Tuesday, October 24, 2017

[Ichthyology • 2017] Roa rumsfeldi • A New Butterflyfish (Teleostei, Chaetodontidae) from Mesophotic Coral Ecosystems of the Philippines


Roa rumsfeldi 
  Rocha, Pinheiro, Wandell, Rocha & Shepherd, 2017
Figure 2. Live specimen of Roa rumsfeldi sp. n. photographed at the California Academy of Sciences’ Twilight Zone exhibit (photo LA Rocha).

Abstract
A new species of the butterflyfish genus Roa is herein described from the Verde Island Passage in the Philippines, West Pacific Ocean. Roa rumsfeldi sp. n. was found on mesophotic coral ecosystems at Puerto Galera and Batangas, and sampled through technical mixed-gas rebreather diving at 100–130 m depth. This represents the fifth known species of Roa. The main differences between Roa rumsfeldi sp. n. and its congeners are the lower number of pored scales in the lateral line, longer snout, longer caudal peduncle, shorter caudal fin, pelvic fin color (dark first spine vs. white in all other Roa), and genetics (8.4% divergence from its closest relative Roa modesta in the mitochondrial COI gene). Roa spp. are usually seen in pairs, but the two specimens we collected were solitary individuals. We have kept one of the specimens alive in the California Academy of Sciences’ Twilight Zone exhibit for more than one year, where it thrives and is feeding on a variety of dried and fresh food.

Keywords: Coral triangle, deep reefs, new species, rebreather diving, reef fish

Figure 1. Roa rumsfeldi sp. n., holotype shortly after death, 77.53 mm SL, PNM 15198 (photo LA Rocha).

Roa rumsfeldi sp. n. 
Deep-blackfin butterflyfish

Diagnosis: Roa rumsfeldi sp. n. differs from all of its congeners by the smaller number of pored scales in the lateral line pored scales (27 versus 37-46 in other Roa), longer snout (35.9% in HL vs. 28.2–35.5%), shorter first dorsal ray (12% in SL vs. 16.6–26.6%), longer caudal peduncle (8.5% in SL vs. 4.2–8.2%), shorter caudal fin (15.9% in SL vs. 19.8–25.9%), and a dark brown pelvic-fin spine (white in all other known Roa species).

Etymology: We name Roa rumsfeldi to honor Donald Rumsfeld who immortalized the quote: “there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know.” He said that when referring to the uncertainties of war, but we think it applies perfectly to the taxonomy of MCE species: We only realized this species was new after we took a good look at it here at the aquarium in San Francisco, so we think it’s a perfect example of an unknown unknown.

Distribution and habitat: Roa rumsfeldi sp. n. is only known to occur in the Verde Island Passage, central Philippines. It was found on MCEs of Puerto Galera, Oriental Mindoro, and Bauan, Batangas, between 100 and 130 m depth. However, the species likely has a wider distribution and remains undetected because of its preferred depth range. The ecosystems where it was found vary from sheltered rocky outcroppings heavily covered by fine sediment to areas exposed to strong currents. The ambient seawater temperature varied between 19 and 21°C during our dives, which were conducted in April-May over several years. Azooxanthellate gorgonians, black corals, and solitary stony corals are the most abundant benthic invertebrates in this habitat.


 Luiz A. Rocha, Hudson T. Pinheiro, Matt Wandell, Claudia R. Rocha and Bart Shepherd. 2017. Roa rumsfeldi, A New Butterflyfish (Teleostei, Chaetodontidae) from Mesophotic Coral Ecosystems of the Philippines. ZooKeys. 709; 127-134.  DOI: 10.3897/zookeys.709.20404

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