Pseudanthias hangapiko, Shepherd & Pinheiro & Phelps & Pérez-Matus & Rocha, 2021

Shepherd, Bart, Pinheiro, Hudson T., Phelps, Tyler A. Y., Perez-Matus, Alejandro & Rocha, Luiz A., 2021, Pseudanthias hangapiko, a new anthiadine serranid (Teleostei, Serranidae, Anthiadinae) from Rapa Nui (Easter Island), ZooKeys 1054, pp. 1-13 : 1

Pseudanthias hangapiko sp. nov.

Figs 1 , 2 , 3

Type locality.

Hanga Piko, Rapa Nui (Easter Island), Chile Holotype. CAS 247252 (Field number LAR2642). Male, 45.2 mm SL, GenBank accession number MZ087699. Location: Hanga Piko, Rapa Nui, Chile (27°9'12"S, 109°26'52"W). Collected by B. Shepherd, L.A. Rocha, T.A.Y. Phelps, and M.V. Bell using a hand-net at 83 m depth, 7 March 2017 (Figs 1 , 2 ). Paratypes. USNM 443821 (Field number LAR2643). Male, 28.1 mm SL, GenBank accession number MZ087700. CAS 247254 (Field number LAR2645). Female, 33.2 mm SL, GenBank accession number MZ087701. Both from the same location as the holotype. Collected by B. Shepherd, L.A. Rocha, T.A.Y. Phelps, and M.V. Bell using a hand-net, 7 March 2017 (Fig. 1 ).

Diagnosis.

The following combination of characters distinguishes Pseudanthias hangapiko sp. nov. from congeners: dorsal rays X, 17; anal rays III, 8; pectoral rays 16 (left side of one specimen 17); vertebrae 10+16; scales relatively large, two scales between lateral line and base of fifth dorsal spine, and 16 (17) circumpeduncular scales; gill rakers 11+22-23; body very slender and compressed, the greatest body depth 3.4-3.8 in SL; caudal peduncle short, its length 2.6-3.3 in HL; sexually dichromatic, with male coloration red dorsally, yellow laterally, silvery-pink on throat and belly; females pink, silvery-pink on operculum, throat and belly; both sexes dark red on top of head, along anterior two-thirds of dorsal fin base; both sexes with rows of irregularly-spaced metallic magenta spots laterally, and red dorsal and caudal fins with yellow highlights.

Description.

Dorsal fin X, 17; anal fin III, 8; pectoral rays 16 (one paratype with 17 rays on left pectoral fin), upper two and lowermost unbranched; pelvic fin I, 5; principal caudal-fin rays 9 + 8 (7 + 6 branched); upper procurrent caudal-fin rays 9 (10); lower procurrent caudal rays 9 (9, 10?); tubed lateral-line scales 40 | 41 (40-43); scales above lateral line to origin of dorsal fin 5 (4); scales above lateral line to base of fifth dorsal spine 2; scales below lateral line to origin of anal fin 11 (12); circumpeduncular scales 16 (17); gill rakers 11+23 (11+22-23); pseudobranchial filaments 10 (9); branchiostegal rays 7; vertebrae 10+16; supraneurals 2; predorsal formula 0/0/2/1+1; main shaft (proximal component) of first dorsal pterygiophore inclined slightly backwards; dorsal pterygiophores in interneural spaces 9-13 1/1/1+1/1+1/1; terminal dorsal pterygiophore in interneural space 19 (18); no trisegmental pterygiophores associated with dorsal fin; proximal tip of first anal-fin pterygiophore near distal tip of haemal spine on first caudal vertebra; terminal anal pterygiophore in interhaemal space 6; no trisegmental pterygiophores associated with anal fin; ribs present on vertebrae 3 through 10; epineurals present on vertebrae 1 through 13 (12?); no paired parapophyses on first caudal vertebra; 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.

Body very slender, compressed, its depth 3.6 (3.4-3.8) in SL, the width 2.0 (2.0-2.4) in depth; head length 3.2 (3.0-3.2) in SL; snout length 4.2 (3.4-3.7) in HL; snout and front of upper lip rounded, lacking fleshy anterior extension; diameter of orbit 3.9 (3.1-3.3) in head; posterior edge of orbit with 13 (12) fleshy papillae; interorbital space smooth, the bony width 4.1 (3.6-3.7) in HL; least depth of caudal peduncle 2.4 (2.2-2.6) in HL; caudal peduncle length 2.6 (3.1-3.3) in HL.

