Abstract
BackgroundIn the marine environment, transitional zones between major water masses harbour high biodiversity, mostly due to their productivity and by containing representatives of species characteristic of adjacent communities. With the aim of assessing the value of larval Anisakis as zoogeographical indicators in a transitional zone between subtropical and sub-Antarctic marine currents, larvae obtained from Zenopsis conchifer were genetically identified. Larvae from Pagrus pagrus and Merluccius hubbsi from two adjacent zoogeographical provinces were also sequenced.ResultsFour species were genetically identified in the whole sample, including Anisakis typica, A. pegreffii, A. berlandi and a probably new species related to A. paggiae. Anisakis typica and A. pegreffii were identified as indicators of tropical/subtropical and sub-Antarctic waters, respectively, and their presence evidenced the transitional conditions of the region. Multivariate analyses on prevalence and mean abundance of Anisakis spp. of 18 samples represented by 9 fish species caught south of 35°S determined that host trophic level and locality of capture were the main drivers of the distribution of parasites across zoogeographical units in the South-West Atlantic.ConclusionsMost samples followed a clear zoogeographical pattern, but the sample of Z. conchifer, composed mostly of A. typica, was an exception. This finding suggests that population parameters of A. typica and A. pegreffii could differ enough to be considered as a surrogates of the identity of larvae parasitizing a given host population and, therefore, a step forward the validation of the use of larval Anisakis as biological indicators for studies on host zoogeography.
Highlights
In the marine environment, transitional zones between major water masses harbour high biodiversity, mostly due to their productivity and by containing representatives of species characteristic of adjacent communities
The only published reports of genetically identified species of Anisakis are that of Anisakis pegreffii in Merluccius hubbsi [4] and the skates Sympterygia bonapartii and Zearaja chilensis [18], and that of a single specimen of Anisakis berlandi in S. bonapartii [18], highlighting the considerable uncertainty existing in the species composition of this genus in this region
Genetic identification The identification through BLAST showed that sequences from the mtDNA cox2 gene of larvae Anisakis Type I exhibited a similarity of 99–100% with sequences for A. typica available on GenBank (n = 20; 16 from Z. conchifer, accession numbers MH443102-MH443117 and 4 from P. pagrus, accession numbers MH443118-MH443121); of 99% with those for A. berlandi (n = 3; 2 from Z. conchifer, accession numbers MH443122-MH443123 and 1 from P. pagrus, accession number MH443124); and of 99–100% with sequences for A. pegreffii (n = 12, 1 from Z. conchifer, accession number MH443127; 2 from P. pagrus, accession numbers MH443126-MH443123; and 9 from M. hubbsi, accession numbers MH443128-MH443136)
Summary
Transitional zones between major water masses harbour high biodiversity, mostly due to their productivity and by containing representatives of species characteristic of adjacent communities. Members of the genus Anisakis are known worldwide because of their implication in human health as the causative agents of anisakiosis, resulting from the ingestion of infective third-stage larvae in raw or undercooked marine fish products [1,2,3,4] and considered as Lanfranchi et al Parasites & Vectors (2018) 11:583 traditional morphological analyses, except to the level of the morphotypes of Berland [10], Anisakis Type I and Type II [11] Some of these cryptic species often occur in sympatry and syntopy in fish hosts and the lack of taxonomic resolution can affect comparative studies. Recent papers, based on genetic identification of larvae and adults, have recorded a higher diversity, A. typica being the most abundant and widely reported species of the genus, occurring in both cetaceans and fish hosts along Brazilian coasts [22, 23]
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