Ceeceenus retractus, Ima, 2013

Ima, Yukimitsu, 2013, Two new paralcyoniid octocorals from Japan (Anthozoa: Alcyonacea), Zootaxa 3652 (4), pp. 424-436 : 426-428

Ceeceenus retractus n. sp. (Japanese name: Kawaritosaka)

( Figs. 1A–D , 2–5 )

Holotype. NSMT-Co 1552, One specimen consisting of two colonies connected to each other attached to an old, dead scleractinian coral, collected off Gongen , Kii-oshima Island, Kushimoto, Wakayama Pref., Japan, 33°28.45'N, 135°48.17'E, 20 m deep, by Mr. Itsuro Miyawaki on 20 Dec., 1989.

Etymology. From the Latin “ retracto ”, retract, in reference to the polyparium completely retractile within the pedicel.

Description. Colony form: Two colonies connected to each other by membranous stolon. Larger one, 40 mm high in somewhat expanded condition, consisting of upper soft polyparium covered with many large polyps, and lower stiff, cylindrical pedicel covered with very thin leathery film ( Fig. 1A ). Polyparium 20 mm long and 16 x 18 mm wide, including polyps. Pedicel 20–25 mm long and 11 mm wide distally, and 15 x 18 mm wide proximally. Pedicel passing into low, dome-shaped stem, this being 4 mm high and dividing into six main branches; stem and branches together comprising the trunk. Main branches dividing into two to four thick secondary branches, these about 7.5 mm long and 1.6 mm wide proximally. All branches with large primary polyp at apex and two to seven pairs of somewhat smaller secondary polyps loosely arranged in bilateral rows ( Fig. 1B ); single polyps rarely arising from ventral sides of branches. Several other small polyps surround the peripheral margin of the proximal part of trunk ( Fig. 1D ). Some longitudinally arranged large spindles visible through leathery film of pedicel. Cortex of trunk very thin, and inner layer of both trunk and pedicel with a few very thin canal walls. Smaller colony, 15 mm high in almost fully expanding condition, arises from narrow membranous stolon of large colony. Polyparium, 11 mm long and 3–4 mm wide including polyps, with a total of 27 polyps 11 of which surrounding peripheral margin of proximal part of trunk, and remaining 16 distributed all over the polyparium in six groups of two to four.

Polyps: Monomorphic. Almost all polyps fully expanded although a few almost fully contracted into terminal branches; tentacles also retractile. In expanded condition, primary polyps 2.1 mm long excluding tentacles and 1.0 mm wide at swollen part of anthocodia ( Fig. 2A ). Tentacles about 1.5 mm long, with bilateral rows of 9–12 pinnules up to 0.2 mm long.

Spiculation of polyps very poorly developed, about one third of polyps, chiefly those in upper part of the polyparium, entirely devoid of sclerites. A few flat, oval platelets present only in tentacles of polyps with sclerites (figs. 2B, 3A), as well as long, flat platelets with somewhat undulating edges (fig. 3C) arranged longitudinally on aboral side of rachis. Flat, oval platelets consisting of pectinate branching crystals flared toward sclerite surface (fig. 3B), but long, flat platelets consisting of non-branching rod-like crystals arranged in parallel oblong rows toward both ends (fig. 3D). Sclerites of anthocodiae Paralcyonium -like and of two kinds: almost smooth, flat, oval platelets sometimes with median waist (figs. 2C, 4A), up to 0.07 x 0.03 mm in size, and elongated rods (fig. 2C) up to 0.18 x 0.02 mm, some tending to be triangular ( Fig. 4C ). These sclerites, few in number and up to ten, are arranged longitudinally to somewhat chevron-like below each tentacle base (fig. 2A). Ultrastructure of anthocodial platelets and rods respectively the same as in above-mentioned two kinds of tentacle sclerites (figs. 4B, D).

Other sclerites: Almost entire trunk devoid of sclerites with exception of a few elongated rods at lowest margin of trunk cortex (figs.1D, 5A), similar to those of anthocodia. Cortex of pedicel with long spindles ( Fig. 5C ) up to 3.0 x 0.35 mm in size, with many minute, rounded, complex warts all over (fig. 5E). These spindles often curved, closely arranged in regular longitudinal rows, and show crystals very similar to those of trunk rods (fig.5, B, D), i.e., similar ultrastructurally to long anthocodial platelets. Sclerites absent in inner layer of trunk and pedicel.

Color: Polyparium dark yellowish-brown, including polyps. Pedicel brown, paler than polyparium. Sclerites of polyps opaque white to grayish white, but those of pedicel translucent white.

Differentiation. This species has the weakest development of anthocodial armature in all species of this genus. It quite differs from the other species in the spiculation of the trunk: this species has a few elongated rods (not flattened) limited to the lowest margin, while previously known species have flattened platelets widely distributed all over the trunk.

FIFURE 3. Sclerites of Ceeceenus retractus sp. nov. (NSMT-Co 1552) under SEM: A, flat oval platelets from tentacles, with ultrastructure, B; C, flat platelet from tentacle, with ultrastructure, D. Scale bars = 0.05 mm (A, C), 0.005 mm (B, D).

Figures

FIGURE 1. Ceeceenus retractus sp. nov., A–D, and Nanalcyon sagamiense sp. nov., E–K: A, holotype of Ceeceenus retractus (NSMT-Co 1552) in alcohol, showing a young colony (in red circle) arise from narrow membranous stolon of large polyp; B, detail of holotype, showing the arrangement of polyps on a branch; C, detail of holotype, showing the arrangement of sclerites in the anthocodia and tentacle; D, detail of holotype, showing the arrangement of polyps and sclerites in the proximal part of the trunk; E, holotype of live Nanalcyon sagamiense, showing secondary polyps (in red circle) arising near the proximal part of a primary polyp; F, holotype in alcohol (NSMT-CoS 119); G, detail of a polyp of holotype (NSMT-CoS 119), showing the arrangement of sclerites in the anthocodial parts and proximal parts of tentacles; H, paratype (NSMT-CoS 120) in alcohol; I, three paratypes (NSMT-CoS 121-1 to 3) in alcohol, showing a young colony (in red circle); J, paratype (NSMT-CoS 122) in alcohol; K, detail of paratype (NSMT-CoS 122), showing a secondary polyp (in red circle) near the proximal part of a primary polyp (in yellow circle). Scale bars = 10 mm (A), 5 mm (D–F, H–J), 1 mm (B, C, G, K).

FIGURE 2. Ceeceenus retractus sp. nov. (NSMT-Co 1552): A, polyps showing several patterns of sclerite arrangement in the anthocodial part and tentacles; B, sclerites of the tentacles; C, sclerites of the anthocodiae. Scale bars = 1 mm (A), 0.1 mm (B, C).

FIGURE 4. Sclerites of Ceeceenus retractus sp. nov. (NSMT-Co 1552) under SEM: A, flat oval platelets from anthocodiae, with ultrastructure, B; C, elongated and triangular rods from anthocodiae, with ultrastructure, D. Scale bars = 0.05 mm (A, C), 0.005 mm (B, D).

FIGURE 5. Sclerites of Ceeceenus retractus sp. nov. (NSMT-Co 1552) under SEM: A, almost half of elongated rod from lowest margin of trunk cortex, with ultrastructure, B; C, long spindles from pedicel cortex, with ultrastructure, D, and detail of warts, E. Scale bars = 1 mm (C), 0.05 mm (A, E), 0.005 mm (B, D).