Acanella scarletae, France, 2017

France, Scott C., 2017, A taxonomic review of the genus Acanella (Cnidaria: Octocorallia: Isididae) in the North Atlantic Ocean, with descriptions of two new species, Zootaxa 4323 (3), pp. 359-390 : 381-382

Acanella scarletae sp. nov.

Figures 15 and 16

Material examined: Holotype: Collected via trawl aboard NOAA Ship Ronald H. Brown, Norfolk Canyon, Atlantic Ocean, 36.8993 -74.4586, 1670̄ 1694 m depth, 7 May 2013, Station RB-13-030, Specimen ID # TR03010. Deposited in the National Museum of Natural History ; USNM 1416576 . GenBank accession # KX 270225 , KX 270214 . Paratype: Collected via trawl aboard NOAA Ship Ronald H. Brown, Norfolk Canyon, Atlantic Ocean, 36.8993 -74.4586, 1670̄ 1694 m depth, 7 May 2013, Station RB-13-030, Specimen ID # TR03033. Deposited in the National Museum of Natural History ; USNM 1416577 . Other material: Three specimens collected via trawl aboard NOAA Ship Ronald H. Brown, Norfolk Canyon, 36.8993 -74.4586, 1670- 1694 m depth, 7 May 2013, Station RB-13-030, Specimen ID #s TR03047, TR03044, TR03049.

Diagnosis: Acanella with 3̄ 4 mm tall polyps. Polyps densely packed with needle-like sclerites running longitudinally up body wall. Body sclerites do not extend to tentacles, leaving distal portion of polyp exposed. Colony has a lobed, root-like holdfast. Primary branching is commonly in whorls of four and secondary branching is in whorls of two.

Description: Colonies bush-like ( Figure 15 ) with primary branching at the node, commonly in whorls of four, and secondary branching dichotomous. Colonies range from 15̄ 22 cm in length and have a lobed root-like holdfast. Internodes cream to white in color, 0.5̄ 1.5 cm in length, and longitudinally ribbed; on main axis internodes at base of colony shorter than those at distal tips. Anastomosis of branches was not observed. Nodes orange to dark brown. Axis covered by thin, pale-orange to red coenenchyme when alive. Coenenchymal sclerites are 75–212 µm (n=100; mean=132 µm ± 0.02 µm) in length, needle-like and covered with small spines.

Polyps when alive are red to brown in color ( Figure 16 ) and brown to dark brown when preserved in ethanol. Polyps tall (3̄ 4 mm; n=95; mean= 3.82 mm ± 0.01 mm) and thin (0.25–0.5 mm; n=95; mean= 0.37 mm ± 0.04 mm) with a distally tubular shape, where tentacles are contracted over oral disk. Polyps arise 45°̄90° from axis and alternately arranged on the branch, and also present on terminal ends of branchlets.

Sclerites of polyp body long and needle-like ( Figure 16 ) and range in length from 648 µm̄ 2.2 mm (n=100; mean=782 µm ± 0.02 µm); they are densely packed and placed longitudinally up the proximal part of the polyp body, stopping just short of the tentacles to leave the distal part of the polyp exposed but for the tentacular sclerites. Intertentacular sclerites not observed. Tentacular sclerites consist of small rods with small spines ranging from 10̄200 µm (n=100; mean=67 µm ± 0.01 µm).

DNA sequences derived from mtMusS -5’ (GenBank accession # KX 270225 ) and 18S ( KX 270214 ) differ from other North Atlantic Acanella Haplotypes by at least 0.20% (4 nucleotide substitutions across 1955 sites).

Etymology: Named in honor of Scarlet Nola Saucier, who was born during the synthesis of this manuscript, and in allusion to the orange to red coenenchyme and polyps.

Remarks: Colonies with Haplotype G ( Figure 16 ) have been found only along the rim of Norfolk Canyon off the coast of the eastern United States. They were collected via trawl along with several A. arbuscula (Haplotype A) colonies. Acanella scarletae differs morphologically from other Acanella species by their lack of intertentacular sclerites. We suspect they live in soft fine mud based on their root-like holdfast and the other organisms collected in the same trawl. Anemones, polychaetes, and brittle stars were found within the branches of the colonies. Distribution: Norfolk Canyon off the coast of eastern United States, 1670̄ 1694 m depth.

Figures

FIGURE 15. Acanella scarletae images of live colony taken prior to preservation. A) Whole colony (TR 03049). B) Whole colony (TR 03010). C) Root-like holdfast (TR 03010). D) Single polyp (TR 03010). E) Longitudinally ribbed skeleton covered with thin red coenenchyme (TR 03049).

FIGURE 16. SEM images of Acanella scarletae (Haplotype G, TR 3010). A) Tentacle sclerites. B) Coenenchyme sclerites. C) Polyp body sclerites.