The discovery of the male Lepeophtheirus lichiae Barnard, 1948 (Copepoda: Caligidae) from the Eastern Mediterranean with morphological description and molecular phylogenetic analysis

The male of a poorly known and rare siphonostomatoid copepod Lepeophtheirus lichiae Barnard, 1948 is described for the first time based on a single specimen collected from the lateral body surface of the common leerfish, Lichia amia (Linnaeus), caught in the Gulf of Taşucu, Mersin, Türkiye. Supplementary data on female morphology are provided using newly collected specimens and modern imaging techniques, including Confocal Laser Scanning Microscopy (CLSM), which revealed several previously overlooked features.

Although molecular data could not be obtained from the male, comparative morphological analysis across the genus Lepeophtheirus supports its conspecific identity with the female. Among the 123 valid species in the genus, both sexes are known for 77, of which only 11—including L. lichiae —possess a two-segmented abdomen. The male of L. lichiae differs from all other two-segmented congeners in several diagnostic traits, such as the proportions of the abdominal and anal somites, the shape of the myxal process, and the configuration of the sternal furca.

Phylogenetic analyses based on mitochondrial COI and nuclear 18S rRNA sequences position L. lichiae as an independent lineage within Lepeophtheirus. The integration of morphological and molecular evidence presented here enhances understanding of the taxonomy and evolutionary relationships of this rare species. Additionally, analyses of the L. hospitalis complex support the reinstatement of L. kareii Yamaguti, 1936 as a valid species, distinct from L. hospitalis Fraser, 1920.