Dendronephthya rigida ( Studer, 1888 ), 1904

Imahara, Yukimitsu, 2013, Redescriptions of Five Species of Japanese Dendronephthya (Octocorallia: Alcyonacea) Based on Type Material Collected by Döderlein in 1879 - 81, Species Diversity 18, pp. 111-134 : 126-132

Dendronephthya rigida ( Studer, 1888)

[New Japanese name: Iga-togetosaka] ( Figs 18– 22, 23E, 25F–K)

Spongodes rigida Studer, 1888: 71 ; Wright and Studer 1889: 223 [reproduced from Studer (1888)].

Dendronephthya rigida: Kükenthal 1905: 620–623 ; Henderson in Thomson and Stimpson 1909: 47.

Not Dendronephthya splendens: Nutting 1912: 14 , 15.

Not Roxasia rigida: Tixier-Durivault and Prevorsek 1960: 259–263 , text-figs 228–230.

? Spongodes splendens Kükenthal 1895: 434–435 ; 1896: 104–106, pl. 6, figs 12, 13; Thomson and Henderson 1905: 283–284, pl. 1, fig. 2; Hickson 1903: 485–486.

? Dendronephthya rigida: Henderson in Thomson and Stimpson 1909: 47.

Material examined. NMBE-308, one colony, missing part of its sterile stalk and probably one main branch; label #1, “ Nr / 308, Klasse Anthozoa, Art. Dendronephthya rigida Stud. Loc. Cc α 2; Alkohol”; label #2, “ Dendronephthya rigida (Stud.) Kükth. Det. 1904 ”; label #3, “ Dendronephthya rigida Stud., Cc α 2, Alkohol” . A fragment of ZMB-6602, approximately half a colony; label #1, “ Dendronephthya rigida (Stud.) (Bern) Döderlein S, Studer det. Japan. Kükenthal rw. 1904, type (*)”; label #2, “6602” . A fragment of ZSM s.n., a complete small colony; label, “ Dendronephthya rigida (Stud.) , China, leg. Bougainville, samml. Kölliker”. A fragment of ZMUC, s.n., an almost complete small colony; label, “ Roxasia rigida (Studer) , Loc. Okinose Sagami Bugt. , Hård bund svaber, 113 m, Datum: 11-6-1914, Legit: Th. Mortensen, Det. Tixier-Durivault, Prevorsek” . A fragment of USNM-30113, a complete small colony; label #1, “ Dendronephthya splendens Kük, Off Goto Ids. , Eastern Sea Str. Albatross , Aug. 9, 1906. C. C. Nutting. Id. Acc. 51381, 4893, 106 Fms”; label #2, “St. 4893, Cat. No. 30113, ALBATROSS”; label #3, “Lent to Utinomi, Feb. 1958 ” .

Description of NMBE-308. Colony form. The colony is extremely contracted, about 36 mm in total height, with a quite rigid polyparium and a short, thick, leathery sterile stalk representing about one-fourth of the total height ( Fig. 25F). The polyparium is slightly laterally flattened with a regularly oblong oval outline, 25–27 mm high and 25× 37 mm across, and formed by several inseparable roundish bunches of polyp masses, all externally covered with many polyps. The sterile stalk passes into the short, stiff stem, which after about 9 mm divides in all directions into several short, thick main branches of 3–5 mm in length. These main branches are markedly clavate and ramify into short, diverging secondary branches at their distal ends, which then give off many short twigs. The undermost several branches are reflexed and foliaceous, giving off many densely set twigs on their upper surface and periphery, thus concealing almost the entire upper half of the sterile stalk. All polyps are arranged in groups of 3–5 at the distal ends of twigs, including those on the undermost foliaceous branches. The sterile stalk is 4–5 mm long and 25.2× 37.2 mm wide in its uppermost part, but it is missing almost the lateral two-thirds of its lower part. The broad holdfast is 4–10mm long and 15 mm wide.

Polyps. The anthocodiae are up to 0.7 mm high and wide and make right or obtuse angles with their short (up to 0.8 mm) stalks ( Fig. 18A, B). The anthocodial armature consists of eight double rows of points and intermediate sclerites, but no crown or supplementary sclerites. As for the lateral armature, below the tentacle base are three to five pairs of point spindles arranged en chevron. The uppermost spindle, which is strongly bent in its lower part ( Fig. 18D, 23E), is extremely large, up to 1.00 mm long, and projects about 0.60 mm above the polyp head. The projecting part has several small teeth ( Fig. 18F) whereas the remaining part has many small but rather complex warts. The lower spindles are more or less bent and up to 0.32 mm long. There are one to two small, thick spindles flanking the points ( Fig. 18E). The supporting bundle is very strong, consisting of two to three large, elongated spindles up to 2.90 mm long, which are sometimes branched apically. One or two of these spindles project beyond the anthocodia for a distance of up to 1.60 mm, and the projecting part bears quite a few simple warts ( Fig. 18G).

The anthocodial grade and formula are as follows: IV=1P+(2−4)p+0Cr+very strong S.B.+(1/2−1)M.

The tentacles are filled with two types of minute sclerites, including a few somewhat flattened rods up to 0.10 mm long and numerous flat sclerites, up to 0.80 mm long, with scalloped edges ( Fig. 18C).

