Plectranthias mcgroutheri, Gill & Pogonoski & Moore & Johnson, 2021

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 : 81-87

Plectranthias mcgroutheri n. sp.

Figures 34–35 ; Tables 1–17, 26–27

Common name: McGrouther’s Perchlet

Plectranthias wheeleri [non Randall 1980].— Allen 1985: 2508 (checklist, Western Australia).— Paxton et al. 1989: 507 (checklist, North West Shelf, Australia).— Baldwin & Johnson 1993: 244 (list of comparative specimens).— Hutchins 2001: 30 (checklist).— Allen et al. 2006: 991 (checklist). — Parenti & Randall 2020: 30 (checklist; in part).

Holotype. AMS I.22828-010, 74.0 mm SL, Australia, North West Shelf , 190 km northwest of Port Hedland, 19°01′S, 117°12′E, 200–202 m, Engel trawl, M. McGrouther & J. R. Paxton aboard RV Soela, 14 Apr 1982.

Paratypes. AMS. I22828 -034 , 76 mm SL (cleared and stained), collected with holotype ; AMS I.22828-035, 5: 49.9–68.6 mm SL, collected with holotype ; CSIRO H 6378-20 , 59.2 mm SL , CSIRO H 6378-21 , 2 : 32.6–42.0 mm SL , CSIRO H 6378-22 , 2 : 24.1–31.6 mm SL, Western Australia, west of Exmouth Gulf , 21°59.17′S, 113°49.20′E to 21°59.79′S, 113°49.14′E, 165–166 m, beam trawl , FRV Southern Surveyor , 11 Dec 2005 (SS1005/153) ; NMV A 29687 -009 , 63.4 mm SL, Australia, Western Australia, Mermaid L24 transect, 17°29.23′S 120°27.63′E to 17°29.72′S 120°28.07′E, 184–187 m, beam trawl, M.F. Gomon aboard RV Southern Surveyor , 20 June 2007 ; WAM P.35175- 001, 55.3 mm SL, collected with CSIRO H 6378-20 , CSIRO H 6378-21 and CSIRO H 6378-22 .

Diagnosis. The following combination of characters distinguishes P. mcgroutheri from congeners: segmented dorsal rays 16; third dorsal spine longest; pectoral rays 14, with all but uppermost branched in adults; lateral line complete, consisting of 27–30 tubed scales; no scales on maxilla, mandibles or lower part of snout; lower part of preopercle with two enlarged antrorse serrations; head length 41.9–44.7 % SL; snout length 7.1–9.2 % SL.

Description. Dorsal rays X,16, all segmented rays branched; anal rays III,7, all segmented rays branched; pectoral rays 14/14, all rays unbranched; pelvic fin I,5, all segmented rays branched; upper procurrent caudal-fin rays 7 (6–7); lower procurrent caudal-fin rays 7 (5–7); principal caudal-fin rays 9+8; branched caudal fin rays?+? (8+7); total caudal-fin rays 31 (29–31); lateral line complete with 28/30 (27–30) scales; scales above lateral line to origin of dorsal fin 3/3 (3–4); scales above lateral line to base of fifth dorsal spine 2/2 (2–4); scales below lateral line to origin of anal fin 11/11 (11–12); diagonal rows of scales on cheek 9 (7–9), including 1 (1–2) over preopercular canal; predorsal scales 24 (21–28), extending to middle to anterior nostrils; circumpeduncular scales 14 (13–15); gill rakers 5+10 (5–6+10–13=15–19), the upper 4 (4–5) and lower 3 (2–5) rudiments; pseudobranchial filaments 18 (15–20); 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+1/1+1 (1/1/1+1/1+1/1 or 1/1/1+1/1+1/1+1); no trisegmental pterygiophores associated with dorsal fin; terminal dorsal pterygiophore in interneural space 18 (17–18); no trisegmental pterygiophores associated with anal fin; terminal anal pterygiophore in interhaemal space 5 (4–5); ribs present on vertebrae 3 through 10; epineurals present on vertebrae 1 through 13 (12–13); 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 distal tips of parapophyses on vertebra 10 ( Figure 34B ).

Dorsal-fin spines with fleshy tabs on their distal tips, the tab on third spine longest and pennant-like; third dorsal spine longest (fourth spine slightly longer in 24.1 mm SL paratype); dorsal fin incised before first segmented-fin ray (tenth spine 52.1–64.9 % length of first segmented ray); second anal-fin spine longest and stoutest; anal fin pointed, second or third segmented ray longest; caudal fin emarginate; lower 8 pectoral fin rays thickened, with membranes between thickened rays incised; eighth (seventh to ninth counting from dorsal-most) pectoral ray longest, reaching vertical through middle of anal-fin base; pelvic fins short, not reaching anus, second segmented ray longest.

Morphometric data are summarised in Table 26.

Mouth large, reaching or almost reaching vertical through posterior margin of orbit; maxilla expanded posteriorly, with long, low, lateral ridge running parallel to dorsal margin, small splint-like supramaxilla present; mouth terminal; upper jaw with pair of fixed outer canines at front, a band of depressible teeth 5–6 rows at symphysis, reducing to 3–4 rows wide posteriorly, the outer row slightly enlarged, and inner teeth in band across front of jaw enlarged and caniniform; lower jaw with 5 rows of teeth at front of jaw, reducing to a single row posteriorly, the teeth in band near symphysis slightly curved, with 1-2 enlarged in outer row on middle of jaw; vomer with 2–3 rows of small conical teeth arranged in a chevron; palatine with a band of 2–3 rows of small conical teeth; ectopterygoid and mesopterygoid edentate; tongue edentate, slender with rounded tip.

