Genetic diversity of Contracaecum rudolphii sp. A (Nematoda: Anisakidae) parasitizing the European Shag Phalacrocorax aristotelis desmarestii from the Spanish Mediterranean coast

Abstract

Sibling species of the Contracaecum rudolphii (s.l.) complex are habitual endoparasites of cormorants of the Phalacrocoracidae family, worldwide. In Europe, the two species, C. rudolphii sp. A and C. rudolphii sp. B, have been identified. However, information regarding the occurrence and distribution of these anisakids in cormorants from Spain is scarce. In the present study, 20 specimens of the European Shag, Ph. aristotelis desmarestii, from the western Mediterranean Spanish marine coast were parasitologically analyzed for the presence of nematodes. All hosts were found parasitized with Contracaecum specimens (n = 1,517). A representative subsample was genetically identified as C. rudolphii sp. A by sequence analysis of the mtDNA cox2 gene and the ITS1 and ITS2 regions of the rDNA. This represents the first report of C. rudolphii sp. A from the Spanish Mediterranean waters. Population genetic analysis was performed including other C. rudolphii sp. A specimens from the west Sardinian and the Tyrrhenian Sea. At the intraspecific level, a significant genetic differentiation (Fst ≈ 0.08, p < 0.00001) between the metapopulation from the Spanish Mediterranean coast and that from the Sardinian waters was observed; whereas, no differentiation was found between metapopulations of the parasite from the Spanish and the Tyrrhenian Italian coast. The findings highly support the hypothesis of the adaptation of the life cycle of C. rudolphii sp. A in brackish and marine ecosystems. Furthermore, the results on the population genetics of C. rudolphii sp. A suggest the possible role of the migration routes of wintering populations of cormorants in the Mediterranean Sea in influencing the parasite genetic structure.

Molecular and morphological studies on Contracaecum rudolphii A and C. rudolphii B in great cormorants (Phalacrocorax carbo sinensis) from Italy and Israel

“…In Spain, Roca-Geronès et al . (2023) analysed only C. rudolphii A, that was considered as single population due to the low genetic diversity (n. haplotypes 40/56, hd = 0.969, nucleotide diversity = 0.00681). In the same study, the comparisons with the sequences of C. rudolphii A from 2 Italian areas showed similar values as obtained in the present study (Tyrrhenian: n. haplotypes 80/110, hd = 0.986, nucleotide diversity = 0.00871; western Sardinia: n. haplotypes 28/33, hd = 0.979, nucleotide diversity = 0.0117).…”

“…In the same study, the comparisons with the sequences of C. rudolphii A from 2 Italian areas showed similar values as obtained in the present study (Tyrrhenian: n. haplotypes 80/110, hd = 0.986, nucleotide diversity = 0.00871; western Sardinia: n. haplotypes 28/33, hd = 0.979, nucleotide diversity = 0.0117). The haplotypes diversity in any case reflect the geographical distributions of the sequences analysed (Amor et al ., 2020; Roca-Geronès et al ., 2023). Amor et al .…”

“…Recent work suggested the possible role of the migration routes of wintering populations of cormorants in the Mediterranean Sea in influencing the distribution and genetic structure of C. rudolphii (Roca-Geronès et al ., 2023). Cormorants migrate from Europe and winter in Israel during November–March, forming large colonies along the Mediterranean and Red Sea coasts and at inland streams and wetlands (Nemtzov, 2008).…”

“…In European cormorants, the sibling species C. rudolphii A and B are reported, with C. rudolphii sp. A having a life cycle more adapted to brackish and marine ecosystems, while C. rudolphii B occurring mainly in freshwater ecosystems (Mattiucci et al ., 2020; Roca-Geronès et al ., 2023). In central and eastern Europe, both species are found, often in mixed infections, in Ph.…”

“…aristotelis aristotelis (Abollo et al, 2001) and Ph. aristotelis desmarestii (Roca-Geronès et al, 2023) from Europe; C. rudolphii B parasitizes Ph. carbo sinensis (Mattiucci et al, 2002(Mattiucci et al, , 2020Amor et al, 2020;Carmeno et al, 2022;Cammilleri et al, 2023) from Europe; C. rudolphii C is reported in the double-crested cormorant Ph.…”