First record of Orthohalarachne attenuata in Arctocephalus australis in mainland Argentina (Parasitiformes, Mesostigmata, Dermanyssoidea, Halarachnidae) with observations on its ambulacral morphology

Abstract

Pinniped respiratory mites of the species Orthohalarachne attenuata have been recorded from various locations around the world but not from continental Argentina. In the present work, we document for the first time the presence of O. attenuata on Arctocephalus australis on the Argentine mainland. A total of 23 adult and 381 immature mites were collected from the nose and nasopharyngeal cavity during a necropsy. The mite ambulacrum is described in adults and larvae. This structure consists of a pretarsus, an extensible pulvillum, a pair of claws and paradactyli (pretarsus opercula). The ambulacral structures also have some peculiarities, such as the presence of longitudinal furrows in the claws, straight claws in legs II and III (as opposed to curved in legs I and IV), and the fin-shaped paradactyli. The morphology of the ambulacrum of this mite is interpreted as an adaptation for anchoring to different surfaces of the host, and the protective structures present in the larvae as an adaptation for the dispersal phase in the external environment.