Opercle with 3 flat spines, middle spine longest; preopercle with 10–27 serrations on posterior border, those nearest the angle largest, with an additional 2 enlarged antrorse serrations on ventral border; interopercle with 1–8 usually strong serrations; subopercle with 1–7 usually strong 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, sometimes with small flap anteriorly.

Scales ctenoid with peripheral cteni; lateral line broadly arched over pectoral fin following body contour to caudal-fin base; no scales on chin, branchiostegal membranes, maxilla or snout; no auxiliary scales on head or body; soft dorsal and anal fins with low scaly sheaths 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 photos of 63.4 mm SL paratype when freshly dead ( Figure 34C ) and of 59.2 mm SL paratype after five years frozen): head and body tan to pale pink; snout, nape and dorsal part of head red to orange-red; posterior part of preopercle and adjacent part of operculum mauve to dusky purple; area behind and narrowly below eye mauve to dusky purple; pectoral base and ventral contour of breast pale pink to dusky purple; lower part of abdomen pale tan or pale pink to white; small dusky purple spot over anus; red to orange-red roughly wedgeshaped blotch extending from beneath anterior half of dorsal base to mid-side; second roughly wedge-shaped, broad red to orange blotch extending from between bases of about seventh dorsal spine and seventh segmented dorsal ray to anterior third of anal-fin base; caudal peduncle and posterior part of body behind red wedge pale pink to reddish tan; a column of three to five small, equally spaced bright yellow to red spots on posterior part of caudal peduncle, just anterior to caudal base, with an additional small yellow to red spot about midway along caudal peduncle, just above ventral border, and several additional yellow to red spots over posterior few lateral-line scales; 59.2 mm SL paratype with additional bright yellow spots scattered over head and body; pectoral fins bright yellow, with orangered spot over upper half of basal part of fin; remaining fins bright yellow, reddish orange distally.

Colour in preservative: Pale tan, sometimes with dusky grey markings on nape; wedge-shaped blotches beneath dorsal-fin base may be indistinctly present, dusky grey; tips of fleshy tabs on dorsal-fin spines dusky brown.

Habitat and distribution. Known only from the holotype and six paratypes trawled in 200–202 m, 190 km northwest of Port Hedland, Western Australia, a paratype trawled in 184–187 m, 190 km west of Broome, Western Australia, and six paratypes trawled in 166 m, west of Exmouth Gulf , Western Australia ( Figure 35 ). Specimens of P. lasti were also collected in the first-mentioned trawl. No other details on habitat are available.

Comparisons. Plectranthias mcgroutheri is similar to P. knappi Randall, 1996 from the Visayan Sea, Philippines, and keys to that species using Randall’s (1996) key. It is also close to P. maekawa Wada, Senou & Motomura, 2018 from the Tokara Islands, Ryukyu Islands, Japan. The three species are unique within the genus in having the following combination of characters: segmented dorsal rays 16 (15–16 in P. maekawa ); third dorsal spine longest; pectoral rays 14, most rays branched; lateral line complete, consisting of 27–30 tubed scales; no scales on maxilla, mandibles or lower part of snout; and lower part of preopercle with two enlarged antrorse serrations. Comparisons between the three species are difficult as P. knappi remains known only from the 66 mm SL holotype and P. maekawa is known only from the 58.2 mm SL holotype and two paratypes (62.3–65.7 mm SL). However, the three species appear to differ substantially in various morphometric details ( Table 27). In addition to those characters, P. knappi appears to have a longer dorsal-fin base than the other two species. Randall’s (1996) value of 33.5 % SL for the dorsal-fin base of P. knappi is obviously in error. His figure 2 of the holotype indicates a value of ca 58.5 % SL, which is substantially higher than recorded for P. mcgroutheri (47.2–54.5 % SL) or P. maekawa (49.4–51.2 % SL).

Comparison of mitochondrial COI barcode DNA sequences with available sequences for other Plectranthias provided a closest match with P. retrofasciatus (5% uncorrected difference). The two species have similar live colorations, particularly in having wedge-shaped red markings extending from the dorsal-fin base. They are distinguished by pectoral ray counts (14 in P. mcgroutheri versus 13 in P. retrofasciatus ) and lower jaw dentition (inner row of teeth not enlarged versus enlarged).

Allen (1985) and subsequent authors have identified the AMS type specimens of P. mcgroutheri as P. wheeleri . The two species are distinguished by their pectoral ray counts (14 in P. mcgroutheri versus 13 in P. wheeleri ), and live coloration (see Wada et al., 2018: fig. 5).

Remarks. The specific epithet is for our friend and colleague Mark McGrouther, former collections manager at AMS, who collected the holotype and six of the paratypes, in recognition of his contribution to Australian ichthyology and support given to all the authors over an extended timeframe.

A moderate-sized Plectranthias species, largest specimen 76 mm SL. Allen’s (1985) identification of the AMS types of this species forms the sole basis for records of P. wheeleri from Australia. The latter species therefore should be removed from Australian faunal lists. Although the record of P. wheeleri in Allen & Swainston (1988) and subsequent editions pertains to this species, the accompanying illustration appears to be based on true P. wheeleri .

Figures

FIGURE 34. Plectranthias mcgroutheri, A) AMS I.22828-010, 74.0 mm SL, preserved holotype, North West Shelf, Australia; B) AMS I.22828-010, holotype, radiograph; C) NMV A 29687-009, 63.4 mm SL, freshly dead paratype, 190 km west of Broome, Western Australia. Photos by (A) A.C. Gill, (C) M.F. Gomon; radiograph by A. Hay and S.E. Reader.

FIGURE 35. Distribution records for P. mcgroutheri (open circles; arrow indicates type locality), Australian specimens of P. retrofasciatus (closed circles) and P. moretonensis (triangle).