Mouth moderately large, slightly oblique, the posterior margin of the maxilla reaching a vertical through the center of the pupil; lower jaw does not protrude when mouth is closed; maxilla width 2.0 (1.7-2.3) in orbit diameter. Upper jaw with two pairs of slightly enlarged canines directed ventrally; a band of small conical teeth, three rows wide at symphysis, reducing to two rows on sides of jaw, with the outer row teeth much larger and slightly curved dorsally, and the inner pair of teeth anteriorly nearest symphysis enlarged and caniniform; dentary with two rows of small conical teeth narrowing to one row and becoming larger posteriorly; lower jaw with one to two enlarged, curved, forward-projecting canine teeth on either side of symphysis; vomer with triangular patch of small conical teeth; palatine with a narrow band of small conical teeth, five rows wide, decreasing to one row posteriorly; tongue small, triangular, pointed, and edentate.

Anterior nostril positioned at middle of snout, with a short fleshy flap on posterior margin; posterior nostril at mid-upper anterior border of orbit, covered by a thin, narrow membrane anteriorly. Opercle with three flat spines, all stout and acute; the middle opercle spine largest and level with center of eye; the upper smallest; ventral margin of preopercle smooth; vertical margin of preopercle with 14 acute spines (11), the largest almost the same size as the inferior opercle spine; posterior margin of subopercle with two strong spines; posterior corner of interopercle with one strong, acute spine.

Scales ctenoid, relatively large, without basal cteni; head and preopercle scaled; distal portion of maxilla covered with scales, head fully scaled except for lips and areas in front of and immediately below nostrils; dorsal fin and anal fin without scales; proximal one-third of pelvic fin scaled; caudal fin with scales extending approximately three quarters distance to posterior margin; scales cover the central portion of the proximal one-fifth of the pectoral fin. Lateral line complete, smoothly curved, mostly follows dorsal contour of body reaching its highest point below the fifth dorsal spine.

Origin of dorsal fin at vertical through base of pectoral fin, the predorsal length 3.4 (2.8-3.2) in SL; first dorsal spine 6.3 (6.6-7.2) in HL; fourth dorsal spine longest (third in smaller paratype), 2.3 (2.0-2.1) in HL; first dorsal ray 2.4 (2.0-2.2) in HL, longest dorsal ray the fourth, 2.0 (1.8) in HL; origin of anal fin below base of third dorsal soft ray, the preanal length 1.8 (1.5) in SL; first anal spine 5.0 (6.6-6.8) in HL; second anal spine the longest, nearly three times the length of the first, 2.3 (2.5-2.6) in HL; third anal spine 2.4 (2.9-3.2) in HL; posterior margin of anal fin rounded, the first segmented ray 1.4 (2.4-3.2) in HL, the longest segmented ray the fourth, 1.5 (2.0-2.1) in HL. Caudal fin lunate with trailing filaments, longer in males, the caudal concavity 3.1 (3.8-4.0) in SL. Pectoral fins 3.8 (3.4-3.6) in SL, extending to a vertical below base of first dorsal soft ray. Pelvic fins moderately long, 5.4 (5.1-5.9) in SL reaching second anal spine.

Color in life: Pseudanthias hangapiko sp. nov. is sexually dichromatic. Males (Fig. 1 ): body pink, with yellow and dark red obscuring most of the ground color, except on belly and throat. Rows of metallic magenta spots, about one per scale, cover body, creating an irregularly spotted pattern starting from behind orbit and extending to base of caudal fin; upper third of body dark red, sides yellow. Dorsal fin dark red, with thin yellow stripe following upper margin; posterior half of soft dorsal-fin base with region of less-pronounced color, extending approximately one quarter of the height of dorsal fin; dark gray region on upper posterior margin of dorsal fin, spanning last five to six fin rays; pectoral fins hyaline; pelvic and anal fins yellow on anterior half, hyaline posteriorly; caudal fin red with yellow-orange filaments; yellow patch at ventral origin of caudal fin. Head pale orange, red along snout and between eyes, operculum yellow. Eye red, darker along outer edge. Females (Figs 1 , 3 ): body predominantly pink with less-pronounced red and yellow markings, silvery-pink on operculum, throat and belly; spotting pattern of metallic magenta scales more widely-spaced than in males; anterior dorsal third of head dark red, pale silvery-pink below; faint orange on tip of snout and lower jaw. Dorsal fin red, with thin yellow stripe following upper margin, region of lighter color on posterior half of soft dorsal-fin base more pronounced in females than in males, same pink as body ground color; dark gray region on upper margin of dorsal fin more pronounced than in males, spanning posteriormost ten to twelve fin rays; pectoral fins hyaline; pelvic and anal fins hyaline with faint yellow markings anteriorly, thin magenta line on distal edge of anal fin; outermost caudal-fin rays yellow with red, especially on upper and lower margins and near base of caudal fin, centermost caudal-fin rays hyaline distally, thin dark gray lines on distal edges of upper and lower caudal fin filaments. Eye silver, darker along outer edge.

