Plectorhinchus unicolor ( Macleay, 1883 )

Johnson, Jeffrey W. & Wilmer, Jessica Worthington, 2015, Plectorhinchus caeruleonothus, a new species of sweetlips (Perciformes: Haemulidae) from northern Australia and the resurrection of P. unicolor (Macleay, 1883), species previously confused with P. schotaf (Forsskål, 1775), Zootaxa 3985 (4), pp. 491-522 : 509-515

Plectorhinchus unicolor ( Macleay, 1883)

English name: Sombre Sweetlips

Figures 1 , 6–9 , 14 ; Tables 1–5.

Diagramma unicolor Macleay, 1883: 261 (type locality: China Strait); Smith, 1962: 498 (as probable junior synonym of P. schotaf (Forsskål) .

Plectorhinchus unicolor (Macleay) : Randall et al., 1997: 195, upper fig.; Johnson, 1999: 736; Hutchins, 2001: 35; Allen & Adrim, 2003: 40; Allen et al., 2003: 172, centre left fig.; Myers & Donaldson, 2003: 627.

Plectorhinchus schotaf (non Forsskål, 1775): Akazaki in Masuda et al., 1984: 172, pl. 160F; Randall et al., 1990: 195, upper fig.; Shimida in Nakabo, 2002: 844; McKay, 2001: 2981 (in part); Allen et al., 2006: 1223; Chen et al., 2010: 232, fig. C; Johnson, 2010: 320, 340.

Plectorhinchus sp.: Francis, 1993: 161.

Plectorhinchus sp. A: Myers, 1999: 151, pl. 67C.

Holotype. AMS I. 13415, 342 mm, China Strait, Papua New Guinea, Mr. Goldie.

Non-types. (25: 107–640 mm) Western Australia, Australia: WAM P.20127-001, 516 mm, Delambre Island, Dampier Archipelago, 20°26’S 117°04’E, R.J. McKay, 29 Oct 1971; WAM P.20287-001, 570 mm, Rottnest Island, west end, 32°00’S 115°30’E, spear, B. Paxman, 1972; WAM P.27178-001, 551 mm, Kalbarri, 27°44’S 114°06’E, handline, T. Jurjevic, May 1976; WAM P.29704-001, 640 mm, Exmouth area, 21°55’S 114°10’E, spear, Australian Underwater Federation, Jan 1988. Queensland, Australia: AMS I. 7743, 131 mm, Moreton Bay, ca 27°25’S 153°20’E, 1906, Amateur Fishermen’s Association of Queensland; AMS I.44723–035, 383 mm, Lizard Island, Mermaid Cove, N of mooring, 14°38’44”S 145°27’18”E, 3–10 m, spear, 8 Sep 2008, J. Johnson; QM I. 6812, 338 mm, Horseshoe Bay, Magnetic Island, 19°07’S 146°51’E, 6 Sep 1939, G. Coates; QM I. 10271, 302 mm, Off Bundaberg, ca 24°50’S 152°29’E, spear, Dec 1972, G. Lowe; QM I. 11321, 199 mm, Off Cairns, ca 16°52’S 145°56’E, spear, 1973, H. Jesse; QM I. 11456, 455 mm, Cairns, offshore reefs, ca 16°55’S 146°10’E, spear, Feb 1974, P. Pike; QM I. 12664, 300 mm, Teewah Beach, Cooloola, 26°17’S 153°04’E, 17 Aug 1974, E.M. Grant; QM I. 12711, 228 mm, Off Bundaberg, ca 24°50’S 152°29’E, spear, 20 Sep 1974, G. Lowe; QM I. 12722, 282 mm, same data as previous; QM I. 12907, 267 mm, Off Cairns, ca 16°52’S 145°56’E, spear, Dec 1974, H. Jesse; QM I. 20130, 289 mm, Frankland Islands, Qld, 17°13’S 146°05’E, 7 m, spear, Nov 1982, J. Johnson; QM I. 20131, 336 mm, same data as previous; QM I. 21124, 357 mm, Cape Moreton, below lighthouse, 27°02’S 153°28’E, spear, 9 Aug 1984, J. Johnson; QM I. 27499, 234 mm, Off Mooloolaba, 26°40’S 153°15’E, 1 Sep 1991, D. Tuma; QM I. 29477, 142 mm, Cowan Cowan, Moreton Island, 27°08’S 153°22’E, 2 m, spear, 31 Oct 1994, J. Johnson; QM I. 39292, 352 mm, NE end of Gloucester Island, 19°58’44”S 148°27’37”E, 3 m, spear, 30 Sep 2014, J. Johnson; QM I. 12708, 285 mm, Off Bundaberg, ca 24°50’S 152°29’E, spear, 20 Sep 1974, G. Lowe (skeleton); QM I.12709, ca 230 mm, same data as previous (skeleton); QM I.12712, ca 240 mm, same data as previous (skeleton); QM I.20298, length not recorded, Frankland Islands, 17°13’S 146°05’E, 7 m, spear, Nov 1982, J. Johnson (skeleton). New South Wales, Australia: AMS I.15838–004, 107 mm, Tweed River mouth, 28°10’S 153°33’E, 1969, J. Lewis. Indonesia: CSIRO H.7681-01, 191 mm, Banyuwangi, East Java, 8°09’S 114°23’E, 27 Feb 2009, W. White; CSIRO H.7681-02, 191 mm, same data as previous. Japan: KPM-NI 28726, 247 mm, Kin Bay, E coast of Okinawa-jima Island, Ryukyu Islands, 26°25’12.151”N 127°49’49.182”E, spear, 2.0– 2.5 m, H. Senou, 6 Jun 2011; MUFS 17430, 302 mm, Meitsu fishing port, Miyazaki Prefecture, H. Motomura, 12 Apr 1999.

