Abstract

A new species of Helicascus satunensis sp. nov. was collected on mature dead fruits of the Nypa palm in Satun Province, southern Thailand. Its morphological characteristics are similar to those of the genus Helicascus. Recently, a genus Helicascus with three species from marine habitats worldwide was studied. The morphology of this fungus was investigated and combined with multigene sequence analyzes of small subunit (SSU), large subunit (LSU), internal transcribed spacer (ITS) ribosomal DNA, translation elongation factor 1-alpha (TEF-1α) and RNA polymerase II (RPB2) genes. Morphologically, H. satunensis sp. nov. is characterized by semi-immersed, lenticular ascomata, multilocules, a bitunicate ascus and smooth, obovoid, dark brown ascospores that are one-septate and unequally two-celled. In addition, 3D visualization using synchrotron X-ray tomography was performed to investigate the interaction between fruiting body and substrata. Molecular phylogeny with multigene revealed that H. satunensis sp. nov. belongs to the family Morosphaeriaceae, order Pleosporales, class Dothideomycetes. Furthermore, H. satunensis sp. nov. forms a well-supported clade with Helicascus species described from marine habitats. Based on the unique morphological and molecular evidence, we propose this fungus, H. satunensis sp. nov., as a new species for Helicascus.