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Description

Paragorgia coralloides n. sp.

 

(Figure 1)

 

Material Examined: Ceram sea, off Gomoemoe Island [= Pulau Gomumu] south of Obi Major: 01° 54' 00" S, 127° 36' 00" E, 602 m (329 fath.), USFC Str. Albatross sta. D-5634, 3 Decem­ber 1909. Part of a larger branch originally preserved but subsequently lost, USNM 50891 (holotype).

 

Diagnosis: Slender Paragorgia with terminal branches only 1 mm in diameter excluding calices; cortex with 8-rayed capstans only, up to 0.06 mm in length, many of the smaller individuals asymmetrically developed as "Opera-glass" forms by hypertrophy of the tubercles of one side; tentacles with irregularly spinose fusiforrn rods 0.1 mm in length. Color, red.

 

Description: The specimen is a branch 9 cm in height, originally part of a large colony, branched in one plane in a lateral manner. The polyps are grouped in clusters along, and at the ends of, short, slender branchlets (Fig. 1 a). The diameter of the terminal branchlets, exclusive of the polyps, is about 1 mm. The diameter of the main branch at its stout­est point is 3.5 mm. The calices of the autozooids are short cylinders, sometimes slightly tapered, sometimes hemispherical, about 1 mm in diameter and the same height; their margins are 8-lobed and the closed apertures form stellate figures. The siphonozooids are visible as small, hemispherical verrucae with simple aperture, less than 0.5 mm in diameter, encir­cling the base of the autozooids. The surface of the coenenchyme is minutely granular ow­ing to the outermost layer of small sclerites. The color of the colony in alcohol is bright red. All but the terminal branchlets are overgrown with a dark brown zoanthid whose walls are filled with accumulated sand grains and other debris, mostly foraminiferans and the sclerites of its host. The original label bears the following field note: "Main stem and large polyps [i.e., the zoanthid] pale dull ochre; hard tips coral red. Beautiful!! F. M. C[hamberlain]."

 

Canal system : The specimen is not in satisfactory condition for histological study, showing evidence of having been partially dried at one time, but free-hand sections permit the following observations.

 

The general plan is in agreement with that of Paragorgia arborea as described by Verseveldt (1940). The gastric cavity of the terminal polyps extends, greatly narrowed, as a gastrodermal canal at the center of the medulla (Fig. 1 b), but the mesenteries terminate within the gastric cavity proper and cannot be traced into the canal. There is no appreci­able zone of mesogloea devoid of sclerites surrounding the longitudinal canals and medul­lar solenia. The calicular walls are divided into an inner and an outer layer by a sole­nial network. The outer layer extends throughout the colony as a thin outer cortex separat­ed by the solenial network from the deeper layer of cortical coenenchyme; the inner layer, immediately surrounding the gastric cavities, also surrounds the coelenteric canals aris­ing from the terminal polyps and follows them down the center of the branches as a reddish medulla. Near the tips of the branchlets, this is the only medullar tissue but, in the lower parts of the branchlets, coenenchyme containing colorless sclerites appears just inside the solenial network and quickly increases in thickness basad until a conspicuous colorless layer intervenes between the red cortex and the red zone surrounding the coelen­teric canals. The central zone is the primary medulla, since it is the only medulla present in the branch tips. Although the colorless intermediate layer makes up the greater part of the medulla in the larger branches (Fig. 1 c), it arises secondarily in an interstitial manner and is here called secondary, or interstitial, medulla. In spite of the fact that the inner layer of the calicular walls is continuous with the primary medulla and is iden­tically spiculated, it is cortical in position and must be so termed. The lateral autozooids are in communication with the superficial solenial system but do not elongate into coelenteric canals. The siphonozooids occur only around the bases of the autozooid calices, and their gastric cavities lie mostly below the solenial network, with which they connect, and therefore within the tissue that surrounds the inner parts of the autozooids and the coelenteric canals.

 

Sclerites: The sclerites of the anthocodiae are arranged in eight interseptal tracts which continue as narrow bands along the backs of the tentacles but do not extend into the pinnules. These sclerites are chiefly small rods at most 0.1 mm in length, irregular­ly sculptured with obtusely conical processes which are occasionally subdivided and show two or three terminal projections (Fig. 1 d). In the interseptal tracts, a number of radiates like those of the cortex, and spindles like those of the inner layer of the cali­cular walls, may occur along with the rods.

 

The thin surface layer of cortex lying outside the solenial network is characterized by the presence of 8-rayed capstans 0.04-0.06 mm in length (Fig. 1 e); a very large propor­tion of these are modified into "opera-glass" sclerites by the enlargement of three lateral and the two terminal radii, just as in some species of Corallium.

 

Immediately surrounding the central coelenteric canals is a zone of red sclerites con­taining blunt rods with obtuse, conical projections (Fig. 1 f); this inner medullar zone follows the coelenteric canals upward to the gastric cavities of the autozooids, which it surrounds, thus forming the inner layer of the calicular walls, separated from the outer layer by the solenial network. The spindles of the inner calicular layer are similar to those of the central medulla, commonly measuring 0.15 mm in length (Fig. 1 f). The pale secondary medulla is filled with colorless rods having prominent processes often branched (Fig. 1 g).

 

Distribution: Known from the type locality only.

 

Associates: An encrusting zoanthid covers the main branches.

 

Comparisons: The terminal branches of Paragorgia coralloides are unusually slender for the genus. In gross appearance, it bears an overall resemblance to Paragorgia splendens Thomson & Henderson, which also is of remarkably slender build, although no measurement of the terminal branches was given (Thomson & Henderson, 1906: 20). Sclerites of P. splen­dens were not illustrated originally, but a fragment of the type specimen kindly provided by the late Dr. W. J. Rees of the British Museum (Nat. Hist.)(now the Natural History Museum), London, makes it possible to present drawings for direct comparison.

 

Specimens identified as Paragorgia splendens Thomson & Henderson were obtained from the Sulu Islands by the Siboga Expedition and reported by Nutting (1911: 16, pl. 3, figs. 4, 4a) without detailed description. Stiasny (1937: 78, text fig. AA; pl. 5, fig. 37) agreed with Nutting's identification and provided additional descriptive information together with drawings of the sclerites. As Stiasny's style of illustration does not give an ade­quate impression of the sclerites, new drawings have been made directly from his slide preparation, permitting comparison with both P. splendens and P. corailoides, n. sp. This reveals that the Siboga specimen is not P. splendens after all. but a distinct species similar to but distinct from P. coralloides.

 

Remarks: Not only do the 8-rayed capstans of Paragorgia coralioides resemble those of Corallium, but the modified forms have also been transformed into the "opera-glass' type of sclerite just as in that genus. So closely do they resemble the sclerites of some species of CoraIlium that a slide preparation of sclerites unassociated with the entire specimen could justifiable be assigned to that genus.”

 

(Bayer, 1993)

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© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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