Diagnosis. A species of Plectorhinchus with dorsal-fin rays XII–XIII (rarely XIII), 17–20 (modally 19); analfin rays III, 6–8 (rarely 6); pectoral-fin rays 16–18 (usually 17); lateral-line scales 54–57 (modally 55); transverse scale rows above lateral line 12–13; gill rakers 10–12 + 16–19 = 27–31 (modally 29); pelvic fins usually reaching slightly short of anus; nostrils large, posterior nostril 0.9–1.5 % SL, 0.9–1.8 times in distance from posterior nostril to eye; fresh colouration of head and body generally olive-brown, tan, or grey-brown; posterior margin of opercular membrane dusky, with underlying cleithrum red; and caudal fin bright yellow in juveniles, to dull yellowish or greenish brown in adults.

Description. Dorsal-fin rays XII, 20 (XII–XIII, rarely XIII, 17–20, modally 19); anal-fin rays III, 8 (III, 6–8, rarely 6); all dorsal- and anal-fin rays branched, last to base; pectoral-fin rays 17 (16–18, rarely 16 or 18), first ray rudimentary, second and lowermost rays unbranched, others branched; pelvic-fin rays I, 5, all branched; principal caudal-fin rays 9 + 8 = 17, uppermost and lowermost rays unbranched; lateral-line scales 55 (54–57, modally 55), plus about 13 smaller tubed scales on anterior third of caudal-fin base; scales above lateral line to base of first dorsal-fin spine 12 (12–13); scales below lateral line to first anal-fin spine 20 (19–21); circumpeduncular scales 31 (31–32); gill rakers on first arch 11 + 17 = 28 (10–12 + 16–19 = 27–31, modally 29); branchiostegal rays 7; vertebrae 11 + 16 = 27.

Body oblong, moderately deep, depth 2.6 (2.2–2.7) in SL, and compressed, width 2.7 (2.3–2.8) in depth; head length 3.4 (3.3–3.9) in SL; dorsal profile of head distinctly convex, a line from its apex forming an angle of about 40° (40–53°) from a horizontal at the snout tip; snout short, length 3.7 (2.9–5.1) in HL; orbit diameter 3.6 (3.0–5.6) in HL, proportionally narrower with growth; interorbital width 3.3 (2.6–3.3) in HL; preorbital width 4.4 (3.6–5.4) in HL; caudal peduncle depth 2.6 (1.9–2.6) in HL; caudal peduncle length 1.5 (1.2–1.6) in HL.

