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USNM 81287.53012

Geographic Distribution

Antarctic Convergence illustration Antarctic convergence

Bathymetric Specimen Dispersal

9 individual specimens found for Aglaoprimnoa stefanii.

Aglaoprimnoa stefanii Bayer, 1996  Species


Original Description
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Original Description
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Aglaoprimnoa stefanii, new species
Figures 5a–c; 6-14

Material Examined.—Off South Georgia: 54°29'S, 39°22'W, 659-686 m, USNS Eltanin sta. 1536, 8 Feb 1966; one colony lacking holdfast, USNM 81287 (SEM 1385-1388, 1403).

Burdwood Bank: 54°41'S, 56°59'W to 54°41'S, 57°03'W, 70 m, USNS ELTANIN sta. 1594, 14 Mar 1966; six more or less complete colonies lacking holdfasts, and three undivided terminal branches, USNM 81288 (SEM 1192, 1193, 1379, 1402, 1415, 1416).

Burdwood Bank: 54°39'S, 57°09'W to 54°39'S, 57°12'W, 124 m, USNS ELTANIN sta. 1596, 14 Mar 1966; 2 colonies, holotype USNM 81289 (SEM 1174, 1175, 1179). paratype USNM 87626.

Diagnosis.—As for the genus.

Description.—Colonies (Fig. 5a–c) are up to 1 m tall, branched three to eight times in an open, lateral manner practically in one plane, with stout whiplike terminal branches up to 60 cm long, mostly about 8 mm in diameter but as much as 10 mm and as little as 5 mm; the first bifurcation occurs from 1.5 to 7 cm above the broken proximal end of the main trunk, commonly 3-5 cm.

The polyps are arranged in closely placed whorls of about 10, bent inward toward the axis and predominantly directed upward, but locally those of one or a few whorls may face downward, and isolated individuals here and there may be oriented in a direction opposite to that of its immediate neighbors; not uncommonly the whorls are placed obliquely on the branches, and in some cases they merge so the polyps form spirals for considerable distances. Conspicuous swell­ings interpreted as brood-chambers are present here and there between the whorls; these are hollow and composed of about four chambers some of which may contain hollow, two-layered oval or spheroidal bodies much distorted by preser­vation, which appear to be planulae. From 9 to 11 whorls occur in 4 cm of branch length, and new whorls of young polyps may be produced between the fully developed whorls. The polyps of the main trunks appear to be in progressive states of degeneration, the whorls become irregular, and in some places the polyps have been completely resorbed into the coenenchyme.

The polyps (Figs. 6, 7) resemble the cones of a coniferous tree owing to their close covering of broad, fan-shaped scales. In immature polyps the arrangement of the scales retains indications of the original longitudinal rows (Fig. 10), but in fully developed individuals virtually all traces of longitudinal arrangement has been lost; because of their shape, the scales cannot form regular longitudinal and transverse rows, but are obliquely arranged in such a way that longitudinal align­ment becomes irregular and indistinct by insertion of new scales between the original ones (Fig. 7). Consequently, it often is impossible to discern longitudinal rows, and the number appears to vary considerably. The adaxial side of the polyps is shorter than the abaxial but is completely covered by scales.

Most of the body scales (Figs. 8b, 14b) are broadly fan-shaped, externally concave, smooth except for several narrow, sharp crests that radiate upward from the proximal margin, which is closely covered by complex tubercles; the inner surface is convex and covered by complex tubercles except for a wide, smooth distal margin ornamented with several radial crests. The radial crests of the inner margin interlock with those of the outer surface of the scales in the transverse row above, apparently serving to prevent lateral displacement during expansion and contraction. Toward the oral end of the polyp the scales become taller than wide (Figs. 8a, 14a), roughly triangular in outline, some symmetrical and some very asymmetrical according to their location, with one or more strong longitu­dinal crests on the inner (i.e., adoral) side; the complex tubercles are confined to the proximal part of the scale on both surfaces, so the free projecting margin is very wide, 3-flanged, and tapered to a blunt apex. These scales converge toward the distal end of the polyp, closing the apical aperture but not clearly differentiated as a distinct operculum of 8 scales with a regular circle of marginal or circu­mopercular scales surrounding them (Figs. 10, bottom; 13).

Near the base of the polyps the scales decrease in size and assume a chalice or bowl shape, concave externally and convex on the inner face, which bears a central cluster of tubercles and often with a ridge or crest dividing the external concavity in two (Figs. 8c, 14c). These sclerites merge with those of the coenen­chyme, which is composed of a superficial layer of small sclerites, some more or less "ascus" shaped (Fig. 8d), reminiscent of the "ascus-like or chalice-like scales" described by Thomson and Rennet (1931: 20, pl. 11, figs. 5, 6) as characteristic of their new genus Ascolepis (=Fannyella Gray, 1873. See Bayer 1990). Others with ridges or crests (Figs. 8e, 14d) overlie a thick layer of small tuber­culate spheroids (Figs. 8f, 14e), which appear to be derived from a basic capstan-like form.

The polyps have very short tentacles with indications of 8 or 9 pairs of pinnules. In contraction, the tentacles are inverted rather than folded inward over the mouth.

Variation.—The armature of the polyps shows some variation among the colonies. The polyps of USNM 81287 from South Georgia (Figs. 10, 11) have body scales (Fig. 14) larger than those of USNM 81289 from Burdwood Bank (Fig. 8), in some polyps very irregularly arranged (Fig. 12). In the polyps of USNM 81288 (Fig. 9), also from Burdwood Bank, the body scales become larger toward the oral end of the polyps, resembling the specimen from South Georgia, while the proximal part of the polyps corresponds with 81289; even within a single whorl, a polyp with irregularly arranged scales may occur adjacent to individuals having regularly arranged scales (Fig. 9, top).

Etymology.—This species is named for Jeffrey Stefani, former contract investi­gator and volunteer collaborator in the Department of Invertebrate Zoology, Na­tional Museum of Natural History.

Remarks.—Superficially, the colonies resemble those of Armadillogorgia cyathel­la Bayer in size and general appearance, but the shape and arrangement of the body scales of the polyps is entirely different.”

(Bayer, 1996)


Type Status Catalog No. Date Collected Location Coordinates Depth (m) Vessel
Holotype 81289 3/14/1966 Scotia Sea 54.6° S, 57.1° W 124 Eltanin R/V
Paratype 87626 3/14/1966 Scotia Sea 54.6° S, 57.1° W 124 Eltanin R/V
  81287 Images Available 2/8/1966 Scotia Sea 54.5° S, 39.4° W 659 – 686 Eltanin R/V
  81288 3/14/1966 Scotia Sea 54.7° S, 57° W 70 Eltanin R/V

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