The complete mitochondrial genome of Argentine red shrimp, Pleoticus muelleri (Bate, 1888) was determined using the MiSeq platform. Its mitogenome (16,189 bp) encoded the canonical 13 protein-coding genes, 22 tRNA genes, two rRNA genes. Start codons of all protein-coding genes were ATN except for ATP8, while incomplete stop codons (T–) were identified in six genes including COXI, COXII, COXIII, NAD3, NAD5, and NAD6. The mitogenome of P. muelleri showed highest sequence identity with Parapenaeopsis hardwickii (82%) and Solenocera crassicornis (81%). Phylogenetic analysis showed three shrimps in Solenoceridae including P. muelleri were grouped together from those in Penaeidae, which suggests taxonomic reexamination for those in those family.

The nicotinic acetylcholine receptor (nAChR) is a member of the ligand-gated ion channel (LGIC) family and is composed of five subunits arranged around a central pore. Expressed sequence tag screening and traditional cloning strategies revealed five full-length cDNAs encoding nAChR subunit homologs (Pajα3, Pajα10, Pajα11, Pajα12, and Pajβ1) in the Morotoge shrimp, Pandalopsis japonica. The nAChR subunits exhibited common structural characteristics, including a signal peptide sequence, a large N-terminal extracellular domain with conserved motifs for ligand binding (loops A-F), and a transmembrane (TM) domain with four hydrophobic TM motifs (TM1-TM4). Based on the conserved GEK motifs located just before TM2, all five nAChR subunits from P. japonica appear to be cation-selective ion channels. Among the five subunits, Pajα3 and Pajβ1 clustered together with insect core groups, whereas Pajα10, Pajα11, and Pajα12 were classified as a divergent group. Three distinct transcripts were identified in Pajα3, presumably due to alternative splicing between TM3 and TM4, which may be involved in channel formation with other subunits. All five nAChR subunits were expressed predominantly in neuronal tissues, including the brain, sinus gland/X-organ complex, thoracic ganglia, and abdominal ganglia, with no significant differences in subunit expression levels among the neuronal tissues. The five shrimp nAChR subunits could not be functionally expressed in Xenopus oocytes, but coexpression of Pajβ1 and rat α4 subunit (Rα4) formed functional channels responding to acetylcholine. Functional expression of vertebrate α subunit (Rα4) with invertebrate β1 subunit (Pajβ1) will expand our knowledge regarding the structural characteristics and molecular gating mechanism of invertebrate nAChRs.