Mouth small, tip of maxilla reaching a vertical just anterior to anterior margin of eye (between posterior nostril and just posterior to anterior margin eye), upper jaw length 4.1 (3.1–4.5) in HL; lips thick and fleshy, upper lip protruding beyond tip of lower jaw; teeth conical, outer series distinctly enlarged, but no canines; in band of up to 5 rows wide anteriorly in upper jaw and up to 6 rows wide anteriorly in lower jaw; band in upper jaw narrowing gradually to become one or two rows wide for about last 4 teeth in series; band in lower jaw narrowing abruptly at about midsection of jaw to become uniserial for about last 7 teeth in series; teeth in outer series of upper jaw about 24 (22–25) on each side, those of lower jaw about 22 (20–22) on each side; numerous small fleshy papillae interdigitating among teeth, fleshy flap behind bands of teeth in each jaw with shorter more flattened papillae that gradually decrease in size posteriorly; vomer and palatines edentate; tongue smooth, with broadly rounded tip; chin with 3 pairs of prominent pores, all fairly evenly spaced; gill rakers moderately short, raker below angle longest, about 3.9 (3.5–4.5) in orbit diameter.

Nostrils moderately large, posterior nostril subequal and dorsoposterior to anterior nostril, its width 5.9 in orbit diameter (5.2–7.9); posterior nostril in front of horizontal from centre of eye; anterior nostril in front of horizontal from lower margin of pupil (posterior nostril on horizontal from centre to lower third of eye; anterior nostril on horizontal from lower margin of pupil to lower margin of eye); internarial distance narrow, 3.3 (2.6–4.3) in distance from posterior nostril to eye; distance from posterior nostril to eye narrow, 6.4 (2.7–7.7) in orbit diameter (2.7–6.4 in specimens> 250 mm SL); posterior nostril with raised membranous rim, the rim widest anteriorly and forming broadly rounded flap about one-quarter nostril width (flap rounded to crenulate, one-quarter to one-third nostril width); anterior nostril with thicker, more fleshy raised rim and wider broadly rounded (rounded to crenulated) flap posteriorly, of almost half nostril width.

Opercle lacking exposed spine; posterior edge of preopercle finely serrate (serrations more distinct in juveniles and subadults); margins of subopercle, including angle and interopercle, smooth.

Scales small and ctenoid on body and most of head, cycloid anteriorly on interorbital and suborbital; lateral line continuous, gently curved anteriorly, following dorsal contour of body and becoming straight on peduncle; head scaled except on snout just forward of anterior nostrils and band from anterior margin of eye to snout, bounded above by an oblique imaginary line from dorsal margin of eye through dorsal edge of anterior and posterior nostrils; small imbedded scales on preorbital reaching anteriorly to vertical from anterior nostril; horizontal scale rows from preorbital margin opposite tip of maxilla across cheek to edge of preopercle about 26, vertical rows below middle of eye obliquely to margin of preorbital about 16 (not feasible to count accurately due to numerous small supplementary scales and irregular size and alignment of scales along rows); basal sheath of scales present on dorsal and anal fins; spinous and soft portions of dorsal fin with 1–2 and about 6–10 scale rows at bases respectively; spinous and soft portions of anal fin with 2–3 and about 7–12 scale rows at bases respectively; minute scales sparsely distributed on soft rays of all fins, except inner base of pelvic fins; axil of pectoral fin with scaly process, fleshy inner base naked.

