Abstract
Two formerly monotypic lumbriculid genera, Guestphalinus Michaelsen, 1933 and Kincaidiana Altman, 1936, are reviewed using morphological and molecular data, following the discovery of new northwestern, Nearctic species. Several populations of Kincaidiana hexatheca Altman, 1936 were examined, and both morphology and DNA data suggest a single, variable species in Pacific drainages extending from northern California through Washington, USA. Specimens of Kincaidiana from the Smith River drainage with a single, median atrium and differing genetically from K. hexatheca are assigned to K. smithi sp. nov. The chaetal morphology of North American Guestphalinus populations is variable, and two basic morphotypes are assigned to G. elephantinus sp. nov. and G. exilis sp. nov. This decision is supported by molecular data. The tree topology, based on the mitochondrial 16S rRNA and Cytochrome Oxidase I (COI), and the nuclear 28S rRNA gene sequences, confirmed the close phylogenetic relationships among the Nearctic Guestphalinus, Kincaidiana and Uktena Fend, Rodriguez & Lenat, 2015. Probable synapomorphies associating these genera include a filiform, ringed proboscis, a forward shift of reproductive organs relative to the usual position in the family, and spermathecae in the atrial segment.
Highlights
Recent worm collections from northwestern USA have yielded many specimens of large, proboscisbearing lumbriculids with spermathecae in the atrial segment, and atria in a segment anterior to X
Rhynchelmis differs from Kincaidiana, Guestphalinus and Uktena in having spermathecae only in segments anterior to the atria, and the semiprosoporous atria are located in segment X
Morphology suggests that Kincaidiana, Guestphalinus and Uktena are phylogenetically related. This relationship is confirmed by the molecular data available at this time: the three genera form a strongly supported clade in the tree topology (Fig. 13), based on a limited set of lumbriculid outgroup taxa
Summary
Recent worm collections from northwestern USA have yielded many specimens of large, proboscisbearing lumbriculids with spermathecae in the atrial segment (a character uncommon within the family), and atria in a segment anterior to X (the most common position in the family). These distinctive worms show affinities with the genera Guestphalinus Michaelsen, 1933, Kincaidiana Altman, 1936 and Uktena Fend et al, 2015. The location of atria in VIII, and other diagnostic characters, such as large spermatophores and numerous copulatory chaetae, were unique to Uktena within the family Lumbriculidae
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