Plectranthias purpuralepis, Tang & Lai & Ho, 2020

Tang, Chi-Ngai, Lai, Nok-Wai & Ho, Hsuan-Ching, 2020, Plectranthias purpuralepis sp. nov., a new anthiadine perchlet from northern Taiwan (Perciformes: Serranidae), Zootaxa 4780 (3), pp. 508-522 : 509-520

Plectranthias purpuralepis sp. nov.

New English name: Purple-scaled perchlet

Figures 1A , 2 , 3A , 4 , 5A , 6A , 7A , 8 ; Tables 1–3 urn:lsid:zoobank.org:act:421111DE-6DAC-463E-A7E4-2DE436361F0C

Holotype. NMMSTP002339 (143.8 mm SL), ca. 25.4– 25.6°N, 121.9– 122.0°E, Three Northern Islands, Northern Taiwan, northwestern Pacific Ocean , collected by angling boat, purchased at Keelung fish market, 25 Sep. 2019.

Paratypes. Fifteen specimens, 93.6–150.9 mm SL. NMMB-P30975 (143.6 mm SL), NMMSTP002340 (144.7), NMMSTP002341 (146.6 mm SL), collected together with the holotype. NMMB-P032937 (137.4) and NMMB- P033386 (131.1), purchased at Keelung fish market, 30 Dec. 2019 ; NMMB-P032938–43 (6, 116.9–133.0), purchased at Keelung fish market, 18 Dec. 2019 ; NMMB-P032944–7 (4, 93.6–145.7), purchased at Keelung fish market, 27 Mar. 2019 ; all these specimens may have been collected near the type locality.

Diagnosis. A species of Plectranthias with pectoral and pelvic fins mostly covered by small scales and scales on the whitish pink blotches turn purple when preserved. It can be further separated from congeners by having the combination of following characters: dorsal-fin elements X, 16–17; 3rd dorsal-fin spine longest; pectoral-fin rays usually 14, all branched except for uppermost ray simple; principal caudal-fin rays 9+8; pored lateral-line scales 32–36; 6 diagonal rows of large scales on cheek; circumpeduncular scales 14; ca. 7 rows of large predorsal scales, 2 irregular rows of small scales extending to a line through posterior nostrils; no scales on maxilla and chin; posterior margin of preopercle serrated, ventral margin with 2 antrorse spines; and greatest body depth 32.6–35.1% SL.

Description. Following data and status are given for the holotype with those of paratypes in parentheses when different, unless otherwise indicated.

Dorsal-fin elements X, 16 (X, 16–17), all rays segmented and branched; anal-fin elements III, 7, all rays branched; pectoral-fin rays 14/14 (13–15), all rays segmented and branched except for the uppermost ray which is segmented and simple; pelvic-fin elements I, 5, all rays segmented and branched; upper procurrent caudal-fin rays 7 (7); lower procurrent caudal fin rays 6 (6–7); principal caudal fin rays 9+8 (branched rays 8+7); total caudal-fin rays 30 (30–31).

Lateral line complete, with 33 tubed scales on both sides (32–34, except 1 paratype with 35 and 1 with 36); 4.5 (4 or 4.5) scale rows between lateral line to origin of dorsal fin (4 and 1 small scale at base of first spine); 2.5 (2.5 or 3.5) scale rows between lateral line to base of middle dorsal spines; scale rows counted from lateral line slanting down posteriorly to origin of anal fin 14 (13–14, except 1 paratype with 17); diagonal rows of large scales on cheek between eye and corner of preopercle 6; ca.7 (7–9) large predorsal scale rows, with 2 irregular rows of small scales extending to a line through posterior nostrils; circumpeduncular scales 14.

Gill rakers 17 (16–20), including 4 (rudimentary)+1 (developed) (4+1–2) on upper limb and 8 (developed)+4 (rudimentary)=12 (7–8+4–6=11–14) on lower limb; pseudobranch filaments 20 (18–26); branchiostegal rays 7.

Vertebrae 10+16=26; supraneurals 3; predorsal formula 0/0+0/2/1+1; ribs present on the 3rd vertebrate to the 10th; epurals 3; epineural bones 11; no trisegmental pterygiophores in either the dorsal or anal fins; numbers of pterygiophores inserting within the 9th through 13th interneural spaces 1/1/2/2/2; single uroneural (posterior uroneural absent).

