Prochaetosoma dokdoense sp. nov. (Nematoda: Draconematidae) from Dokdo, Korea: First record of the genus Prochaetosoma from a shallow subtidal zone in the northwest Pacific Ocean

Abstract

A draconematid nematode Prochaetosoma dokdoense sp. nov., first discovered in December 2006 at a subtidal zone of Dokdo, Korea, the northwest Pacific Ocean, is described. This new species was obtained from coarse detritus and shell gravels. Prochaetosoma dokdoense sp. nov. differs from all the species hitherto described by the following combination of characteristics: longer slender body (910–1175 μm), elongate loop-shaped amphidial fovea in male (distal end of ventral arm slightly curved anteriorly), eight cephalic adhesion tubes in both sexes positioned just anterior to swollen pharyngeal region, number of posterior sublateral adhesion tubes (6 in male and 6–10 in female) and posterior subventral adhesion tubes (7–8 in male and 8–9 in female), longer spicule length (78–86 μm), long cylindro-conoid tail (114–131 μm in male and 116–131 μm in female) and higher ratio c′ (6.5–7.5 in male and 7.4–9 in female). A table comparing the major differential diagnostic characteristics of the species of the genus Prochaetosoma Micoletzky, 1922 is presented. For a reliable understanding of the geographic distribution and species identification of the genus Prochaetosoma, a pictorial key showing the relative length of non-annulated tail terminus to total tail length in both sexes is included, together with a dichotomous species identification key based on adults and fourth-stage juvenile as far as known. This is the first record of the genus Prochaetosoma in the northwest Pacific Ocean.

Keywords:

• DIC photomicrographs
• key
• morphology
• morphometrics
• taxonomy

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

The first author thanks the Director General Dr C. Pisani of the Royal Belgian Institute of Natural Sciences for the kind hospitality and assistance. Special thanks go to the chairman of the East Sea Research Institute of KORDI, Dr. Chan Hong Park. The authors are grateful to Teawook Kang and Sunyoung Kim for their assistance in collecting samples. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) to Hyun Soo Rho (KRF-2007-357-C00105) and also has been conducted with the support through the research programme of KORDI with contract No. PM53901 (A sustainable research and development of Dokdo) to Hyun Soo Rho and Dong Sung Kim. This work was also partially supported by the project of ‘The survey of indigenous biological resources of Korea’.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark