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 used basic morphological data, mitochondrial Cytochrome Oxidase I (COI) gene, and Internal Transcribed Spacer two (ITS2) regions to evaluate the Terpios samples collected from four coastal sites along the northeastern Mediterranean Sea, covering a distance of approximately 450 km. For this purpose, 81 COI and 11 ITS2 records of the order Suberitida were mined from GenBank, and species delimitation analysis was performed using both the Automatic Barcode Gap Discovery method and the Poisson Tree Process (PTP), along with 11 samples from the present study. While we observed slight differences in spicule sizes, the overall morphology of all samples from our study was 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.