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Description

Xenogorgia sciurus spec. nov. (figs. 8-10; pl. 7A-B)

 

Material examined. — Off Lamberts Bay, South Africa, 32°03.3'S 16°02' E, 680-800 m, September 25, 1971; foraminiferal sandy ooze; 5 nearly com­plete colonies and 3 fragments.

 

Description. — Unbranched or weakly branched main stem arises from a small expansion of the trunk, marginally calcified, attached to solid objects (pl. 7A, B). Numerous short branches arise on all sides of the main stem, singly or rarely in opposite pairs, often in groups close together but not in whorls, separated by as much as 5 mm of main axis. The branches produce short lateral branchlets which may bear still smaller branchlets, arising at ap­proximately right angles from any side, without any apparent regularity (fig. 8).

 

The polyps are scattered on all sides of the branches and branchlets, not in whorls, sometimes close together, more often separated by 1 mm or more; they are tall, cylindrical, curved toward the tips of the branches, about 1.75-2.00 mm tall and 0.75 mm in diameter (fig. 9). They are covered with a layer of thin, oval scales up to about 0.26 mm long and o.o8 mm broad, usu­ally with a slight median constriction (fig. 10). Their edges are finely dentate, and the surface has a very fine granular texture that is scarcely visible even at high magnification with the light microscope; near the margins there are a few weak, radially disposed striations, especially near the ends of the scales. Twinned forms occur in small numbers as usual.

 

On the body of the polyps, the scales are arranged mostly longitudinally, and extend into the bases of the tentacles. No sclerites are present in the distal part of the tentacles nor in the pinnules. Toward the base of the polyps, the scales assume an irregularly oblique orientation and merge into those of the coenenchyme. The scales of the coenenchyme are like those of the polyps in size and shape, and for the most part are longitudinally disposed. On the main stem and branches, the coenenchyme is densely filled with scales, but toward the tips of the final branchlets they may be sparse, not sufficiently close together to form a complete layer.

 

The axis is smooth, translucent, amber colored in the main stem, becoming paler distally, where it is only faintly yellowish in the terminal parts. The axial material is weakly calcified, but there is no detectable metallic sheen or iridescence. Even after decalcification in hydrochloric acid, the axial sub­stance is brightly birefringent when viewed with crossed Nicols or crossed polarizing filters. A narrow structural core is visible in the terminal parts of the axis, but it is neither hollow nor cross-chambered.

 

Holotype. USNM 54424.

 

Paratypes. — RMNH Coel. Coll. 11056; British Museum (Nat. Hist.), London; University of Cape Town, Rondebosch, South Africa.

 

Etymology. — From Greek, σχίουρος, squirrel, in allusion to the brush­like colonial form.

 

Comparisons. — Although the colonies of Xenogorgia sciurus are tall, cylindrical and branched all around, they bear a closer superficial resem­blance to some primnoids such as Thouarella than to Chrysogorgia because the branches arise from the main stems in an irregular manner rather than in a regular spiral sequence. The subdivision of the secondary branches is simi­larly irregular, not stiffly dichotomous as in Chrysogorgia. The polyps are not regularly distributed on the internodes of the branches but are irregularly scattered on all sides, sometimes closely placed, sometimes more distant.

 

The species of Chrysogorgia having the closest gross similarity to X. sciurus is C. agassizii (Verrill) from deep water off Georges Bank in the western North Atlantic. However, in that species the colonies are more delicate, the branches arise in a regular 2/5 spiral to the right and are subdivided in a dichotomous manner, and the polyps contain spindles as well as flat scales.”

 

(Bayer & Muzik, 1976)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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