Color in alcohol: All specimens straw-colored, except dorsally, where all specimens are darkly pigmented above lateral line where red in life; dorsal fin translucent with dark pigment, all other fins translucent.

Etymology.

The species is named for the location where it was collected, Hanga Piko, meaning "hidden bay" in the Rapa Nui language. To be treated as a noun in apposition.

Common name.

Rapa Nui Fairy Basslet.

Distribution and habitat.

The new species is currently known only from Rapa Nui. The holotype and paratypes were collected at a depth of 83 m at a small, rocky patch reef surrounded by a large sandy area (Fig. 3 ). Other species collected at this location and recently described by our team include Plectranthias ahiahiata , Luzonichthys kiomeamea , and Chromis mamatapara ( Shepherd et al. 2018, 2019, 2020). Due to geographical isolation and the high degree of endemism (21.7%) among the shore fishes of Rapa Nui ( Delrieu-Trottin et al. 2019), it is likely that Pseudanthias hangapiko sp. nov. is endemic to the island.

Remarks.

Coloration is important for the identification of Pseudanthias ( Randall and Pyle 2001). Pseudanthias hangapiko sp. nov. is distinguished from all congeners in coloration of adult individuals: males with red and yellow mostly obscuring a pink ground color; females mostly pink; both sexes silvery-pink on throat and belly, with rows of irregular metallic magenta spots, a dark red region along the anterior-dorsal portion of the body, and predominantly red and yellow dorsal and caudal fins. In morphology, Pseudanthias hangapiko sp. nov. most resembles Pseudanthias connelli Heemstra & Randall, 1986, Pseudanthias randalli Lubbock & Allen, 1978, and P. squamipinnis , sharing overlapping counts in the number of spines and rays on the dorsal and pectoral fins, the number of lateral line scales, and the number of gill rakers. However, it can be differentiated from all of these species by coloration and morphology, especially in the number of segmented rays on the anal fin (8, vs. 7 in P. connelli , P. randalli , and P. squamipinnis ), by having a very slender body (greatest body depth 3.4-3.7 in SL), and in the small number of circumpeduncular scales (16-17, vs. 22-25 in P. connelli , P. randalli , and P. squamipinnis ). Pseudanthias hangapiko sp. nov. lacks the scaly dorsal and anal fins and auxiliary scales present in P. squamipinnis , and has only two supraneurals, not three as in P. squamipinnis . Male Pseudanthias hangapiko sp. nov. lack the pennant-like extension on the third dorsal spine occurring in P. squamipinnis , and male Pseudanthias hangapiko sp. nov. do not possess a fleshy, protruding upper lip, present in the subgenus Pseudanthias Mirolabrichthys , but rather have a rounded snout. It should be noted that the diagnostic validity of this latter character is questionable, as some species exhibit various degrees of hypertrophy and the character may have risen independently multiple times within the anthiadine fishes ( Gill et al. 2017).

The most similar DNA barcodes (mitochondrial COI gene) are from Pseudanthias ventralis and P. hawaiiensis , with 16.8% and 17.0% uncorrected divergence, respectively. These distances are much higher than average divergences between sister species ( Rocha 2004), and even between genera, so it is not surprising that P. hangapiko can be differentiated from these two species by several characters, including the number of anal-fin rays (III, 8 vs. III, 9-10 in P. ventralis and P. hawaiiensis ), body depth (3.4-3.8 vs 2.3-3.0), and also by body coloration.

Figures

Figure 1. Holotype CAS 247252, male specimen (upper), 45.2 mm SL. Paratype CAS 247254, female specimen (lower), 33.2 mm SL. Photos by LA Rocha.

Figure 2. Radiograph of holotype, CAS 247252. Photo by J Fong.

Figure 3. An aggregation of Pseudanthias hangapiko sp. nov. on a rocky mesophotic coral ecosystem at Rapa Nui (Easter Island) at 80 m depth.