Morphology and molecular phylogeny of a new ciliate Anteholosticha nanjiensis sp. nov. (Ciliophora, Hypotrichia) collected from the coastal intertidal zone of the East China Sea

A new hypotrich ciliate, Anteholosticha nanjiensis sp. nov., was isolated from a sandy beach in Wenzhou, China. Its morphology was investigated using detailed live observation and protargol staining, and its phylogenetic position was assessed through small subunit ribosomal DNA (SSU rDNA) sequence analyses. The new species is characterized as follows: size in vivo 90–115 × 40–50 µm; body shape elliptical and dorsoventrally flattened; 2–4 globular macronuclear nodules; 8–14 midventral cirral pairs; colourless cortical granules (about 0.5 µm in diameter) arranged in short longitudinal rows.

Phylogenetic analyses robustly placed A. nanjiensis sp. nov. within a clade containing A. pseudomonilata Li et al., 2011 a and A. marimonilata Xu et al., 2011. However, it differs from these congeners by having 13 and 14 nucleotides in its SSU rDNA sequence, respectively, supporting its status as a distinct species. Morphologically, A. nanjiensis sp. nov. can be distinguished from related species by its body size, number of macronuclear nodules, transverse cirri count, and cortical granulation distribution.

This study provides comprehensive morphological and molecular data establishing foundational references for resolving the apparent polyphyly of Anteholosticha. While full resolution may require integration of additional evidence (e. g. morphogenetic data or TEM ultrastructure), our dataset delivers essential comparative frameworks for future taxonomic revisions.