Thesea nivea Deichmann, 1936

Devictor, Susan T. & Morton, Steve L., 2010, Identification guide to the shallow water (0 - 200 m) octocorals of the South Atlantic Bight 2599, Zootaxa 2599 (1), pp. 1-62 : 43-44

Thesea nivea Deichmann, 1936

( Figure 39 )

Thesea nivea Deichmann, 1936:122 ; Plate 7 fig. 7; Plate 11 figs. 16–18.— Cairns et al. 2002:34.

Material examined. USNM 16836, 27 m, off Cape Fear , North Carolina, October 20 1885 . SERTC S2692 , 24.5 m, off Charleston , South Carolina, 20 March 1976 . SERTC S 2693, 29 m, off Hilton Head , South Carolina, June 4, 2004 . SERTC S 2695, 24 m, off Charleston , South Carolina, August 15, 2006 . SERTC S2696 , 24.1 m, off Charleston , South Carolina, August 15, 2006 . SERTC S 2703, 49 m, off Charleston , South Carolina, July 28, 1981 .

Remarks. This species grows more or less in one plane with slender branches that bend upward, occasionally at a right angle. In life, the colony is reddish violet, with dark red to purple polyps with white centers. Under magnification, the tissue of the polyps and coenenchyme is violet, but colorless sclerites are visible on the surface of the branches and at the base and neck of the expanded polyps. When preserved in alcohol the coenenchyme color is gray, creamy white or light brown. The dome-like calyces form an eightlobed star and are scattered around the branches. The branches are 3–4 mm in diameter and tips on some branches are slightly inflated. This species may be fouled with epibionts such as ascidians and barnacles, and colonies often have multiple galls that are occupied by invertebrates such as the spionid worm Polydora sp. and the crab Pilumnus floridanus (DeVictor, pers. obs.).

Sclerites are colorless and consist of large, warty, acute spindles and small double heads, and some spiny or warty curved rods. The polyp armature consists of curved or arched rods in a collaret and points arrangement. The spindles range from 0.3–0.5 mm; double heads, 0.1– 0.2 mm; and the curved rods, 0.3–0.6 mm.

Some colonies have a bushy appearance that departs from the typical flat, planar growth form, with slightly shorter and more crooked branchlets. These colonies also have thicker branches up to 5 mm in diameter, but the sclerite assemblage remains consistent with the more slender colonies.

In addition to the identified specimens examined, one Thesea specimen was collected and examined but remains unidentified. The specimen is approximately 63 mm in height with a lateral branching growth form. All branches appear to be 1–2 mm in width and gently curve upward from the main stem. The calyces are moderately protruding and domelike with retracted polyps. The most obvious character about this specimen is the sclerites, which range from 0.1 mm to over 1 mm in length. The largest of the sclerites are bluntly elongate to globular with two distinct sides. The outer side displays undulating, irregular humps which are quite smooth with the exception of the clusters of low, fine spines at the apex of each hump. The opposing side, which tends to face the axis, displays a very coarse texture and crowded, fine tubercles. The smaller sclerites tend to be concentrated toward the calyces and are warty, elongate spindles with acute tips. All sclerites are coral red with the exception of the yellow anthocodial rods and calicular spindles. Although several of the western Atlantic Thesea species in Deichmann (1936) are described as having large, ridged or undulating outer sclerites, identification of the specimen to species level was not possible.

Atlantic distribution: North Carolina to South Carolina, 24–49 m ; Dry Tortugas, 71 m ; St. Lucia, 371 m ;

Guadalupe, 358 m (type) ( Deichmann, 1936; NMNH collections; SERTC collection) .

Figures

FIGURE 39. Thesea nivea: A, sclerites (USNM 16836): a) curved rod from anthocodia; b–e) coenenchymal sclerites; b) double head; c–f) spindles (scale bar = 0.05 mm); B, colony with expanded polyps (live specimen, S2695; height approximately 15 cm); C, calyx arrangement on stem (live specimen, S2695); D, partly contracted (left) and expanded (right) polyps (live specimen, S2695).