Callogorgia galapagensis, 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 : 5-6

Callogorgia galapagensis sp. n. Figures 2a, 5

Material examined.

Types. Holotype: JSL-I-1933, large colony and SEM stubs 2295-2297, 2308-2311, USNM 1161744. Paratypes: JSL-I-1915, partial colony, USNM 1161750; JSL-I-1930, partial colony, USNM 1161746; JSL-I-1934, 1 branch, USNM 1161745; JSL-I-1942, 1 branch, USNM 1161748.

Type locality.

JSL-I-1933: 0°17.072'S, 91°04.208'W (off northwest tip of Fernandina, Galápagos), 663-788 m deep.

Distribution.

Galápagos: Tagus Cove between Isabela and Fernandina, north of Española, 308-633 m deep; Cocos Island, 628-656 m deep.

Description.

Colonies are uniplanar and taller than broad, the holotype (Figure 2a) measuring 49 cm in height and 18 cm in width, with a broken basal branch diameter of 5.9 mm. Another colony fragment (JSL-I-1915) has a broken basal branch diameter of 8.9 mm, suggesting a colony height of close to 1 m. Branching is alternate pinnate (sympodial and geniculate), the terminal branchlets up to 13 cm in length. The polyps are arranged in whorls of five or six (Figure 5a); four to five whorls occur per cm branch length; the whorl diameter ranges from 2.5-3.1 mm. The polyps are 1.5-2.0 mm in length, slightly curved, and clavate (Figure 5 b–d). The color of the colony and polyps is white.

There are eight longitudinal rows of body wall scales, decreasing in number from ab- to adaxial polyp side, the body wall sclerite formula being: 10 –12:10–12:4– 5:2. The distal five or six pairs of abaxial scales (Figure 5f) are narrow (0.31-0.35 mm wide), each bearing four to seven prominent (up to 0.08 mm in height) longitudinal ridges that terminate as projections on the distal edge of the scale. More proximal abaxial body wall scales are broader (up to 0.48 mm) and flat, lacking radial ridges. The outer lateral body wall scales (Figure 5h) are sculpted similarly, the basal pairs being even wider than those on the abaxial face. The ridges of these distal scales are so tall and closely spaced that it is difficult to determine the lateral margins of the scales. The inner lateral body wall scales (Figure 5g) are even broader (up to 0.56 mm in width) and have a finely serrate distal edge. The two pairs of adaxial scales (Figure 5i) are small, only 0.22-0.25 mm in width, below which the polyp is naked (Figure 5c). At the junction of the lowest body wall scales and the branch coenenchymal sclerites is a pair of crescentric infrabasal scales (Figure 5j) that forms a transition, each about 0.6 mm wide and 0.25 mm in height. The distalmost body wall scales in each row fold over the operculum as a short circumoperculum (Figure 5c). The opercular scales (Figure 5e) range in length from 0.50-0.65 mm, decreasing in length from ab- to adaxial polyp side, forming a prominent operculum; their L:W ranges from 1.7-2.25. Their outer surface is covered with tall serrate ridges and their edges are finely serrate. Their inner face is tuberculate, the distal third bearing a multiply serrated keel. The coenenchymal sclerites (Figure 5k) are elongate (L:W = 5-6), thick sclerites, arranged parallel to the branch axis, measuring up to 0.8 mm in length and 0.13-0.14 m in width. Their outer surface is coarsely granular.

Comparisons.

Callogorgia galapagensis belongs to a group of eight species that have highly cristate abaxial body wall scales, the other seven species listed in Cairns (2016), the Pacific component indicated in the key above by asterisks. The prominent ridges on these body wall scales often make it difficult to see the boundaries between adjacent rows of body wall scales. Callogorgia galapagensis can be distinguished from the other seven species by its sclerite formula, being the only species to have 10-12 abaxial and outer lateral body wall scales. This character is not used in the key above, and thus C. galapagensis keys closest to C. sertosa and C. tessellata , but can be distinguished by its unique sclerite formula.

Etymology.

Named for the type locality of the species.