Novel markers in a multilocus genotyping approach for the detection of interspecific hybridization between Anisakis berlandi and A. pegreffii in the sympatric area of the Southwestern Atlantic Ocean

PALOMBA, M.; ACO ALBURQUEQUE, R.; BELLI, B.; CIPRIANI, P.; TIMI, J.T.; BRAICOVICH, P.E.; IRIGOITIA, M.M.; NASCETI, G.; MATTIUCCI, S.

Copenhague

Congreso; 15th International Congress of Parasitology; 2022

World Federation of Parasitologists

INTRODUCTIONIn recent years, new nuclear diagnostic markers between the species of the A. simplex (s.l.) complex (i.e. A. simplex s.s., A. pegreffii, A. berlandi) at the EF-1-α nDNA (Mattiucci et al.,2016, Parasitol, 143, 998–1011 ), nas10 nDNA (Palomba et al., 2020 Parasité, 27, 39), and DNA microsatellite (SSR loci) (Mattiucci et al., 2019 Parasitol,146,1387–1403) were developed, in the aim to use a multilocus approach for recognition of parental species and hybridization/introgression events in their sympatric areas.The Austral Region, between 30°S and 60°S, is known to be a sympatric area of Anisakis pegreffii and A. berlandi (Mattiucci et al., 2018 Adv Parasitol, 99:93-263). Hybridization events between the two species were previously discovered in New Zealand waters (Bello et al., 2021 Inf Gen Ev 92:104887). Aim of the present study was to use newly developed nuclear gene loci in a multilocus genotyping approach to recognise parental taxa of A. simplex (s.l.) complex and their mixed ancestry in the sympatric area of the southwestern Atlantic Ocean. MATERIALS AND METHODSA total of N=144 adults and N=156 L3 larvae of Anisakis, respectively collected in Orcinus orca and Merluccius hubbsi from Argentine waters, previously identified by cox2 and nas10, were genotyped at two novel nuclear loci (i.e. sequences analysis of superoxide-dismutase Sod, adenylate-kinase Adk), and at diagnostic SSRs loci. Primers for Adk and Sod were designed starting from a partial genome deposited of A. simplex. To investigate instances of gene exchange between A. pegreffii and A. berlandi, the Bayesian clustering algorithm by STRUCTUREv.2.3.3 (Pritchard et al.2000 Genetics,155:945-959), and NEWHYBRIDS (Anderson & Thompson,2002Genetics,160,1217–1229) to assess the occurrence of hybridization events between them, were performed on nuclear genetic data set.RESULTS AND CONCLUSIONSA total of N=60 and N=84 adults from O. orca were assigned, respectively, to A. pegreffii and A. berlandi, as well as N=143 and N=13 larvae from M. hubbsi respectively, to A. pegreffii and A. berlandi by mtDNA cox2. STRUCTURE analysis of genotypes obtained from the nuclear data set, allowed the assignment (100% probability) to the two “pure parental” taxa, except in the case of 2 adults and 1 larva specimens. Those specimens were identified as admixed between A. pegreffii and A. berlandi, having a Q-value=50%. NEWHYBRIDS assigned (100% probability) most of individuals as belonging to the two “pure parental” taxa; those 3 admixed individuals to the F1 hybrid class. They showed A. pegreffii maternal inheritance at the mtDNA cox2.The two novel nuclear loci (Sod and Adk) showing, respectively, N=9 and N=7 fixed alternative SNPs between A. pegreffii and A. berlandi, resulted 100% diagnostic. The multilocus nuclear genotyping approach will be useful to study hybridization and/or introgression events occurring between the two species in other sympatric areas, as well as in other sibling species of the A. simplex (s.l.) complex.