Dorsal fin with shallow notch, its origin just posterior to vertical from upper corner of opercle (between upper corner and just anterior to posterior margin of opercle); base of soft dorsal-fin subequal to that of spinous portion, 1.1 (1.0–1.2) in its length; interspinous membranes moderately incised; dorsal-fin spines strong, first spine 7.3 (4.6–6.7) in HL; fourth dorsal-fin spine longest, 2.4 (2.2–3.0) in HL; fifth spine next longest, followed by third; 12th (10th to 12th) soft dorsal-fin ray longest, 2.2 (1.7–2.8) in HL; origin of anal fin below base of 8th (6th to 8th) soft dorsal-fin ray; first anal-fin spine short, 3.2 (2.1–3.4) in second; second anal-fin spine more robust and slightly longer than third (slightly shorter than third in some larger specimens), 2.1 (1.6–3.2) in HL; second anal-fin ray longest, 1.7 (1.4–2.0) in HL; anal-fin base short, 1.4 (1.2–1.6) in its height; caudal fin emarginate (truncate in juveniles), 1.4 (1.1–1.5) in HL; fifth pectoral-fin ray longest, 1.2 (1.1–1.5) in HL, slightly longer than pelvic fins (slightly shorter to slightly longer); origin of pelvic fins posterior to lower base of pectoral fins, on vertical from base of 5th (5th to 7th) dorsal-fin spine; pelvic-fin tips slightly short of anus (reaching anus in juveniles and some subadults, more than eye diameter short of anus in specimens> 500 mm SL), first ray longest (second subequal to first), 1.4 (1.1–1.6) in HL.

Colour when fresh. Fresh colouration of holotype, 342 mm SL, unknown.

Non-type QM I. 39292, 352 mm SL, underwater in life: mostly uniform grey-brown on head and body, fins except caudal darker, caudal fin pale greenish yellow. The specimen underwent a series of significant colour changes after capture, until death ( Fig. 8–9 ). Initial live phase on capture ( Fig. 8 A): upper half of head and body medium brown, lower head and body pearly white, with small irregular scattered brownish blotches. Groove above upper lip and behind maxilla, first branchiostegal membrane below lower edge of operculum and cleithrum, bright red. Opercular membrane dusky. Dorsal and anal fins mostly black, but membranes darker than spines and rays. Caudal fin olive-brown. Pectoral fins dusky, with pearly white base. Pelvic fins dusky, with leading edge white. Secondary phase in life after capture ( Fig. 8 B): Head and body tan overall, with paler scale edges, lower lip and dentary pale cream, otherwise similar to above. Immediately on death ( Fig. 9 A): Head and body mostly pale yellowish white, with faint dusky blotching on upper body above pectoral fins, caudal fin pale yellowish green, markings otherwise similar to the above. Fresh, after freezing ( Fig. 9 B): Head and body mostly dark brownish grey, with pale edges to most scales and light grey on chest, belly, pectoral-fin base and scaly sheath of anal fin. Upper lip creamy white, infused with grey; lower lip and dentary pale cream. Opercular membrane dusky. Dorsal fin mostly black, but membrane near base of most spines with a small pale grey blotch, and soft dorsal-fin rays contrasting as lighter than intervening membranes. Anal fin dusky to black. Caudal fin uniformly olive-brown. Pectoral fins with distal two-thirds dusky. Pelvic fins with leading edge of spine white and remainder black.

Juvenile QM I. 29477, 142 mm SL, when fresh had violet reflections on the cheeks and snout and caudal fin uniformly pale yellow.

Colour in alcohol. Holotype, preserved prior to 1883 ( Fig. 6 A), mostly uniformly brown on head and body, fading slightly to a lighter brown on underside of head, branchiostegal membranes, chest and belly. Upper lip and maxilla dusky. Lower lip pale. Opercular membrane dusky. Spinous dorsal fin with pale spines and dusky membranes. Soft dorsal and anal fins with brown rays, contrasting strongly against dusky intervening membranes. Caudal fin brown. Pectoral fins brown, with distal third slightly dusky. Pelvic fins faintly dusky.

