Pomacentrus bangladeshius, Habib & Islam & Nahar & Neogi, 2020

Habib, Kazi Ahsan, Islam, Md Jayedul, Nahar, Najmun & Neogi, Amit Kumer, 2020, Pomacentrus bangladeshius, a new species of damselfish (Perciformes, Pomacentridae) from Saint Martin’s Island, Bangladesh, Zootaxa 4860 (3), pp. 413-424 : 415-421

Pomacentrus bangladeshius , n. sp.

English common name: Bengal demoiselle

Local common name: Pettoli

Figures 2 , 3

Zoobank No. urn:lsid:zoobank.org:act:F8892626-8F5E-413A-9613-F031E6934CCA

Holotype. F1710SM-11; 77 mm SL ( Fig. 2 ); Bangladesh, Cox’s Bazar , Teknaf, Saint Martin’s Island; coordinates: 20°36’47.0” N 92°19’36.0” E ( Fig. 1 ); collected by K.A. Habib and M.J. Islam; 10 October 2017; local time 4:00 PM ( GMT +6); GenBank accession number for COI is MK 340681 .

Paratypes. F1801SM-06; 71 mm SL ( Fig. 3A ); F1802SM-14; 67 mm SL ( Fig. 3B ); collected by K.A. Habib and A.K. Neogi; 18 January 2018 and 16 February 2018, respectively. GenBank accession numbers for COI are MK 340682 and MK 340683 , respectively .

Diagnosis. Dorsal-fin elements XIV, 13; anal-fin elements II, 14; pectoral-fin rays 19; lateral-line scales 18–19 (18); total gill rakers on first arch 17–19 (19); body depth 1.68–1.88 (1.88) in SL. Lateral line single and interrupted. Body color olive to dark brown in freshly caught condition; premaxilla dark brown; iris of adult mostly yellow with a narrow bronze eye ring around pupil. Pectoral-fin base without black spot. Margin of suborbital and preopercle with distinct serrations. A prominent notch present between preorbital and suborbital. Snout scaly to about level of nostrils or beyond, scales absent on preorbital and suborbital ( Fig. 4 ). Axillary scale present above base of pelvic fin. Single scale row on preopercle behind the eye and 3 rows of scales present on preopercle below the eye. Circumpeduncular scales 14. Meristic measurements are given in Table 1 .

Description. Body ovate, depth 1.68–1.88 (1.88) in SL and compressed, width 2.56–3.08 (2.56) in body depth; head length 2.91–3.09 (3.08) in SL; dorsal profile of head evenly rounded from dorsal-fin origin to snout; snout length 4.17–4.60 (4.17) in head length (HL); interorbital width 2.56–3.29 (3.13) in HL; eye diameter 3.13–3.29 (3.13) in HL; caudal-peduncle length 3.57–3.83 (3.57) in HL ( Table 2).

Mouth terminal, small, oblique, and superior; forming an angle of about 30° to horizontal axis of head and body; maxilla extending to anterior end of pupil; lower jaw longer than upper jaw, jaw gape 3.13–3.29 (3.13) in HL. Teeth incisiform to conical, uniserial posteriorly, becoming biserial anteriorly. Tongue triangular with rounded tip and placed far back in mouth. Gill rakers cylindrical and long, longest on lower limb near angle and about two-thirds length of longest gill filament. Nostril rounded, level with lower edge of pupil and about midway between anterior edge of eye and upper lip. Opercle ending posteriorly with flat spine, tip obtuse, just projecting from underneath a large scale; preopercle margin usually with distinct serrations; the posterior margin of preopercle expanding dorsally to just behind the eye.

Scales ctenoid; snout scaly to about level of nostrils or beyond; head scaled except lips and tip of snout; subopercle scaly; preorbital (lacrimal) and suborbital naked; single scale row on preopercle behind the eye and 3 rows of scales present on preopercle below the eye; circumpeduncular scales 14 ( Table 1 ). Lateral line extending to base of 1st or 2nd dorsal-fin soft ray. Dorsal-fin and anal-fin base with scaly sheath, averaging about 80% pupil width at base of dorsal fin and approximately equal to pupil width at base of anterior part of anal fin, tapering in width on anteriormost and posteriormost portions; scale columns on each membrane of dorsal and anal fins, tapering distally, those on spinous part of dorsal fin gradually longer, extending at least three-fourths distance to spine tips on posterior membranes, and covering as much as 65% of soft dorsal fin and about 70% of anal fin; small scales on caudal fin extending about 65–75% distance to posterior margin; small scales covering about 30–35% of pectoral-fin base. Axillary scale present above base of pelvic fin.

