Integrative taxonomy of new xenophyophores (Rhizaria, Foraminifera) from the abyssal northwest Pacific
Abstract
Xenophyophores dominate the abyssal megafauna across many areas of the Pacific Ocean. These giant agglutinated foraminifera have been studied mainly in the tropics, including within the Clarion-Clipperton Zone (CCZ), from where the majority of recently described taxa have originated. Here, we describe three new species, one of them assigned to a new genus, from an area further north (30–32.5° N) near the Japanese Archipelago. Specimens were collected in pushcores during dives of the manned submersible Shinkai 6500 and preserved in the cores after removal of fragments for genetic analyses, allowing them to be examined in life position using X-ray micro-computed tomography (µCT). The three species have basically plate-like tests composed largely of mineral grains. Two, both from 32.5° N, are assigned to the genus Psammina. They are closely related to each other and to P. tenuis from the western CCZ. In Psammina yokosukae sp. nov., the test comprises curved plates, whereas in Psammina contorta sp. nov., it comprises a confusing array of contorted plates and other poorly defined structures. The third new species, Laminarena variabilis gen. et sp. nov., is genetically distinct from the others. In typical specimens from 30° N, the plates are large, curved or sinuous, relatively thin, and marked by a distinct surface pattern of concentric zones, traversed by closely spaced, radial ridges that correspond to internal partitions. A form from 32.5° N is shown to be conspecific with the 30° N specimens based on molecular evidence but is morphologically more complex, comprising elongate bar- and plate-like elements, some with fan-like terminations. A fourth taxon, resembling a bumpy pebble and occupied by bubble-like internal compartments, is described informally. These new taxa enhance our knowledge of Pacific xenophyophores, as well as our understanding of the morphological diversity of xenophyophores in general.
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Copyright (c) 2025 Andrew J. Gooday, Yoshiyuki Ishitani, Chong Chen, Maria Holzmann, Julien Richirt, Koji Seike, Momo Yamashita, Masashi Tsuchiya, Hidetaka Nomaki
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