Other sclerites. The surface layer of the branches and stem has two types of spindles ( Fig. 19A), including large ones up to 5.30 mm long that are arranged almost longitudinally and covered with complex small warts ( Fig. 19B, C), as well as small, slender spindles or needles about 0.52 mm long, which are sparsely provided with spines or simple warts. The surface layer of the upper part of the sterile stalk has thick spindles that are sometimes branched and curved and up to 1.65 mm long ( Fig. 20A), with large, complex warts ( Fig. 20B, C). The surface layer of the lower part of the sterile stalk and holdfast has the same sort of thick spindles, up to 2.42 mm long ( Fig. 21A), as well as numerous club-like and knee-shaped spindles that are up to 0.55 mm long ( Fig. 21C) and, like the above thick spindles, are covered with large, complex warts. In the branch interior are a few small, flattened rods up to 0.12 mm long ( Fig. 19D) and flattened radiates up to 0.20 mm long ( Fig. 19E), the latter usually with long rays. In the interior of the stem and the upper part of the sterile stalk, the canal walls contain many thick, curved spindles up to 3.20 mm long ( Fig. 20D, E) that are covered with many complex warts, as well as flattened radiates ( Fig. 20F) like those of the branch interior. In addition, there are flattened radiates and flattened rods, both up to 0.13 mm long with scalloped edges ( Fig. 20G). In the canal walls of the lower part of the stalk and holdfast are thick, branched spindles up to 0.70 mm long covered with many complex warts ( Fig. 21D), as well as many flattened radiates up to 0.17 mm long ( Fig. 21E) and a few small rods up to 0.15 mm long with a few large, simple warts ( Fig. 21F).

Color. In alcohol, the deep red sclerites lend their color to the supporting bundles, twigs, secondary branches, and upper parts of the main branches. The anthocodiae and tentacles are yellowish-white, and their sclerites are colorless. As a result, the polyparium looks red to purplish-red with pale yellow polyps. The sterile stalk, stem, and the bulk of the main branches are white to dirty white, and the holdfast is partly pink.

Remarks. Studer’s (1888: 71) original description was clearly based on just one colony, i.e., “The colony is a loosely ramified, shortly pediculate, head-like mass of rigid consistence .... Height of the colony 33 millim., diameter 35 millim.”, and only a single colony was found in the Naturhistorisches Museum der Burgergemeinde Bern. However, Kükenthal’s (1905: 620) redescription mentioned two

E,F

specimens: “Diese Form, welche von Studer als neue Art aufgestellt und kurz, besonders inbezug auf ihren Aufbau, beschrieben worden ist, lag mir in den beiden Originalexemplaren zur Nachuntersuchung vor” . The second specimen seems to be the one in the Zoologisches Museum of Berlin (ZMB-6602) . Consisting of almost half of a colony, it is 28 mm in total height and 21× 24 mm in diameter ( Fig. 25H), thus slightly smaller than the specimen in Bern . Because both specimens have a sterile stalk, they must be distinct colonies and not separated pieces of one original colony. Because both colonies agree in such features as the anthocodial formula ( Fig. 22A), both appear to belong to Dendronephthya rigida . The label shows that the Berlin specimen was collected by Döderlein from Sagami Bay in Japan, as was NMBE-308 . However, since the colony size of NMBE-380 is almost the same as that reported in Studer’s (1888) original description, NMBE- 380 in Bern is considered to be the holotype of this species .

The growth form of the holotype is characteristic of the spinosa -group of Umbellatae; Kükenthal (1905: 611), however, considered D. rigida to be a member of the rigida - group of Divaricatae, despite the fact that “Die Polypen sitzen in Bündeln von 3–5 an den Endzweigen, so dass sie alle an der Oberfläche stehen, die dadurch sehr dicht wird” ( Kükenthal 1905: 621). It is clear that this species belongs to Umbellatae, because numerous polyps group to form umbels, and all polyps are disposed on the surface of the colony ( Fig. 25G).

Kükenthal (1905: 621–625) considered D. splendens Kükenthal, 1895 to be a junior synonym of D. rigida . In fact, the large point spindles of D. splendens shown in his figure ( Kükenthal 1896: pl. 6, fig. 13) closely resemble those of this species in shape. Unfortunately, the anthocodial formula of D. splendens is not clear, but the figure and description of Kükenthal (1896) suggest VI=1P+(3−4)Cr+medium S.B.+2 M, which is different from that of D. rigida . The anthocodial formula of a Chinese specimen of D. rigida (ZSM) deposited in the Zoologische Staatssammlung, München ( Fig. 25I), which is part of the material that Kükenthal (1905) discussed in relation to this supposed synonymy, is almost the same as that of the holotype of D. rigida , except for the lack of intermediate sclerites, viz., VI=1P+(3−4)p+0Cr+medium S.B.+0 M, but the sharpness and size of the point spindles are quite different ( Fig. 22B). The characteristic large, bent point spindles were not found in any polyp of the Chinese specimen, which therefore seems to belong to another species. Nutting (1912) reported D. splendens from western Japan, but his specimen ( USNM 30113 ) is quite different from this nominal species in colony appearance ( Fig. 25K), size and shape of polyps, anthocodial formula ( Fig. 22C), etc. Tixier-Durivault and Prevorsek (1960) described another specimen ( Fig. 25J) from Japan under the name of D. rigida (ZMUC) , which was placed by them in the genus Roxasia , but the polyp sclerites are very long and slender ( Fig. 22A), different from those of the holotype and the Berlin specimen from Japan.

Geological distribution. Japan ( Studer 1888; Kükenthal 1905).