Plectranthias melanesius Randall

Gill, Anthony C., Pogonoski, John J., Moore, Glenn I. & Johnson, Jeffrey W., 2021, Review of Australian species of Plectranthias Bleeker and Selenanthias Tanaka (Teleostei: Serranidae: Anthiadinae), with descriptions of four new species, Zootaxa 4918 (1), pp. 1-116 : 89-93

Plectranthias melanesius Randall

Figures 11 , 37 ; Tables 1–16, 21, 28

Common name: Melanesian Perchlet

Plectranthias kelloggi melanesius Randall 1980: 147 , table 11 (type locality, south of Isle of Pines, New Caledonia). Plectranthias sp. B.— Williams et al. 2006: appendix 8: 29 (colour photo).

Plectranthias kelloggi [non Anthias kelloggi Jordan & Evermann 1903].— Anderson 2018: 29 (checklist, in part). Plectranthias kelloggi melanesicus .— Parenti & Randall 2020: 27 (checklist; subspecific epithet misspelled).

Diagnosis. A species of Plectranthias with the following combination of characters: dorsal rays X,15–16; pectoral rays 15; lateral line complete with 32–34 tubed scales; no antrorse serrations on lower edge of preopercle; scales with basal cteni; melanophores on caudal peduncle form a bar that extends to ventral margin of peduncle.

Description of Australian specimens. Dorsal rays X,15–16, all segmented rays branched; anal rays III,7, all segmented rays branched; pectoral rays 15, uppermost and lowermost rays unbranched; pelvic fin I, 5, all segmented rays branched; upper procurrent caudal-fin rays 7–8; lower procurrent caudal-fin rays 7–8; principal caudal-fin rays 9+8; branched caudal fin rays 8+7; total caudal-fin rays 31–33; lateral line complete with 32–34 scales; scales above lateral line to origin of dorsal fin 3–4; scales above lateral line to base of fifth dorsal spine 2–3; scales below lateral line to origin of anal fin 12–14; diagonal rows of scales on cheek 7–9; predorsal scales 27–37, extending to area ranging from just short of posterior nostrils (38.7 mm SL specimen) to just short of upper lip (97.0 mm SL specimen); circumpeduncular scales 14–16; gill rakers 6–7+15–16=21–23, the upper 3–5 and lower 1–2 rudiments; pseudobranchial filaments 12–17; branchiostegal rays 7.

Vertebrae 10+16; supraneurals 3; predorsal formula 0/0+0/2/1+1; dorsal pterygiophores in interneural spaces 9–13 1/1/1/1+1/1 or 1/1/1/1+1/1+1; 0 trisegmental pterygiophores associated with dorsal fin; terminal dorsal pterygiophore in interneural space 18; 2 trisegmental pterygiophores associated with anal fin; terminal anal pterygiophore in interhaemal space 5–6; ribs present on vertebrae 3 through 10; epineurals present on vertebrae 1 through 13; parhypural and hypurals autogenous; well-developed hypurapophysis on parhypural; epurals 3; single uroneural (posterior uroneural absent); ventral tip of cleithrum with well-developed posteroventral process; proximal tip of first anal-fin pterygiophore near parapophyses on vertebra 10.

Dorsal-fin spines with fleshy tabs on their distal tips; fourth or fifth dorsal spine longest; dorsal fin incised before first segmented-fin ray (tenth spine 55.7–67.0 % length of first segmented ray); second anal-fin spine longest and stoutest; anal fin rounded with third segmented ray longest; caudal fin truncate to emarginate, with filamentous ray on upper lobe; lower nine pectoral fin rays somewhat thickened, with membranes between thickened rays deeply incised; ninth (counting from dorsal-most) pectoral ray longest, reaching vertical through anal origin to anterior third of anal-fin base; pelvic fins short, not reaching anus, second segmented ray longest.

Morphometric data are summarised in Table 28.

