Hemicorallium cf. abyssale ( Bayer, 1956 )

Nonaka, Masanori & Hayashibara, Takeshi, 2021, A Report on Coralliidae (Cnidaria: Octocorallia) Specimens Collected from the Emperor Seamounts with Descriptions of Three New Species, Species Diversity 26, pp. 297-342 : 308-310

publication ID	https://doi.org/ 10.12782/specdiv.26.297
publication LSID	lsid:zoobank.org:pub:1E87A39C-02DE-4710-BFEF-E5C2FBCD54FB
persistent identifier	https://treatment.plazi.org/id/CC5187C7-FFC5-FF8E-FC0F-FEB3FD97FA65
treatment provided by	Felipe
scientific name	Hemicorallium cf. abyssale ( Bayer, 1956 )
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Treatment

Hemicorallium cf. abyssale ( Bayer, 1956) View in CoL ( Figs 14–20 View Fig View Fig View Fig View Fig View Fig View Fig ; Tables 2, 4)

Corallium abyssale Bayer, 1956: 76–77 View in CoL , figs 4, 5a, 7a–d; Nonaka and Muzik 2010: 100–101, figs 30–32; Tu et al. 2012: 5 (in key), fig. 10; Nonaka and Muzik 2012: 79 (in key), table 1.

Hemicorallium abyssale: Tu et al. 2015b: 181 View in CoL (in list), table 1; Tu et al. 2016: 1035 (in key), table II; Nonaka and Muzik 2016: 16 (in list).

and color to the present specimens collected from the Emperor seamounts. However, Tu et al. (2012) only provided photos of a whole colony and sclerites, without any detailed descriptions (e.g., arrangement of autozooids, diameter of autozooids, size of sclerites etc.) of the specimen. The sizes of the sclerites can be inferred from the scale for the image with the length of the largest sclerite (8-radiate) being about 0.07 mm. The 8-radiate lengths of the specimens in our study average 0.08–0.09 mm (Table 3), suggesting that their specimen, USNM 1010758, is probably a different species from ours.

Bayer (1956) provided a detailed description and drawings of P. secundum . According to his description, some of the characters of this species are “the autozooids verrucae are evenly distributed and not clustered in groups except at the tips of the twigs where there may be two or three”, “wellformed 8-radiates are present but not common”, “the rind is salmon pink”, “the axis is pale pink, often almost white”. The diameter of the autozooids was approximately 1.0 mm, which could be inferred from the scales of his precise drawing ( Bayer 1956: figs 5-d, 6-d). Because these characters of P. secundum do not fit our specimens, such as autozooid clusters ( Figs 3B View Fig , 4B), 8-radiate sclerites (Table 3) and coenenchyme and axis color ( Figs 3–7 View Fig ), they cannot be identified as P. secundum .

Since P. pusillum was described as “n. sp.” in Kishinouye (1904), we have reported that it was described as a new spe-

Material examined. NSMT-Co 1728, C-H Seamount, 1,121 m, 4 June 2010; NSMT-Co 1729, C-H Seamount, 861– 942 m, 26 July 2012.

Diagnosis. Colony is zig-zag, with branching in one plane in an asymmetrically dichotomous manner. Angles of branching are acute and right. Contracted autozooids making cylindrical mounds, distributed biserially on the branches, very scarce, about 2–5 mm apart, about 1.5 mm in diameter. Siphonozooids are visible, forming small warts concentrated around the autozooids. Coenenchyme is thin, about 0.1 mm thick, pale pink in color. Axis is stout, surface with inconspicuous longitudinal grooves, reddish pink in color. Tentacles contain long (about 0.1 mm long) rods, coenenchyme contains mainly 6-radiates, 7-radiates and 8-radiates. Sclerites have rough surfaces. Inhabits depths of about 1000m.

Description of specimen NSMT-Co 1728. Colony form. The specimen is in two parts, one the base of the colony and the other a small branch ( Fig. 14A View Fig ). The main stem is zig-zag, with branching in one plane in an asymmetrically dichotomous manner ( Fig. 14A View Fig ). Angles of branching are acute and right. The base of the colony is about 8 mm in diameter, and the sharp branchlet is about 2 mm in diameter. The cross section of the main branch is rounded.

Polyps. The contracted autozooids form cylindrical mounds in the coenenchyme ( Fig. 14B View Fig ). These mounds are distributed biserially on the branches, very scarcely, about 3–5 mm apart ( Fig. 14B View Fig ). They are 1.55± 0.19 mm in diameter and 1.76± 0.43 mm in height ( Table 2). Siphonozooids are visible, forming small warts concentrated around the autozooids ( Fig. 14B View Fig ), 0.03± 0.01 mm in diameter ( Table 2).

Axis. The surface of the axis is inconspicuously longitudinally grooved, the grooves visible through the thin coenenchyme ( Fig. 14B View Fig ), at about 0.33 mm in intervals ( Table 2). There are no rounded pits on the surface of the axis at the position of each autozooid.

Coenenchyme. There are small and inconspicuous warts 0.29± 0.06 mm in diameter ( Table 2) distributed on both sides ( Fig. 14B View Fig ). There is a brittle star tangled up in the branches.

Color. The dry coenenchyme is pale pink. The axis is red ( Fig. 14 View Fig ).

Sclerites. The tentacles contain mainly rods (69%; 0.106± 0.019 mm long, 0.027± 0.006 mm wide), multi-radiates (15%; 0.079± 0.016 mm long, 0.036± 0.006 mm wide) and a few asymmetric 6-radiates, 7-radiates and asymmetric 8-radiates ( Figs 15 View Fig , 16 View Fig ; Table 4).

