Chromis abadhah, Rocha & Pinheiro & Najeeb & Rocha & Shepherd, 2024

Rocha, Luiz A., Pinheiro, Hudson T., Najeeb, Ahmed, Rocha, Claudia R. & Shepherd, Bart, 2024, Chromis abadhah (Teleostei, Pomacentridae), a new species of damselfish from mesophotic coral ecosystems of the Maldives, ZooKeys 1219, pp. 165-174 : 165-174

Chromis abadhah sp. nov.

Figs 1 , 2 , 3 , Table 1 Suggested Maldivian name: Abadhah Chromis Suggested English name: Perpetual Chromis

Type material.

Holotype (Figs 1 , 2 ) • CAS 248401 (field code LAR 2969), 68.7 mm SL, GenBank PQ 410417 , Maafilaafushi, Faadhippolhu Atoll , 5°21'40"S, 73°24'45"E, hand nets 101 m, H. T. Pinheiro, B. Shepherd, L. A. Rocha, 15.XII.2022 . Paratypes • CAS 248403 (field code LAR 2968), 66.1 mm SL, GenBank PQ 410416 , same data as holotype • USNM 470765 (field code LAR 2970), 64.5 mm SL, GenBank PQ 410418 , same data as holotype • CAS 248402 (field code LAR 2965), 50.2 mm SL, Maafilaafushi, Faadhippolhu Atoll , 5°21'40"S, 73°24'45"E, hand nets 118 m, H. T. Pinheiro, B. Shepherd, L. A. Rocha, 14.XII.2022 .

Diagnosis.

The following combination of characters distinguishes Chromis abadhah sp. nov. from all of its congeners: dorsal-fin rays XIII, 12–13; anal-fin rays II, 11–12; pectoral-fin rays 17–18; tubed lateral-line scales 17; gill rakers 7 + 17–18 = 24–25; body pearly white; large black marking covering anterior two-thirds of anal fin; small black spot on upper edge of pectoral-fin base; no markings on caudal peduncle.

Description.

Dorsal-fin rays XIII, 12 (XIII, 12–13); anal-fin rays II, 11 (II, 12); all soft dorsal- and anal-fin rays branched, the last to base, the last two soft rays associated with a single complex pterygiophore; fourth (third) dorsal ray longest, 25.8 % (20.8–28.2) SL; pectoral-fin rays 18 | 18 (17 | 18), the uppermost and lowermost unbranched; first pectoral ray the longest, 34.6 % (31.6–34.5) SL; pelvic-fin rays I, 5; principal caudal-fin rays 7 + 6 (6–7 + 6), the uppermost and lowermost unbranched; upper and lower procurrent caudal-fin rays 6, the anteriormost 3 rays (dorsally and ventrally) spiniform; tubed lateral-line scales 17; scales above lateral line to origin of dorsal fin 3; scales below lateral line to origin of anal fin 9; circumpeduncular scales 16 (16–18); gill rakers 7 + 17 = 24 (7 + 17–18 = 24–25); supraneural bones 3; vertebrae 11 precaudal + 15 caudal = 26.

Body moderately deep, depth 56.3 % (55.0–59.0) SL, and compressed, the width 21.1 % (18.3–20.2) SL; head length 35.6 % (35.6–36.8) SL; profile of head slightly convex above orbit, nape slightly convex; snout length 9.6 % (8.9–9.8) SL; eye large, orbit diameter 15.0 % (12.6–14.2) SL; interorbital width 14.3 % (12.2–13.4) SL; caudal-peduncle depth 14.3 % (15.4–15.7) SL; caudal-peduncle length 8.0 % (7.8–10.3) SL.

Mouth terminal, oblique, upper jaw angle about 45 ° to the horizontal axis of head and body; posterior edge of maxilla extending slightly beyond vertical at anterior edge of eye, upper jaw length 12.6 % (10.5–11.5) in head length; teeth multi-serial, outer row of conical teeth in each jaw, much larger anteriorly; narrow band of villiform teeth lingual to outer row, in three irregular rows anteriorly, narrowing to a single row on side of jaws; tongue triangular with rounded tip; gill rakers long and slender, longest on lower limb near angle about half the length of gill filaments; anterior nostril relatively large with a short fleshy rim, more elevated on posterior edge and located at level of horizontal line through middle of pupil, slightly less than halfway between front of snout and anterior edge of orbit; posterior nostril much smaller and slit-shaped, located above and behind anterior nostril, close to edge of orbit. Opercle ending posteriorly in flat spine, the tip relatively acute and not obscured by scales; preopercular margin smooth, posterior margin extending dorsally to almost level of upper edge of orbit; suborbital with free lower margin extending nearly to a vertical at posterior edge of orbit.

