Leduc, D.; Zhao, Z. Q. (2018). Morphological and molecular characterisation of Spirinia antipodea Leduc n. sp. (Nematoda: Desmodoridae), a cryptic species related to S. parasitifera, from the coast of New Zealand. Nematology.
Spirinia parasitifera is a common nematode species recorded from coastal habitats of the White, North and Barents Seas,
the Northwest Atlantic, the Maldives and Australia, and exhibits a high degree of variability in some morphological characters. For
these reasons it has been suggested that S. parasitifera is a species complex comprised of several distinct but potentially cryptic species.
However, no study has yet combined molecular and morphological approaches to verify this assertion. Here, we describe S. antipodea n.
sp., a species morphologically very similar to S. parasitifera, from the coast of New Zealand. Spirinia antipodea n. sp. differs from the
original description of S. parasitifera as well as subsequent descriptions by other authors in at least one body dimension, but no single
trait differs consistently between the New Zealand specimens and all descriptions of S. parasitifera. Phylogenetic analyses showed
that the new species is distinct from other species of the genus, including S. parasitifera specimens sampled near the type locality.
The S. antipodea n. sp. SSU sequence differed from other Spirinia sequence by 2.9-5.3%, whilst D2-D3 of LSU sequences differed
by 12.5-18.9%. The consensus SSU tree also recovered three distinct S. parasitifera clades, which provides support for the existence
of a species complex. Because it is not possible to determine whether the variability in morphological characters observed among
descriptions of S. parasitifera is intra- or interspecific, and therefore to determine which trait can reliably be used to differentiate
between S. antipodea n. sp. and S. parasitifera, the new species is best differentiated from S. parasitifera and other closely related
species based on SSU sequences rather than morphological characters.