A new species of Clausidium Kossmann, 1874 (Copepoda: Cyclopoida) associated with ghost shrimps from the Persian Gulf, including female-male interlocking mechanisms and remarks on host specificity.

A new clausidiid copepod was found associated with the ghost shrimp Neocallichirus jousseaumei (Nobili) in the Persian Gulf, on the Iranian coast. The new species shares the armature formula of swimming legs 2 to 4 with C. persiaensis, but can be easily distinguished from its congeners by unique characteristics of the females: the prominent spine on endopodal segment 1 of the antenna, the armature of the maxilliped, and the elongated basis of the swimming legs. Distinguishing features observed in males include the distinct projections on the maxilliped and the armature of legs 1 and 4. In addition to traditional light microscopy-based descriptions, confocal laser scanning microscopy (CLSM) was used to obtain high resolution images and 3-D reconstructions of entire copepods. Structures of taxonomic importance that exhibit complex shapes (male maxilliped and female urosome) were scanned to generate 3-D prints that gave valuable insights about female/male interlocking mechanisms. The taxonomic status and host specificity of Clausidium spp. are discussed and a key to valid species is provided.