Parachurabana shinseimaruae Kise, 2023

Kise, Hiroki, Nishijima, Miyuki, Iguchi, Akira, Minatoya, Junpei, Yokooka, Hiroyuki, Ise, Yuji & Suzuki, Atsushi, 2023, A new hexactinellid-sponge-associated zoantharian (Porifera, Hexasterophora) from the northwestern Pacific Ocean, ZooKeys 1156, pp. 71-85 : 71

Parachurabana shinseimaruae Kise sp. nov.

Figs 1 , 2 , 3

Material examined.

Holotype. NSMT-Co 1819, Takuyo-Daigo Seamount off southwestern Minami-Torishima Island, 23°23'N, 153°04'E, 935 m depth, coll. RV Shinsei-maru, 19 June 2020, fixed in 99.5% ethanol.

Material examined for comparison.

Churabana kuroshioae RUMF-ZG-04447 (holotype), collected from near Iejima Island , Motobu, Okinawa, Japan by T. Higashiji, 02 Mar. 2018 . Vitrumanthus schrieri RMNH.COEL.42429 (holotype), collected from SubStation , Curaçao by B.W. Hoeksema, 31 Mar. 2014 . Vitrumanthus vanderlandi RMNH.COEL.42623 (holotype), Cape Verde Islands , Sao Tiago , Ilheus Rombos east of Cima by RV HNIMS Tydeman, 24 Aug. 1986 . Vitrumanthus oligomyarius CMNH ZG-4785, off Katsuura , Chiba, Japan by A. Tamura, 19 Jan. 2006 .

Description.

External morphology. Cylindrical polyps that appear solitary and sparsely distributed on the hexactinellid sponge Farrea Bowerbank, 1862 (Fig. 1a, b ). Surface of column rough, and ectoderm continuous. Polyps attached to hexactinellid sponge surfaces with pedal-disk-like structure (Fig. 1c, d ). In contracted polyp, tentacles poorly covered by capitulum and actinopharynx visible. Preserved column creamy white in color and heavily encrusted with sand and silica particles. Capitulary ridges discernible, 12-14 in number (Fig. 1c ). Tentacles 24-28 in number, shorter than or equal to expanded oral disk diameter. Living expanded polyps to ca. 10.0 mm in height and 5.0 mm in diameter. Preserved contracted polyps to 0.5-1.0 mm in height and 0.5-3.0 mm in diameter. Living column white and/or yellowish; capitulum and tentacle transparent (Fig. 1a ).

Internal morphology. Zooxanthellae absent. Cteniform endodermal marginal muscle with comb-like mesogleal pleats (Fig. 2a ). Ectoderm and mesoglea heavily encrusted with numerous sand and silica particles of various size (Fig. 2b, c ). Basal canals of mesenteries absent and encircling sinus visible (Fig. 2c ). Single siphonoglyph and complete mesenteries possibly fertile.

Cnidae. Basitrichs and microbasic b-mastigophores, microbasic p-mastigophores, holotrichs, special b-mastigophores, and spirocysts (See Fig. 3 and Table 1 for size).

Distribution and habitats.

Northwestern Pacific Ocean: Takuyo-Daigo Seamount off southwestern Minami-Torishima Island at depths of 900-1000 m.

Associated host.

Farrea sp. ( Porifera: Hexactinellida)

Molecular phylogeny.

Both ML and BI phylogenetic analyses using the concatenate dataset indicate that Parachurabana shinseimaruae sp. nov. is basal to the clade containing the genera Bergia , Parazoanthus , and Umimayanthus (Fig. 4 ; ML, 62%; BI, 0.99). ML phylogenetic analyses place Churabana and Vitrumanthus in a clade with octocoral-associated genera such as Corallizoanthus Reimer in Reimer, Nonaka, Sinniger & Iwase, 2008 with no support (ML <50%), whereas BI phylogenetic analyses place Churabana and Vitrumanthus in a sister clade to that containing Parachurabana , Bergia , Parazoanthus , and Umimayanthus (Suppl. material 3). The topology of a phylogeny for ITS-rDNA dataset was similar with the concatenate dataset (Suppl. material 4).

Remarks.

Parachurabana shinseimaruae sp. nov. has so far only been identified on one seamount off southwestern Minami-Torishima Island. However, Parachurabana shinseimaruae sp. nov. may be distributed across the Pacific Ocean, as several specimens associated with farreid sponges have been observed in Australian waters (M. Ekins personal communication). Although Parachurabana shinseimaruae sp. nov. is morphologically similar to Vitrumanthus schrieri , Parachurabana shinseimaruae sp. nov. and V. schrieri can be separated by marginal muscle (cteniform endodermal marginal muscle vs cyclically transitional marginal muscle). Furthermore, Parachurabana shinseimaruae sp. nov. can be distinguished from Churabana kuroshioae by polyp size (0.5-1.0 mm in height by 0.5-3.0 mm in diameter vs 3.0-4.0 mm in height by 2.8-4.0 mm in diameter).

Etymology.

The species is named after RV Shinsei-maru, as the type specimens were collected by this vessel.

Figures

Figure 1. External morphology of Parachurabana shinseimaruae sp. nov. a photographic record from Takuyo-Daigo Seamount off southwestern Minami-Torishima Island b-d NSMT-Co 1819 a living polyps on a hexactinellid sponge Farrea sp. b preserved specimen c close-up image of a single preserved polyp d close-up, side-view image of a single preserved polyp attached to a hexactinellid sponge Farrea sp. Scale bars: 20 mm (a, b); 1 mm (c, d).

Figure 2. Images of the internal morphology of Parachurabana shinseimaruae sp. nov. NSMT-Co 1819 a close-up image of cteniform endodermal marginal muscle in a longitudinal polyp section b cross-section at the height of tentacles c cross-section at the height of the actinopharynx. Abbreviations: CEMM, cteniform endodermal marginal muscle; CM, complete mesentery; CW, column wall; DD, dorsal directives; ES, encircling sinus; IM, incomplete mesentery; T, tentacles. Scale bars: 200 µm (a); 500 µm (b, c).

Figure 3. Cnidae in the tentacles, column, actinopharynx, and mesenterial filaments of the holotype of Parachurabana shinseimaruae sp. nov. Abbreviations: HL, holotrich large; O, basitrichs and microbasic b-mastigophores; SBM, special microbasic b-mastigophores; PM, microbasic p-mastigophores; S, spriocysts.

Figure 4. Maximum-likelihood tree based on combined dataset of COI, 12 S-rDNA, 16 S-rDNA, 18 S-rDNA, 28 S-rDNA, and ITS-rDNA sequences. Number at nodes represent ML bootstrap values (> 50 % are shown). White circles on nodes indicate high support of Bayesian posterior probabilities (> 0.95).