Distribution and genetic diversity of Anisakis spp. in cetaceans from the Northeast Atlantic Ocean and the Mediterranean Sea

Parasite biodiversity in cetaceans represents a neglected component of the marine ecosystem. This
study aimed to investigate the distribution and genetic diversity of anisakid nematodes of the genus
Anisakis sampled in cetaceans from the Northeast Atlantic Ocean and the Mediterranean Sea. A total
of 478 adults and pre-adults of Anisakis spp. was identifed by a multilocus genetic approach (mtDNA
cox2, EF1 α− 1 nDNA and nas 10 nDNA gene loci) from 11 cetacean species. A clear pattern of host
preference was observed for Anisakis spp. at cetacean family level: A. simplex (s.s.) and A. pegrefi
infected mainly delphinids; A. physeteris and A. brevispiculata were present only in physeterids, and A.
ziphidarum occurred in ziphiids. The role of cetacean host populations from diferent waters in shaping
the population genetic structure of A. simplex (s.s.), A. pegrefi and A. physeteris was investigated
for the frst time. Signifcant genetic sub-structuring was found in A. simplex (s.s.) populations of the
Norwegian Sea and the North Sea compared to those of the Iberian Atlantic, as well as in A. pegrefi
populations of the Adriatic and the Tyrrhenian Seas compared to those of the Iberian Atlantic waters.
Substantial genetic homogeneity was detected in the Mediterranean Sea population of A. physeteris.
This study highlights a strong preference by some Anisakis spp. for certain cetacean species or
families. Information about anisakid biodiversity in their cetacean defnitive hosts, which are apex
predators of marine ecosystems, acquires particular importance for conservation measures in the
context of global climate change phenomena.