The miR-430 microRNA family has been described in multiple fish species as one of the first microRNAs expressed by the zygote. It has been suggested that this family is implicated in maternal mRNA elimination, but may also play a role in steroidogenesis, sexual differentiation, and flatfish metamorphosis. The miR-430 sequences have been found in multiple-copy tandem clusters but evidence of their conservation outside of teleost fishes is scarce. In the present study, we have characterized the tandem repeats organization of these microRNAs in different fish species, both model and of interest in aquaculture. A phylogenetic analysis of this family has allowed us to identify that the miR-430 duplication, which took place before the Chondrostei and Neopterygii groups’ divergence, has resulted in three variants (“a”, “b”, and “c”). According to our data, variant “b” is the most closely related to the ancestral sequence. Furthermore, we have detected isolated instances of the miR-430 repeat subunit in some species, which suggests that this microRNA family may be affected by DNA rearrangements. This study provides new data about the abundance, variability, and organization of the miR-430 family in fishes.

The striped soldier shrimp, Plesionika edwardsii (Brandt, 1851) is a pandalid with economic value in the Mediterranean region. We have sequenced and assembled its complete mitochondrial genome, which is 15,956 bp in length and contains the same 37 genes found in most metazoan mitochondrial genomes. Its gene order and nucleotide content are similar to most of the caridean mitochondrial genomes. In the comparative analysis, however, we detected in other species changes in the gene order that could be mediated by the recombination of transfer RNA genes, as well as AT skew shifts that could indicate changes in the origins of replication. All protein-coding genes of the mitochondrial genome of P. edwardsii seem to be under purifying selection, although the differences in Ka:Ks ratios suggest a disparity in the mutational constraints of some genes. This genome also presents a 1,118 bp-long non-coding sequence that encompass the control region. We have been able to find a previously described conserved sequence block in this region and assess that it forms a stem-loop structure in different species of Pandalidae, which is a shared feature with the conserved sequence blocks described in the family Alvinocarididae. We also detected microsatellites in the control region of P. edwardsii and in other species of Pandalidae and minisatellites in Lysmata vittata (Stimpson, 1860) that can account for around 20% of the additional non-coding region of this species. The phylogenetic relationships of P. edwardsii with other pandalids were assessed by two analyses: one based on the complete mitochondrial sequences and another based only on the protein-coding genes. Our study, thus, contributes to the genomic resources available for P. edwardsii and expands the current biological knowledge about the mitochondrial genomes of other caridean species.