1 Department of Invertebrate Zoology and Geology, California Academy of Sciences, Golden
Gate Park, 55 Music Concourse Drive, San Francisco, California 94118, USA.; 2 Centro de

Investigación en Estructuras Microscópicas, Centro de Investigación en Ciencias del Mar y Lim-
nología, Escuela de Biología, Universidad de Costa Rica. P.O. Box 11501-2060, San José, Costa

Rica; 3 Smithsonian Tropical Research Institute, P.O. Box 0843-03092, Republic of Panama;
4 Corresponding Author: Gary C. Williams (gwilliams@calacademy.org)

Recent offshore benthic surveys utilizing Remotely Operated Vehicles in the Nation- al Marine Sanctuaries along the California coastline under the auspices of the National Oceanic and Atmospheric Administration and the Ocean Exploration Trust, have yielded newly collected material and imagery of octocoral cnidarians from mesophotic and deep-sea habitats. As part of this effort, a new species of gorgonian coral is here described that was first observed at Cordell Bank, approximately 112 km WNW of San Francisco. The species is allocated to the gorgonian genus Chromoplexaura based on morphological considerations, and has since been collected or observed from four localities in central and southern California, 86–107 m in depth.

KEYWORDS: Corals, sea fans, gorgonian octocorals, Central California, Cordell Bank, mesophotic zone, taxonomic key to the genus and related taxa.
Chromoplexaura is currently regarded as a monotypic octocoral genus (Cordeiro et al. 2018c), represented by C. marki (Kükenthal, 1913), and is distributed from central Oregon to southern California on the west coast of North America. Bathymetric distribution of this species varies from nine to at least 90 m (Williams 2013). The new species described here represents a second species of the genus and is known from central to southern California with a depth range of 86 to 106 m. The two species currently share several morphological similarities. Herein we describe a new species that was first observed, but not collected in 2007 by ROV imagery at Cortes Bank in southern California, near the border between California and Mexico. In 2017, colonies were observed (also not collected) by ROV in the Cordell Bank National Marine Sanctuary in central California. In 2018, four specimens were collected by ROV and one was recorded by benthic ROV imagery on board the National Oceanic and Atmospheric Administration (NOAA) ship FSV Bell M. Shimada, at three locations in central and southern California: Cordell Bank NMS, Monterey Bay NMS, and Channel Islands NMS.

MATERIALS AND METHODS

The type material was collected during the benthic surveys of Cordell Bank and Greater Farallones National Marine Sanctuaries on board the NOAA ship FSV Bell M. Shimada (Fig. 1), between 28 July and 11 August 2018. The holotype and paratypes of the new species are deposit- ed in the marine invertebrate collections of the Department of Invertebrate Zoology and Geology at the California Academy of Sciences in San Francisco, California. Underwater video and still imagery were taken on board the ship by NOAA and MARE staff. Images of preserved material and scanning electron micrographs were taken by the first author at the California Academy of Sciences in 2018.
Abbreviations used in the text are as follows: FSV – Fisheries Survey Vessel, MARE – Marine
Applied Research and Education; CASIZ – California Academy of Sciences Invertebrate Zoology;
CBNMS – Cordell Bank National Marine Sanctuary; MBNMS – Monterey Bay National Marine Sanctuary; CINMS – Channel Islands National Marine Sanctuary; NMS – National Marine Sanc- tuary; NOAA – National Oceanic and Atmospheric Administration; ROV – Remotely Operated Vehicle.
Depths used in the text include: Shallow-water (0–40 m); Mesophotic (40–150 m); Deep-Sea (>150 m). Material used for comparative purposes: Chromoplexaura marki; CASIZ 190436; NOAA Sample S-17; Gulf of the Farallones National Marine Sanctuary, Rittenburg Bank (37.88°N 123.32°W); 89.4 m depth; 08 October 2012; ROV Beagle (MARE) from R/V Fulmar (NOAA); three terminal branches, wet-preserved in 95% ethanol. Euplexaura sp.; CASIZ 220608; Western Pacific Ocean, Caroline Islands, Palau (7.54°N 134.47°E); 7-31 m depth; 08 December 2016; cool G.C. Williams; one partial colony, wet-preserved in 95% ethanol. Swiftia torreyi; CASIZ 220958; Cordell Bank National Marine Sanctuary (37.98°N 123.49°W); 948.82 m depth; 10 August 2017;
ROV Hercules/Argus from E/V Nautilus; one whole colony, wet-preserved in 95% ethanol. 144

