Calcigorgia gracilis, Matsumoto & Van Ofwegen & Bayer, 2019

Matsumoto, Asako K., Van Ofwegen, Leen P. & Bayer, Frederick M., 2019, A revision of the genus Calcigorgia (Cnidaria, Octocorallia, Acanthogorgiidae) with the description of three new species, Zootaxa 4571 (1), pp. 1-27 : 6-10

Calcigorgia gracilis sp. n.

Figures 1b , 6 a–c, 7–8

http://zoobank.org/ 0433555C-8C5E-40A8-8B5F-3C9306A86EC5

Acanthogorgiidae sp. Takahashi et al. 2016: 32 (Nojima Submarine Canyon, Japan).

Material examined. Holotype USNM 60280, Shio Misaki Light N75°E, 9.6 mi, Japan, 33°23'30"N, 135°34'E, 1188 m, U.S. F. C. str . Albatross sta. 4971, 27 August 1906, SEM 2537, 2538 of Bayer; other material: JAMSTEC No.1120034415, Nojima canyon branch, So-O Trough, Sagami Trough, off Boso, Japan, 34°46'42.60"N, 139°50'18.66"E, 1497m, dive HPD# 1426, B05, R/V Natsushima , NT12-22, coll. R. Mimori, 23 August 2012.

Description (modified after the manuscript of Bayer). The holotype is 4 cm wide and 5.2 cm high, 8 cm if the extremely flexible main branch is fully stretched out ( Figure 6a ). The stem is 1.5 cm long and about 1 mm wide. The colony is sparsely branched in an openly pinnate manner, not strictly in one plane. Six lateral branches arise from the primary axis in alternating sequence, the lowest three of these giving rise in turn to shorter twigs. The principal axis extends about 5.5 cm beyond the uppermost lateral branch. Regular lateral branching forms the colony, with branches thread-like, less than a mm wide. The brown axis is visible through the thin coenenchyme. The denuded axis of the main trunk is about 0.6 mm in diameter roughly 5 mm above the base; the extremely slender branches taper little if at all distally, being about 0.35–0.4 mm in diameter throughout. The non-retractile polyps are arranged spirally around the branches, they form cylindrical polyps 1.75 mm high and 0.75–0.8 mm in diameter with tentacles folded in over the mouth; they are distantly spaced, sometimes alternate, sometime opposite or nearly so, in most cases two opposite polyps at the summit of each terminal twig. Tentacles with scales, up to 0.12 mm long, with a few simple tubercles ( Figure 7a ). These intergrade proximally with the sclerites of the body wall of the polyp, which include slender tuberculate spindles and club-like sclerites up to 0.3 mm long ( Figure 7b ). The clubs with less tuberculate to smooth handles. Coenenchyme with capstans, small spindles and cylinders, up to 0.12 mm long, with simple or complex tubercles ( Figure 7c ). A few crosses are also present ( Figure 7d ).

Colour. The preserved holotype is white, and all sclerites are colorless. The colony in situ is pink ( Figure 6c ). Etymology. From the Latin gracilis , slender, referring to the colony shape with its slender branches, following Bayer’s manuscript. Distribution. Pacific side of Japan mainland: off Boso peninsula, Shio Misaki in 1188–1497 m ( Figure 1b ). Variability. The holotype has somewhat less developed sclerites than the other material ( Figure 8 ), polyp spindles with two smooth ends and clubs with a smooth handle. It also shows some crosses ( Figure 7d ) not

observed in the other examined material. The size of polyps of the other material is larger, about 1.5 mm high and 1 mm wide.

Comparisons. When first examined superficially, this specimen was identified as C. beringi owing to its slender colonial form contrasting with the coarser aspect of C. spiculifera , and to its deep-water habitat. However, the growth form is even more delicate and the branches more slender and flexible than in C. beringi , which lacks the slender clubs of the polyp walls, so it clearly cannot be accommodated in that species as defined by its original type material, which is now fully illustrated by SEM for the first time.

The robust colonial form, crowded polyps, and larger polyps immediately distinguish C. spiculifera from C. gracilis as well as from C. beringi . Moreover, neither of those species has slender clubs of the type characteristic for C. gracilis .

Commensals. Two of the lateral branches of holotype each bear a small ophiuroid tightly entwined around it.

Remarks. The other examined material is the specimen mentioned by Takahashi et al as Acanthogorgiidae sp. When viewed with standerd illumination under the traditional stereomicroscope, the polyps of C. gracilis have a distinctly rough, even prickly aspect, owing to the spindles and slender clubs of the body wall.

Figures

FIGURE 1. Distribution map of Calcigorgia species: a. C. beringi (Δ) and C. gigantea. (D) b. C. gracilis sp. n.(-) and C. pacifica sp. n. (+), c. C. japonica (O) (including the type locality data from Dautova 2007) and C. matua (×) and C. matua from Dautova 2018 (•), d. C. spiculifera (Ɨ), type locality data from Broch 1935 (Ɨ), C. simushiri(= C. spiculifera) from Dautova, 2018 (D),? C. spiculifera in Dautova, 2018 (-).

FIGURE 6. a. Calcigorgia gracilis sp. n., holotype USNM 60280. b. C. gracilis sp. n. JAMSTEC No.1120034415 c C. gracilis sp. n. live images (JAMSTEC No.1120034415, depth 1497 m, dive HPD# 1426)

FIGURE 7. Calcigorgia gracilis sp. n., holotype USNM 60280, a tentacle scales b clubs c capstans, spindles and cylinders d crosses.

FIGURE 8. Calcigorgia gracilis sp. n., JAMSTEC No.1120034415 a tentacle scales b clubs c capstans, spindles and cylinders.