Mouth large, oblique, posterior margin of maxilla reaching vertical through posterior edge of pupil in smaller specimens, almost to posterior edge of orbit in largest specimen; maxilla expanded posteriorly; small, splint-like supramaxilla present; mouth terminal, lower jaw projecting; upper jaw with a stout outer canine on either side at front of jaw, flanked internally by villiform band with about 5–6 rows of depressible, smaller, sharp-tipped teeth, the posterior few teeth nearest symphysis enlarged and caniniform; band of villiform teeth reducing to 2–3 rows posteriorly, those of outer row largest and curved inwards; lower jaw with 1–2 stout fixed conical teeth either side of symphysis, flanked internally by villiform band of about 4–5 rows of small depressible teeth at symphysis, the posterior few teeth nearest symphysis enlarged and caniniform; band of teeth reducing to 2–3 on middle of jaw, behind which 1–2 enlarged canines, followed by single row of inwardly curved small teeth on posterior half of jaw; vomer with 2 rows of curved teeth in V-shaped patch; palatine with a band of 2–3 rows of small, sharp-tipped conical teeth; ectopterygoid and mesopterygoid edentate; tongue narrow, pointed and edentate.

Opercle with 3 flat spines, middle spine longest, upper spine concealed by scales; posterior and ventral margin of preopercle with 19 weak (smallest specimen) to 64 strong (in largest specimen) serrations, serrations continuous around angle; interopercle with 2 weak (smallest specimen) to 15 strong (largest specimen) serrations; subopercle with 3–12 serrations, strongest in largest specimen; posttemporal with 0–5 irregular serrations. Anterior nostril positioned at middle of snout, tubular with small flap on posterior rim; posterior nostril at anterior border of orbit, with slightly raised rim but no flap.

Scales ctenoid with basal cteni; lateral line broadly arched over pectoral fin following body contour to caudalfin base; scales present on maxilla (not apparent in smallest specimen), upper part of snout almost to upper lip, except for naked wedge medially (only to near posterior nostrils in smallest specimen), all infraorbitals except first, mandibles (only posteriorly in smallest specimen) and chin (not apparent in two smaller specimens); no scales on branchiostegal membranes or lips; no auxiliary scales on head or body; soft dorsal fin and anal with fin with low scaly sheath basally, with some small scales extending on to fin membranes; caudal fin with scaly basal sheath, with small scales extending on to basal third to half of fin membranes; pectoral fins with basal sheath and small scales extending on to fin membranes.

Colour in life (based on colour photo of 38.7 mm SL when freshly dead; Figure 37A ): Head reddish brown dorsally, becoming yellow-brown on snout, lips and in broad oblique stripe from lower part of orbit to angle of preopercle, below which abruptly white; iris yellow, greenish brown dorsally and reddish brown posteriorly, with narrow brown ring around pupil and large black blotch in front of pupil; body tan, becoming white on abdomen, with small dark grey spot in front of dorsal fin origin; broad reddish brown bar from anterior nape to base of third dorsal spine, extending ventrally to mid-side; dark grey-brown bar between bases of seventh dorsal spine and second segmented ray, extending ventrally to ventral edge of body between anus and base of second segmented anal ray; two indistinct yellow-brown bars from soft part of dorsal fin to mid-side; caudal peduncle with bar about 3–4 scales wide extending from dorsal to ventral edges of peduncle, bar grey-brown dorsally, paler reddish brown ventrally below lateral line; mid-body dark bar extending broadly on to dorsal fin, remainder of dorsal and anal fins pale to hyaline with bars from body extending on to fin bases; caudal whitish to hyaline, with small orange-brown elongate spot near base of middle few rays of upper lobe; pectoral and pelvic fins hyaline.