Non-type QM I.39292, preserved in 2014, dark grey-brown on head and body, lighter creamy brown on chest and belly. Lower portion of upper lip, lower lip and dentary to level of isthmus pale cream. Opercular membrane dusky. Spinous dorsal-fin spines and membrane mostly black, but membrane near base of first 10 spines with irregular pale blotch about one eighth height of membrane. Soft dorsal and anal fins with dark grey rays, contrasting against black intervening membranes. Caudal fin uniformly pale grey-brown. Pectoral fins grey-brown basally, with distal half faintly dusky. Pelvic fins with leading edge of spine pale, rays dark grey and membranes dusky. Colouration of juveniles similar to adults, except caudal fin contrasting paler against body.

Genetics. The phylogenetic analyses indicate that P. unicolor is most closely related to a well-supported clade comprised of P. chubbi , P. playfairi and P. sordidus and differs from those species by an average of 5.13%, 5.38% and 5.49% respectively ( Figure 1 , Table 2). This group is also clustered with the two molecular forms of P. schotaf , A and B, to which P. unicolor differs by an average of 14.45% and 14.92% sequence divergence respectively ( Table 2).

Distribution and abundance. Known from southern Japan (Miyazaki Prefecture and Ryukyu Islands), Taiwan (Kenting National Park), Micronesia ( Guam), West Malaysia ( Pulau Redang), Indonesia (Bali and Banyuwangi, East Java), New Guinea ( China Strait) and northern Australia, from Rottnest Island north to Dampier Archipelago, Western Australia on the west coast, and Lizard Island, Queensland south to Tweed River, New South Wales, and Lord Howe Island on the east coast ( Fig. 14 ). Usually found in small groups, or solitary, around rocky headlands, coastal rocky reef, or continental islands, in depths of 1–10 m, with a rich growth of brown macroalgae and moderate wave action. Small juveniles are rarely seen or collected, possibly due to their preference for subtidal rocky reef with moderately high wave action. The species appears to be uncommon in Western Australia, with only four very large specimens (516–640 mm SL) held in collections of the Western Australian Museum. In contrast, P. unicolor is often encountered by divers on the east coast of Australia, but the largest specimen available for examination in museum collections was only 455 mm SL. The species appears to be rare in Japanese waters ( Akazaki, 1984: 172; Iwatsuki pers. comm., 2015).

Discussion. Plectorhinchus unicolor ( Fig. 6–9 ) is physically most similar to P. schotaf ( Figs. 10–11 ), sharing similar morphology, meristic formulae, and colouration of adults, including head and body mostly uniform greybrown and skin of cleithrum beneath the opercular margin crimson red. It differs most obviously in having fresh colouration of the margin of the opercular membrane dusky (crimson red, as in cleithrum, in P. schotaf ) and colour in life of the caudal fin yellowish (dark grey or dusky, similar to body, in P. schotaf ). Colouration of small juveniles is also strikingly different between the two species. Juveniles of P. unicolor are similar to the adults, except the caudal fin is consistently pale yellow. In contrast, small P. s c ho t af have about six narrow longitudinal pale blue lines along the head and body on a yellowish background ( Fig. 11 ; see also Randall, 1995, Fig. 538; specimen BPBM 30410, 45 mm SL, labelled as P. sordidus ). Although meristics for both species mostly overlap, there is a modal difference in soft dorsal-fin rays (17–20, modally 19, versus 18–21, modally 20 in P. schotaf ) and a strong modal difference in pectoral-fin rays (16–18 (rarely 16 or 18), modally 17, versus 16–18 (rarely 18), modally 16 in P. schotaf ) ( Table 4). Differences also exist in various proportional measurements at a given length, with P. unicolor having a deeper body, wider caudal peduncle depth, longer spinous dorsal-fin base, higher soft dorsal fin, and longer pectoral and pelvic fins ( Table 5 ). Data presented by Smith & McKay (1986) and McKay (2001) for P. schotaf were a compilation, as their material examined included both P. schotaf and P. unicolor , and the species were not differentiated.

