Chromoplexaura marki ( Kuekenthal , 1913)

Horvath, Elizabeth Anne, 2019, A review of gorgonian coral species (Cnidaria, Octocorallia, Alcyonacea) held in the Santa Barbara Museum of Natural History research collection: focus on species from Scleraxonia, Holaxonia, Calcaxonia - Part II: Species of Holaxonia, families Gorgoniidae and Plexauridae, ZooKeys 860, pp. 67-182 : 67

Chromoplexaura marki ( Kuekenthal, 1913) Figures 28, 29A, B, 30A, B, 31 A–C, 32A, B, 33A, B, 34 A–C, 35 A–E, 36, 37A1-37, 4, B1,, 3, 38 A–E

Euplexaura marki Kükenthal, 1913: 266-269; text figs G, H, J, K, pl 8 fig. 11; 1924: 93-94.

Chromoplexaura marki ( Kükenthal, 1913): Williams 2013a: 36-39; figs 12-17.

Type locality.

For the original specimen, USA, Southern California, 64-616 m. (Identification cannot be confirmed.) For proposed Neotype, collected in Northeastern Pacific, USA, California, Monterey County, Monterey, BLM Reference Station 360 (Burch #40128), ~22 m; coll. T Burch, 18 August 1940.

Type specimens.

Repository for the original type specimen unknown. Proposed Neotype (designated here), SBMNH 423060 [dry].

Material examined.

~60 lots (see Appendix 1: List of material examined).

Description.

Colony (Figures 28, 29A, 30A, 31A, 32A, 33A) shape can be a wide, broad, moderate to sparsely branched fan, typically in one plane or simple, unbranched; initial branching lateral, progressing to branches that tend to project more up than out; sometimes projecting/winding more in a “front” or “back” direction; with broader membranous base; main branches can divide repeatedly, all secondary branches off larger ones having same diameter; round in cross-section; distal ends often slightly swollen; see Figures 29B, 30B, 31B, C (See Remarks below for further discussion of overall colony shape). Axis proteinaceous, generally well calcified, not very flexible, with hollow core. Color of axis variable between white, yellowish, and light brown. Color of living colony base, stem and branches bright coral red (orange-red), bright red, or dark red; red color enhanced by color of the sclerites, which are a bright, pale, transparent red. Polyps are (pale) yellow-colored when living; ( Johnson and Snook (1927) stated the color of E. marki to be coral-red, with the living polyps yellowish white). When polyps visible in preserved specimens, they appeared white/cream. Coenenchyme moderately thick, rising in wall of polyp as eight very short folds. Polyps sit ~2.0 mm distant; polyps ~2.0 mm high, 1.0 mm broad, when extended; polyps fully retractile into coenenchyme surface, forming very low, rounded bumps ( “polyp-mound”); aperture suggestive of a goblet/chalice shape; fortification of polyps weak. Kükenthal (1913 a) stated that there are no calyces in this species, or at least are so negligible as to be virtually nonexistent (in describing Euplexaura marki , he indicated that there should be two transverse rings of large sclerites, one over folds in the polyp head and a second just below insertion of the tentacles). Sclerites of polyp body red, while sclerites of tentacles smaller, colorless, transparent, but of similar form. Occasionally, tentacle sclerites can be a bent spindle (Figures 34 A–C, 35 A–E, 36, 37A1-4, B1-3, 38 A–E). Found initially in a specimen identified as this species (USNM 51500) was a sclerite form that was not clearly featured in sclerite descriptions for the genus, or other known species (Figures 34 A–C, 35C, 36, 37A1, B1, 38B): in outer surface of branch coenenchyme lie sclerites whose basic form is a thick spindle, but on these sit two or more belts of very big, jagged warts. Through the development of these large warts, the spindle can have a contour that is nearly oval (these might be the tuberculate spheroids mentioned in original description; apparently a key sclerite form, for the genus Euplexaura , at least) to a distinct diamond shape. Occasionally, one can find on both ends of these spindles, dense triangular caps (Figure 34 A–C, 35C, 36, 37A1, B1, 38B) separated by a smooth, usually thin, median waist, so that in this case, the term double spindle (double-head) could apply; these are characteristic and conspicuous of multiple specimens examined, and henceforth referred to as the double-dunce cap. Size of these outer spindles fluctuated considerably, with smallest only 0.05 mm in length, but often bigger (~0.2 mm). Those deeper into coenenchyme of branches had similar form, but warts were more rounded (Figures 35B, 37A3, B3, 38C). All of the more superficial sclerites are red, making the strong bright red color of the colony fairly pronounced.

