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United States Department of Agriculture

Agricultural Research Service

Title: Reassignment of the Genus Lamanema from Nematodirinae to Molineinae (Nematoda: Trichostrongyloidea)

Authors
item Rickard, Lora - MISS. STATE. UNIV., MS
item Hoberg, Eric

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 1999
Publication Date: N/A

Interpretive Summary: Trichostrongyloid nematodes are significant pathogens in ruminants, and accurate taxonomy is at the foundation of understanding their host and geographic distribution. The genus Lamanema is considered to be critically important in understanding the evolution of certain of the trichostrongyloids. We found inconsistencies in morphological characters for Lamanema and those that are important in diagnosing its relationship to nematodes in the subfamily Nematodirinae within a phylogenetic context. Among seven putative derived characters for Nematodirinae, Lamanema possesses only one, large eggs. This attribute is equivocal with respect to placement of Lamanema; it is considered that possession of this primitive character alone is insufficient justification to retain the genus in Nematodirinae. Lamanema is retained in the family Molineidae and Molineinae as it possesses all characters of the family as currently defined. The origin of Lamanema represents a secondary colonization of ruminants by molineids and provides no context for elucidating the history of the Nematodirinae and Nematodirus the most economically significant genus in the subfamily. Thus, previous misconceptions about the evolution of these pathogenic nematodes are resolved.

Technical Abstract: The monospecific genus Lamanema historically has been assigned to the subfamily Nematodirinae within the Molineidae. Inconsistencies in morphological characters, within a phylogenetic context for Nematodirinae, led to a re-evaluation of the putative relationships and taxonomic placement of Lamanema. Among seven putative synapomorphies for Nematodirinae, Lamanema possesses only one, large eggs. Large eggs, sporadically present in phylogenetically disparate taxa of trichostrongyles (e.g. Marshallagia)are equivocal with respect to placement of Lamanema; it is considered that possession of this homoplasious character alone is insufficient justification to retain the genus in Nematodirinae. Affinities with the Trichostrongylidae (Cooperiinae or Haemonchinae)have also been proposed, however, Lamanema possess neither of 2 synapomorphies that diagnose monophyly of the family. Lamanema is retained in the Molineidae and Molineinae as it possesses all characters of the family as currently defined. The origin of Lamanema represents a secondary colonization of ruminants by molineids and provides no context for elucidating the history of the Nematodirinae and Nematodirus.

Last Modified: 11/28/2014
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