 |
| Chromis mamatapara
Shepherd, Pinheiro, Phelps, Easton, Pérez-Matus & Rocha, 2020
|
Abstract
A new species of Chromis (Teleostei: Pomacentridae) is described from three specimens collected at 90 m depth in a mesophotic coral ecosystem at Rapa Nui, Chile. Chromis mamatapara, new species, can be distinguished from its congeners by the following combination of characters: dorsal-fin rays XIV,13–14; pectoral-fin rays 18–19, third from top of fin longest; tubed lateral-line scales 18; total gill rakers on first arch 30–32; vertebrae 11+15; and by coloration of living specimens, especially the presence of a single, pronounced, white spot, roughly the same diameter as the orbit, located where the posterior base of the dorsal fin intersects the caudal peduncle. The most similar DNA barcode (mitochondrial COI gene), among those available, is Chromis tingting from Japan (3.5% uncorrected divergence); however, C. mamatapara, new species, also superficially resembles other species for which sequences are unavailable for comparisons, including C. okamurai from Japan and C. struhsakeri from Hawaii. Due to the high geographic isolation and consequently high endemism in the Rapa Nui region, we believe that C. mamatapara, new species, is endemic to mesophotic ecosystems of Rapa Nui, Isla Salas y Gómez, and nearby seamounts, a discovery that contributes to the high endemism of the region and thus the need for conservation efforts.
 |
| Fig. 1 Chromis mamatapara, new species (A) Holotype (CAS 247107), shortly after death. Photo by L. A. Rocha. (B) Preserved holotype, lateral view. Photo by J. Fong. (C) Radiograph of holotype (CAS 247107). Photo by J. Fong. (D) Preserved holotype, dorsal and ventral views. Photos by J. Fong. |
Chromis mamatapara, new species
English Common Name: Michel's Chromis
Spanish Common Name: Castañeta de Michel
Diagnosis.—The following combination of characters distinguishes Chromis mamatapara, new species, from all of its congeners: dorsal-fin rays XIV (versus XV in C. randalli, the only other congener in the area, and XII–XIII or XV in most other Indo-Pacific species), 13–14 (versus 10 in C. randalli); anal-fin rays II,12 (versus II,10–11 in C. randalli); pectoral-fin rays 18–19 (versus 21–22 in C. randalli); principal caudal-fin rays 8+7; spiniform procurrent caudal-fin rays 2; tubed lateral-line scales 18 (versus 21–22 in C. randalli); posterior, mid-lateral scales with pore or deep pit 8–9; vertebrae 11+15; gill rakers 9–10+21–23; total gill rakers 30–32 (versus 33–37 in C. randalli); body moderately deep, depth 1.8–2.0 in SL (versus 2.3–3.0 in C. randalli); tail and caudal peduncle yellow; distal edge of caudal peduncle at junction of posterior dorsal fin with a large white spot, its diameter about width of orbit (Fig. 1).
Etymology.— The specific epithet is a compound word meaning “yellow damselfish” (māmata para) in Rapanui, in reference to the overall body coloration in life. To be treated as a noun in apposition. The suggested English common name, Michel's Chromis (Castañeta de Michel in Spanish), is in honor of the late Michel Garcia, who greatly assisted our field work in Rapa Nui, and unfortunately died in May 2018.
 |
| Fig. 2 (A) Aggregation of juvenile Chromis mamatapara, new species, in a field of Stichopathes sp. whip corals at a depth of 165 m on Pukao. Photo by M. Gorny, Oceana. (B) Aggregation of adult Chromis mamatapara, new species, photographed at a depth of 175 m on Pukao. Photo by M. Gorny, Oceana. (C) Collection site of Chromis mamatapara, new species, Rapa Nui, Chile, at a depth of 90 m. Two specimens are visible in the foreground, exhibiting the diagnostic white spot at the posterior base of the soft dorsal fin. Associated fishes include Chaetodon litus, Chromis randalli, Pseudolabrus semifasciatus, the recently described Plectranthias ahiahiata, Luzonichthys kiomeamea, and an undescribed member of the Serranidae. Photo by L. A. Rocha. |
Habitat and distribution.— Chromis mamatapara is only known to occur at Rapa Nui (Easter Island), Isla Salas y Gómez, and the seamount Pukao (∼85 km west of Rapa Nui). Due to the high degree of endemism (21.7%) among the shore fishes of Rapa Nui (Delrieu-Trottin et al., 2019), it is likely that Chromis mamatapara is endemic to this region.
The collected fish were recorded at a depth of 90 m in a rocky patch reef surrounded by a large sandy area. Adults have also been observed with ROV surveys at Rapa Nui at 90–230 m and Pukao at 150–190 m in rocky patch reefs surrounded by sandy areas, around rhodoliths and fields of whip coral (Stichopathes), along rock walls interspersed with sandy areas, and dead or mostly dead reefs of Leptoseris. Juveniles of the new species have been observed during ROV surveys in association with Stichopathes at Pukao at 165 m and Rapa Nui at and 150–157 m (Easton et al., 2019; Fig. 2A).
Bart Shepherd, Hudson T. Pinheiro, Tyler A. Y. Phelps, Erin E. Easton, Alejandro Pérez-Matus and Luiz A. Rocha. 2020. A New Species of Chromis (Teleostei: Pomacentridae) from Mesophotic Coral Ecosystems of Rapa Nui (Easter Island) and Salas y Gómez, Chile. Copeia. 108(2); 326-332. DOI: 10.1643/CI-19-294
