Chrysogorgia laevorsa, Cairns, Stephen D., 2018

Cairns, Stephen D., 2018, Deep-Water Octocorals (Cnidaria, Anthozoa) from the Galapagos and Cocos Islands. Part 1: Suborder Calcaxonia, ZooKeys 729, pp. 1-46 : 23-26

Chrysogorgia laevorsa sp. n. Figures 3f, 15a, c–f

Material examined.

Types. Holotype: colony and SEM stubs 2320-2322, JSL-I-1929, USNM 1409029. Paratypes: Alb-2818, 13 denuded stems, USNM 1409031; JSL-I-1938, 1 colony, USNM 1160584.

Type locality.

0°14'40"N, 91°36'32"W (off Roca Redonda, Galápagos), 806 m depth.

Distribution.

Galápagos: Roca Redonda, west of Santa Cruz, 717-806 m deep; Cocos Islands, 614-785 m deep.

Description.

The colony is bottlebrush in shape (Figure 3f), the holotype 11 cm tall and 6 cm in maximum diameter, having a basal branch diameter of 2.3 mm. Branching is sympodial, the branching formula being consistently 2/5L. The orthostiche interval varies from 10 to 23 mm, the shorter intervals near the base of the colony, the higher intervals near the top. The length of the internodes on the branchlets is 3-5 mm, up to five or six nodes occurring on each branchlet; each internode supports two polyps. The polyps are 1.5-1.9 mm in length and cylindrical in shape, with a slightly swollen base (Figure 15a). The axis is metallic gold in color tinged with a greenish hue.

The upper body wall sclerites (Figure 15c), those associated with the cylindrical part of the polyp, consist of slightly flattened rotund rods that are 0.19-0.24 mm in length and having a L:W of 3.5-4.7. They are straight, longitudinally oriented, and uniformly covered with very small granules. Distal to the body wall are the tentacles, which may compose as much as half of the polyp length. They are also composed of slightly flattened rods (Figure 15c), but these rods are longer and more slender, 0.25-0.32 mm in length, with a L:W of 5.1-9.0. Like the upper body wall rods, they are straight and similarly granulated. The pinnular scales (Figure 15f) are smaller (0.073-0.16 mm in length) curved platelets, having a L:W of 3.4-4.5. The swollen base of the polyp is covered with flattened rods similar in shape to those of the tentacles (Figure 15d), as well as waisted scales 0.17-0.21 mm in length and having a L:W of 2.4-3.4. Otherwise, the coenenchyme seems to be devoid of sclerites.

Comparisons.

Having rods in its body wall and tentacles places C. laevorsa in Chrysogorgia Group A, the largest of the four groups of Chrysogorgia , having 38 species. Chrysogorgia laevorsa is the only species in this group to have a 2/5L branching formula, whereas 14 species in this group have a 2/5 R formula (Figure 15b). The 2/5L formula is found in only four species of Chrysogorgia , all belonging to Group C.

Etymology.

Named laevorsa (from the Latin laevorsus, meaning "towards the left") in allusion to the direction of the branching formula (2/5L).