Revising the Taxonomy and Biology of Ornamental Worms (Polychaeta: Sabellidae) around the Arabian Peninsula

Abstract

Polychaetes are among the most abundant and diverse groups in the benthic environment; however, the diversity of marine polychaetes remains underexplored. On coral reef ecosystems, scientists predict 80-90% of species are still undescribed due to low sampling efforts in certain regions and the understudied nature of smaller invertebrates, such as polychaetes. Sabellidae, a prominent family of polychaetes, are known for their widespread distribution and are recognized as an ornamental worm due to their feather-like appendages. Here, we detail the diversity of Sabellidae around the understudied Arabian Peninsula. The Arabian Peninsula is surrounded by diverse marine ecosystems (e.g., coral reefs, seagrass beds) occurring in extreme environmental conditions (e.g., higher seawater temperature and strong seasonal variation). Our samples included 178 sabellids from the Saudi Arabian Red Sea, the Arabian Sea, and the Arabian Gulf. Collected from February 2019 to February 2020, these sabellids were sampled from hard and soft substrate on coral reefs and their associated habitats. We used two molecular markers, the cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA alongside an array of morphological analyses, including widely used characters, meristic counts, and morphometric measurements, to identify seven morphotypes. Environmental and biological information was also recorded to understand more about the ecology of these relatively understudied polychaetes. Our combined morphological and genetic analyses acknowledge the presence of six species from the genera Sabellastarte, Bispira, Branchiomma, and Acromegalomma. Our study identified the existence of potential undescribed species in the region and proposed expanded geographic ranges for three accepted species, Sabellastarte sanctijosephi, Branchiomma luctuosum, and Acromegalomma nechamae. The present work increases the current knowledge about the overall systematics of marine polychaetes in the Arabian Peninsula and ultimately contributes to the reassessment of the family’s biogeography.