Gyrodactylus orecchiae sp. n. (Monogenea, Gyrodactylidae) is described from the skin, fi ns, eyes and gills of juvenile
Sparus aurata L. (gilthead seabream) following two outbreaks of gyrodactylosis amongst stocks held in inshore fl oating cages on
the Adriatic coast of Albania and Croatia. Fish were heavily infected (1000+ gyrodactylids/fi sh) with G. orecchiae which reportedly
resulted in ~2\u201310% mortality amongst the infected stock. Morphologically, the haptoral hooks of G. orecchiae most closely
resemble those of Gyrodactylus arcuatus Bychowsky, 1933 in the approximate shape of the ventral bar with its pronounced ventral
bar processes and marginal hook sickles which possess a square line to the inner edge of the sickle blade and large rounded heels.
The marginal hooks are also morphologically similar to those of Gyrodactylus quadratidigitus Longshaw, Pursglove et Shinn, 2003
and Gyrodactylus colemanensis Mizelle et Kritsky, 1967, but G. orecchiae can be readily discriminated from all three species by
the characteristic infolding of the hamuli roots and the shape of the marginal hook sickle. Molecular sequencing of the ITS1, 5.8S,
ITS2 regions (513+157+404 bp, respectively) of G. orecchiae and alignment with other gyrodactylids for which these same genomic
regions have been determined, suggests that this is a new species. No similarities were found when the ITS1 region of G. orecchiae was compared with 84 species of Gyrodactylus available on GenBank
