Chromis brevirostris, 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: 10-12

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Chromis brevirostris

new species

Chromis brevirostris   ZBK   , new species

Shortsnout Chromis

(Figs. 2a -2c; Tables 2 & 3; Morphbank82; GenBank83; Barcode84)

Holotype. BPBM 4080485 (63.7 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 303386].   GoogleMaps

Paratypes. BMNH 2007.10.31.287 (55.2 mm SL), Belau (Palau) Islands; Augulpelu Reef, W side (7°16'24.6"N, 134°31'26.4"E): shelf flanked by numerous small caves, 90 m, hand net, R.L. Pyle, 16 May 1997.   GoogleMaps BPBM 3767188 (55.4 mm SL), same collecting data as BMNH 2007.10.31.2, except collected on 6 May 1997. BPBM 3771389 (59.6 mm SL), same locality and depth as and BPBM 37671: cave in drop-off, rotenone, R.L. Pyle and J.L. Earle, 12 May 1997. BPBM 3999390 (62.5 mm SL), Fiji Islands; Viti Levu Island; outside of Suva Harbor; S of "Fish Patch"; southern wall (18°9'32.7"S, 178°23'58.44"E): sloping sand and rubble with rock outcroppings, 87-92 m, rotenone, R.L. Pyle and D.F. Pence, 3 February 2002.   GoogleMaps BPBM 4042291 (3; 25.5-46.9 mm SL), Marshall Islands; Kwajalein Atoll, S end; Ennubuj (= Carlson) islet; ocean side: cave within ledge, 100 m, rotenone, B.D. Greene, 30 December 2005. BPBM 4070392 (2; 50.9-59.5 mm SL), Vanuatu; Espiritu Santo; off W coast (15°33'39.28"S, 167°16'29.82"E): steep slope with rubble and sand, with some rocky outcrops with small caves and undercuts; many gorgonians, 60 m, quinaldine and hand net, B.D. Greene, 7 October 2006.   GoogleMaps CAS 22575693 (2; 46.5-50.8 mm SL), same collecting data as BPBM 39993. MNHN 2007-192394 (57.9 mm SL), Vanuatu; Espiritu Santo; off N end of Tutuba Island (15°32'28.57"S, 167°16'51.17"E): at base of outer reef drop-off ranging from 60-100 m, 100 m, rotenone and vacuum device, R.L. Pyle, 10 October 2006.   GoogleMaps USNM 39113795 (4; 41.6-68.5 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 307296, 307397, 307498, 307599].   GoogleMaps WAM P.32899- 001100 (2; 58.1-61.4 mm SL), Belau (Palau) Islands; Augulpelu Reef, W side; shelf flanked by numerous small caves (7°16'24.6"N, 134°31'26.4"E), 90 m, hand net, R.L. Pyle and J.L. Earle, 17 May 1997.   GoogleMaps

Diagnosis. Dorsal rays XIII,13-14 (usually 14); anal rays II,15-16; pectoral rays 18-19 (usually 19); spiniform caudal rays 2-3 (usually 3); tubed lateral-line scales 14-16; gill rakers 6-8+19-22 (usually 6-7+19-21; total 26-29); body depth 1.57-1.77 in SL; color when fresh pale lavender-tinged gray dorsally, paler ventrally; three or four rows of scales dorsally from nape to upper caudal peduncle with gold edges; small scales on basal sheath of dorsal fin almost entirely gold; median fin membranes lavender gray or translucent blue, suffused with gold color; iris yellow.

Description. Dorsal rays XIII,14 (two paratypes with 13); anal rays II,16 (one paratype with 15, another paratype deformed with only 13); all dorsal and anal rays branched, the last to base; pectoral rays 18 (one paratype with 19 on only the right side), the upper 2 and lowermost unbranched; pelvic rays I,5; principal caudal rays 8+7=15 (one paratype with 7+7=14); upper and lower procurrent caudal rays 5, the anterior 3 (2-3) spiniform (when 3, the anteriormost vestigial and not penetrating scales), the posterior 2 segmented and unbranched; tubed lateral-line scales 15 (14-16); posterior midlateral scales with a pore or deep pit 7 (0-8); scales above dorsal fin to origin of dorsal fin 4 (3.5-4); scales below lateral line to origin of anal fin 10 (9-10, usually 10); gill rakers 8+21=29 (6-8+19-22=26-29, 6 gill rakers on upper limb of gill arch in one paratype, 22 gill rakers on lower limb of gill arch in one paratype); surpaneural (predorsal) bones 3; vertebrae 12+13.

Body moderately deep, depth 1.69 (1.57-1.77) in SL, and compressed, the width 3.04 (2.94-3.75) in body depth; head length 3.13 (2.71-3.26) in SL; dorsal profile of head smoothly convex, sometimes with a very slight concavity anterior to eye; snout shorter than orbit diameter, its length 4.25 (3.45-4.80) in head length; orbit diameter 2.41 (2.00-2.66) in head length; interorbital space convex, its width 2.60 (2.56-3.39) in head length; caudal-peduncle depth 2.05 (1.86-2.24) in head; caudal-peduncle length 3.49 (2.82-4.49) in head.

Mouth terminal, small, oblique, the upper jaw forming an angle of about 42º 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 3.28 (2.91-3.57) in head; teeth multi-serial, an outer row of conical teeth in each jaw, largest anteriorly; about 25 upper and about 21 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 two-thirds 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-sixth distance from front of snout to base of upper lip.

Opercle ending posteriorly in a flat spine, the tip broadly 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 orbit.

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 four-fifths 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-sixth 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-half length of spine.

