A new Asterocheres (Copepoda, Siphonostomatoida) symbiont of the sea star Nidorellia armata (Gray, 1840) (Echinodermata, Asteroidea) in the Eastern Tropical Pacific

Abstract
A new species of the diverse and widely distributed symbiotic copepod genus Asterocheres is described from the sea star Nidorellia armata (Gray, 1840) in Mexican waters of the Eastern Tropical Pacific. The new species resembles various other congeners by sharing several characters including: (1) a siphon extending to the intersection of the maxilliped, (2) a 21-segmented antennule, and (3) a 2-segmented mandible palp. It can be distinguished by the unique structure and ornamentation of the maxilla, the armature and proportions of the fifth leg, and its body shape. This is the first documented record of Asterocheres from the Mexican Pacific and the first finding of a symbiotic copepod on this sea star host. Males, ovigerous females and copepodites were recorded from the host, thus suggesting a well-established symbiotic association. It is likely that copepods feed on the host’s tegument. Further studies will be needed to assess the reproductive traits and seasonality of this copepod as a symbiont. A new species of the diverse and widely distributed symbiotic copepod genus Asterocheres is described from the sea star Nidorellia armata (Gray, 1840) in Mexican waters of the Eastern Tropical Pacific. The new species resembles various other congeners by sharing several characters including: (1) a siphon extending to the intersection of the maxilliped, (2) a 21-segmented antennule, and (3) a 2-segmented mandible palp. It can be distinguished by the unique structure and ornamentation of the maxilla, the armature and proportions of the fifth leg, and its body shape. This is the first documented record of Asterocheres from the Mexican Pacific and the first finding of a symbiotic copepod on this sea star host. Males, ovigerous females and copepodites were recorded from the host, thus suggesting a well-established symbiotic association. It is likely that copepods feed on the host’s tegument. Further studies will be needed to assess the reproductive traits and seasonality of this copepod as a symbiont.