Plectranthias megalophthalmus Fourmanoir & 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 : 87-89

Plectranthias megalophthalmus Fourmanoir & Randall

Figures 30 , 36 ; Tables 1–16, 25

Common name: Citron Perchlet

Plectranthias megalophthalmus Fourmanoir & Randall 1979: 316 , fig. 1, tab. 1 (type locality: south of Isle of Pines , New Caledonia).

Plectranthias sp.— Last et al. 2014: 217 (list, Marion Plateau, western Coral Sea).

Diagnosis. The following combination of characters distinguishes P. megalophthalmus from congeners: dorsal rays X,15; pectoral rays 15, all but the uppermost 1–2 rays branched; edge of preopercle smooth; lateral-line complete with 31–33 tubed scales; scales below lateral line to origin of anal fin 12–13.

Description of Australian specimen. Dorsal rays X,15, all segmented rays branched; anal rays III,7, all segmented rays branched; pectoral rays 15/15, all but upper 2/1 rays branched; pelvic fin I, 5, all segmented rays branched; upper procurrent caudal-fin rays 6; lower procurrent caudal-fin rays 6; principal caudal-fin rays 9+8; branched caudal fin rays undetermined owing to fin damage; total caudal-fin rays 29; lateral line complete with 32/33 tubed scales; scales above lateral line to origin of dorsal fin 2/3; scales above lateral line to base of fifth dorsal spine 2/2; scales below lateral line to origin of anal fin 13/13; diagonal rows of scales on cheek 6; predorsal scales 22, extending to posterior nostrils; circumpeduncular scales 12; gill rakers 6+12, the upper 4 and lower 3 rudiments; pseudobranchial filaments 12; branchiostegal rays 7.

Vertebrae 10+16; supraneurals 2; predorsal formula 0/0/2/1+1; dorsal pterygiophores in interneural spaces 9–13 1/1/1+1/1+1/1+1; 8 trisegmental pterygiophores associated with dorsal fin; terminal dorsal pterygiophore in interneural space 17; 4 trisegmental pterygiophores associated with anal fin; terminal anal pterygiophore in interhaemal space 4; ribs present on vertebrae 3 through 10; epineurals present on vertebrae 1 through 12; 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 distal tips of parapophyses on vertebra 10.

Fleshy tabs present on distal tips of at least some dorsal spines (difficult to determine owing to fin damage); fourth dorsal spine longest (though with tip broken); dorsal fin incised before first segmented-fin ray; second analfin spine longest and stoutest; anal fin shape not determined owing to damage; caudal fin shape not determined owing to damage; lower 7 pectoral fin rays somewhat thickened, with membranes between thickened rays deeply incised; tenth (counting from dorsal-most) pectoral ray longest, reaching vertical through base of second segmented anal ray; pelvic fins short, just reaching anus, second segmented ray longest.

Morphometric data are summarised in Table 25 .

Mouth large, posterior margin of maxilla reaching vertical through posterior margin of pupil; maxilla expanded posteriorly, with long, low, lateral ridge running parallel to dorsal margin; small splint-like supramaxilla present; mouth terminal; upper jaw with a short caniniform tooth either side of symphysis, flanked internally by villiform band with about 6 rows of smaller conical teeth, the band narrowing posteriorly without reduction in number of tooth rows; inner teeth nearest symphysis of upper jaw enlarged, caniform and depressible; lower jaw with villiform band of about 5–6 rows of small conical teeth at symphysis, reducing to 2 rows posteriorly, the outer row teeth slightly larger and depressible; middle of lower jaw with 2 outer caniniform teeth; vomer with 2–3 rows of small conical teeth arranged in U-shaped band; palatine with narrow band of small conical teeth, 3–4 rows at widest point; ectopterygoid and mesopterygoid edentate; tongue narrow, rounded and edentate.

Opercle with 3 flat spines, middle spine longest, upper spine concealed by scales; preopercle, interopercle and subopercle smooth. Anterior nostril positioned at middle of snout, tubular with flap on posterior rim, flap reaching posterior nostril when depressed; posterior nostril at anterior border of orbit, with slightly raised rim but no flap.

Scales ctenoid with basal cteni present on at least some head and anterior and dorsal body scales (other scales with peripheral cteni only); lateral line broadly arched over pectoral fin following body contour to caudal-fin base; scales present on maxilla and all but first infraorbitals, none on mandibles, chin, branchiostegal membranes or anterior snout; no auxiliary scales on head or body; soft dorsal and anal 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: Not known for the Australian specimen (holotype evidently yellow; Fourmanoir & Randall 1979).

Colour in preservative ( Figure 36 ): head and body pale tan; upper body with four indistinct dusky blotches, first below dorsal spines 3 through 5, second below dorsal spines 8 and 9, third beneath segmented dorsal rays 4 through 6, and fourth beneath segmented dorsal rays 11 through 13; sides of body 1–2 scale rows beneath lateral line with three indistinct dusky blotches, first two beneath first two blotches on upper body, third slightly posterior to third spot on upper body; fins pale without markings.

Habitat and distribution. Known only from the holotype, trawled in 360 m off the Isle of Pines , New Caledonia, and a specimen trawled in 312–318 m, in the Coral Sea northeast of the Whitsunday Islands ( Figure 30 ). Records of the species from the North West Shelf of Australia are based on the related P. lasti .

Comparisons. Plectranthias megalophthalmus resembles P. lasti and P. fijiensis in having relatively small canine teeth in the jaws and a smooth preopercle. It differs from P. lasti in having more dorsal segmented rays (15 versus 14) and more scales below the lateral line to the anal origin (12–13 versus 9–10), and from P. fijiensis in pectoral ray branching (only upper 1–2 rays unbranched in P. megalophthalmus versus first and ninth through 12 th unbranched in P. fijiensis ), the absence of scales on the mandibles (versus posterior part of mandible scaled), and a shallower body (greatest body depth 27.8–29.4 versus 37.2 % SL).

Remarks. Although P. megalophthalmus has been previously recorded from Australia, the three North West Shelf specimens that form the basis for those records are here identified as P. lasti . We tentatively identify a specimen collected from the Marion Plateau off Queensland as P. megalophthalmus . It agrees well with Fourmanoir & Randall’s (1979) original description and figure of the species, particularly in having a smooth preopercle, no enlarged canine teeth, X,15 dorsal rays, 15 mostly branched pectoral rays, similar numbers of lateral line scales, 12 circumpeduncular scales, similar scalation of the head, similar morphometric values, and similar preserved coloration. However, the Queensland specimen differs in a few minor details, notably numbers of lateral line scales 32–33 (versus 31) and upper gill rakers 6 (versus 5), and in having a smaller eye (12.6 versus 13.8 % SL) and a deeper caudal peduncle (13.7 versus 11.1 % SL). Until additional specimens from both localities become available for comparison, we regard our identification as tentative.

Material examined. CSIRO H 643-4 , 53.2 mm SL, Australia, Queensland, northeast of Whitsunday Group , 19°38.1′S, 150°32.7′E to 19°37.6′S, 150°30.3′E, 312–318 m, trawl , FRV Soela , 15 Nov 1985 (field station SO0685/2) .

Figures

FIGURE 30. Distribution records for Plectranthias lasti (open circles) and Australian P. megalophthalmus (closed circle).

FIGURE 36. Plectranthias megalophthalmus, CSIRO H 643-4, 53.2 mm SL, northeast of Whitsunday Group, Queensland, Australia. Photo by A.C. Gill.