Callogorgia cracentis, Cairns, 2018

Cairns, Stephen D., 2018, Primnoidae (Cnidaria: Octocorallia: Calcaxonia) of the Okeanos Explorer expeditions (CAPSTONE) to the central Pacific, Zootaxa 4532 (1), pp. 1-43 : 3-6

Callogorgia cracentis , n. sp.

Figs. 1A , 2 A–G

Etymology. Named cracentis (Latin for neat or graceful), an allusion to the uniform length of the branchlets of the colony.

Type and Type Locality. Holotype: partial colony, SEM stubs 2499-2501, USNM 1453718 . Type Locality: EX 1703-7-01, 0.39˚S, 176.2˚W ( Titov Seamount , south of Baker Island, Phoenix Island Group), 1760 m.

Material Examined. Holotype.

Description. The holotype is a tall, uniplanar colony about 1 m in height, consisting of a basal main stem about 15 cm in length, which supports three large branches from which smaller branchlets originate in an alternate pinnate manner ( Fig. 1A ). The branchlets are uniformly 7–8 mm in length. Polyps are arranged in whorls of three or four, the whorl diameter being 2.4–2.8 mm; polyps are 1.7–2.2 mm in horizontal length.

The body wall scales are arranged in eight longitudinal rows, with progressively fewer scales per row from ab- to adaxial side, the adaxial side being largely bare. The body wall sclerite formula is: 8-10: 2-3+3-4:1-2:1-2, the abaxials being closely spaced and thus heavily shingled ( Fig. 2A ). The plus mark in the formula for the outer lateral body wall scales indicates that this is a discontinuous row of scales, occurring distally and proximally, but missing at mid-polyp, this space being occupied by overly broad abaxial scales ( Fig. 2C ). The distal edges of the abaxial and outer lateral marginals and submarginals bear tall ridges, and thus qualify as cristate scales ( Figs. 2A, E ), but the remaining body wall scales are flat and have a serrate distal edge. The distal-most cristate abaxial body wall scales are relatively narrow (0.45–0.50 mm wide), becoming broader (up to 0.8 mm wide) and curved toward the base of the polyp, where they almost encircle the polyp and occupy the space normally occupied by the outer lateral scales. The inner lateral scales are also quite broad (0.6–0.7 mm).

The operculum is prominent, composed of symmetrical, triangular, pointed scales, all having a relatively high L:W ratio; occasionally the lateral operculars bear two points ( Fig. 2F ). The abaxials are 0.9–1.0 mm in length, with an L:W of 2.1–2.6. The lateral operculars are 0.7–0.9 mm in length, with an L:W of 2.2–2.3. The adaxial operculars are 0.65–0.70 mm in length, with an L:W of about 2.1. The distal inner and outer faces of the operculars are covered with multiple serrate ridges, and the tip is sometimes somewhat cylindrical in cross section.

The coenenchymal scales ( Fig. 2G ) are elongate (up to 1.1 mm in length, with an L:W of 4–7.5), pointed, and uniformly covered with low granules.

Comparisons. Using the key to the Indo-Pacific Callogorgia species recently published by Cairns (2018), Callogorgia cracentis keys closest to C. gilberti ( Nutting, 1908) and C. flabellum (Ehrenberg, 1834) . Callogorgia gilberti (redescribed by Cairns 2010), and known from the Hawaiian Islands at 326–965 m, differs in having more abaxial body wall scales (11–13 per row), more polyps per whorl (3–7), cristate body wall scales extending up to five scales from the polyp margin, and smaller polyps (1.2–1.5 mm). Callogorgia flabellum (redescribed by Bayer 1982), known from throughout the Indo-Pacific at 540–1250 m, differs in having all its abaxial and outer lateral body wall scales cristate, blunt opercular scales, and many fewer outer lateral scales. C. cracentis is distinctive in having a discontinuous row of outer lateral body wall scales and branchlets that are uniform in length. Callogorgia cracentis is also quite similar to C. ramosa (K̹kenthal & Gorzawsky, 1908)( Japan, 600 m), especially in having cylindrical opercular tips, but that species lacks inner lateral and adaxial body wall scales.

Remarks. At least a dozen ophiuroids were attached to the holotype colony ( Fig. 1A ).

Distribution. Known only from the type locality.

Figures

FIGURE 1. In situ images of various species: A, Callogorgia cracentis, holotype. B, Calyptrophora lyra, holotype (not in situ). C, C. diaphana, EX1606-9-1. D, C. carinata, holotype. E, C. clarki, EX1605-L3-6. F, C. pourtalesi, holotype. G, C. distolos, holotype. H, Candidella gigantea, EX1606-6. I, Macroprimnoa ornata, holotype. J, Narella virgosa, holotype. K-L, N. aurantiaca, holotype. M, N. merga, holotype. N, N. horrida, EX1703-2-3. O, N. fordi, holotype. P, N. calamus, holotype. Q, N. virgosa, paratype, EX1504-L4-9-4. R, N. macrocalyx, EX1606-7. S, N. hawaiiensis, EX1504-9-2. T, Paracalyotrophora hawaiiensis, EX1703-2-1. U, P. echinata, EX1703-10-1. V, P. spiralis, holotype. W, Plumarella circumoperculum, EX1603-2-3. X, Thouarella hilgendorfi, EX1605-L1-17.

FIGURE 2. Callogorgia cracentis, holotype: A, stereo view of a polyp whorl. B–D, stereo views of abaxial, lateral and adaxial side of a polyp. E, body wall scales. F, opercular scales. G, coenenchymal scales. Scale bars in mm.