Morphological and molecular characterization of Monticelli, 1907 (Monopisthocotylea, Monogenea) from the gilthead seabream Linnaeus (Teleostei, Sparidae) from the southwestern Mediterranean and notes on host specificity of the genus Diesing, 1850.

Incomplete original descriptions, the unavailability or poor conditions of specimens and the lack of detailed redescriptions have caused the validity of several species of the genus Diesing, 1850 to be questioned. To date, seven of the recognized species were described upon one or two specimens, hindering study of intraspecific variations. This was made worse by considering few morphoanatomical differences sufficient to erect new species. Among spp. occurring in Mediterranean waters, was first described from the gilt-head bream (Sparidae) off Italy. Although beautifully illustrated for a paper from that century, morphometric data for from the type-host remain unavailable. Previous records of provided either morphometrical or molecular data, and its validity was questioned. We provide a redescription of based on newly collected specimens from the from the southwestern Mediterranean (off Algeria) using integrative taxonomy. Analysis of 1 sequences of from , compared to sequences from other sparid hosts, mainly , revealed a divergence not exceeding 2%, suggesting a stenoxenic specificity for this monogenean. Given that is the type-host for , we were tempted to suggest a synonymy between and We refrained from doing so because was first described from the Atlantic coast off Brest, France. Morphological data for from are warranted assessing the host specificity of and whether there might be a species complex within individual sparid fish species.