Calyptrophora distolos, 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 : 16

Calyptrophora distolos , n. sp.

Figs. 1G , 8 A–H

Etymology. Named distolos (Greek for “in pairs”), in allusion to the paired nature of the polyps.

Types and Type Locality. Holotype: colony fragment and SEM stubs 2398-2399, USNM 1424085 . Paratypes: EX 1702-11-02, 15.73˚S, 167.26˚W ( American Samoa), 2994 m , branch fragments, USNM 1453657 . Type Locality: EX 1605-L 1-4-03, 11.41˚N, 144.78˚E ( Enigma Seamount , south of Guam), 3737 m .

Material Examined. Types.

Description. The holotype is flagelliform (unbranched), about 21 cm in length, although only the distal half was collected ( Fig. 1G ). The paratype is extremely sparsely branched. When alive the polyps project perpendicular to the branch and when dead they fold in a 90˚ angle (i.e., buccal scales parallel to the branch), typical of the genus, but because the entire colony was not collected, the direction that the polyps face was indeterminate. The polyps are arranged in widely spaced (about 2 per cm) pairs ( Fig. 1G ), not arranged in whorls, approximately 40 pairs occurring on the holotype. Individual polyps are 2.9–3.2 mm in horizontal length, the opercular scales adding significantly to this length.

The basal scale ( Fig. 8E ) is 1.4–1.5 mm in height, usually including a short (about 0.2 mm tall) inconspicuous blunt lobe on either side of the straight articular ridge. The basal scale usually bears a dorsolateral ridge as well as several more ridges on its lateral face ( Fig. 8A ), but sometimes these ridges are inconspicuous or lacking altogether. The buccal scale is slightly longer (1.4–1.6 mm in length) and usually bears a similar longitudinal ridging ( Figs. 8 C–D); its distal edge is finely serrate. No infrabasal scales were noted.

The operculum is quite long ( Figs. 8 A–B), in fact longer than either of the body wall scales. The opercular scales ( Fig. 8H ) are all rather similar in shape (elongate and triangular with a high L:W ratio). The abaxial operculars are up to 1.8 mm in length with an L:W of 2.5–3.0, and sometimes bear a low longitudinal ridge on their outer surface. The lateral operculars are 1.0– 1.35 mm in length, with an L:W of 2.5–3.1, and often terminate in two tips. The small adaxial operculars are 0.9–1.0 mm in length with an L:W of 2.8–3.3. In addition to the typical eight opercular scales, there are sometimes additional smaller accessory scales at the base of some of the opercular scales ( Fig. 8F ), these being circular to elliptical, 0.45–0.50 mm in diameter, and highly concave.

The coenenchymal scales ( Fig. 8H ) are quite long and narrow, up to 2 mm in length, and with an L:W ranging from 4.4–9.0. Each coenenchymal scale bears a single, tall (up to 0.3 mm, thus a sail scale) ridge, which meanders down the center of the scale.

Comparisons. Calyptrophora distolos is unique among the 27 species in the genus in having paired polyps (not arranged in whorls of three or more) and in having auxiliary opercular scales. It is one of four species having a predominantly unbranched mode of growth, the other three being: P. juliae Bayer, 1952 ; C. clinata Cairns, 2007a ; and C. persephone Cairns, 2016a (Clarion-Clipperton Fracture Zone, 4123–4244 m). It is most similar to C. persephone in morphology, geography and depth range, but that species differs in having whorls of three or four smaller polyps, basals with two prominent pointed distal spines, lobate buccal scales, and in lacking accessory opercular scales. Because the orientation of the polyps is indeterminate, the species cannot at this time be assigned to the wyvillei or japonica species complex.

Distribution. American Samoa and Guam, 2994–3737 m.

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 8. Calyptrophora distolos, holotype: A–B, lateral stereo views of paired polyps. C, stereo view of ridged buccal scale. D, stereo view of inner face of a buccal scale. E, two views of a basal scale. F, an accessory buccal scale. G, opercular scales. H, coenenchymal scales. Scale bars in mm.