Reassessing the species status of Pseudodiaptomus malayalus Wellershaus, 1969 and P. binghami Sewell, 1912 (Calanoida: Pseudodiaptomidae) from India based on morphology and mitochondrial cytochrome oxidase I gene sequences

Abstract

Pseudodiaptomus binghami Sewell, 1912 was first described from the Rangoon River (now Yangon River) estuary, Myanmar. Pseudodiaptomus malayalus Wellershaus, 1969 previously known as P. binghami malayalus, is a typical brackish-water calanoid copepod from Cochin Estuary, Kerala. Morphological examination of P. malayalus and P. binghami collected from Cochin Estuary and the Nambur canal in Andhra Pradesh revealed crucial differences between the two congeners. Female specimens of P. malayalus exhibited marked differences from those described by Wellershaus. They are (1) the number of terminal spines on P5, (2) ornamentation of GS, (3) ornamentation of Ur1–4, (4) length ratio of the Ur and CR segments and (5) length:width ratio of the CR setae. Furthermore, significant and discrete morphological differences were observed between the two Indian species in their P5 and urosome. But the male specimens of P. malayalus did not show any major differences from the original description. In addition, distance matrix data revealed 22% interspecific divergence values which in turn confirmed the status of P. malayalus and P. binghami as two distinct species.

Keywords:

• Calanoid copepods
• cytochrome oxidase subunit I
• DNA barcoding
• P. malayalus
• P. binghami
• taxonomy

Acknowledgements

We express our sincere thanks to University Grants Commission India, for funding this study as a part of the UGC project ‘Systematics and molecular phylogeny of pelagic copepods (crustaceans) from the coastal wetlands of south west coast of India’. The authors also extend their gratitude to the Head, Department of Marine Biology, Microbiology and Biochemistry for providing the facilities to conduct the work. The authors are also thankful to Dr. Shabuddin Shaik for providing Pseudodiaptomus binghami species from Namubur Kanal, Andhra Pradesh. We also express our sincere thanks to T Chad Walter, Smithsonian Institution, Department of Invertebrate Zoology, USA for reasonable criticism that improved the text. The authors are also thankful to the Sophisticated Test and Instrumentation Centre (STIC), Kochi, for SEM micrographs.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

We express our sincere thanks to University Grants Commission India, for funding this study as a part of the UGC project ‘Systematics and molecular phylogeny of pelagic copepods (crustaceans) from the coastal wetlands of south west coast of India’.