin olivebrown, distal one-fourth yellowish white; basal half of soft dorsal fin dark brown with almost black outer margin, distal half very light yellowish white to translucent on some specimens; caudal fin olive-brown, inner rays yellowish white; anal fin spines yellowish white, rays and membranes on basal half light olive-brown becoming distally yellowish white; black blotch smaller than orbit centered in posterior distal anal fin, more apparent in large specimens; pectoral fin translucent; pelvic-fin spine and first ray white, successive rays and membranes on basal half olive-brown, distal half yellowish white; iris brownish yellow; juveniles bluish gray; a bright yellow blotch on the distal half of the soft dorsal fin, covering the second through fifth dorsal soft rays, rays 6 to last paler than anterior part of soft dorsal fin; a bright yellow stripe from posterior base of soft dorsal fin in a band approximately the width of 2 scales continuing dorsally to tip of outer rays of dorsal lobe of caudal fin; lower caudal rays with a similar yellow band commencing ventrally on caudal peduncle and extending to distal tip of lower caudal fin rays, approximately 7 median caudal rays white; third through seventh anal-fin rays and intervening membranes bright yellow on distal third, succeeding rays white. Color in alcohol similar to fresh color, except paler brown overall.

Distribution. Observed or collected throughout the Caroline Islands, from Puluwat to Palau. A Chromis resembling the juvenile of this species was observed in Fagatele Bay in May 2001 by the senior author.

Etymology. Named degruyi to honor Michael V. DeGruy, in recognition of the sincere enthusiasm and determination he demonstrated while attempting to collect the first adult specimen of this species.

Remarks. The habitat of this species is similar to that of other species described herein: deep outer-reef slopes at depths of 85-120 m, usually in the vicinity of rock outcrops with small holes and caves, and around limestone talus. It is generally not as abundant as other species of Chromis described here, usually found in small groups and observed feeding low in the water column.

The species appears most similar to other deep-dwelling species of Chromis described previously (see Remarks section of C. abyssus ). Juveniles superficially resemble C. opercularis 136 (Guenther in Playfair and Guenther 1867) in color, but are easily distinguished from that species on several morphological characters (e.g., usually XIV dorsal-fin spines in C. degruyi , vs. XIII in C. opercularis ; body depth 1.84-1.99 in SL vs. 2.1-2.3 in C. opercularis ), as well as adult coloration. Some aspects of the adult coloration are similar to C. planesi Lecchini and Williams 2004, but C. degruyi differs from that species in many other aspects of adult coloration as well as number of pectoral-fin rays (20 in C. planesi vs. 18 in C. degruyi ), dorsal-fin soft rays (usually 13 vs. usually 12), and tubed lateral-line scales (17 vs. usually 15-16).