Scales finely ctenoid; tubed portion of lateral line ending beneath rear portion of spinous dorsal fin (base of 13 th dorsal-fin spine); head scaled except lips; scaly sheath at base of dorsal and anal fins, progressively thicker towards body; column of scales on each membrane of dorsal fin, narrowing distally, those on spinous portion of dorsal fin progressively longer, reaching about two-thirds the distance to spine tips on posterior membranes; two or three columns of scales on anal-fin membranes, progressively smaller distally; small scales on caudal fin extending about one-third distance to posterior margin; small scales only on base of pectoral fins; median scaly process extending posteriorly from between bases of pelvic fins, its length about half that of pelvic spine; axillary scale above base of pelvic spine about half the length of pelvic spine. Origin of dorsal fin above second lateral-line scale; pre-dorsal length 41.9 % (42.1–42.7) SL; spinous dorsal-fin base length 49.4 % (46.2–50.9) SL; soft dorsal-fin base length 15.6 % (14.5–16.3) SL; first dorsal spine 6.7 % (8.5–10.3) SL; second dorsal spine 13.4 % (13.2–15.9) SL; third dorsal spine 15.8 % (16.8–18.4) SL; fourth dorsal spine 17.5 % (17.7–21.4) SL; fifth dorsal spine 17.1 % (17.7–21.0) SL; sixth dorsal spine 18.3 % (17.6–20.5) SL; last dorsal spine 12.1 % (11.8–14.4) SL; fourth dorsal ray longest, 25.8 % (20.8–28.2) SL; first anal spine 7.5 % (7.1–7.5) SL; second anal spine 23.5 % (21.9–23.3) SL; longest anal-fin ray first, 22.2 % (19.4–20.2); caudal fin forked, with filamentous extensions, its length 33.9 % (32.1–39.2) SL, and concavity 15.0 % (15.4–20.3) SL; first pectoral-fin ray longest, 34.6 % (31.6–34.5) SL; pelvic spine 20.1 % (20.6–23.2) SL; first pelvic soft ray 29.5 % (29.5–32.6) SL.

Color. In life (Fig. 3 ): Body pearly white with pale blue undertones, darker dorsally, with light gray pigment, especially between lateral line and dorsal fin. Belly and cheeks bright white. Row of scales below bottom half of eye very reflective. Bright silvery-blue circle surrounds darker, central part of iris. Area on head between eyes and above iris greenish silver. Lips pale blue. Anterior two-thirds of anal fin black. Distal portions of the soft dorsal, caudal, and posterior third of anal fin transparent. Small black spot on upper margin of pectoral-fin base. Pelvic fins pale blue to pearly white. Recently deceased and in alcohol (Figs 1 , 2 ): Head and body overall gray in color (brown in alcohol), lighter ventrally. Dorsal, caudal, ventral, and pectoral fins pale gray (brown in alcohol) with distal portions translucent. Anal fin dark brown to black (black in alcohol); other black markings as described in life.

Habitat and distribution.

Chromis abadhah is only known from the Maldives. It has been recorded at eight locations spanning 180 km (from Faadhippolhu to Dhaalu Atoll) so we presume it should be widely distributed across the Maldivian Archipelago. The type specimens were collected on a steep slope between 101 and 118 m depth off Maafilaafushi Island, and other individuals were observed elsewhere between 80 and 120 m depth. Habitat complexity was medium to high (small crevices and caves) but of low relief, with an apparently high diversity of encrusting sponges.

Etymology.

The work that led to the discovery of this species was funded by the Rolex Perpetual Planet initiative through a Rolex Award for Enterprises to LAR. To honor this initiative, we name this species “ abadhah ” (pronounced aa-BAH-duh), which means “ perpetual ” in Dhivehi, the local language of the Maldives. We also hope that this species and its habitat remain perpetual. To be treated as a noun in apposition.

Figures

Figure 1. Holotype of Chromis abadhah, CAS 248401, 68.7 mm SL, shortly after collection. Photo by Luiz Rocha.

Figure 2. Preserved holotype and x-ray of Chromis abadhah, CAS 248401, 68.7 mm SL. Photo and x-ray by Jon Fong.

Figure 3. Chromis abadhah in its natural habitat in Faadhippolhu Atoll, Maldives, at approximately 110 m depth. Photo by Luiz Rocha.