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Series 4, Volume 65, No. 6

FIGURE 1. The National Oceanic and Atmospheric Administration (NOAA) Fisheries Survey Vessel, FSV Bell M. Shimada, conducts fisheries and oceanographic research throughout the Pacific coast of the United States. All type speci-mens of the new coral species described herein were collected by Remote Operational Vehicle (ROV) on board this ship in2018. Photo by Gary C. Williams.

SYSTEMATIC ACCOUNT
Subclass Octocorallia Haeckel, 1866
Order Alcyonacea Lamouroux, 1812
Family Plexauridae Gray, 1859
Chromoplexaura Williams, 2013

Euplexaura Kükenthal, 1913:266; 1924:93.
Chromoplexaura Williams, 2013:17.
GENERIC DIAGNOSIS.— Growth form planar and sparse, branching lateral. Retracted polyps form low rounded protuberances, mound-like to hemispherical in shape. Polyps are present on all sides of the branches, but can be arranged biserially on some narrow terminal branches. Coen-
cenchymal sclerites are primarily robust warty spindles, somewhat ovoid in shape or approaching girdled spindles. Other sclerite types that may be present include radiates, crosses, and spindles with a median waist that approach capstans. Anthocodial sclerites are rods that are straight or curved to sinuous. Colony color red or yellow due to conspicuous color of the sclerites.
TYPE SPECIES.— Euplexaura marki Kükenthal, 1913. Chromoplexaura cordellbankensis Williams and Breedy, sp. nov. Figures 2–10.
HOLOTYPE.— CASIZ 228195; NOAA Sample SH-18-09-017; Cordell Bank, Cordell Bank National Marine Sanctuary, CBNMS Transect-127; ca. 51 km W. of Point Reyes Peninsula (38°03′ 15.465′′N 123°28′48.072′′W); 100.5 m depth; 08 August 2018; ROV Beagle (MARE) from FSV
Bell M. Shimada (NOAA); one partial specimen (missing holdfast), wet–preserved in 95% ethanol.
PARATYPES.— CASIZ 228194. NOAA Sample SH-18-09-016; Cordell Bank, Cordell Bank

National Marine Sanctuary, CBNMS Transect-127; ca. 51 km W. of Point Reyes Peninsula, California, USA (38°03′15.915′′N 123°28′49.874′′W); 101.6 m depth; 08 August 2018; ROV Beagle

(MARE) from FSV Bell M. Shimada (NOAA); one partial specimen (14 mm long branch frag- ment), wet-preserved in 95% ethanol. CASIZ 207519; La Cruz Canyon, Monterey Bay National

Marine Sanctuary; California, USA (35.7694°N 121.4475°W); 106.8 m depth; 28 October 2018; coll. by ROV on board FSV Bell M. Shimada (NOAA); one whole specimen. CASIZ 207520; Anacapa Island, Channel Islands National Marine Sanctuary; California, USA (33.992°N
119.3722°W); 86 m depth; 31 October 2018; coll. by ROV on board FSV Bell M. Shimada (NOAA); one specimen in two pieces.

HABITAT AND DISTRIBUTION.— Found on rugose, rocky substrata often with conspicuous vertical relief, or on rounded boulders in boulder fields (Fig. 3). Distributed off the central and southern coasts of California, between 38.2° and 32.5°N latitude (Figs. 8–9); at mesophotic depths between 86 and 107 m. The type locality is Cordell Bank in the Cordell Bank National Marine Sanctuary, ca. 70 miles WNW of San Francisco, California, 100 m depth.
ETYMOLOGY.— The specific epithet is derived from Cordell Bank and the Latin suffix – ensis (belonging to); referring to the region of discovery of the new species and collection of the holotype – Cordell Bank National Marine Sanctuary.

