A couple of days ago we published the genome of a brachiopod species, in specific Discradisca antillarum in the journal G3. Brachiopods are a group of shelled, filter-feeding marine invertebrates also known as lamp shalls. Though they superficially resemble bivalve mollusks, brachiopods are not. Brachiopods have the shells on the dorsal and ventral side instead of left and right, have unequal shells instead of equal ones and have a hole in the shell for the stalk fixing them to the ground.
They belong to a clade called Lophophorata, which additionally comprises also moss animals (Bryozoa) and horseshoe worms (Phoronida). All of which are characterized by a tentacle crown, which looks a bit like a horseshoe and is called lophophor. Brachiopods possess an abundant and diverse fossil record spanning more than 500 million years. This long evolutionary history makes Brachiopoda particularly important for understanding the evolution of the morphological disparate animal group known as Lophotrochozoa. Understanding the relationships within Lophotrochozoa is part of the goals of the InvertOmics project.
Given their possession of shells, brachiopods also can provide insight into the evolution of biomineralization. Most lineages produce skeletons of calcium carbonate while linguliforms use calcium phosphate. However, genomic resources for brachiopods are limited. To enable comparative and evolutionary genomic studies of this clade, we generated a chromosome-level assembly for the discinid brachiopod D. antillarum.
In the paper, we presented both a primary (N = 8) and haplotype-resolved (2N = 16) assembly. The primary assembly comprises besides the 8 chromosome-level scaffolds also an additional 200 unplaced scaffolds, with the 8 chromosome-level scaffolds representing 96.6% of the genome. The genome has a BUSCO score of 95.5% and comprises 29,208 protein-coding genes. With this is well within the range for other lophotrochozoan taxa such as mollusks.
Comparison of the general genome architecture between D. antillarum and other lophotrochozoans showed that the genome conserves all proposed ancestral lophotrochozoan fusion-with-mixing events while also revealing new fusions involving several bilaterian ancestral linkage groups. On the other hand, in this it also shows substantial differences to the other brachiopod genome of Lingula anatina. The genome of D. antillarum will enable significant insights into brachiopod evolution.
