Data from: Chromosomal level reference genome of Tachypleus tridentatus provides insights into evolution and adaptation of horseshoe crabs

Horseshoe crabs including Tachypleus tridentatus are a group of marine
arthropods living fossil species which have existed on the earth for 500
million years. However, the genetic mechanisms underlying their unique
adaptive ability are still unclear. Here, we assembled the first
chromosome-level T. tridentatus genome, and proofed that this genome is of
very high quality with contig N50 1.69 Mb. By comparison with other
arthropods, some gene families of T. tridentatus experienced significant
expansion, whichare related to several signaling pathways, endonuclease
activity, and metabolic processes. Based on the comparative analysis of
genomics and 27 transcriptomes from 9 tissues, we found that the expanded
Dscam genes usually locate at the key hub positions of immune network.
Furthermore, the Dscam genes showed higher levels of expression in the
yellow connective tissue, the birthplace of blood cells with strong
differentiation capability, than the other 8 tissues. Besides, Dscam genes
are positively correlated with the expression of the core immunity gene,
clotting factor B, which is implicated in the coagulation cascade
reaction. The effective and unusual immune ability endowed by the
expansion and expression of Dscam genes in horseshoe crabs may be a factor
that makes horseshoe crabs having a strong environmental adaptability with
~500 million years. The high-quality chromosome-level genome of a
horseshoe crab and unique genomic features reported in this study provide
important data resources for future studies on the evolutionary history of
marine ecological systems.