DESCRIPTION OF THE HOLOTYPE

EXTERNAL MORPHOLOGY.— The holotype is part of a colony, 35 mm in length. The holdfast and basal portion of the colony are missing. Branching is sparse and lateral. The main stem gives rise to two lateral side branches, about 9 mm apart and 2–2.5 mm in diameter (including polyp mounds). The longest branch is 3.4 mm in length (Fig. 2). The retracted polyps form low-rounded to hemispherical polyp mounds, each < 1 mm in length. The polyps are largely distributed biserially on the thinner distal-most portions of branches (Fig. 2B), but occur all around the stouter and more basal parts of the lateral branches and main stem (Fig. 2E). There are approximately ten mounds per cm of branch length. Finger-shaped portions of the coenenchyme-covered internal axis
extend from the apical tips of some branches (Fig. 2B).
ANTHOCODIAE.— Most of the anthocodiae are preserved totally retracted into the polyp mounds, while a few are partially exserted. The walls of the anthocodiae and bases of the tentacles are relatively densely set with narrow rods that have conspicuous tuberculation (Fig. 7). Due the retracted condition of the polyps, an en chevron arrangement of sclerites was not observed or easily apparent. The sclerites of the anthocodiae are lighter in color than the coenenchymal sclerites, many appearing virtually colorless, thus resulting in a white coloration of the polyps.

The polyp mounds are represented by conspicuous rounded protuberances along the branches, usually expanded at the base while some are hemispherical in shape. Adjacent polyp mounds are generally separated by about 1.0–1.5 mm of bare rachis, and vary in width from 1.5–2.0 mm at the base, and are usually less than 1.0 mm in height (Fig. 2).

SCLERITES.— Coenenchymal sclerites vary from 0.06 to 0.22 mm in length (Figs. 4–6, 10A). They are predominantly wide, warty spindles with heavily warted tubercles, while some are narrower with less ornamentation (Figs. 4–5, 10A). Radiates and various immature forms are also present (Fig. 6). Polyp sclerites are elongate rods (Fig. 7), often slightly curved or sinuous with variable tuber- culation, while some are weakly club-shaped (Fig. 7, left). Small, flat rods (Fig. 7, center) are also present and could possibly be from the tentacles. Polyps sclerites vary in length from 0.08–0.24 mm in length.

COLOR.— Coenenchyme color is uniform lemon yellow throughout (Figs. 2–3), due to the conspicuous yellow coloration of the sclerites (Fig. 2F). The anthocodiae are colorless (Fig. 2E).

REMARKS

VARIATION: Although the holotype specimen exhibits only three branches including the main stem, the paratypes as well as additional colonies observed in underwater still images taken by ROV, all exhibit relatively sparse branching, but may possess as many as ten branches including the main stem. One of the paratype colonies (CASIZ 207519), branches up to four times and produces seven lateral branchlets.

