Morphological and molecular studies of the life-cycle stages of the monorchiid Monorchis parvus (Looss, 1902) (Digenea) from the Southern Mediterranean coast (Tunisia).

The elucidation of life-cycles of digeneans, with their successive larval stages, is facilitated by the use of molecular markers. Samples of sporocysts containing cercariae and metacercariae belonging to Monorchis Monticelli, 1893 were collected from naturally infected bivalves, Cerastoderma glaucum (Bruguière, 1789), and adult forms of Monorchis spp. were collected from sparid fishes of the genus Diplodus. All specimens were collected in the Gulf of Gabès, southern Tunisia. The identities of the examined molluscs and fishes were determined via molecular barcoding of their COI gene. Sequences of COI and ITS1 genes were also obtained for both larval and adult stages of collected parasite specimens. Genetic sequence data generated for the collected larval specimens only differed minimally from the sequence data of adults identified as Monorchis parvus; we attribute the difference to intraspecific variation. The morpho-anatomical study showed that the different stages of M. parvus collected from the Tunisian coasts had the same morphology as those reported in European waters with a lag in maturity and lower measurements. The species is recorded and molecularly characterised for the first time off the Tunisian coasts.

Molecular evidence for the existence of species complexes within Macvicaria Gibson & Bray, 1982 (Digenea: Opecoelidae) in the western Mediterranean, with descriptions of two new species.

Morphological and molecular characterisation of specimens of Macvicaria spp. (Digenea: Opecoelidae) from five species of Mediterranean sparids (Teleostei: Sparidae) sampled in the Bizerte Lagoon and the Bay of Bizerte (Tunisia) revealed the presence of two species complexes designated as "obovata" and "crassigula" groups. Detailed comparative morphological and phylogenetic analyses revealed that two of the specimen sets, one from each complex, represent species new to science. M. maamouriae n. sp. from Sparus aurata L. and Lithognathus mormyrus (L.) appeared genetically similar to M. obovata (Molin, 1859) but differs in having a much larger ventral sucker relative to body width, a cirrus-sac extending dorsally to the posterior margin of the ventral sucker or more posterior, vitelline fields comprising distinctly more abundant vitelline follicles, reaching the level of the pharynx both ventrally and dorsally and confluent dorsally in the forebody, and an ovary contiguous with the anterior testis. Macvicaria bartolii n. sp. from Diplodus annularis (L.) and Spondyliosoma cantharus (L.) belongs to the "crassigula" group and is characterised by having almost exclusively dorsal vitelline follicles forming two non-confluent fields in the forebody. Additional morphological data are provided for Macvicaria dubia (Stossich, 1905), a poorly known parasite of Oblada melanura (L.). Morphological descriptions are associated with ITS1-5.8S-ITS2 and 28S rDNA sequences for the three Mediterranean species of Macvicaria Gibson & Bray, 1982. The results of our study suggest that further exploration of the species diversity within this genus should be based on both morphological and molecular data.