taxonID	type	description	language	source
03A887B7FFDD5A2DFF79FD65171D43B0.taxon	diagnosis	Diagnosis: This species differs from the other four species of Oceanitis, namely O. scuticella, O. cincinnatulum, O. unicaudatum and O. viscidulum by having unicellular ascospores that are fusiform, curved or sigmoid in shape, two type of ascospores appendages: one polar uncoiling appendage and tree-like appendages that develops throughout the ascospores’ length; semi-persistent asci and cream-colored, drop-shaped ascomata (Dupont et al. 2009; Kohlmeyer 1977; Jones & Le Campion-Alsumard 1970 a, 1970 b). Type: The Northwest Pacific Ocean, off the coast of Japan, (35 ° 55.61 ′ N, 144 ° 57.87 ′ E) under the Kuroshio Extension, on the sunken wood found on the abyssal plain at 5707 m water depths, 2 Sep 2019, Y. Nagano, holotype TNS-F- 70722. Gene sequences holotype: LC 789975 (LSU), LC 777827 (ITS), LC 789976 (SSU). Etymology: The epithet abyssalis refers to the abyssal plain where this species was collected. Ascomata 1.2 – 1.6 mm high, 0.98 – 1.2 mm diam., superficial, drop-shaped, papillate, ostiolate, cream-colored, yellowish or brownish, subiculate, fleshy, single or gregarious. Ostioles 470 – 545 μm in length, 90 – 110 μm diam., ostiolar canal periphysate; periphyses 21 – 39 μm in length, 1 – 2 μm wide. Peridium 290 – 400 μm wide at the upper part of the ascomata, 120 – 160 μm wide at the lower part of the ascomata, 3 - layered, forming a textura angularis; outer layer 40 – 50 μm wide in the upper part of the ascomata and consists of 5 – 7 cell layers of light-brown, thick-walled, polygonal cells, 10 – 20 μm wide in the lower part of the ascomata and consists of 2 – 4 cell layers of flattened, thick-walled cells; median layer 230 – 280 μm wide in the upper part of the ascomata and consists of 15 – 28 cell layers of hyaline, thick-walled, polygonal cells that are with large lumina and elongated to outside and small to inside, 10 – 20 μm wide in the lower part of the ascomata and consists of 5 – 9 cell layers of polygonal, thick-walled cells; inner layer 28 – 45 μm thick, consists of 7 – 11 cell layers of hyaline, flattened, parallel, thick-walled cells. Paraphyses absent, center of immature ascomata is filled with hyaline, thin-walled, polygonal pseudoparenchymatous cells which are eventually compressed by the asci. Asci 83 – 115 × 15 – 20 μm (mean = 95.7 × 17.1 μm, n = 25), 8 - spored, unitunicate, clavate or fusiform, thin-walled, with rounded apex, semi-persistent, short pedicellate, ripening successively on an ascogenous tissue at the bottom of the ascomatal venter, becoming detached at maturity at the base and pushed upward by young asci. Ascospores 58 – 77 × 4 – 5 μm, elongate fusiform, curved or sigmoid, unicellular, hyaline, guttulate, with one apical appendage; appendages 6 – 16 μm long, 0.5 – 2 μm diam, filamentous, uncoiling, tapering toward the apex, wavy, adhering with its base to the apex of the ascospore, deciduous; occasionally ascospores develop tree-like appendages throughout its length while within the ascus or after its release (Fig. 3).	en	Nagano, Yuriko, Abdel-Wahab, Mohamed A., Nakajima, Ryota, Yabuki, Akinori (2024): Oceanitis abyssalis sp. nov., a new deep-sea fungus from sunken wood collected at the depth of 5707 m in the Northwest Pacific Ocean. Phytotaxa 663 (4): 171-183, DOI: 10.11646/phytotaxa.663.4.1, URL: https://doi.org/10.11646/phytotaxa.663.4.1
03A887B7FFDA5A27FF79FA681087469A.taxon	description	... continued on the next page ... continued on the next page In order to clarify the phylogenetic position of O. abyssalis and Oceanitis scuticella - like organisms, the LSU rDNA region of O. abyssalis was aligned with other Oceanitis sequences and other appropriate sequences retrieved from GenBank (Fig. 4). The new species, O. abyssalis is well placed in the genus Oceanitis clade with 100 % support in the ML phylogenetic analysis. Oceanitis abyssalis was placed with the Kuril-Kamchatka Trench material (M 0229768) but located separately from other Oceanitis taxa. The LSU and ITS rDNA sequences of O. abyssalis showed 100 % match with the Kuril-Kamchatka Trench material (M 0229768). Both Oceanitis abyssalis and the Kuril-Kamchatka Trench material (M 0229768) have drop-shaped ascomata and unicellular ascospores. They were collected from a similar environment, the abyssal plain of the North Pacific Ocean. From a morphological perspective, as well as considering the 100 % similarity in ITS rDNA sequences and ecological aspects of the collected material, we inclined to consider that M 0229768 reported as O. scuticella in Dupont & Schwabe (2016) is a representative of O. abyssalis. Although there are slight morphological differences between M 0229768 and O. abyssalis (Table 1), specifically, they differ in the dimensions of the ascospores (58 – 77 × 4 – 5 µm for O. abyssalis vs. 52 × 2.3 µm for M 0229768), and ascomata of Oceanitis abyssalis are larger in size with a thicker, three-layer peridial wall (Dupont & Schwabe 2016). Also, ascospores of Oceanitis abyssalis have two types of appendages, while the collection of the Kuril-Kamchatka Trench has one polar uncoiling appendage. Some of these differences may result from a lack of detailed comprehensive observation and further findings of the specimens and detailed analyses will be needed to determine their precise identification. Therefore, we concluded in the present study that the Kuril-Kamchatka Trench material (M 0229768) should be treated as Oceanitis cf. abyssalis (Table 1 and Fig. 4). The South China Sea material (CP 4157) was closely related to O. abyssalis and Kuril-Kamchatka Trench material (M 0229768) but placed independently within the Oceanitis scuticella - like clade and showed 3 nucleotide differences in the LSU rDNA sequence and one nucleotide difference in the SSU rDNA sequence from O. abyssalis (ITS rDNA sequence data is not available). As the detailed morphological information of the South China Sea material (CP 4157) is not available, it cannot be discussed further. The Vanuatu materials (CP 2457 b, CP 2429, CP 2421) formed a clade being separate from CP 4157 and O. abyssalis. There are 3 to 4 nucleotide differences in the LSU rDNA sequence and 11 to 14 bases (2.5 – 3.0 %) differences in ITS rDNA sequence between the Vanuatu materials and O. abyssalis. Morphological and phylogenetic analyses suggested that the Vanuatu materials (CP 2457 b, CP 2429, CP 2421) are likely another undescribed Oceanitis species different from the original O. scuticella and O. abyssalis. Therefore, we concluded in the present study that the Vanuatu materials (CP 2457 b, CP 2429, CP 2421) should be treated as unidentified Oceanitis spp. (Table 1 and Fig. 4). The South China Sea material (CP 4157), of which details are unknown, might be an another unidentified Oceanitis sp. because of its independent phylogenetic position. To clarify the taxonomy of these collections and to understand the diversity within the genus Oceanitis more accurately, additional collections, including O. scuticella sensu stricto from the type locality, are needed. Furthermore, comprehensive morphological and phylogenetic studies are essential to formally describe these species.	en	Nagano, Yuriko, Abdel-Wahab, Mohamed A., Nakajima, Ryota, Yabuki, Akinori (2024): Oceanitis abyssalis sp. nov., a new deep-sea fungus from sunken wood collected at the depth of 5707 m in the Northwest Pacific Ocean. Phytotaxa 663 (4): 171-183, DOI: 10.11646/phytotaxa.663.4.1, URL: https://doi.org/10.11646/phytotaxa.663.4.1