Etymology.

Species named in honor of EL Mark of Harvard University.

Common names.

MBARI (seen in a hall display, Summer 2008) referred to this species (and to any species from northern California appearing as a "red whip") as "Red licorice gorgonian".

Distribution.

Southern California; littoral and coast-abyssal ( Kükenthal, 1924, as Euplexaura marki ). Johnson and Snook (1927) noted the species living in deep water, taken with a dredge; specimens were collected off the Oregon coast, and are either in the Oceanography Department of Oregon State University, or in the personal collection of FP Belcik. Nutting (1909) reported numerous collection points, at stations near San Nicolas Island, and for stations near Point Piños Lighthouse, Monterey Bay. Likely, range extends from southern California to waters off Washington coast. There is the possibility that the species extends further north, to Alaska; further examinations of specimens from that area are in progress.

Biology.

An unidentified, anecdotal comment indicated that this form is seen in the assemblage of organisms found at the head of Carmel Submarine Canyon, located offshore at San Jose Creek Beach, near Carmel, California; considered part of a deep-water assemblage that begins to appear at depths between 21-30 m, where turbulence is minimal and fine sediments accumulate on surface irregularities of rock walls. Between 30-61 m, the fauna appears to change very little, suggesting that many of these deep-water forms extend to greater depths.

The neotype designated here (SBMNH 423060, Figure 29) bears on several branches, enlargements that are in actuality gall-like growths, containing epizoic barnacles of the genus Conopea (likely Conopea galeata ). This is a consistent, common obligate commensal barnacle of gorgonians ( Langstroth and Langstroth 2000). On SBMNH 423069 (previously SBMNH 40612), a large cluster of commensal acorn barnacles was seen, on bare-axis portions of the branches. Another specimen, SBMNH 423078, had attached to its bare axis something having, in general appearance, the wooly, cotton-like spittle-bug mass that insects are known to produce on plant stems. Conspicuous brittle stars are intertwined on branches on the specimen from off Newport, Oregon, SBMNH 423073.

Remarks.

Cordeiro et al. (2018f) lists Chromoplexaura marki as the only species in the genus Chromoplexaura in the WoRMS Database.

Kükenthal (1913 a) had initially suggested that this species may equal Psammogorgia arbuscula (Nutting, 1909) but later stated that characteristics of this species were completely different. The separation of these two species is reflected in Kükenthal (1924), with separate descriptions for E. marki and P. arbuscula (syn. Echinogorgia arbuscula ). Bayer (1956 a), in his description of the two genera in question, Euplexaura Verrill, 1869 (colony in one plane) and Psammogorgia Verrill, 1868 (colony bushy), indicated some slight overlap.

Kükenthal (1913 a; 1924) noted that prior to the discovery of this species, other species in the genus ( Euplexaura ) had only been found in the area of East Asia, from Japan to Singapore and West Australia. It appeared that this was the first red-colored member seen in Euplexaura and was the first of the genus from the west coast of North America.

In overall colony shape, some branching occurs; however, more often colony is a single, or rarely branched, stem; any branching from base results in a single or very scarcely branched “whip.” This would have been unique to this eastern Pacific species, along with its obvious, predominantly red sclerites, if it were truly in the genus Euplexaura (in most species of the genus, the sclerites are colorless); hence the need for the establishment of the new genus by Williams (2013a). In general colony color and shape, it would be quite easy to simply assume that this organism is Leptogorgia chilensis , but an examination of sclerites reveals the distinct differences.

