An integrative analysis of Plectocapillus antarcticus gen. et sp. nov. from Antarctica: Morphology, chemical composition, and phylogeny

In this study, Plectocapillus antarcticus gen. et sp. nov., belonging to the Family Pseudobolivinidae Wiesner, 1931, Superfamily Spiroplectamminoidea Cushman, 1927, was described from Maxwell Bay, King George Island, Antarctica. The species is distinguished by its elongate, slender, and entirely biserial test, fragile, thin agglutinated wall, a globular, organic proloculus, and the areal, rounded to arch-like aperture. Notably, this species previously assigned taxonomically as Spiroplectammina filiformis Earland, 1934 or Textularia tenuissima Earland, 1933, in nearby areas. However, morphological comparison revealed differences in chamber arrangement, biserial pair number, test width, and proloculus wall composition. SEM-DES analysis identified Al, Ca, Fe, Mg, Si, and Ti as major chemical elements present in the test wall, along with the traces of K, Mn, Na, P, Ce, Cl, F, S, Sr, and Zr. Phylogenetic analysis of partial SSU rRNA and mitochondrial COI gene sequences confirmed that P. antarcticus forms a well-supported clade, sister to Spiroplectammina biformis. The slender, flexible test, organic proloculus, and inclusion of heavy element-rich minerals suggests potential adaptation to hypoxic or interstitial habitats. By integrating morphological, chemical, and molecular data, this study contributes to the expanding fundamental database and understanding of Antarctic foraminiferal diversity and emphasizes the necessity for continued research in the region.