New nematode species from the continental slope of New Zealand (Chromadorea, Microlaimida, and Chromadorida), and unexpected placement of the genus Molgolaimus Ditlevsen, 1921

  • Daniel LeducEmail author
  • Sujing Fu
  • Zeng Qi Zhao
Original Paper


The current nematode classification comprises three primarily marine basal Chromadorean orders: the Microlaimida Leduc et al., 2018; Desmodorida De Coninck, 1965; and Chromadorida Chitwood, 1933. The phylogenetic placement of several taxa within these orders, however, is unclear due to the paucity of taxonomically informative morphological characters for high-level classification and is yet to be tested by molecular phylogenetic analyses due to the absence of molecular sequences. Here, we describe Molgolaimus kaikouraensis sp. nov. and Aponema pseudotorosum sp. nov. from the continental slope of New Zealand and investigate phylogenetic relationships of these species and that of the rare desmodorid genera Onepunema and Pseudonchus, using SSU phylogenetic analyses for the first time. Whilst our analyses provided support for the current classification of Aponema within the family Microlaimidae and of Pseudonchus within the Desmodorida, we could not confirm relationships of Onepunema. We found no support for the placement of Molgolaimus with either the Desmodorida or Microlaimidae/Microlaimida as in the current and previous classifications. Instead, Molgolaimus was classified with the Chromadorida with moderate and strong support in maximum likelihood and Bayesian analyses, respectively. Congruence analysis suggests that in some cases at least, the structure of the female reproductive system is a more taxonomically informative trait for marine nematode classification than the male reproductive system or cuticle.


Aponema pseudotorosum sp. nov. D2-D3 region of large subunit (LSU) 28S rDNA gene Microlaimidae Molgolaimus kaikouraensis sp. nov. Conway trough Pseudonchinae Small subunit (SSU) 18S rDNA gene 



We thank the crew and scientific personnel of RV Tangaroa (voyages TAN1701 and TAN1708). We thank two anonymous reviewers for providing constructive criticisms on the manuscript.


This research was funded by the NIWA under Coasts and Oceans Research programme 2 (2018/19 SCI) and supported by core funding for Crown Research Institutes from the Science and Innovation Group of the Ministry of Business, Innovation and Employment.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All applicable international, national, and/or institutional guidelines for animal testing, animal care and use of animals were followed by the authors.

Sampling and field studies

All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable. The study is compliant with CBD and Nagoya protocols.

Data availability

All data sources on which this manuscript is based are either provided in the manuscript or available in GenBank.


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Copyright information

© Senckenberg Gesellschaft für Naturforschung 2019

Authors and Affiliations

  1. 1.National Institute of Water and Atmospheric ResearchWellingtonNew Zealand
  2. 2.Key Laboratory of the Ministry of Education for Coastal and Wetland EcosystemsXiamen UniversityXiamenChina
  3. 3.Landcare ResearchAucklandNew Zealand

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