AN UPDATED KEY TO THE GENERA OF CALIGIDAE (COPEPODA: SIPHONOSTOMATOIDA).

Members of the copepod family Caligidae are some of the most common parasites of marine fishes. There are 503 recognized species divided into about 30 genera, with 75% of species belonging to the 2 largest genera, Caligus and Lepeophtheirus. More than 30 caligid species are known to cause serious pathologic changes as ectoparasites in marine teleost aquaculture. This study was undertaken to provide a key to the valid genera of Caligidae, to examine their morphology in new detail with confocal laser scanning microscopy, and to review uncertainties concerning boundaries between several genera. There have been several substantial changes to the taxonomy of Caligidae over the last decade: Metacaligus, Sciaenophilus, and Sinocaligus have been synonymized with Caligus and the validity of Midias has been questioned. Here, we formally propose that Midias and Markevichus are junior subjective synonyms of Caligus. In total, we recognize 27 valid genera; provide a key to these genera; present confocal laser scanning micrographs for 25 of the genera, many of which have never been imaged before; and highlight helpful diagnostic features used in the key. We also discuss some concerns regarding the generic boundaries separating Belizia, Caritus, Parapetalus, Parechetus, Pseudechetus, and Synestius from Caligus and those separating Anuretes, Pseudanuretes, and Mappates from Lepeophtheirus.