Parastenella pomponiae, 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 : 19-20

Parastenella pomponiae sp. n. Figures 3c, 12

Material examined.

Types. Holotype: colony and SEM stubs 2303-2305, JSL-I-1922, USNM 1410289. Paratypes: JSL-I-1922, 1 colony, USNM 1410290; JSL-I-3912, 1 branch, USNM 1410291; Nautilus NA064-125-01-A, 1 colony, CDRS.

Type locality.

0°23.68'N, 90°26.341'W (off northeastern Marchena), 475-578 m deep.

Distribution.

Galápagos: off Marchena, Santiago, and Isabela, 446-578 m deep.

Description.

The colony is uniplanar, the largest colony (the holotype, Figure 3c) measuring 44 cm in height, and having a basal branch diameter of 6.5 mm. Branching is lateral and somewhat irregular; the longest terminal branchlets are less than 2 cm in length. The axis is golden bronze and the polyps and coenenchyme are white. The polyps are 2.8-3.1 mm in height and stand perpendicular to the branches, arranged in pairs (Figures 12a, b), whorls of three, and often as singles; about five polyp whorls (or pairs) occur per cm branch length.

The body wall scales (Figure 12d) are arranged in eight rows, each row with six scales, the lateral edges of all scales overlapping with those of adjacent rows. The eight marginal scales form an asymmetrical rosette: six of the marginals consist of elongate scales (up to 0.9 mm in length and 0.4 mm wide) with broad shallow flutes, whereas the two adaxial marginals are much wider but shorter (up to 0.6 in length and 0.9 mm in width) and are flat (without a flute) or bear only a very shallow flute (Figure 11c). A nematocyst pad (Figure 12c) is present on the distal inner face of each fluted marginal. The body wall scales proximal to the marginals (Figure 12b) are never fluted and are elliptical in shape, about 0.60-0.85 mm in width; they have a concave granular outer surface, their lateral and distal edges turned upward. The opercular scales (Figures 12b, c, f) are fairly uniform in length (0.7-0.8 mm) but variable in width. The abaxial and adaxial operculars are symmetrical, the abaxial having two lateral lobes (H:W about 1.2), the adaxials lacking lobes (H:W about 2); the lateral operculars are asymmetrical, each having only one lobe on the adaxial lateral side. All opercular scales have a deeply longitudinally creased outer surface that corresponds to a sharply keeled inner surface. The coenenchymal scales (Figure 12g) are irregular in shape, although usually longer than broad, and up to 1.1 mm in length. Their outer surface is concave, like that of the body wall scales, and bears low granules and occasionally short ridges.

Comparisons.

Parastenella pomponiae is morphologically most similar to P. ramosa (Studer, 1894), known from the eastern Pacific from the Gulf of Alaska to Panama, but differs from that species in having eight (not five) rows of body wall scales, concave (not flat) coenenchymal scales, wider fluted marginal scales, and in lacking submarginal fluted body wall scales.

Etymology.

Named in honor of Shirley Pomponi (formerly of HBOI), who participated in the JSL-I expedition of 1986, during which this species was collected.