On the South American species of the genus Meridiosignum (Crustacea: Isopoda: Asellota: Paramunnidae)

Abstract

Meridiosignum undulatum n. sp. and M. disparitergum n. sp. are described from off the Río de la Plata estuary. These two new species are easily distinguished from other members of the genus Meridiosignum in having the lateral margins of pereonites 2 and 3 bilobed (the concavity is much more pronounced in M. disparitergum), and those of pereonite 4 produced into a single process. The terminal male instar of Meridiosignum menziesi (Winkler, 1994) is described, and this species is herein reported from the Beagle Channel and Puerto Deseado. All the species currently placed in Meridiosignum were found in shallow waters in the southern hemisphere, M. undulatum n. sp. and M. disparitergum n. sp. being the species recorded at the greatest depth (129 m).

Keywords:

• taxonomy
• Isopoda
• Meridiosignum
• new species
• South Atlantic Ocean

Acknowledgements

We are grateful to Mr Fabrizio Scarabino (Dirección Nacional de Recursos Acuáticos, DINARA, Montevideo) for providing the material of the two new species herein described; Dr Jean Just (Zoologisk Museum, Copenhagen) and Dr George “Buz” Wilson (Australian Museum, Sydney) for many valuable comments and for the unpublished manuscript they have shared with us during the preparation of this paper; and Dr Oliver Coleman (Museum für Naturkunde, Berlin) for the loan of the type material of Paramunna menziesi. We are also indebted to Dr Wiebke Brökeland (Deutsches Zentrum für Marine Biodiversitätsforschung, Wilhelmshaven) and an anonymous reviewer for their useful suggestions. This study was partially supported by the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT, PICT 02‐11180), the Universidad de Buenos Aires (UBACyT X162), and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina).