Oceanitis abyssalis (Dupont & Schwabe, 2016)

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), pp. 171-183 : 181

Ecology of Oceanitis abyssalis

Both O. abyssalis and the Kuril-Kamchatka Trench materials were collected from abyssal depths of deep-sea and both had drop-shaped ascomata with unicellular ascospores on intact bark with absence of wood-boring bivalves ( Dupont & Schwabe 2016). In contrast, the original O. scuticella and the Vanuatu materials were collected from bathyal depths of deep-sea and they had ascomata with one-septate ascospores on barkless wood along with wood-boring bivalves ( Kohlmeyer 1977; Dupont et al. 2009). It would be interesting to disclose their ecological characteristics and phylogenetic relationship within the genus Oceanitis . It was previously believed that the presence of bark inhibits the colonization of deep-sea fungi on wood ( Dupont et al. 2009). However, recent observations have shown that some deep-sea fungal species, such as O. abyssalis , are capable of colonizing wood with intact bark. In addition, tree-like appendages have been observed in O. abyssalis . Tree-like appendages have also been observed in some marine fungi and aquatic fungi ( Abdel-Wahab et al. 2012; Noureldin et al. 2022). These structures may help these fungi to settle on sunken wood. Also, it is very interesting to see if there is any habitat segregation between the deep-sea fungi and wood-boring bivalves. However, the presence/absence of wood-boring bivalves may be just related to their habitable water depths or the dimension of wood materials, as it is known that marine wood-degrading fungi are believed to contribute to the settlement and growth of wood-borers in shallow marine environments ( Vishwakiran et al. 2001).

The genus Oceanitis occurs on various plant species with or without bark in various aquatic environments, littoral to deep-sea areas. It is also widely distributed in geologically separated deep-sea regions as one of the most successful fungal taxa in the environment. Dupont et al. (2009) suggested that the thick peridium of O. scuticella could be an adaptation to the extreme conditions of the deep sea. A thick three layered peridial walled of O. abyssalis is consistent with this hypothesis. Since there are shallow marine species and deep-sea species within the Oceanitis , these organisms are useful subjects to study the mechanism of adaptations from the littoral to the deep areas. Comparative genome analysis within the Oceanitis may provide key insights into the adaptation, evolution and ecology of deep-sea fungi. It would also be interesting to investigate its wood-degrading enzymes, as they degrade sunken wood in a completely different environment from terrestrial.