Comparative genomics of the coconut crab and other decapod crustaceans: exploring the molecular basis of terrestrial adaptation

• Published in: BMC Genomics
• Main Authors: Werner Pieter Veldsman, Ka Yan Ma, Jerome Ho Lam Hui, Ting Fung Chan, J. Antonio Baeza, Jing Qin, Ka Hou Chu
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2021
• Subjects: Birgus latro; Nuclear genome; Panulirus ornatus; Paralithodes camtschaticus; Biotechnology; TP248.13-248.65; Genetics; QH426-470; Red king crab
• Online Access: https://doi.org/10.1186/s12864-021-07636-9; https://doaj.org/article/e000d138103646e8af7d8f5d481f062f

Abstract Background The complex life cycle of the coconut crab, Birgus latro, begins when an obligate terrestrial adult female visits the intertidal to hatch zoea larvae into the surf. After drifting for several weeks in the ocean, the post-larval glaucothoes settle in the shallow subtidal zone, undergo metamorphosis, and the early juveniles then subsequently make their way to land where they undergo further physiological changes that prevent them from ever entering the sea again. Here, we sequenced, assembled and analyzed the coconut crab genome to shed light on its adaptation to terrestrial life. For comparison, we also assembled the genomes of the long-tailed marine-living ornate spiny lobster, Panulirus ornatus, and the short-tailed marine-living red king crab, Paralithodes camtschaticus. Our selection of the latter two organisms furthermore allowed us to explore parallel evolution of the crab-like form in anomurans. Results All three assembled genomes are large, repeat-rich and AT-rich. Functional analysis reveals that the coconut crab has undergone proliferation of genes involved in the visual, respiratory, olfactory and cytoskeletal systems. Given that the coconut crab has atypical mitochondrial DNA compared to other anomurans, we argue that an abundance of kif22 and other significantly proliferated genes annotated with mitochondrial and microtubule functions, point to unique mechanisms involved in providing cellular energy via nuclear protein-coding genes supplementing mitochondrial and microtubule function. We furthermore detected in the coconut crab a significantly proliferated HOX gene, caudal, that has been associated with posterior development in Drosophila, but we could not definitively associate this gene with carcinization in the Anomura since it is also significantly proliferated in the ornate spiny lobster. However, a cuticle-associated coatomer gene, gammacop, that is significantly proliferated in the coconut crab, may play a role in hardening of the adult coconut crab abdomen in order to ...