Body relatively long, oblong, greatest body depth 34.0% (32.6–35.1%) SL; dorsal profile of head slightly convex, spinous dorsal-fin base nearly straight. Head moderately large, its length 40.8% (40.7–43.4%) SL; snout relatively short, 9.9% (9.9–11.5%) HL; eye moderately large, its diameter 26.4% (23.8–27.2%) HL; interorbital space flatten to slightly concave, its width 10.2% (8.5–10.7%) HL.

Mouth large, slightly oblique, posterior margin of maxilla slightly before the vertical through middle of eye; maxilla expanded posteriorly, with long, low, lateral ridge running parallel to dorsal margin; a small rod-shaped supramaxilla above posterior portion of maxilla; mouth terminal, lower jaw extending slightly beyond tip of upper jaw.

Upper jaw with 1 (1 or 2 in paratypes) large fixed canine on either side of symphysis, flanked internally by villiform band with about 12 (11–14) rows of depressible, smaller, sharp-tipped teeth, with inner rows becoming progressively longer, band reduced to 3 rows posteriorly; lower jaw with 1 or 2 (1 or 2) moderately large fixed canines on either side of symphysis, flanked internally by villiform band of about 9 (7–9) rows of small depressible teeth at symphysis, teeth becoming progressively longer on inner rows, 1 (1 or 2) enlarged, curved canine on middle of jaw on either side, band reduced to single row posteriorly; vomer with roughly V-shaped band of 4 (4; 6 in 1 paratype) rows of sharp-tipped conical teeth; palatine with a band of 3 (3–5) rows of small, sharp-tipped conical teeth; ectopterygoid and mesopterygoid edentate; tongue narrow, pointed and edentate.

Three flat spines on opercle, middle one longest, uppermost one covered by scales, others naked. Posterior margin of preopercle irregular, serrated, about 27/27 (17–26) small serrae; two antrorse spines on ventral margin. Interopercle and subopercle exposed margins smooth. Anterior nostril at middle of snout, tubular, a small flap on posterior rim; posterior nostril at orbit anterior border, rim slightly raised, no flap.

Dorsal fin with fleshy filament only on the tip of third spine; third dorsal-fin spine longest; dorsal fin moderately incised before first ray, the last dorsal-fin spine slightly shorter than the penultimate spine; second anal-fin spine longest and thickest; anal fin pointed with third ray longest; caudal fin truncate, third principal ray on upper lobe slightly elongated, but not filamentous; lower 7 pectoral-fin rays thickened, membranes between these rays deeply incised; ninth (counting from the uppermost) ray thickest and longest, reaching a vertical through base of second dorsal-fin ray (first or second rays in paratypes); pelvic fins short, when appressed far in front of anus, second ray longest.

Body covered by large ctenoid scales, simple, without ctenial bases in posterior field; lateral line broadly arched over pectoral fin following body contour to caudal-fin base, each lateral-line scale with single opening directed dorsoposteriorly; no scales on maxilla, chin, and branchiostegal membranes. All fins partially scaled; dorsal fin with intermittent row of scales along basal 1/3 of soft ray portion; anal fin mostly covered by small ctenoid scales, membranes between the 3rd spine to 4th soft ray nearly entirely covered by scales; pectoral and pelvic fins covered by small ctenoid scales at basal 1/3, scales gradually narrower, smaller and becoming cycloid, extending to more than 2/3 of the fin; caudal fin covered with narrow ctenoid scales extending more than half of the fin.

Coloration. When fresh ( Figs. 1A , 2 ), head and body yellowish to reddish yellow; five to six whitish pink stripes or blotches on dorsum, along dorsal-fin base and caudal peduncle, their width restricted to one scale. First stripe longest, extending from membranes of third and fourth dorsal-fin spines and slanting down to upper portion of opercle anteriorly; second stripe from membranes between ninth and tenth dorsal-fin spines, extending downward to below lateral line; third stripe divided into 2 blotches, upper blotch at bases of fourth to seventh dorsal-fin rays and lower at lateral line; fourth stripe from bases of the tenth to twelfth dorsal-fin rays, extending right above lateral line; fifth and sixth stripes (blotches) at upper margin of caudal peduncle. Five irregular yellowish red blotches along lower portion of body; abdomen area usually whitish pink or uniformly white. Maxilla white, upper part of lips yellowish to pinkish; iris yellow, with two orange stripes on upper and lower margin, a blackish bar through the iris horizontally; cheek and opercle pinkish, yellowish margins on several scales; margin of preopercle yellowish, white bordered; chin and branchiostegal membranes white.