Dorsal-fin origin over third tubed lateral-line scale; predorsal length 2.16–2.39 (2.33) in SL; dorsal-fin spines gradually increasing in length to last spine; first dorsal-fin spine 3.53–4.60 (3.53) in HL; seventh dorsal-fin spine 1.92–2.09 (1.92) in HL; last dorsal-fin spine 1.77–1.79 (1.79) in HL; longest dorsal-fin soft ray 1.44–1.56 (1.56) in HL; first anal-fin spine 3.13–3.29 (3.13) in HL; second anal-fin spine 1.67–1.77 (1.67) in HL; longest anal-fin soft ray 1.44–1.56 (1.56) in HL; caudal fin moderately forked with rounded to moderately angular lobes, its length 1.05–1.32 (1.32) in SL; pelvic-fin spine 1.92–2.3 (1.92) in HL ( Table 2).

Color of freshly caught specimen. Body color olive to dark brown in freshly caught condition; premaxilla dark brown. Iris of adult mostly yellow with a narrow bronze eye ring around pupil. Dorsal spines and spinous membrane olive brown; dorsal-ray membrane dark brown. Membrane of pectoral, pelvic, anal, and caudal fins dark brown ( Figs. 2–4 )

Coloration in preserved condition. Body color olive brown to nearly black in long-term preserved condition; premaxilla black. Iris of adult mostly yellow with a narrow bronze ring around pupil. Margin of dorsal, pectoral, pelvic and anal fin chocolate brown. Dorsal spines and spinous membrane olive to dark brown; dorsal-ray membrane chocolate brown to nearly black. Membrane of pectoral, pelvic, anal, and caudal fins chocolate to dark brown ( Figs. 2–4 )

Distribution and habitat. Pomacentrus bangladeshius is currently known only from Saint Martin’s Island, Bangladesh. This island has a coral community that extends from near shore to about 200 m offshore. Large areas of sand ridges, rocky reefs with some mangrove formations, Pandanus vegetation, and scattered boulders/dead corals are the major characteristics of this island.

Etymology. The new species is named bangladeshius (Latin: belonging to Bangladesh) in reference to its only known occurrence in Bangladesh. The common name ‘Bengal demoiselle’ is proposed for this species based on its existence in the Bay of Bengal.

Remarks. Most Pomacentrus species possess XIII dorsal-fin spines, but 20 species have XIV dorsal-fin spines, of which 13 species occur in the Indian Ocean ( Allen & Wright, 2003; Frable & Tea, 2019; Froese & Pauly, 2019). Color patterns are very distinctive for most species of Pomacentrus , and color is generally considered a reliable means for separating them ( Allen & Wright, 2003). Pomacentrus bangladeshius occurs in the northern Bay of Bengal of the Indian Ocean and displays XIV dorsal-fin spines. The measurements and coloration of P. bangladeshius are different from all of the other Pomacentrus species found in the Indian Ocean. Pomacentrus bangladeshius is readily separated from P. aquilus Allen & Randall, 1980 in having deeper body (1.68–1.88 vs. 1.9–2.0 in SL), fewer gill rakers on first arch (17–19 vs. 19–22), more lateral-line scales (18–19 vs. 16–18), pectoral fin without spot vs. a black spot at upper base of pectoral fin, and, moreover, P. aquilus is restricted to the western Indian Ocean ( Allen & Randall, 1980). Further, P. bangladeshius is different from P. arabicus Allen, 1991 in having fewer dorsal-fin soft rays (13 vs. 14–15), more pectoral-fin rays (19 vs. 17–18), fewer lateral-line scales (18–19 vs. 19–22), larger head (2.91–3.0 vs. 3.1–3.5; 3.3) in SL, smaller snout (4.17–4.60 vs. 2.9–3.4; 3.4) in HL, and occurrence of P. arabicus is restricted to the Gulf of Oman ( Allen, 1991); from P. atriaxillaris Allen, 2002 in having fewer dorsal-fin soft rays (13 vs. 14), fewer gill rakers on first arch (17–19 vs. 21–24), pectoral fin without spot vs. black spot at upper base of pectoral fin and axil; from P. baenschi Allen, 1991 in having fewer dorsal-fin soft rays (13 vs. 14–15) and fewer gill rakers on first arch (17–19 vs. 19–21); from P. indicus Allen, 1991 in having more pectoral-fin rays (19 vs. 17–18), fewer gill rakers on first arch (17–19 vs. 20–23), and pectoral fin without spot vs. black spot at base of pectoral fin and axil; from P. milleri Taylor, 1964 in having more pectoral-fin rays (19 vs. 17–18) and fewer gill rakers on first arch (17–19 vs. 19–20); from P. pikei Bliss, 1883 in having fewer gill rakers (17–19 vs. 19–23), more lateral-line scales (18–19 vs. 16–18), and pectoral fin without spot vs. small black spot at upper base of pectoral fin; from P. polyspinus Allen 1991 in having more pectoral-fin rays (19 vs. 16–19), dorsal fin without ocellus vs. a black ocellus with pale margin on posterior soft dorsal fin, and dark brown pectoral fin vs. yellowish pectoral fin; from P. proteus Allen, 1991 in having fewer gill rakers on first arch (17–19 vs. 19–20) and dorsal fin without ocellus vs. a black ocellus with pale margin on posterior soft dorsal fin; from P. rodriguesensis Allen & Wright 2003 in having fewer anal-fin rays (14 vs. 15–16), fewer gill rakers on first arch (17–19 vs. 19–21), and pectoral fin without spot vs. dark brown spot at base of pectoral fin; from P. sulfureus Klunzinger, 1871 in having more lateral-line scales (18–19 vs. 14–17), fewer gill rakers on first arch (17–19 vs. 18–23), and pectoral fin without spot vs. black spot at pectoral fin base; from P. trichrourus Günther, 1867 in having fewer dorsal-fin soft rays (13 vs. 14–16), fewer anal-fin rays (14 vs. 15–16), more pectoral-fin rays (19 vs. 16–17), fewer gill rakers on first arch (17–19 vs. 19–24), and dark brown caudal fin vs. white caudal fin; from P. vatosoa Frable & Tea, 2019 in having fewer lateral-line scales (18–19 vs. 19–20), fewer gill rakers on first arch (17–19 vs. 22–24), pectoral fin without spot vs. small black spot at upper base of pectoral fin, and body without spots vs. two prominent black spots on body—one situated midlaterally behind the pectoral fin and the other on the dorsal edge of the caudal peduncle.

