Antipathozoanthus obscurus, Kise, Hiroki, Fujii, Takuma, Masucci, Giovanni Diego, Biondi, Piera & Reimer, James Davis, 2017

Kise, Hiroki, Fujii, Takuma, Masucci, Giovanni Diego, Biondi, Piera & Reimer, James Davis, 2017, Three new species and the molecular phylogeny of Antipathozoanthus from the Indo-Pacific Ocean (Anthozoa, Hexacorallia, Zoantharia), ZooKeys 725, pp. 97-122 : 99-102

Antipathozoanthus obscurus sp. n. Fig. 2a, b

Antipathozoanthus sp. 3 sensu Reimer and Fujii 2017, 394, fig. 14.4e.

Material examined.

Holotype: NSMT-Co1602 (MISE-BISE1), collected from the wall of a shallow cave in a coral reef. Preserved polyps are approximately 3.0-4.5 mm in diameter, and approximately 3.0-8.0 mm in height from the coenenchyme. Approximately 15-20 polyps connected by a stolon form a mesh network, with additional solitary polyps close by (n = 6). Polyps and coenenchyme are heavily encrusted by various fine sand particles. External color light orange when alive, light beige when fixed. Collected from Cape Bise, Motobu, Okinawa-jima Island, Japan (26°42'34.4"N, 127°52'49.2"E) at a depth of 5 m by James Davis Reimer (JDR), 14 August 2014.

Paratypes: RUMF-ZG-4390 (MISE-JDR190), collected from Al Wajh Shaybarah, Saudi Arabia, (25°21'N, 36°54'E) at a depth of 3 m by JDR, 3 October 2013; RUMF-ZG-4391 (MISE-JDR191), collected from Al Wajh Shaybarah, Saudi Arabia, (25°21'N, 36°54'E) at a depth of 3 m by JDR, 3 October 2013; RUMF-ZG-4392 (MISE-JDR192), collected from Al Wajh Shaybarah, Saudi Arabia, (25°21'N, 36°54'E) at a depth of 3 m by JDR, 3 October 2013; RUMF-ZG-4393 (MISE-JDR279), collected from Shib Nazar, Saudi Arabia, (22°19'N, 38°51'E) at a depth of 3 m by JDR, 3 October 2013; RUMF-ZG-4394 (MISE-KU1), collected from Kume-jima Island, Okinawa, Japan (26°19'15.0"N, 126°45'21.3"E) at a depth of 15 m by Takuma Fujii (TF), 20 November 2009; RUMF-ZG-4395 (MISE-TF54), collected from Cape Zanpa, Yomitan, Okinawa-jima Island, Japan (26°26'26.5"N, 127°42'43.7"E) at a depth of 3 m by TF, 6 April 2009, divided into two pieces, one portion fixed in 99.5% ethanol, and other in 5-10% saltwater formalin; RUMF-ZG-4396 (MISE-TF78), collected from Cape Manza, Onna, Okinawa-jima Island, Japan (26°30'18.3"N, 127°51'02.3"E) at a depth of 5 m by TF, 2 October 2009, divided into two pieces, one portion fixed in 99.5% ethanol, and other in 5-10% saltwater formalin; RMNH.Coel.42320 (MISE-TF148), collected from Cape Manza, Onna, Okinawa-jima Island, Japan (26°30'18.3"N, 127°51'02.3"E) at a depth of 10 m by TF, 22 October 2012.

Other materials examined: MISE-BISE3, collected from Cape Bise, Motobu, Okinawa-jima Island, Japan (26°42'34.4"N, 127°52'49.2"E) at a depth of 5 m by JDR, 14 August 2014.

Diagnosis.

External morphology: Open oral disks are approximately 5-10 mm in diameter, and polyps approximately 5-10 mm in height when open (Fig. 2). Polyps of a single colony are usually connected by a stolon forming a mesh-like network. Antipathozoanthus obscurus sp. n. has approximately 26-32 bright brown and/or orange tentacles that are as long as or longer than oral disk diameter. Polyps and coenenchyme have a heavily encrusted ectoderm including numerous various sand particles (usually 1 to 8 mm in size). Capitular ridges (= number of complete mesenteries) are slightly visible on tops (= capitulum) of closed polyps.

Internal morphology: Azooxanthellate. Fine sand particles and silica heavily encrusted into ectoderm and mesoglea. We could not obtain cross-sections or images to observe internal morphology such as mesenterial arrangement, marginal muscle or siphonoglyph due to heavy sand and silica encrustation.

Cnidae: Holotrichs (large), basitrichs and microbasic p-mastigophores (usually difficult to distinguish), spirocysts (Fig. 3; Table 2).

Habitat and distribution.

Antipathozoanthus obscurus sp. n. is found in low-light environments such as within crevasses of reef slopes and reef floors, and coral reef caves. Specimens were found from 3 to 15 m. This species has been found from the Red Sea and Okinawa.

Differential diagnosis.

Antipathozoanthus obscurus sp. n. is easily distinguished from all other Antipathozoanthus species, including the two other new species in this study, which all have associations with antipatharians. A. obscurus sp. n. is not associated with antipatharians and instead is found on coral reef carbonate substrate within caves or cracks. Additionally, the cnidome of A. obscurus sp. n. is different from all other known Antipathozoanthus species, including the other new species in this study, as there are no medium holotrichs in any tissue of A. obscurus sp. n., and instead only large holotrichs are found in all tissues.

Although A. obscurus sp. n. is not associated with antipatharians, phylogenetic data indicate that A. obscurus sp. n. is very closely related to other Antipathozoanthus species associated with antipatharians, with identical COI and 16S-rDNA sequences to those of A. macaronesicus (EU591618).

Remarks.

The samples of Antipathozoanthus obscurus sp. n. in the present study contain two morphotypes; one with bright brown tentacles that are longer than the oral disk (MISE-TF54); and the other morphotype with orange tentacles that are only as long as the oral disk (MISE-BISE1, MISE-BISE3, MISE-JDR190, MISE-JDR191, MISE-JDR192, MISE-JDR279, MISE-KU1, MISE-TF78, MISE-TF148). However, the sequences of all specimens formed a monophyletic clade and therefore we have described A. obscurus sp. n. in this study as containing two morphotypes. Genetic vari ation in all three genetic markers in the samples of A. obscurus sp. n. was observed, and the possibility remains that A. obscurus sp. n. may contain cryptic species. Thus, we have excluded specimen MISE-BISE3 from the type series, although it was tentatively identified as A. obscurus sp. n. Further specimens and fine-scale genetic analyses are required to better understand if there is any cryptic diversity within this species.

Etymology.

Antipathozoanthus obscurus sp. n. is named from the Latin "obscura" meaning "dark", as this species can be found in dark environments.

Common name.

Tsuno-nashi-sunaginchaku (new Japanese name).