Spinous dorsal fin mostly yellow or reddish yellow, membranes whitish between the second and fourth spines and ninth and tenth spines; soft dorsal fin with red margin, base yellow to reddish yellow with two whitish pink areas between fourth to seventh soft rays and tenth to twelfth soft rays; caudal fin reddish yellow with a broad reddish margin and two whitish pink blotches at caudal fin base; pectoral fin pale crimson; pelvic fin mostly white; anal fin pale to reddish yellow.

When preserved in alcohol ( Fig. 3 ), body pale; no blackish band along the median line of the nape; reddish yellow pigment above lateral line still present after a month in preservation; white stripes extending from dorsal-fin base become a distinct purple color. One specimen still shows the distinct purple marking after ten months ( Fig. 3C ); groups of melanophores present below the dorsal base; all fins transparent.

Size. The largest specimen examined is 151 mm SL.

Distribution and habitat. Only known from northern Taiwan, near the “Three Northern Islands,” collected by anglers at depths of 200 m or below, judging from other specimens collected together, such as Parapercis spp., Plectranthias kamii , P. sheni , and Helicolenus hilgendorfii (Döderlein, 1884) . The habitat of this species is assumed to be rocky reef bottom or slope in the mesophotic zone.

Etymology. The specific name purpuralepis is a combination of the Latin “purpura” and “lepis,” meaning purple scales, in reference to the distinct purple color only present after preservation. The name is treated as a noun in apposition.

Comparison. Plectranthias purpuralepis can be distinguished from most members of the genus by the following combination of characters: pectoral and pelvic fin mostly covered by scales; a relatively large body size (up to 151 mm SL); two antrorse spines ventrally on ventral margin of the preopercle; bony interorbital width narrow; no scales on maxilla or chin; 14 circumpeduncular scales; body color reddish yellow, with 5 to 6 white stripes or patches slanting anteriorly from dorsal-fin base.

According to the keys to species of Plectranthias provided by Randall (1980, 1996), the species is most similar to P. jothyi and P. anthioides in having almost the same meristics and body proportions. Table 3 lists selected characters for comparison of the similar species.

ric data are shown as a multiple of SL or HL.

Plectranthias purpuralepis differs from P. jothyi from a combination of characters: a shorter head, its length 40.7–43.4% SL (vs. 43.6–44.8% in P. jothyi ); 3rd dorsal-fin spine much shorter, its length 29.1–38.5 HL (vs. 41.1– 44.7%); 2nd anal-fin spine and pelvic fin shorter, their lengths 32.6–37.2% and 43.7–53.0% HL, respectively (vs. 39.1–45.0% and 50.0–54.8%, respectively); circumpeduncular scales 14 (vs. 16); 1+7–8 developed gill rakers on first gill arch (vs. 2+10); two small irregular rows of scales on interorbital space extending to a line through the posterior nostrils (vs. scales extending to middle of interorbital space); no black bars on upper half of body (vs. six diagonal blackish bars present); no whitish patch on nape (vs. a small patch present on nape); three whitish bars, restricted to one scale wide on dorsum below dorsal-fin base, the third usually breaking into three small patches (vs. whitish bars three scales wide and the third bar not broken; see Randall, 1996: fig. 1).

Our specimens have one moderately large canine at each side of front of lower jaw, which is distinctly larger than the neighboring ones, whereas the holotype of P. jothyi does not have such a tooth ( Randall, 1996: 123); there are 4–6 and 3–5 tooth rows on the vomer and palatines, respectively, in P. purpuralepis , whereas there are only 2–3 and 1–2 tooth rows on the vomer and palatines, respectively, in P. jothyi ( Randall, 1996: 123) . However, our specimens are much larger than the holotype of P. jothyi and these differences may be attributed to size differences.