Pomacentrus bangladeshius is also different from other species of similar appearance with XIV dorsal-fin spines distributed outside of the Indian Ocean. Pomacentrus bangladeshius can be separated from P. australis Allen & Robertson, 1974 in having fewer gill rakers on first arch (17–19 vs. 19–21) and deeper body (1.68–1.88 vs. 2.2–2.6 in SL); from P. bellipictus Allen, Erdmann & Hidayat, 2018 in having no prominent facial markings vs. blue facial markings and yellow iris vs. dark grey iris; from P. fakfakensis Allen & Erdmann, 2009 in having more pectoral-fin rays (19 vs. 17) and opercle without spot vs. small black spot on upper edge of opercle; from P. opisthostigma Fowler, 1918 in having more tubed lateral-line scales (18–19 vs. 15–17), fewer gill rakers (17–19 vs. 26–29), and more pectoral-fin rays (19 vs. 18).

Genetic description. The COI sequences obtained from three specimens (one holotype and two paratypes) of P. bangladeshius displayed a single haplotype, i.e., there is no nucleotide variation among sequences. Phylogenetic analysis resulted in a well-resolved tree of relationships at the species level. In the ML tree, sequences of three specimens of P. bangladeshius formed a separate clade with 95% bootstrap support, distinct from other congeneric species used in the analysis ( Fig. 5 ). Moreover, the clade formed by P. taeniometopon and P. tripunctatus was found as the sister group of P. bangladeshius ( Fig. 5 ). Genetic divergences between P. bangladeshius and each of these two species of P. tripunctatus and P. taeniometopon were found as 7.7% and 14.4%, respectively. Further, genetic divergence of P. bangladeshius varied between 7.7% and 17.5% from the other congeneric species used in the phylogenetic analysis.

Figures

FIGURE 1. Map of the Saint Martin’s Island and its location in Bangladesh and the Bay of Bengal (District: Cox’s Bazar; Subdistrict/Upazilla: Teknaf; 20°34’–20° 38’ N and 92°18’–92°21’ E).

FIGURE 2. Holotype of Pomacentrus bangladeshius n. sp., F1710SM–11, 77 mm SL; freshly caught specimen; Saint Martin’s Island, Bangladesh (K.A. Habib).

FIGURE 3. A. Paratype 1 (preserved) of P. bangladeshius n. sp., F1801SM–06, 71 mm SL; B. Paratype 2 (preserved) of P. bangladeshius n. sp. F1802SM–14, 67 mm SL, Saint Martin’s Island, Bangladesh (K.A. Habib).

FIGURE 4. Pomacentrus bangladeshius n. sp., paratype, F1802SM–14, distinct serrations on suborbital and preopercle; preorbital and suborbital naked.

FIGURE 5. Maximum-likelihood tree constructed for COI gene sequences of Pomacentrus bangladeshius and its genetically closely related congeneric species retrieved from GenBank. Values of bootstrap support of>80% are shown above branches. The sequence of Pomacentrus auriventris Allen, 1991 marked by an asterisk (*) was obtained from the aquarium trade and therefore lacks locality information (Frédérich et al., 2013). Scale bar indicates number of nucleotide substitutions per site.