Colour in preservative: ( Figures 37 B–C) Two larger (58.5 and 97.0 mm SL) specimens very faded, but have indistinct dusky melanophores of anterior bar (from bases of seventh dorsal spine to second segmented ray) to about 2 scale rows below lateral line, with very indistinct finer melanophores scattered to ventral edge of body; caudal peduncle bar similar, with bar present mostly as fine, scattered very indistinct melanophores, and distinct melanophores only in mid-lateral, horizontally elongate spot (about 2 scales wide); caudal fin with small dark grey spot near base of middle few rays of upper caudal lobe, remainder of fins pale. Smallest (38.7 mm SL) specimen generally pale tan; dark mid-body and caudal peduncle bars remain, though strong only dorsally, but with indistinct fine melanophores extending to ventral edge of body and peduncle.

Habitat and distribution. Originally described from New Caledonia by Randall (1980), P. melanesius is here newly recorded from Australia based on specimens collected off Stradbroke Island, Queensland, and from a large seamount north of Middleton Reef , Tasman Sea ( Figure 11 ). It has been collected at depths of 260–360 m.

Comparisons. Plectranthias melanesius closely resembles P. azumanus , P. kelloggi and P. maculicauda . Comparisons between the four species are summarised in Table 21 (but see Remarks below).

Remarks. Our use of the species name P. melanesius for Australian specimens is somewhat tentative. Randall (1980) considered Pseudanthias azumanus Jordan & Richardson, 1910 from Japan to be a valid subspecies of Plectranthias kelloggi ( Jordan & Evermann, 1903), and erected an additional subspecies, P. kelloggi melanesius , for five specimens from New Caledonia. We are confident in recognising P. azumanus as a full species (see Remarks for P. azumanus ) but are less certain of the status of P. kelloggi melanesius , as it is possibly a synonym of P. azumanus . According to Fourmanoir (in Randall 1980), the live coloration of the New Caledonian type specimens was very similar to P. azumanus . Our only fresh photo of the Australian specimens, a 38.7 mm SL juvenile ( Figure 37A ), suggests slight differences in live coloration ( Table 21), though more, larger specimens are needed for proper comparison. Randall distinguished azumanus and melanesius only on the basis of counts of tubed lateral-line scales (32–34, mean 33.2 in melanesius versus 33–36, mean 34.3 in azumanus ). With the exception of Lee (1990), who reported lateral line scales counts of 33–42 for Taiwanese specimens, other studies have reported the same counts of 33–36 for Japanese and Taiwanese specimens of P. azumanus (e.g., Katayama 1960, 1984). However, we recorded counts of 34–37 (mean 35.0) from four specimens of P. azumanus from Japan, and 34 for the two specimens from Western Australia. Our three specimens from eastern Australia and north of Middleton Reef conform with Randall’s values for melanesius (32–34, mean 33.0).

Sih et al. (2017) recorded P. kelloggi from the Great Barrier Reef based on video footage from baited cameras in 155– 179 m. However, their observations appear to be based on P. retrofasciatus (see Remarks for that species).

Material examined. Australia. AMS I.42721-004, 38.7 mm SL, Lord Howe Rise, large seamount north of Middleton Reef, 29°13.09′S, 158°59.85′E, 298–307 m, Sherman sled, NORFANZ team, 21 May 2003 (field number 0308/049) ; QM I.21167, 2: 58.5–97.0 mm SL, Queensland, east of Stradbroke Island, 27°32′S, 153°54′E, 260 m, trawl, Queensland Fisheries Service , 15 Dec 1982 .

Figures

FIGURE 11. Distribution records for Australian specimens of Plectranthias azumanus (triangle), P. melanesius (open circles) and P. nanus (closed circles).

FIGURE 37. Plectranthias melanesius, Australian specimens:A) AMS I.42721-004, 38.7 mm SL, freshly dead, large seamount north of Middleton Reef, Tasman Sea; B) AMS I.42721-004, preserved; C) QM I.21167, 97.0 mm SL, preserved, east of Stradbroke Island, Queensland. Photos by (A) NORFANZ team, (B,C) A.C. Gill.