Origin of dorsal fin over second lateral-line scale, the pre-dorsal distance 2.50 (2.37-2.76) in SL; base of spinous portion of dorsal fin contained 2.09 (2.02-2.42) in SL; base of soft portion of dorsal fin contained 5.20 (4.69-5.38) in SL; first dorsal spine 9.41 (7.61-11.00) in SL; second dorsal spine 6.83 (5.54-8.20) in SL; third dorsal spine 6.07 (4.51-6.98) in SL; fourth dorsal spine 5.79 (4.35-6.45) in SL; fifth dorsal spine 5.73 (4.18-6.31) in SL; sixth dorsal spine 5.67 (3.94-6.14) in SL; last dorsal spine 5.91 (4.71-6.25) in SL; membranes of spinous portion of dorsal fin moderately incised; fourth dorsal soft ray longest, usually with a filamentous extension, its length 4.20 (2.55-4.34) in SL; first anal spine 9.30 (8.03-10.29) in SL; second anal spine 4.95 (4.32-5.44) in SL; eleventh anal soft ray the longest, its length 4.99 (3.05-5.05) in SL; caudal fin forked, its length 1.59 (1.19-2.44) in SL, the third or fourth principal caudal ray (upper and lower) with filamentous extension, the caudal concavity 2.31 (1.52-4.19) in SL; fourth pectoral-fin ray longest, 2.41 (2.30-2.76) in SL; pelvic spine 4.99 (3.99-5.63) in SL; first soft ray of pelvic fin filamentous, usually reaching to second anal-fin ray (when not broken or otherwise damaged), its length 3.94 (2.41-3.76) in SL.

Color of adults and juveniles when fresh pale lavender-tinged gray dorsally, fading to pale bluish-white on thorax; pale bluish gray ventrally from anus to caudal fin; three or four rows of scales dorsally from nape to upper caudal peduncle with gold edges; small scales on basal sheath of dorsal fin can be almost entirely gold; faint gold tinge on posterior operculum and on scales along ventral margin anterior to pelvic-fin origin; intensity of gold color variable, appearing more pearlescent underwater in some individuals; dorsal- and anal-fin membranes pale translucent blue, suffused with gold, particularly basal 2/3 and distal portion of spinous dorsal fin, and basal and distal 1/3 of anal fin; soft dorsal fin gold tinged except for median portion; the extreme distal margin of the dorsal fin, anal fin and pelvic fin pale turquoise blue; caudal fin lavender gray with faint gold wash on membranes; pectoral fin translucent; pelvic fins white; iris yellow, fleshy membrane of orbit turquoise blue, especially dorsally; interorbital space turquoise above upper lip, extending dorsally into nape in some specimens.

Color in alcohol drab grayish light brown over most of body, darker brown above lateral line; scales above lateral line with pale spot corresponding to gold markings in life; dorsal fin uniform brown except for a pale gray submarginal line; anal fin brown with pale grayish brown markings and submarginal line; interorbital region and anterior head uniform brown; thorax slightly lighter than body color, with pale ventral edge.

Distribution. This species has been observed or collected from the Marshall Islands southward to Fiji, across the Caroline Islands from Puluwat to Palau, and south to Vanuatu. An underwater photo of what seems to be this species (or an undescribed species very similar to C. brevirostris   ZBK   ) taken in Bali, Indonesia, appears as " Chromis   ZBK   sp." on p. 531 of Kuiter & Debelius, 2006. C. brevirostris   ZBK   was not observed at Rarotonga (Cook Islands), Kiritimati (Line Islands), or American Samoa during brief surveys of deep reefs at those localities.

Etymology. Named brevirostris   ZBK   , an adjective derived from the Latin words brevis (meaning "short") and rostrum (meaning "beak" or "snout"), in reference to the very short snout of this species relative to other species in the genus.

Remarks. Generally abundant in its typical environment, which is characterized by steep slopes and drop-offs at depths of about 90-120 m. Usually found in association with small holes and limestone talus, often in aggregations ranging from a half-dozen to several dozen individuals feeding low in the water column.

Chromis brevirostris   ZBK   , as well as the new species C. earina   ZBK   (described herein) are both deep-dwelling Chromis   ZBK   species with XIII dorsal spines, a deep body (1.57-1.9 in S.L.), short snout (3.45-4.8 in head), and large eye (2.0-2.6 in head). Most counts are similar, and these two species appear to have more affinities with each other than with any other species in the genus. They can be readily distinguished from each other on the basis of color and by differences in general body shape (particularly the shape of the head profile, which is smoothly convex in C. brevirostris   ZBK   , as opposed to slightly concave dorsal to the eye in C. earina   ZBK   ), and dorsal- and anal-fin soft ray counts. Chromis brevirostris   ZBK   has 13-14 dorsal-fin soft rays and 15-16 anal-fin soft rays (except for one deformed individual with only 13 anal-fin soft rays); whereas C. earina   ZBK   has 11-12 dorsal-fin soft rays and 12 anal-fin soft rays. Table 3 lists selected characters for four Indo-Pacific Chromis   ZBK   species which seem to be most similar to C. brevirostris   ZBK   and C. earina   ZBK   . These four species, including C. alpha   ZBK   101 Randall1988a, C. nigroanalis   ZBK   102 Randall 1988b, C. ovatiformis   ZBK   103 Fowler 1946, and C. pembae   ZBK   104 Randall and McCosker 1992 (which we collectively and informally refer to here as the " Chromis alpha   ZBK   complex") all have XIII dorsal spines, a roughly similar body shape, and have been recorded at a depth of 40 m or greater. For each of these species, at least one count, and all gill raker counts, range outside the respective ranges for C. brevirostris   ZBK   and C. earina   ZBK   .