Plectranthiasahiahiata, a new species of perchlet from a mesophotic ecosystem at Rapa Nui (Easter Island) (Teleostei, Serranidae, Anthiadinae).

Bart Shepherd,Luiz A Rocha,Alejandro Pérez-Matus,Tyler Phelps,Hudson T Pinheiro

doi:10.3897/zookeys.762.24618

Abstract

A new species of the perchlet genus Plectranthias is herein described from a single specimen found at Rapa Nui (Easter Island) in the South Pacific. Plectranthiasahiahiata sp. n. was collected at a depth of 83 m in a mesophotic coral ecosystem at Rapa Nui. The main difference between Plectranthiasahiahiata and other members of the genus is higher fin-ray counts (X, 18 dorsal; 18 pectoral) and its distinctive coloration. Compared to the three other known eastern South Pacific species, P.ahiahiata has more dorsal-fin rays, more pectoral-fin rays, fewer tubed lateral-line scales, fewer gill rakers, a longer head relative to SL, a very short first dorsal spine relative to SL, and a short third anal spine relative to SL. Plectranthiasahiahiata is distinguished from western Pacific species, by having more dorsal- and pectoral-fin rays. The closest relative based on genetic divergence (with 12.3% uncorrected divergence in the mitochondrial COI gene) is Plectranthiaswinniensis, a widely distributed species, suggesting important links between Rapa Nui and western Pacific islands. This new species adds to the high endemism of the Rapa Nui ichthyofauna, and is further evidence of the importance of mesophotic reefs as unique communities.

Highlights

Rapa Nui (Easter Island) is the most isolated inhabited island in the Indo-Pacific, located approximately 3,700 km west of Chile and 2,000 km from the nearest inhabited island, Pitcairn (Randall and Cea 2010; Easton et al 2017)
DNA sequences were compared to the ten Plectranthias species available in GenBank (P. bennetti Allen and Walsh 2015: KT601636; P. flammeus Williams, Delrieu-Trottin and Planes 2013: KC565477– KC565480; P. fourmanoiri Randall 1980: KC567662, KC567663; P. japonicus: JQ681323, JQ681324; P. kamii Randall 1980: KU943548; P. kelloggi Jordan and Evermann 1903: KP267643; P. longimanus Weber 1913: JF494178; P. nanus Randall 1980: JQ432001–JQ432004, KC565481, KC567661; P. randalli Fourmanoir and Rivaton 1980: KP267613; P. winniensis: KC565482, KC565483)
Plectranthias ahiahiata is currently only known to occur at Rapa Nui (Easter Island)

Summary

Introduction

Rapa Nui (Easter Island) is the most isolated inhabited island in the Indo-Pacific, located approximately 3,700 km west of Chile and 2,000 km from the nearest inhabited island, Pitcairn (Randall and Cea 2010; Easton et al 2017). Recent advances in technical mixed-gas rebreather diving are allowing scientists to safely document small, active, cryptic, and demersal fishes in ways that have been previously impossible (Pyle 2000; Pyle et al 2016; Rocha et al 2017) Using these techniques, our team collected a distinctive new species of Plectranthias off Hanga Piko, Rapa Nui. The anthiadine genus Plectranthias Bleeker 1873 currently comprises 56 valid species from tropical and temperate waters in the Atlantic, Pacific, and Indian oceans (Eschmeyer et al 2017). The anthiadine genus Plectranthias Bleeker 1873 currently comprises 56 valid species from tropical and temperate waters in the Atlantic, Pacific, and Indian oceans (Eschmeyer et al 2017) Most of these fishes are found in relatively deep waters (90-420 m) on hard substrates such as mesophotic coral ecosystems and rocky formations (Allen and Walsh 2015; Gill et al 2016). Plectranthias ahiahiata sp. n. is described and illustrated from a single specimen collected at Rapa Nui

Materials and methods

Findings

Discussion