Blažeković, K.: Genetic structure and population dynamics of the Anisakis spp. nematode isolated from toothed whales (Odontoceti) of the Adriatic sea. MSc Thesis. University of Split. Split, 2013

Abstract

The purpose of the presented research was to identify Anisakis Dujardin, 1845 (Nematoda, Anisakidae) species from definitive hosts in the Adriatic Sea, and to investigate genetic structure and population dynamics of the most abundant parasite species. Nematodes showing morphological features of genus Anisakis were isolated from gastrointestinal tract of 4 toothed whale species (Odontoceti): bottlenose dolphin (Tursiops truncatus), striped dolphin (Stenella coeruleoalba), Risso's dolphin (Grampus griseus) and Cuvier's beaked whale (Ziphius cavirostris), stranded in the Croatian part of the Adriatic Sea from 1999 to 2012. Parasite population dynamics values were determined on 181 hosts. Anisakis species identification was conducted by molecular analysis of 165 samples, isolated from 26 toothed whales, by amplification of 600 bp long mitochondrial DNA fragment, locus for cytochrome oxidase subunit 2 (COII) by polymerase chain reaction. Overall prevalence in toothed whales (N=181) was 28.73%, and 31.90% when excluding one-year old host (N=163). Mean abundance in 163 hosts was 1209.96 and mean intensity 3781.13 of parasites per infected host. Striped dolphins had the highest prevalence (52%), then Risso's dolphins and Cuvier's beaked whales (50%), while bottlenose dolphins had the lowest value (26.92%). Phylogenetic analysis indicated presence of three Anisakis species in stranded cetaceans of Adriatic Sea: A. pegreffii (96.73%), A. simplex (1.96%) and A. physeteris (1.31%). Last two species were detected for the first time in the Adriatic area. Molecular diversity analysis of A. pegreffii (N=148) detected 47 polymorphic sites, 38 haplotypes, high haplotype diversity (h=0.6360 +/- 0.0471) and low nucleotide diversity (π=0.004520 +/- 0.002706).