title: Molecular systematics of pinniped hookworms (Nematoda: Uncinaria): species delimitation, host associations and host-induced morphometric variation.
abstract: Hookworms of the genus Uncinaria have been widely reported from juvenile pinnipeds, however investigations of their systematics has been limited, with only two species described, Uncinaria lucasi from northern fur seals (Callorhinus ursinus) and Uncinaria hamiltoni from South American sea lions (Otaria flavescens). Hookworms were sampled from these hosts and seven additional species including Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), South American fur seals (Arctocephalus australis), Australian fur seals (Arctocephalus pusillus), New Zealand sea lions (Phocarctos hookeri), southern elephant seals (Mirounga leonina), and the Mediterranean monk seal (Monachus monachus). One hundred and thirteen individual hookworms, including an outgroup species, were sequenced for four genes representing two loci (nuclear ribosomal DNA and mitochondrial DNA). Phylogenetic analyses of these sequences recovered seven independent evolutionary lineages or species, including the described species and five undescribed species. The molecular evidence shows that U. lucasi parasitises both C. ursinus and E. jubatus, whereas U. hamiltoni parasitises O. flavescens and A. australis. The five undescribed hookworm species were each associated with single host species (Z. californianus, A. pusillus, P. hookeri, M. leonina and M. monachus). For parasites of otarids, patterns of Uncinaria host-sharing and phylogenetic relationships had a strong biogeographic component with separate clades of parasites from northern versus southern hemisphere hosts. Comparison of phylogenies for these hookworms and their hosts suggests that the association of U. lucasi with northern fur seals results from a host-switch from Steller sea lions. Morphometric data for U. lucasi shows marked host-associated size differences for both sexes, with U. lucasi individuals from E. jubatus significantly larger. This result suggests that adult growth of U. lucasi is reduced within the host species representing the more recent host-parasite association. Intraspecific host-induced size differences are inconsistent with the exclusive use of morphometrics to delimit and diagnose species of Uncinaria from pinnipeds.
authors.affiliation: Department of Entomology and Nematology, University of California, One Shields Avenue, Davis, CA 95616, USA. Electronic address: sanadler@ucdavis.edu.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Nadler
authors.forename: Eugene T
authors.initials: ET
authors.lastname: Lyons
authors.forename: Christopher
authors.initials: C
authors.lastname: Pagan
authors.forename: Derek
authors.initials: D
authors.lastname: Hyman
authors.forename: Edwin E
authors.initials: EE
authors.lastname: Lewis
authors.forename: Kimberlee
authors.initials: K
authors.lastname: Beckmen
authors.forename: Cameron M
authors.initials: CM
authors.lastname: Bell
authors.forename: Aurelie
authors.initials: A
authors.lastname: Castinel
authors.forename: Robert L
authors.initials: RL
authors.lastname: Delong
authors.forename: Padraig J
authors.initials: PJ
authors.lastname: Duignan
authors.forename: Cher
authors.initials: C
authors.lastname: Farinpour
authors.forename: Kathy Burek
authors.initials: KB
authors.lastname: Huntington
authors.forename: Thijs
authors.initials: T
authors.lastname: Kuiken
authors.forename: Diana
authors.initials: D
authors.lastname: Morgades
authors.forename: Soraya
authors.initials: S
authors.lastname: Naem
authors.forename: Richard
authors.initials: R
authors.lastname: Norman
authors.forename: Corwin
authors.initials: C
authors.lastname: Parker
authors.forename: Paul
authors.initials: P
authors.lastname: Ramos
authors.forename: Terry R
authors.initials: TR
authors.lastname: Spraker
authors.forename: Bárbara
authors.initials: B
authors.lastname: Berón-Vera
mesh_terms: D000723:Ancylostomatoidea / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D000818:Animals; D001699:Biometry; D010872:Caniformia / Q000469:parasitology*; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D004275:DNA, Ribosomal
keywords: Cophylogeny; Hookworm; Molecular systematics; Morphometrics; Phylogenetics; Pinniped; Species