Plectranthias purpuralepis can be separated from P. anthioides in having a much shorter second anal-fin spine, its length 32.6–37.2% HL (vs. 49.0%, in P. anthioides ), when appressed, the tip of spine reaching posterior end of anal-fin base (vs. well behind base); and a shorter pelvic fin, its length 43.7–53.0% HL (vs. 57.8% in P. anthioides ), when appressed, tip of the fin well in front of anus (vs. reaching anus); caudal fin truncated (vs. rounded in P. anthioides ); no irregular and indistinct blackish spots on back and blackish line along the median line of the nape (vs. present in life color of P. anthioides in original description; Randall, 1980).

In Taiwan, P. purpuralepis is also similar to P. sheni and P. kamii , but distinctly different in coloration pattern and combination of meristic and morphometric characters. Plectranthias purpuralepis can be separated from P. sheni and P. kamii by having scales covering more than 2/3 of both sides of pelvic fin (vs. scales restricted to base of pelvic fin) and dorsal profile of head relatively convex (vs. nearly straight). Moreover, P. purpuralepis differs from P. sheni and/or P. kamii by having a combination of the following characters: 16 or 17 segmented and branched dorsal-fin soft rays (vs. 18 in P. kamii ); 14 total pectoral-fin rays (vs. 13 in both P. sheni and P. kamii ); small predorsal scales extending to a line through posterior nostrils (vs. not reaching the line in P. kamii ); number of scale rows below lateral line to origin of anal fin 13 or 14 (vs. 18 in P. kamii ); a relatively shallower body, the greatest body depth 32.6–35.1% SL (vs. 34.6–39.0% in P. sheni and 34.7–37.7% in P. kamii ); a shorter head, HL 40.7–43.4% SL (vs. 42.8–43.6% in P. sheni and 42.8–44.9% in P. kamii ); longest dorsal-fin spine (3rd) 29.1–38.5% HL (vs. 38.7–42.7% in P. sheni and 39.4–50.7% in P. kamii ); usually 33 tubed lateral-line scales (vs. 38 in P. kamii ); pelvic-fin mostly scaled on both sides (vs. not scaled in P. kamii and scaled at base of the fin in P. sheni ); body lacking series of brown blotches (versus 2 series of brown blotches).

Figures

FIGURE 1. Fresh coloration. A. Plectranthias purpuralepis sp. nov., NMMSTP002339, 143.8 mm SL, holotype. B. P. sheni, NMMSTP002342, 120.5 mm SL. C. P. kamii, NMMSTP002338, 152.9 mm SL.

FIGURE 2. Paratypes of Plectranthias purpuralepis sp. nov. A. NMMB-P32943, 143.6 mm SL; B. NMMB-P33386, 144.7 mm SL; C. NMMB-P32937, 146.6 mm SL.

FIGURE 3. Preserved coloration of Plectranthias purpuralepis sp. nov. A–B. holotype, NMMSTP002339, C. paratype, NMMB-P032946, 140.2 mm SL. A. after two-day and consequently one-week preservation in formalin and 70% ethanol, respectively; B. after one-month preservation in ethanol (note that gill cover and fins are slightly stained by red color artificially); C. after ten-month preservation in ethanol.

FIGURE 4. Plectranthias purpuralepis sp. nov., holotype, NMMSTP002339, radiograph.

FIGURE 5. Squamation on interorbital space.A. Plectranthias purpuralepis sp. nov., holotype. B. P. sheni, NMMSTP002343, 114.4 mm SL. C. P. kamii, NMMSTP002338, 152.9 mm SL. Arrows indicates the right posterior nostril.

FIGURE 6. Color patterns on dorsum. A. Plectranthias purpuralepis sp. nov., holotype; B. P. sheni, NMMSTP002342, 120.5 mm SL; and C. P. kami, NMMSTP002333, 158.0 mm SL.

FIGURE 7. Dorsal view of preserved specimens. A. Plectranthias purpuralepis, NMMSTP002339, holotype. B. P. sheni, NMMSTP002342. C. P. kamii, NMMSTP002333.

FIGURE 8. Squamation on pectoral fin (A) and pelvic fin (B) fin of Plectranthias purpuralepis sp. nov., NMMB-P30975, 143.6 mm SL, stained by Alizarin Red S.