DISCUSSION AND CONCLUSION

Key to species of Chromoplexaura and related taxa in California 1a. Colonies planar and sparsely branched. Coenenchymal sclerites are broad to ovoid spindles
with densely set tubercles, capstans, girdled spindles, elongated radiates, and/or tuberculated crosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1b. Colonies unbranched to copiously branched or bushy. Coenenchymal sclerites may include elongate to needlelike spindles, compact radiates, double discs, and/or disc spindles. . . . . . 3
2a. Colonies red. Coenenchymal sclerites include ovoid spindles and girdled spindles . . . . . . . . .. . . . . . . . .  . . . . . . . . . . . Chromoplexaura marki (Kükenthal, 1913)
2b. Colonies yellow. Coenenchymal sclerites include capstans, elongated radiates, and crosses . .. . . . . . . . . . . . . . . . . . . Chromoplexaura cordellbankensis sp. nov.
3a. Colonies unbranched or Y-shaped. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3b. Colonies branched – copiously branched or bushy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4a. Colonies white; polyp mounds low-rounded. . Swiftia farallonesica Williams & Breedy, 2016
4b. Colonies coral red to dark red. Polyp mounds prominent – conical to low cylindrical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Swiftia simplex (Nutting, 1909)
5a. Branching bushy, polyp mounds prominent – conical to cylindrical . . . . . . . . . . . . . . . . . . . . 6
5b. Branching sparse, polyp mounds low-rounded. Colonies coral red with white polyps. . . . . . . . . . . . Swiftia spauldingi (Nutting, 1909)
6a. Polyp mounds truncated conical; sclerites are radiates and elongate spindles with rounded tubercles . . . . . . . . . . . . . . . . . . . . . . Swiftia torreyi (Nutting, 1909)
6b. Polyp mounds stout, conical to cylindrical; sclerites are primarily elongate spiny spindles, often needle-like and curve . . . . . . . Swiftia kofoidi (Nutting, 1909)

TAXONOMIC ASSESSMENT

The genus Chromoplexaura is superficially similar to several Pacific coast Swiftia species. The latter is currently regarded as a gorgonian genus of twenty species (Cordeiro et al. 2018b). The type species of Swiftia is Swiftia exserta (Ellis and Solander, 1786) from the western Atlantic Ocean. Several species from the Pacific coast of the Americas have been allocated to the genus Swiftia, and it is not clear at present whether the Atlantic vs. Pacific species represent the same genus or
separate genera (Williams 2013:17). In addition, there appears to be two distinguishable groups of eastern Pacific species of Swiftia based on morphological characteristics. Preliminary molecular analyses (Everett and Park 2018; Everett, personal communication) have shown that the two
groups (Chromoplexaura and Swiftia) have not exhibited a conspicuous differentiation, but from the morphological point of view are different (Fig. 10A, B, D). An overall detailed molecular analysis and morphological comparison are necessary to provide a cogent taxonomic assessment of the relevant taxa.
Chromoplexaura cordellbankensis sp. nov. shares superficial morphological similarities with some species of Eastern Pacific Swiftia regarding external morphology – such as branching pattern, low-rounded to hemispherical polyp mounds, and elongate-tubercated anthocodial sclerites. However, the coenenchymal sclerites differ markedly from those of Swiftia, while most closely resembling the sclerite complement of Chromoplexaura marki (Williams, 2013:20–21) – i.e. the presence of robust to ovoid, highly warty spindles in the coenenchyme, which are not found in species of
Swiftia (Fig. 10A, B, D).

Chromoplexaura marki was originally placed in the Indo-Pacific genus Euplexaura by Kukenthal, 1913. However, the coenenchymal sclerites of Euplexaura species differ markedly from the two California species of Chromoplexaura, by the possession of tuberculate spheroids, subspheroids, double heads, and plump ovoid to irregular spindles (Fig. 10C; Fabricius and Alderslade 2001:190; Williams 2013:21, 24).

ACKNOWLEDGMENTS

We express our thanks to the staff scientists of NOAA (National Oceanic and Atmospheric Administration), for their support, in particular — Dan Howard and Danielle Lipski (Cordell Bank National Marine Sanctuary), Jan Roletto (Greater Farallones National Marine Sanctuary), Enrique WILLIAMS & BREEDY: NEW SPECIES OF GORGONIAN OCTOCORAL  Salgado (NCCOS, National Centers for Coastal Ocean Science), and Meredith Everett (Northwest
Fisheries Science Center). We are grateful to Guy Cochrane (USGS, United States Geological Survey), Kirsten Lindquist (Gulf of the Farallones Association), the technical staff of MARE (Marine Applied Research and Exploration) — Dirk Rosen, Andy Lauermann, Heidi Lovig, Rick Botman, and Steve Holz, as well as the Marine Operations staff and crew of the NOAA ship FSV Bell M. Shimada.

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