Octopus vulgaris (Cuvier, 1797) in the Mediterranean Sea: Genetic Diversity and Population Structure

Abstract

The common octopus, Octopus vulgaris Cuvier 1797, is a largely exploited cephalopod species in the Mediterranean Sea and the Atlantic Ocean, as well as along the coasts of Africa, Brazil and Japan, where its taxonomic identity is still debated. The assessment of its genetic structure is a pressing need to correctly manage the resource and to avoid overfishing and collapsing of local stocks. Here we analysed genetic variation and population structure of O. vulgaris using thirteen microsatellite loci in seven sampling localities from the Mediterranean Sea and one from the Atlantic Ocean. We also used a DNA barcoding approach by COI gene fragment to understand the phylogenetic relationships among the specimens here investigated and the ones whose sequences are available in literature. Our results reveal high levels of allelic richness and moderate heterozygosity in all samples investigated, and a pronounced differentiation of the Atlantic and Sicilian specimens. This latter aspect seems to support the isolation of the biota within the Strait of Messina. A certain degree of differentiation was detected among the other geographic samples within the Mediterranean Sea, which is more compatible with an island model than isolation by distance. The occurrence of null alleles affected more genetic diversity indices than population structure estimations. This study provides new insights about the genetic diversity and structure of O. vulgaris in the area of interest, which can be used as guidelines for a fisheries management perspective.

Genomic signatures of evolution inNautilus—An endangered living fossil

“…The apparent lack of genetic subdivision could be due to either substantial gene flow among populations, very large population sizes or a combination of both. Our population size estimates are high (Table ) compared to other cephalopods (e.g., octopus: de Luca, Catanese, Procaccini, & Fiorito, ; jumbo squid: Ibáñez et al., ) but very consistent with the limited previous estimates for Nautilus . For example, Williams et al.…”

“…Although our estimates of effective population sizes were smaller for the South Pacific and the Coral Sea clades than for the Indo‐Pacific clade, they are still higher than what has been estimated for other closely related groups (Ibáñez et al., ; de Luca et al., ). This validates our third hypothesis that living fossils tend to generally exhibit high population sizes and reduced genetic drift compared to nonliving fossil taxa.…”

Contrasted phylogeographic patterns on mitochondrial DNA of shallow and deep brittle stars across the Atlantic-Mediterranean area

“…III do not allow us venturing any hypothesis about the current distribution of this species within the Mediterranean, although its absence in NW Mediterranean deep subtidal areas, where O. fragilis is commonly found, might indicate that its distribution limit in the Mediterranean is at the AOF, as observed in other marine invertebrates e.g. refs 9, 13 and 34. Nevertheless, further sampling in deep waters of the SW Mediterranean and Eastern Mediterranean sub-basin would be necessary to have a complete picture of the geographical distribution of this species.…”

Phylogeography of the insular populations of common octopus, Octopus vulgaris Cuvier, 1797, in the Atlantic Macaronesia

“…Significant structure was also detected within the central Mediterranean, with a break between western and eastern Mediterranean basins [26]. Recent studies on microsatellite genetic variation along the central-western Mediterranean have suggested a differentiation consistent with an island model of isolation [27]. On the South African coast, a dominant haplotype, found also on the Senegal coast, was identified as divergent from those in the northeastern Atlantic; a rare divergent haplotype likely associated with an invasive event was also identified [28].…”