Digitogorgia brochi, Zapata-Guardiola, Rebeca & López-González, Pablo J., 2010

Zapata-Guardiola, Rebeca & López-González, Pablo J., 2010, Redescription of Thouarella brucei Thomson and Ritchie, 1906 (Cnidaria: Octocorallia: Primnoidae) and description of two new Antarctic primnoid species, Zootaxa 2616, pp. 48-68 : 57-63

publication ID	https://doi.org/ 10.5281/zenodo.197916
DOI	https://doi.org/10.5281/zenodo.6494513
persistent identifier	https://treatment.plazi.org/id/03A387A7-BC24-FFD1-FF65-5E69FBA88E50
treatment provided by	Plazi
scientific name	Digitogorgia brochi
status	sp. nov.

Treatment

Digitogorgia brochi View in CoL sp. nov.

Figures 8–12 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12

Thouarella (Euthouarella) brucei, Broch, 1965: 27 View in CoL –28, pl.4, fig. 11–13.

Material examined. Holotype: NHM B969, “Brategg” Expedition, “Tromso-Tral 2”, 54º43’S, 60º14’W, Burdwood Bank, SubAntarctic, 111.5 m depth, 0 9 March 1948.

Description of the holotype. Fragment of a colony ( Figure 8 View FIGURE 8 A), probably a main side branch, of 16 cm in total height and about 4.5 cm in width, with simple branchlets ( Figure 8 View FIGURE 8 B) up to 3cm in length arising all around the branch forming a bottlebrush shape. Axis brown. Main side branch basal axis diameter 2.3 mm. Main stem basal axis diameter 2.9 mm.

Polyps ( Figure 9 View FIGURE 9 ) on branchlets in whorls of 3, 4–5 whorls per cm, directed upwards. Polyps relatively elongate, slightly clavate, about 1.6–2.2 mm in height and 0.6–0.8 mm in diameter. Polyp body with eight complete longitudinal rows of scales, those in adaxial rows slightly smaller. About 6–7 scales in each adaxial row ( Figure 10 View FIGURE 10 A) and 12–13 scales on each abaxial row ( Figures 9 View FIGURE 9 B, 10C). Adaxial rows slightly disorganized basally, but without any reduction in number of rows ( Figure 9 View FIGURE 9 ).

Accessory operculars ( Figure 11 View FIGURE 11 A) eight in number, 0.25–0.44 mm in height and 0.08–0.14 mm in width, more or less triangular and pointed. Proximal inner surface tuberculate, covering about 20–50% of their length, distal inner surface smooth. Outer surface quite granular with several warts on the most proximal portion. Basal margin with digitate processes.

Opercular scales ( Figure 11 View FIGURE 11 B) eight in number, 0.30–0.45 mm in height and 0.16–0.24 mm in width, more or less triangular or oval shaped. Proximal inner surface tuberculate, covering around half of their length, distal surface smooth without keel or thorn. Proximal outer surface granular with several warts on the most proximal part, distal portion quite smooth. Basal margin often with long digitate processes, free margin entire laterally but digitate apically.

Marginal scales ( Figure 11 View FIGURE 11 C) eight in number, 0.33–0.43 mm in height and 0.23–0.46 mm in width, broad, oval shaped. Proximal inner surface tuberculate, covering up to 80% of the length, distal inner surface smooth, without keel or thorn. Outer surface granular, most proximal part with several warts. Basal margin with long digitate processes, free margin entire laterally but digitate apically.

Body scales ( Figure 12 View FIGURE 12 A) more-or-less oval to fan shape, 0.17–0.37 mm in height and 0.26–0.45 mm in width. Inner surface almost completely tuberculate, outer surface granular with several warts on the most proximal part. Free margin as in marginal scales.

Coenenchymal sclerites ( Figure 12 View FIGURE 12 B) in two layers: outer layer with round, oval-shaped sclerites, 0.11– 0.24 mm in maximum length, inner surface tuberculate, outer surface granular or smooth, free margin entire or scalloped; inner layer with irregular tuberculate sclerites, 0.06–0.08 mm in maximum length.

Geographic and bathymetric distribution. At present, Digitogorgia brochi sp. nov., has only been reported from Burdwood Bank, SubAntarctic ( Figure 1 View FIGURE 1 ), at a depth of 111.5 m.

Etymology. This species is dedicated to Hjalmar Broch, in recognition of his contribution to our knowledge of octocorals.

Remarks. The present material was initially identified by Broch (1965) as Thouarella brucei . This author had already found differences in the shape of the opercular and marginal scales between his specimen and the original description of Thomson’s and Ritchie’s species. Nevertheless, he attributed those differences to a possible contamination in Thomson’s and Ritchie’s sample, and placed his specimen in T. brucei . But it seems that Broch never saw any type specimens of T. brucei , as he only mentions the original description and drawings.

The present study of a single specimen identified by Broch as Thouarella brucei from Burdwood Bank, and deposited at the NHM, shows a set of characters that is clearly different from that of the type material of T. brucei . This set of characters is: the polyps are arranged in whorls of three, the number of scales on each abaxial row is about 12 and distinct opercular and marginal scales are without a keel, while in T. brucei the polyps are singly placed in spirals around branchlets, the number of scales on each abaxial row is about 5 and opercular and marginal scales present a strong keel on their inner surface.

Broch’s specimen, described above, has a bottlebrush colony shape, the scales are not reduced in the adaxial rows, there are eight marginal scales, without a keel, folding over the operculars and there are distinct, distal, pointed processes in opercular, marginal and body scales. Due to these characters it should be included in the genus Digitogorgia , as Digitogorgia brochi sp. nov.

Till now the genus Digitogorgia only included one species, Digitogorgia kuekenthali . Digitogorgia kuekenthali and D. brochi differ in the number of scales in the abaxial row (8-9 scales in the former and 12-13 in the later), in the shape of the accessory opercular scales (more pointed in the former), the operculars (more elongate and multi-digitate in the former), and the marginals (with more developed and pointed processes in the latter). In general, the proximal, long processes in both polyp and coenenchymal sclerites and the presence of tubercles on the proximal outer surface are more pronounced in D. brochi .