A draft de novo assembly of Diadema antillarum, a keystone herbivore of the Caribbean reefs

Abstract

We generated the first reference-level nuclear genome assembly of the keystone Caribbean long-spined black sea urchin species, Diadema antillarum (Philippi, 1845). Using whole-genome sequencing data from PacBio HiFi, Oxford Nanopore, and Illumina platforms, we employed multiple assembly strategies to generate a high-quality, near-complete genome. The final assembly spans 1.73 Gbp, consists of 2,964 scaffolds, and has an N50 of 1.56 Mbp. BUSCO analysis (metazoa_odb10) indicates 98.4% completeness. The genome displays a heterozygosity rate of 2.52% and contains 42.85% repetitive elements, of which 29.96% are unclassified. Coverage analysis reveals that while most of the genome was assembled at 11x depth, certain regions exhibit up to 530x coverage. Notably, regions exceeding 33x coverage account for 30.53% of the repetitive content, suggesting localized expansion of repeats. Duplication analysis of the assembled contigs shows that approximately 66% of contigs have duplicated, which supports segmental genome duplication in the past, and is further evidenced by the moderate level of heterozygosity of the assembly. While these characteristics contribute to the complexity of the genome, they do not diminish the quality of our assembly. Despite this complexity, our assembly maintains high completeness and contiguity. Our assembly provides a valuable resource for future genetic studies and serves as a critical framework for conservation, monitoring, and restoration of D. antillarum populations across the Caribbean.