Differences between P. unicolor and P. caeruleonothus are outlined above under the discussion for P. caeruleonothus . Among other species of Plectorhinchus with a uniform body colouration, P. unicolor can most readily be distinguished from P. ceylonensis and P. gibbosus by dorsal-fin spine and ray counts (XII-XIII (rarely XIII), 17–20, versus XIV, 19 in P. ceylonensis and XIII–XIV (rarely XIII), 15–17 in P. gibbosus ); from P. chubbi by dorsal-fin spine and ray and gill raker counts (XII-XIII, 17–20 and 10–12 + 16–19, versus XI–XII (rarely XII), 16– 17 and 13–16 + 22–24 in P. chubbi ); from P. griseus by dorsal-fin ray counts and lateral profile of the forehead (XII-XIII, 17–20, lateral profile of forehead at snout evenly convex, versus XII, 21–23, lateral profile of forehead at snout with distinct concavity in P. g r i s e us); and from P. sordidus (fig. 13a–b) by gill raker counts (10–12 + 16– 19 = 27–31, versus 9–11 + 15–16 = 25–26 in P. sordi dus ), a narrower distance from posterior nostril to the eye, and a longer caudal peduncle ( Table 5 ).

Figures

FIGURE 1. Majority-rule consensus tree of species of Plectorhinchus and outgroup taxa based on 4 independent runs of the DNA barcoding CO 1 fragment. Posterior probabilities are detailed above the branches. Branches with <60 % support were collapsed. Scale bar represents 3 % uncorrected sequence divergence. Details of specimen data and GenBank / BOLD accession numbers are provided in Table 1.

FIGURE 6. Plectorhinchus unicolor. A. Holotype, AMS I. 13415, 342 mm SL, China Strait, Papua New Guinea, preserved. (Photo: P. Waddington); B. Adult, ca 40 cm TL, Southport Seaway, Queensland, underwater. (Photo: I. Banks).

FIGURE 7. Plectorhinchus unicolor. A. Subadult, KPM-NI 28726, 247 mm SL, Okinawa-jima Isl., Ryukyu Isls., Japan, fresh condition. (Photo: H. Senou); B. Juvenile, CSIRO H. 7681 - 02, 191 mm SL, Banyuwangi, East Java, Indonesia, fresh condition. (Photo: W. White); C. Juvenile, QM I. 29477, 142 mm SL, Cowan Cowan, Moreton Bay, Queensland, preserved. (Photo: J. W. Johnson).

FIGURE 8. Plectorhinchus unicolor, colour variation in life within an individual, QM I. 39292, 352 mm SL, Gloucester Island, Queensland. A. Alive, immediately on capture. (Photo: J. W. Johnson); B. Alive, shortly after capture. (Photo: J. W. Johnson)

FIGURE 9. Plectorhinchus unicolor, colour variation post mortem within an individual, QM I. 39292, 352 mm SL, Gloucester Island, Queensland. A. Fresh, upon death. (Photo: J. W. Johnson); B. Fresh, after freezing. (Photo: J. W. Johnson).

FIGURE 10. Plectorhinchus schotaf, adult and subadult colouration. A. Adult, ca 40 cm TL, Gulf of Oman, underwater. (Photo: R. Field); B. Adult, ca 40 cm TL, Gulf of Oman, underwater. (Photo: R. Field); C. Subadult, BPBM 20766, 243 mm SL, Port Sudan, Red Sea, fresh condition. (Photo: J. E. Randall)

FIGURE 11. Plectorhinchus schotaf, juvenile colouration. A. Juvenile, ca 15 cm TL, Persian Gulf, underwater. (Photo: R. Field); B. Juvenile, BPBM 30410, 45 mm SL, Saudi Arabia, Persian Gulf, fresh condition. (Photo: J. E. Randall)

FIGURE 14. Distribution of Plectorhinchus caeruleonothus sp. nov. (stars), P. schotaf (diamonds) and P. unicolor (triangles), based on material examined and confirmed photographs taken underwater, or from fresh specimens.