Radicipes spiralis

Radicipes spiralis (Nutting, 1908)

Fig. 7

Lepidogorgia spiralis Nutting, 1908: 588, P. 45, fig. 5.

Radicipes spiralis, Kükenthal 1919: 549.— Grigg & Bayer, 1976: 172, tab. 2 (liSted).— ParriSh & Baco, 2007: 188, Appendix 4.1. (liSted).— Watling et al., 2011: 66, tab. 2.2 (liSted).

Types and Type-locality. Syntypes: USNM 25355 (one colony and four fragments) and USNM 22558 (three small fragments), Alb- 4103, 21°02'20"N, 156°46'20"W, 241–258 m (Hawaii).

New record. Okeanos Station D 2-EX1504-L2-16, 25°38'37.32"N, 168°50'49.2"W, 1462 m, photo only—no specimen, thus record not confirmed (Fig. 1 A,D).? Alb -3989, 22°06’55”N, 159°16’51”W, 704–914 (USNM 1438878).

Description. Brittle colonies, slightly fleXible in mid and terminal portions, coiled in clockwise ascendent manner from base to apeX. AXis diameter from 0.2 mm to 1.3 mm. Presence of non-horny nodes at proXimal portion of larger colony. Polyps 1.2 to 3.2 mm long, uniserially and longitudinally distributed, two to four polyps per centimeter (usually three), with 0.3 mm to 2.0 mm distance between polyps. In their distal portion, polyps juXtaposed with almost no space between. Polyps completely naked or covered with sparse body wall rods that lack order, 0.15–0.25 mm long and 0.01–0.03 mm wide (Fig. 7). Tentacular and pinnular flattened rods, when present, 0.08–0.15 mm long and 0.01–0.03 mm wide. Coenenchymal sclerites rare or completely absent. Some areas of aXis with tiny isolated, flattened rods embedded in coenenchyme. Presence of many micro-silicoclastic inclusions in tentacles of some polyps.

Comparisons. There are no species in the genus similar to R. spiralis. The virtual absence of sclerites in the body wall and the delicate nature of the colonies resemble in some ways the Atlantic species Radicipes challengeri (Wright & Studer, 1889) and Radicipes kopelatos Cordeiro, Castro & Pérez, 2015. However, R. spiralis is the only species with no conspicuous sclerites.

Remarks. The syntype consists of brittle basal fragments and one entire colony without a holdfast collected from a single station (Albatross 4103). Although the original description (Nutting, 1908) of this species mentions no sclerites, with some effort it is possible to find some rods in the body wall.

An additional specimen (USNM 1438878), named Radicipes sp., resembles the general morphology of R. spiralis, with a virtually naked body wall (Fig. 8 A), however its “saddle bag” region is densely filled by flattened rods and scales, usually with a low, irregular longitudinal ridge (Fig. 8 B). The tract between two full-sized polyps might have a narrow line of the same sclerites from saddle bag region (Fig. 8 A). The mentioned specimen was collected in Hawaii by the USFWS Albatross (sta. 3989), several kilometers from the type locality of R. spiralis. Due to the lack of colonies with intermediate morphological features between the latter and Radicipes sp., we consider it inadequate to adjust the diagnosis of R. spiralis to include this specimen. Descriptions made by C. C. Nutting are often challenged and must be considered with caution.

Since its original description, no new collections of R. spiralis have been made. Thus, all subsequent publications about this species are simply compilations of Versluys’ (1902) statements.

Today the area where this species occurs belongs to the Papahānaumokuākea Marine National Monument, the world’s largest marine protected area. Recent NOAA deep-sea surveys visually documented several chrysogorgiid communities in Hawaii (please visit http://oceaneXplorer.noaa.gov/okeanos), including colonies of Radicipes (Figs. 1 A,D), which could be R. spiralis or Radicipes sp. (as discussed above). If the identification is R. spiralis, the deepest bathymetric record of that species would be eXtended from 257 to 1462 m. Only future collection efforts will better characterize this species and test this hypothesis.

Distribution. Known only in the type locality, 241–? 1462 m depth.