New species of Monstrilloida (Crustacea: Copepoda) from the Eastern Tropical Pacific

Abstract

Monstrilloid copepods were collected from the oceanic island Isla del Coco in the Eastern Tropical Pacific; two undescribed species were found, one of Cymbasoma and one of Monstrillopsis. The first species, represented by females only, is distinguished by the structure of its fifth legs, the antennular armature and the position of the ovigerous spines. The new Monstrillopsis, represented by male specimens, is distinguished by its genital lappets and details of the antennule armature. The isolation of this island, 532 km from the mainland, and the limited dispersal means of monstrilloids suggest potential endemism of these species. A recent record of Cymbasoma tumorifrons from the Mexican Pacific was found to represent a new species of Cymbasoma. It can be distinguished from C. tumorifrons, probably a Mediterranean form, by its body shape and antennular armature. These findings double the number of monstrilloid species known from the Eastern Tropical Pacific.

Keywords:

• copepods
• Costa Rica
• Mexican Pacific
• diversity
• marine zooplankton
• protelean parasites

Acknowledgements

We thank J. Picado for collecting the specimens examined from Isla del Coco.Valuable literature was provided by the Wilson Copepod Library (National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA), managed by Chad Walter. ECOSUR provided funds to one of us (AM-R) to visit Chetumal and analyse the specimens studied herein. Rosa Ma. Hernández-Flores deposited and catalogued the specimens in the collection of ECOSUR. Two anonymous reviewers provided valuable comments to improve this contribution.