Species delimitation analysis indicates cryptic speciation for Terpios gelatinosus (Porifera, Demospongiae) from coastal regions of the northeastern Mediterranean Sea

Sponges, comprising over 9000 recorded species, represent one of the most primitive groups of metazoans. Given the importance of species distribution records and the identification of new species in scientific research, these endeavors play a crucial role in enhancing ecological insights, conserving biodiversity, facilitating a better understanding of the relationships between various groups of organisms, advancing our knowledge of evolution, and potentially expanding biomedical implications. In this study, we utilized basic morphological data, mitochondrial Cytochrome Oxidase I (COI) gene analysis, and ITS2 regions to evaluate taxonomy of Terpios samples collected from four coastal sites along the northeastern Mediterranean Sea, spanning a distance range of approximately 450 km. Eighty-one COI records and eleven ITS2 records of the order Suberitida were mined from NCBI and species delimitation analysis was performed using both the Automatic Barcode Gap Discovery method and the Poisson Tree Process (PTP), together with 11 samples from the present study. While we noted slight differences in spicule sizes, the general morphologies of all samples from our study were strikingly similar. Within the scope of this research, we report the first-ever presence record of T. gelatinosus in the northeastern Mediterranean Sea. Furthermore, we document evidence pointing to the potential existence of cryptic speciation in the region. ### Competing Interest Statement The authors have declared no competing interest.