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Abstract Farfantepenaeus duorarum (Burkenroad, 1939) is a commercially harvested decapod shrimp that ranges from the eastern coast of the United States, through the Gulf of Mexico, and as far south as Isla Mujeres, Mexico. We report for the first time the complete mitochondrial genome of F. duorarum. The mitochondrial genome is 15,971 base pairs in length and is comprised of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. An intergenic space 982 bp in length located between the rrnS (12S) and trnI (Isoleucine) genes is presumed to be the D-loop. The mitochondrial gene order in F. duorarum is identical to that reported for congeners. To assess selection pressures within the mitochondrial genome, KA/KS ratios were calculated for all PCGs, and show values < 1, indicating that all genes are evolving under purifying selection. This work contributes one more mitochondrial genome to the penaeid shrimps, an economically targeted group. 

Extreme morphological disparity within Mollusca has long confounded efforts to reconstruct a stable backbone phylogeny for the phylum. Familiar molluscan groups—gastropods, bivalves, and cephalopods—each represent a diverse radiation with myriad morphological, ecological, and behavioral adaptations. The phylum further encompasses many more unfamiliar experiments in animal body-plan evolution. In this work, we reconstructed the phylogeny for living Mollusca on the basis of metazoan BUSCO (Benchmarking Universal Single-Copy Orthologs) genes extracted from 77 (13 new) genomes, including multiple members of all eight classes with two high-quality genome assemblies for monoplacophorans. Our analyses confirm a phylogeny proposed from morphology and show widespread genomic variation. The flexibility of the molluscan genome likely explains both historic challenges with their genomes and their evolutionary success.