Adhaerentella dendrocorona gen. and sp. nov: An Attached Monothalamid Foraminifera From the Abyssal Pacific

A new genus and species of a monothalamid foraminifera, Adhaerentella dendrocorona, has been identified through phylogenetic and morphological assessment from the Pacific Ocean abyssal plain at Station M, off California. After at least 1 year of colonization time on the seafloor at 4000 m, 141 specimens belonging to the new species were observed attached to plastic substrate deposited on the bottom as a part of the Seafloor Epibenthic Attachment Cube (SEA³) experiments. Adhaerentella dendrocorona is characterized by agglutinated hemispherical tests connected with dendritic tubes. The delicate phyllosilicate branches collapse when not immersed, but embedding in agar or resin facilitates imaging. MicroCT images reveal compositional differences between the agglutinated base and branching tube structures, consisting of phyllosilicates. Despite sharing some morphological similarities with other attached agglutinated genera, such as Capsammina, Crithionina, and Hemisphaerammina, Adhaerentella dendrocorona is genetically different from the latter genera and branches in the monothalamid Clade M. Adhaerentella dendrocorona has a close relationship with undescribed monothalamids from Antarctica, suggesting the possible global distribution of the genus. This study indicates that monothalamid foraminifera are important components of attached abyssal meiofauna, which have evolved morphologies that are likely adapted for suspension feeding in oligotrophic environments that feature hard substrates.