Population genetic structure of the European squid Loligo vulgaris (Cephalopoda: Loliginidae) in the Eastern Adriatic Sea

Knowledge of genetic diversity and population structure is the foundation of responsible and sustainable exploitation of every species, that ensures the sustainability of wildlife populations. In order to gain insight into the recent state of genetic diversity of Loligo vulgaris populations in the north, central and south part of the Eastern Adriatic, a part of the nucleotide sequence of the mitochondrial gene of the cytochrome c oxidase subunit I, known as COI, was analyzed. This genetic marker today represents the basis for the identification of all Metazoa, the study of their phylogenetic relationships as well as population structures. During the autumn- winter period of 2019, a total of 30 squids were collected. Sequencing of mitochondrial DNA fragments produced good quality results. The length of the sequenced region in most samples was about 630 base pairs (bp). A total of 9 polymorphic sites and 10 haplotypes were identified in the total sample of L. vulgaris. Of the 9 polymorphic sites, 5 were singletons with two possible variants. Of the 4 phylogenetically informative sites, all had two variants. Of the 10 haplotypes defined, 5 are represented by a single individual. Haplotype 1 (H1) showed the highest total frequency in the total sample. According to genetic diversity indices, high total haplotype diversity (Hd = 0.8005) and low nucleotide diversity (Pi = 0.00199) were found. The total mean difference between sequence pairs (k) was 1.26108. Obtained results indicate that there is a unique homogeneous stock of L. vulgaris in the Adriatic Sea.