Cairns et al. (2003) had this species listed as a junior synonym of Leptogorgia caryi Verrill, 1868; as noted previously, this is not the case. According to unpublished notes by Bayer, C. (E.) marki might have been synonymous with Psammogorgia spauldingi (now referred to as Swiftia spauldingi ). A possible synonymy was considered, with both Swiftia spauldingi (Nutting, 1909), and/or Swiftia simplex (Nutting, 1909). After examinations of multiple samples of what has been labeled as this species and those labeled as S. spauldingi or S. simplex , if any synonymy were to exist, it would be that between C. (E.) marki and S. spauldingi. With the very obvious large, broad spindles, the double-dunce sclerite, I consider this a separate species, but it does exhibit a strong superficial similarity to S. spauldingi and there are some shared sclerite forms. An initial conclusion arrived at some years ago (regarding synonymy with S. spaulding ), seemed to have support with the discovery of a comment made by Bayer (1979). While the statement was an unexpected one to find in this particular article, finding it was noteworthy. It read "The colonies of A(delogorgia) telones are similar in general aspect to those of Euplexaura marki Kükenkthal (= Psammogorgia abuscula sensu Nutting, not Verrill) and the closely related (if not identical) Psammogorgia spauldingi Nutting, both of which have longer and less sinuous branches." However, no anthocodial rods in the form of a fingerbiscuit, a key characteristic sclerite of species in the genus Swiftia Duchassaing & Michelotti, 1864, have been found in C. (E.) marki specimens, and the initial conclusion was dismissed. A further discussion of California "red whip" diversity follows below and correlations are discussed in Part III of this collection review, on Swiftia cf. spauldingi , but also in the description for Swiftia simplex .

An examination of several specimens (collected by P Etnoyer on a West Coast Survey for NOAA, in the Fall of 2010) was done at Etnoyer’s request. Made available were actual specimens, along with several in situ shots. In digital images, the little-branched colonies were a dirty brick-red or pink (Figure 28); coloring was seen in both extended polyps and throughout branch coenenchyme. An initial diagnosis of the specimens via still images was Swiftia simplex . However, upon physical examination, the polyps themselves were actually white (indicating that only the tentacles were the pinkish color of the coenenchyme) and an examination of the sclerites revealed the large, broad double-dunce spindles so characteristic of C. (E.) marki . If one were to see a colony with little branching, having an overall dirty brick-red to pink color, and did not dissect out a polyp to reveal their white color, or examine the sclerites, an erroneous identification could be made. These specimens presented something of a quandary. Superficially, they looked very much like confirmed Swiftia simplex , yet the sclerites revealed something different. There is a possibility that C. (E.) marki has color variants, with one looking very much like Swiftia simplex . Thus, specimens previously identified in various museum collections as C. (E.) marki may not belong to the genus Chromoplexaura at all if double-dunce sclerites are not found, but finger-biscuit rods are.

MBARI has encountered many single or few-branched whips in their investigations. Many of these specimens have been recorded in video and in still photography; a few have actually been collected. A number of principal investigators identify many of these distinct whips as being this species (in genus Euplexaura , now Chromoplexaura ). However, some of those identified as this species may actually be Swiftia simplex ; in overall shape very comparable, but in S. simplex , the color leans to a dull brick red rather than the usual bright red hue, and polyps of S. simplex are always the same color as the coenenchyme, not the "....white, cream or yellow" polyps described for this species by Kükenthal (1913 a, 1924), Johnson and Snook (1927) or Williams (2013). Collection of an array of these “whips” when encountered, along with examination of their sclerites and molecular testing of tissue could help to clear up any confusion surrounding these red whip species; in collaboration with E Berntson, M Everett and their colleagues at Northwest Fisheries Science Center (Port Orchard and Seattle, Washington), those needed examinations are currently being conducted.