Expanding on our knowledge of ecdysozoan genomes, a contiguous assembly of the meiofaunal priapulan Tubiluchus corallicola.

Genomic data for priapulans are limited to a single species, restricting broad comparative analyses, and thorough interrogation of questions spanning phylogenomics, ecdysozoan physiology, and development. To help fill this void, we present here a high-quality priapulan genome for the meiofaunal species Tubiluchus corallicola. Our assembly combines Nanopore and Illumina sequencing technologies, and makes use of a whole genome amplification, to generate enough DNA to sequence this small meiofaunal species. We generated a moderately contiguous assembly (2547 scaffolds), with a high level of completeness (Metazoan BUSCOs n = 954, single copy complete = 89.6%, duplicated = 3.9%, fragmented = 3.5%, missing = 3.0%). We then screened the genome for homologs of the Halloween genes, key genes implicated in the ecdysis (moulting) pathway of arthropods, recovering a putative homolog of shadow. The presence of a shadow orthologue in two priapulan genomes suggests that the Halloween genes may not have evolved in a stepwise manner in Panarthropoda, as previously thought, but may have a deeper origin at the base of Ecdysozoa.