The autozooid mounds contain mainly asymmetric 6-radiates (37%; 0.063± 0.008 mm long, 0.039± 0.004 mm wide), 7-radiates (23%; 0.067± 0.007 mm long, 0.039± 0.003 mm wide), asymmetric 8-radiates (19%; 0.070± 0.005 mm long, 0.040± 0.003 mm width). A few symmetric 6-radiate, 8-radiates and multi-radiates are present ( Figs 15 View Fig , 16 View Fig ; Table 4).

The branch tips contain mainly asymmetric 6-radiates (35%; 0.057± 0.004 mm long, 0.035± 0.002 mm wide), 7-radiates (18%; 0.063± 0.008 mm long, 0.038± 0.003 mm wide) and asymmetric 8-radiates (26%; 0.066± 0.008 mm long, 0.039± 0.003 mm wide), and a few double-clubs, symmetric 8-radiates and multi-radiates ( Figs 15 View Fig , 16 View Fig ; Table 4).

The coenenchyme on the base of the colony contains mainly asymmetric 8-radiates (48%; 0.058± 0.008 mm long, 0.034± 0.003 mm wide), with a few 6-radiates, double-clubs, 7-radiates, symmetric 8-radiates and multi-radiates ( Figs 15 View Fig , 16 View Fig ; Table 4).

Description of specimen NSMT-Co 1729. Colony form. The specimen consists of the base of the colony and four small branches without distal tips ( Fig. 17A View Fig ). The main stem zig-zag and branching is asymmetrically dichotomous ( Fig. 17A View Fig ). Angles of branching are right or acute. The base of the colony is about 15 mm diameter, and the distal parts about 2–3 mm in diameter. The cross section of the main branch is rounded.

Polyps. The autozooids are not retracted, instead contracting to make cylindrical mounds with eight grooves on the tops ( Fig. 17B View Fig ). These mounds are distributed biserially on the branches, very scarce, about 2–5 mm apart ( Fig. 17B View Fig ). They are 1.66± 0.19 mm in diameter and 1.25± 0.32 mm in height ( Table 2). Siphonozooids are visible, forming small warts tending to concentrate around the autozooids ( Fig. 17B View Fig ), 0.04± 0.01 mm in diameter.

Axis. The surface of the axis is inconspicuously longitudinally grooved, at about 0.28 mm in intervals ( Table 2). There are no rounded pits on the surface of the axis at the position of each autozooid.

Coenenchyme. The coenenchyme is 0.10± 0.03 mm thick ( Fig. 18 View Fig ; Table 2) and the longitudinal axial grooves are invisible through it ( Fig. 17B View Fig ). There are small and inconspicuous warts 0.51± 0.28 mm in diameter distributed on both sides ( Fig. 17B View Fig ). There are no commensal organisms.

Color. The dry coenenchyme is pale pink. The axis is reddish pink ( Figs 17 View Fig , 18 View Fig ).

Sclerites. The tentacles contain mainly rods (46%; 0.100± 0.016 mm long, 0.027± 0.004 mm wide), asymmetric 6-radiates (18%; 0.053± 0.007 mm long, 0.035± 0.001 mm wide) and a few symmetric 6-radiates, 7-radiates, 8-radiates and multi-radiates ( Figs 19 View Fig , 20; Table 4).

The autozooid mounds contain mainly asymmetric 6-radiates (33%; 0.060± 0.008 mm long, 0.039± 0.004 mm wide), 7-radiates (21%; 0.064± 0.007 mm long, 0.040± 0.002 mm wide), multi-radiates (24%; 0.074± 0.009 mm long, 0.038± 0.003 mm wide). A few symmetric 6-radiates and 8-radiates are present ( Figs 19 View Fig , 20; Table 4).

The branch tips contain mainly asymmetric 6-radiates (68%; 0.053± 0.004 mm long, 0.036± 0.003 mm wide), and some symmetric 6-radiates, 7-radiates and multi-radiates ( Figs 19 View Fig , 20; Table 4).

The coenenchyme on the base of the colony contains mainly symmetric 6-radiates (32%; 0.045± 0.004 mm long, 0.032± 0.002 mm width), 7-radiates (31%; 0.048± 0.004 mm long, 0.032± 0.002 mm wide) with some asymmetric 6-radiates, 8-radiates and a few multi-radiates ( Figs 19 View Fig , 20; Table 4).

Remarks. Hemicorallium abyssale was described in 1956 based on a specimen collected from about 2000 m deep in Hawaii in 1902 ( Bayer 1956). Tu et al. (2012) showed SEM images of sclerites from the holotype. According to these descriptions, the colony was slender, its branching alternate, producing a main stem with a zig-zag shape, with autozooids less dense than in other species, having 8-radiates and double-clubs with a smooth surface.

The present specimens (NSMT-Co 1728 and 1729) fit that of the original description, such as branching pattern autozooid arrangement, and the presence of long, blunt spindle sclerites in the tentacles, and relatively deep sampling depth (around 1000 m deep). However, the autozooids are smaller (1.5–1.7 mm in diameter, 1.2–1.8 mm in height) than those described for the holotype (about 2 mm in height). Further- more, there are no double-clubs with a smooth surface ( Figs 15 View Fig , 19 View Fig ) from the autozooids, and the coenenchymal sclerites of NSMT-Co 1729 (6-radiates dominant) do not fit that of the holotype (8-radiates dominant). Therefore, these specimens cannot be conclusively identified as H. abyssale , and are recorded herein as H. cf. abyssale .